diff --git a/CHANGELOG.md b/CHANGELOG.md
index badfc014..dfa6e989 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,465 +1,468 @@
-# Changelog
-
-## Unreleased
-
-
-
-## v1.25.0-preview.1
-- Implement per-orchestration and per-activity versioning ([#695](https://github.com/microsoft/durabletask-dotnet/pull/695))
-- Add es-metadata.yml to schema 1.0.0 ([#722](https://github.com/microsoft/durabletask-dotnet/pull/722))
-- Release v1.24.2 ([#724](https://github.com/microsoft/durabletask-dotnet/pull/724))
-- Add per-task versioning via `[DurableTask(Version = "...")]`, `TaskOptions.Version`, and `StartOrchestrationOptions.Version` ([#695](https://github.com/microsoft/durabletask-dotnet/pull/695))
-
-
-## v1.24.2
-- Bump DI.Abstractions and Bcl.AsyncInterfaces to 9.0.1 ([#3433](https://github.com/microsoft/durabletask-dotnet/pull/3433)) (#723)
-- Validate UseWorkItemFilters names against registered tasks at worker build time ([#719](https://github.com/microsoft/durabletask-dotnet/pull/719))
-- Bump `Microsoft.Extensions.DependencyInjection.Abstractions` from 8.0.2 to 9.0.1 (and `Microsoft.Bcl.AsyncInterfaces` from 8.0.0 to 9.0.1, which the former transitively floors at 9.0.1) to align with the floor declared by `Microsoft.Azure.WebJobs 3.0.45 -> Microsoft.Extensions.Logging.Abstractions 9.0.1`. Fixes NU1605 in downstream Azure Functions Worker isolated apps consuming `Microsoft.DurableTask.Extensions.AzureBlobPayloads` ([Azure/azure-functions-durable-extension#3433](https://github.com/Azure/azure-functions-durable-extension/issues/3433)).
-- Validate explicit `UseWorkItemFilters(filters)` filter names against the worker's `DurableTaskRegistry`. Filters that reference an orchestration, activity, or entity name not registered with the worker now throw `OptionsValidationException` at worker startup instead of silently waiting for work items that will never arrive. No customer-side validation call is required. ([#719](https://github.com/microsoft/durabletask-dotnet/pull/719))
-
-## 1.24.1
-- Add retry to grpc calls that failed due to transient errors by @sophiatev ([#714](https://github.com/microsoft/durabletask-dotnet/pull/714))
-
-## v1.24.0
-- Harden grpc worker and client against silent disconnects by @berndverst ([#708](https://github.com/microsoft/durabletask-dotnet/pull/708))
-- Preserve late events after continue-as-new by @berndverst ([#711](https://github.com/microsoft/durabletask-dotnet/pull/711))
-- Fix inprocesstesthost continueasnew stuck-instance race condition by @bachuv ([#707](https://github.com/microsoft/durabletask-dotnet/pull/707))
-- Fix continue-as-new race condition at inprocesstesthost by @nytian ([#703](https://github.com/microsoft/durabletask-dotnet/pull/703))
-- Add opt-in timeout to purgeinstancesfilter for partial purge by @yunchuwang ([#680](https://github.com/microsoft/durabletask-dotnet/pull/680))
-
-## v1.23.3
-- fix: revert shared framework packages to 8.x for net8 Functions host compatibility ([#698](https://github.com/microsoft/durabletask-dotnet/pull/698))
-- Release v1.23.2 ([#693](https://github.com/microsoft/durabletask-dotnet/pull/693))
-
-## v1.23.2
-- fix: improve large payload error handling — better error message and prevent infinite retry and fix conflict with auto chunking ([#691](https://github.com/microsoft/durabletask-dotnet/pull/691))
-- Bump dotnet-sdk from 10.0.103 to 10.0.201 ([#673](https://github.com/microsoft/durabletask-dotnet/pull/673))
-- Bump Microsoft.Azure.DurableTask.Core from 3.7.0 to 3.7.1 ([#685](https://github.com/microsoft/durabletask-dotnet/pull/685))
-- feat(copilot): add evidence-based Copilot customizations ([#690](https://github.com/microsoft/durabletask-dotnet/pull/690))
-
-## v1.23.1
-- Fix CHANGELOG line ending preservation in Prepare Release workflow ([#687](https://github.com/microsoft/durabletask-dotnet/pull/687))
-- Add Prepare Release GitHub Action for automated release kickoff ([#686](https://github.com/microsoft/durabletask-dotnet/pull/686))
-- Add ContinueAsNewOptions with NewVersion support ([#682](https://github.com/microsoft/durabletask-dotnet/pull/682))
-- Fix concurrent timer race condition in InMemoryOrchestrationService ([#678](https://github.com/microsoft/durabletask-dotnet/pull/678))
-
-## v1.23.0
-- Generate extension methods in task namespace instead of Microsoft.DurableTask ([#538](https://github.com/microsoft/durabletask-dotnet/pull/538))
-- Fix #668: Change work item filters from auto opt-in to explicit opt-in ([#669](https://github.com/microsoft/durabletask-dotnet/pull/669))
-- Add `ReplaySafeLoggerFactory` for context wrappers ([#670](https://github.com/microsoft/durabletask-dotnet/pull/670))
-- Add NuGet publish job for Microsoft.DurableTask.Analyzers ([#662](https://github.com/microsoft/durabletask-dotnet/pull/662))
-- Bump Azure.Identity from 1.17.1 to 1.18.0 ([#656](https://github.com/microsoft/durabletask-dotnet/pull/656))
-- Bump Microsoft.Azure.Functions.Worker.Extensions.DurableTask from 1.12.1 to 1.15.0 ([#658](https://github.com/microsoft/durabletask-dotnet/pull/658))
-- Add missing input validation to SuspendInstanceAsync and ResumeInstanceAsync ([#652](https://github.com/microsoft/durabletask-dotnet/pull/652))
-- Add ExportHistory package to NuGet publish pipeline ([#651](https://github.com/microsoft/durabletask-dotnet/pull/651))
-- Add OpenTelemetry sample and update deps ([#637](https://github.com/microsoft/durabletask-dotnet/pull/637))
-- Fix build warnings and clean up exception message ([#647](https://github.com/microsoft/durabletask-dotnet/pull/647))
-
-## v1.22.0
-- Changing the default dedupe statuses behavior by sophiatev ([#622](https://github.com/microsoft/durabletask-dotnet/pull/622))
-- Bump Analyzers package version to 1.22.0 stable release (from 0.3.0)
-- Add DURABLE0011: ContinueAsNew warning for unbounded orchestration loops ([#660](https://github.com/microsoft/durabletask-dotnet/pull/660))
-
-## 1.21.0
-- Introduce WorkItemFilters into worker flow by halspang ([#616](https://github.com/microsoft/durabletask-dotnet/pull/616))
-- Fix Analyzers treating passed in variable argument name as null by wangbill ([#640](https://github.com/microsoft/durabletask-dotnet/pull/640))
-- Move DURABLE0009/0010 from Unshipped to Shipped for v0.3.0 by cgillum ([#641](https://github.com/microsoft/durabletask-dotnet/pull/641))
-
-## 1.20.1
-- Fix GrpcChannel handle leak in AzureManaged backendby nytian ([#629](https://github.com/microsoft/durabletask-dotnet/pull/629))
-
-## 1.20.0
-- Partial orchestration workitem completion support (merge after next dts dp release) by wangbill ([#514](https://github.com/microsoft/durabletask-dotnet/pull/514))
-- Export history job by wangbill ([#494](https://github.com/microsoft/durabletask-dotnet/pull/494))
-- Add dependency injection support to durabletasktesthost by Naiyuan Tian ([#613](https://github.com/microsoft/durabletask-dotnet/pull/613))
-
-## v1.19.1
-- Throw an `InvalidOperationException` for purge requests on running orchestrations by sophiatev ([#611](https://github.com/microsoft/durabletask-dotnet/pull/611))
-- Validate c# identifiers in durabletask source generator by Copilot ([#578](https://github.com/microsoft/durabletask-dotnet/pull/578))
-- Document orchestration discovery and method probing behavior in analyzers by Copilot ([#594](https://github.com/microsoft/durabletask-dotnet/pull/594))
-
-## v1.19.0
-- Extended sessions for entities in .net isolated by sophiatev ([#507](https://github.com/microsoft/durabletask-dotnet/pull/507))
-- Adding the ability to specify tags and a retry policy for suborchestrations by sophiatev ([#603](https://github.com/microsoft/durabletask-dotnet/pull/603))
-- Improve durabletask source generator detection and add optional project type configuration by Copilot ([#575](https://github.com/microsoft/durabletask-dotnet/pull/575))
-- Add timeprovider support to orchestration analyzer by Copilot ([#573](https://github.com/microsoft/durabletask-dotnet/pull/573))
-- Expand azure functions smoke tests to cover source generator scenarios by Copilot ([#604](https://github.com/microsoft/durabletask-dotnet/pull/604))
-- Fix "syntaxtree is not part of the compilation" exception in orchestration analyzers by Copilot ([#588](https://github.com/microsoft/durabletask-dotnet/pull/588))
-- Add waitforexternalevent overload with timeout and cancellation token by Copilot ([#555](https://github.com/microsoft/durabletask-dotnet/pull/555))
-- Fix source generator for void-returning activity functions by Copilot ([#554](https://github.com/microsoft/durabletask-dotnet/pull/554))
-
-## v1.18.2
-- Add copy constructors to TaskOptions and sub-classes by halspang ([#587](https://github.com/microsoft/durabletask-dotnet/pull/587))
-- Change FunctionNotFound analyzer severity to Info for cross-assembly scenarios by Copilot ([#584](https://github.com/microsoft/durabletask-dotnet/pull/584))
-- Add Roslyn analyzer for non-contextual logger usage in orchestrations (DURABLE0010) by Copilot ([#553](https://github.com/microsoft/durabletask-dotnet/pull/553))
-- Add specific logging categories for Worker.Grpc and orchestration logs with backward-compatible opt-in by Copilot ([#583](https://github.com/microsoft/durabletask-dotnet/pull/583))
-- Fix flaky integration test race condition in dedup status check by Copilot ([#579](https://github.com/microsoft/durabletask-dotnet/pull/579))
-- Add analyzer to suggest input parameter binding over GetInput() by Copilot ([#550](https://github.com/microsoft/durabletask-dotnet/pull/550))
-- Add strongly-typed external events with DurableEventAttribute by Copilot ([#549](https://github.com/microsoft/durabletask-dotnet/pull/549))
-- Fix orchestration analyzer to detect non-function orchestrations correctly by Copilot ([#572](https://github.com/microsoft/durabletask-dotnet/pull/572))
-- Fix race condition in WaitForInstanceAsync causing intermittent test failures by Copilot ([#574](https://github.com/microsoft/durabletask-dotnet/pull/574))
-- Add HelpLinkUri to Roslyn analyzer diagnostics by Copilot ([#548](https://github.com/microsoft/durabletask-dotnet/pull/548))
-- Add DateTimeOffset.Now and DateTimeOffset.UtcNow detection to Roslyn analyzer by Copilot ([#547](https://github.com/microsoft/durabletask-dotnet/pull/547))
-- Bump Google.Protobuf from 3.33.1 to 3.33.2 by dependabot[bot] ([#569](https://github.com/microsoft/durabletask-dotnet/pull/569))
-- Add integration test coverage for Suspend/Resume operations by Copilot ([#546](https://github.com/microsoft/durabletask-dotnet/pull/546))
-- Bump coverlet.collector from 6.0.2 to 6.0.4 by dependabot[bot] ([#527](https://github.com/microsoft/durabletask-dotnet/pull/527))
-- Bump FluentAssertions from 6.12.1 to 6.12.2 by dependabot[bot] ([#528](https://github.com/microsoft/durabletask-dotnet/pull/528))
-- Add Azure Functions smoke tests with Docker CI automation by Copilot ([#545](https://github.com/microsoft/durabletask-dotnet/pull/545))
-- Bump dotnet-sdk from 10.0.100 to 10.0.101 by dependabot[bot] ([#568](https://github.com/microsoft/durabletask-dotnet/pull/568))
-- Add scheduled auto-closure for stale "Needs Author Feedback" issues by Copilot ([#566](https://github.com/microsoft/durabletask-dotnet/pull/566))
-
-## v1.18.1
-- Support dedup status when starting orchestration by wangbill ([#542](https://github.com/microsoft/durabletask-dotnet/pull/542))
-- Add 404 exception handling in blobpayloadstore.downloadasync by Copilot ([#534](https://github.com/microsoft/durabletask-dotnet/pull/534))
-- Bump analyzers version to 0.2.0 by Copilot ([#552](https://github.com/microsoft/durabletask-dotnet/pull/552))
-- Add integration tests for exception type handling by Copilot ([#544](https://github.com/microsoft/durabletask-dotnet/pull/544))
-- Add roslyn analyzer to detect calls to non-existent functions (name mismatch) by Copilot ([#530](https://github.com/microsoft/durabletask-dotnet/pull/530))
-- Remove preview suffix by Copilot ([#541](https://github.com/microsoft/durabletask-dotnet/pull/541))
-- Add xml documentation with see cref links to generated code for better ide navigation by Copilot ([#535](https://github.com/microsoft/durabletask-dotnet/pull/535))
-- Add entity source generation support for durable functions by Copilot ([#533](https://github.com/microsoft/durabletask-dotnet/pull/533))
-
-## v1.18.0
-- Add taskentity support to durabletasksourcegenerator by Copilot ([#517](https://github.com/microsoft/durabletask-dotnet/pull/517))
-- Bump azure.identity by dependabot[bot] ([#525](https://github.com/microsoft/durabletask-dotnet/pull/525))
-- Bump google.protobuf by dependabot[bot] ([#529](https://github.com/microsoft/durabletask-dotnet/pull/529))
-- Configure dependabot for dotnet-sdk updates by Tomer Rosenthal ([#524](https://github.com/microsoft/durabletask-dotnet/pull/524))
-- Add code review guidelines to copilot-instructions.md by Copilot ([#522](https://github.com/microsoft/durabletask-dotnet/pull/522))
-- Remove webapi sample by sophiatev ([#520](https://github.com/microsoft/durabletask-dotnet/pull/520))
-- Fix functioncontext check and polymorphic type conversions in activity analyzer by Naiyuan Tian ([#506](https://github.com/microsoft/durabletask-dotnet/pull/506))
-- Align waitforexternalevent waiter picking order to lifo by wangbill ([#509](https://github.com/microsoft/durabletask-dotnet/pull/509))
-- Update project to support .net 6.0 alongside .net 8.0 and .net 10 by Tomer Rosenthal ([#512](https://github.com/microsoft/durabletask-dotnet/pull/512))
-- Update project to target .net 8.0 and .net 10 and upgrade dependencies by Tomer Rosenthal ([#510](https://github.com/microsoft/durabletask-dotnet/pull/510))
-- Support worker features announcement by wangbill ([#502](https://github.com/microsoft/durabletask-dotnet/pull/502))
-- Introduce custom copilot review instructions by halspang ([#503](https://github.com/microsoft/durabletask-dotnet/pull/503))
-- Add API to get orchestration history ([#516](https://github.com/microsoft/durabletask-dotnet/pull/516))
-
-## v1.17.1
-- Fix Worker Registry and Add Documentation Notes by nytian in [#462](https://github.com/microsoft/durabletask-dotnet/pull/495)
-- Initial attempt to fix carryover events issue on continue-as-new by cgillum in [#496](https://github.com/microsoft/durabletask-dotnet/pull/496)
-- Fix encoding of entity unlock events by sebastianburckhardt in [#462](https://github.com/microsoft/durabletask-dotnet/pull/462)
-
-## v1.17.0
--Add Microsoft.DurableTask.Extensions.AzureBlobPayloads to nuget publish by YunchuWang in [#488](https://github.com/microsoft/durabletask-dotnet/pull/488)
--Add API for In-process Testing and Add Class-Syntax Integration Tests by nytian in [#476](https://github.com/microsoft/durabletask-dotnet/pull/476)
--Fix Purge Instance Comments by sophiatev in [#489](https://github.com/microsoft/durabletask-dotnet/pull/489)
--Fix ServiceCollectionExtensions.AddDurableTaskClient by sophiatev in [#490](https://github.com/microsoft/durabletask-dotnet/pull/490)
--Update zuremanaged sdks to official version by YunchuWang in [#493](https://github.com/microsoft/durabletask-dotnet/pull/493)
--Add Rewind to .NET isolated by sophiatev in [#479](https://github.com/microsoft/durabletask-dotnet/pull/479)
--Add tags field to CompleteOrchestratorAction by sophiatev in [#492](https://github.com/microsoft/durabletask-dotnet/pull/492)
-
-## v1.16.2
-- Generate changelog script + update changelog for v1.16.1 by wangbill ([#486](https://github.com/microsoft/durabletask-dotnet/pull/486))
-- Remove unnecessary project reference to grpc.azuremanagedbackend in azureblobpayloads.csproj by wangbill ([#485](https://github.com/microsoft/durabletask-dotnet/pull/485))
-- Large payload azure blob externalization support by wangbill ([#468](https://github.com/microsoft/durabletask-dotnet/pull/468))
-
-## v1.16.1
-- Include exception properties in failure details when orchestration throws directly by Naiyuan Tian ([#482](https://github.com/microsoft/durabletask-dotnet/pull/482))
-- Set low priority for scheduled runs by Daniel Castro ([#477](https://github.com/microsoft/durabletask-dotnet/pull/477))
-
-## v1.16.0
-- Include Exception Properties at FailureDetails by nytian in([#474](https://github.com/microsoft/durabletask-dotnet/pull/474))
-
-## v1.15.1 
-- Add version check to activities by @halspang in ([#472](https://github.com/microsoft/durabletask-dotnet/pull/472))
-
-## v1.15.0
-- Abandon workitem if processing workitem failed by @YunchuWang in ([#467](https://github.com/microsoft/durabletask-dotnet/pull/467))
-- Extended Sessions for Isolated (Orchestrations) by @sophiatev in ([#449](https://github.com/microsoft/durabletask-dotnet/pull/449))
-  
-## v1.14.0
-- Add RestartAsync API Support at DurableTaskClient ([#456](https://github.com/microsoft/durabletask-dotnet/pull/456))
-
-## v1.13.0
-- Add orchestration execution tracing ([#441](https://github.com/microsoft/durabletask-dotnet/pull/441))
-
-## v1.12.0
-
-- Activity tag support ([#426](https://github.com/microsoft/durabletask-dotnet/pull/426))
-- Adding Analyzer to build and release ([#444](https://github.com/microsoft/durabletask-dotnet/pull/444))
-- Add ability to filter orchestrations at worker ([#443](https://github.com/microsoft/durabletask-dotnet/pull/443))
-- Removing breaking change for TaskOptions ([#446](https://github.com/microsoft/durabletask-dotnet/pull/446))
-- Expose gRPC retry options in Azure Managed extensions ([#447](https://github.com/microsoft/durabletask-dotnet/pull/447))
-
-## v1.11.0
-
-- Add New Property Properties to TaskOrchestrationContext ([#415](https://github.com/microsoft/durabletask-dotnet/pull/415))
-- Add automatic retry on gateway timeout in `GrpcDurableTaskClient.WaitForInstanceCompletionAsync` ([#412](https://github.com/microsoft/durabletask-dotnet/pull/412))
-- Add specific logging for NotFound error on worker connection ([#413](https://github.com/microsoft/durabletask-dotnet/pull/413))
-- Add user agent header to gRPC called ([#417](https://github.com/microsoft/durabletask-dotnet/pull/417))
-- Enrich User-Agent Header in gRPC Metadata to indicate Client or Worker as caller ([#421](https://github.com/microsoft/durabletask-dotnet/pull/421))
-- Change DTS user agent metadata to avoid overlap with gRPC user agent ([#423](https://github.com/microsoft/durabletask-dotnet/pull/423))
-- Add extension methods for registering entities by type ([#427](https://github.com/microsoft/durabletask-dotnet/pull/427))
-- Add TaskVersion and utilize it for version overrides when starting orchestrations ([#416](https://github.com/microsoft/durabletask-dotnet/pull/416))
-- Update sub-orchestration default versioning ([#437](https://github.com/microsoft/durabletask-dotnet/pull/437))
-- Distributed Tracing for Entities (Isolated) ([#404](https://github.com/microsoft/durabletask-dotnet/pull/404))
-
-## v1.10.0
-
-- Update DurableTask.Core to v3.1.0 and Bump version to v1.10.0 by @nytian in ([#411](https://github.com/microsoft/durabletask-dotnet/pull/411))
-
-## v1.9.1
-
-- Add basic orchestration and activity execution logs by @cgillum in ([#405](https://github.com/microsoft/durabletask-dotnet/pull/405))
-- Add default version in `TaskOrchestrationContext` by @halspang in ([#408](https://github.com/microsoft/durabletask-dotnet/pull/408))
-
-## v1.9.0
-
-- Fix schedule sample logging setup by @YunchuWang in ([#392](https://github.com/microsoft/durabletask-dotnet/pull/392))
-- Introduce versioning to the DurableTaskClient by @halspang in ([#393](https://github.com/microsoft/durabletask-dotnet/pull/393))
-- Support for local credential types for DTS by @cgillum in ([#396](https://github.com/microsoft/durabletask-dotnet/pull/396))
-- Add utilities for easier versioning usage by @halspang in ([#394](https://github.com/microsoft/durabletask-dotnet/pull/394))
-- Add tags to CreateInstanceRequest by @torosent in ([#397](https://github.com/microsoft/durabletask-dotnet/pull/397))
-- Partial Purge Support by @YunchuWang in ([#400](https://github.com/microsoft/durabletask-dotnet/pull/400))
-- Dts Grpc client retry support by @YunchuWang in ([#403](https://github.com/microsoft/durabletask-dotnet/pull/403))
-- Introduce orchestration versioning into worker by @halspang in ([#401](https://github.com/microsoft/durabletask-dotnet/pull/401))
-
-## v1.8.1
-
-- Add timeout to gRPC workitem streaming ([#390](https://github.com/microsoft/durabletask-dotnet/pull/390))
-
-## v1.8.0
-
-- Add Schedule Support for Durable Task Framework ([#368](https://github.com/microsoft/durabletask-dotnet/pull/368))
-- Fixes and improvements
-
-## v1.7.0
-
-- Add parent trace context information when scheduling an orchestration ([#358](https://github.com/microsoft/durabletask-dotnet/pull/358))
-
-## v1.6.0
-
-- Added new preview packages, `Microsoft.DurableTask.Client.AzureManaged` and `Microsoft.DurableTask.Worker.AzureManaged`
-- Move to Central Package Management ([#373](https://github.com/microsoft/durabletask-dotnet/pull/373))
-
-### Microsoft.DurableTask.Client
-
-- Add new `IDurableTaskClientBuilder AddDurableTaskClient(IServiceCollection, string?)` API
-
-### Microsoft.DurableTask.Worker
-
-- Add new `IDurableTaskWorkerBuilder AddDurableTaskWorker(IServiceCollection, string?)` API
-- Add support for work item history streaming
-
-### Microsoft.DurableTask.Worker.Grpc
-
-- Provide entity support for direct grpc connections to DTS ([#369](https://github.com/microsoft/durabletask-dotnet/pull/369))
-
-### Microsoft.DurableTask.Grpc
-
-- Replace submodule for proto files with download script for easier maintenance
-- Update to latest proto files
-
-## v1.5.0
-
-- Implement work item completion tokens for standalone worker scenarios ([#359](https://github.com/microsoft/durabletask-dotnet/pull/359))
-- Support for worker concurrency configuration ([#359](https://github.com/microsoft/durabletask-dotnet/pull/359))
-- Bump System.Text.Json to 6.0.10
-- Initial support for the Azure-managed [Durable Task Scheduler](https://techcommunity.microsoft.com/blog/appsonazureblog/announcing-limited-early-access-of-the-durable-task-scheduler-for-azure-durable-/4286526) preview.
-
-## v1.4.0
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `3.0.0`
-
-## v1.3.0
-
-### Microsoft.DurableTask.Abstractions
-
-- Add `RetryPolicy.Handle` property to allow for exception filtering on retries ([#314](https://github.com/microsoft/durabletask-dotnet/pull/314))
-
-## v1.2.4
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.17.1`
-
-## v1.2.3
-
-### Microsoft.DurableTask.Client
-
-- Fix filter not being passed along in `PurgeAllInstancesAsync` (https://github.com/microsoft/durabletask-dotnet/pull/289)
-
-### Microsoft.DurableTask.Abstractions
-
-- Enable inner exception detail propagation in `TaskFailureDetails` ([#290](https://github.com/microsoft/durabletask-dotnet/pull/290))
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.17.0`
-
-## v1.2.2
-
-### Microsoft.DurableTask.Abstractions
-
-- Fix `TaskFailureDetails.IsCausedBy` to support custom exceptions and 3rd party exceptions ([#273](https://github.com/microsoft/durabletask-dotnet/pull/273))
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.2`
-
-### Microsoft.DurableTask.Client
-
-- Fix typo in `PurgeInstanceAsync`  in `DurableTaskClient` (https://github.com/microsoft/durabletask-dotnet/pull/264)
-
-## v1.2.0
-
-- Adds support to recursively terminate/purge sub-orchestrations in `GrpcDurableTaskClient` (https://github.com/microsoft/durabletask-dotnet/pull/262)
-
-## v1.1.1
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.1`
-
-## v1.1.0
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.0`
-
-## v1.1.0-preview.2
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.0-preview.2`
-
-## v1.1.0-preview.1
-
-Adds support for durable entities. Learn more [here](https://learn.microsoft.com/azure/azure-functions/durable/durable-functions-entities?tabs=csharp).
-
-### Microsoft.DurableTask.Abstractions
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.0-preview.1`
-
-## v1.0.5
-
-### Microsoft.DurableTask.Abstractions
-
-- Microsoft.Azure.DurableTask.Core dependency increased to `2.15.0` (https://github.com/microsoft/durabletask-dotnet/pull/212)
-
-### Microsoft.DurableTask.Worker
-
-- Fix re-encoding of events when using `TaskOrchestrationContext.ContinueAsNew(preserveUnprocessedEvents: true)` (https://github.com/microsoft/durabletask-dotnet/pull/212)
-
-## v1.0.4
-
-### Microsoft.DurableTask.Worker
-
-- Fix handling of concurrent external events with the same name (https://github.com/microsoft/durabletask-dotnet/pull/194)
-
-## v1.0.3
-
-### Microsoft.DurableTask.Worker
-
-- Fix instance ID not being passed in when using retry policy (https://github.com/microsoft/durabletask-dotnet/issues/174)
-
-### Microsoft.DurableTask.Worker.Grpc
-
-- Add `GrpcDurableTaskWorkerOptions.CallInvoker` as an alternative to `GrpcDurableTaskWorkerOptions.Channel`
-
-### Microsoft.DurableTask.Client.Grpc
-
-- Add `GrpcDurableTaskClientOptions.CallInvoker` as an alternative to `GrpcDurableTaskClientOptions.Channel`
-
-## v1.0.2
-
-### Microsoft.DurableTask.Worker
-
-- Fix issue with `TaskOrchestrationContext.Parent` not being set.
-
-## v1.0.1
-
-### Microsoft.DurableTask.Client
-
-- Fix incorrect bounds check on `PurgeResult`
-- Address typo for `DurableTaskClient.GetInstancesAsync` (incorrectly pluralized)
-    - Added `GetInstanceAsync`
-    - Hide `GetInstancesAsync` from editor
-
-## v1.0.0
-
-- Added `SuspendInstanceAsync` and `ResumeInstanceAsync` to `DurableTaskClient`.
-- Rename `DurableTaskClient` methods
-    - `TerminateAsync` -> `TerminateInstanceAsync`
-    - `PurgeInstanceMetadataAsync` -> `PurgeInstanceAsync`
-    - `PurgeInstances` -> `PurgeAllInstancesAsync`
-    - `GetInstanceMetadataAsync` -> `GetInstanceAsync`
-    - `GetInstances` -> `GetAllInstancesAsync`
-- `TaskOrchestrationContext.CreateReplaySafeLogger` now creates `ILogger` directly (as opposed to wrapping an existing `ILogger`).
-- Durable Functions class-based syntax now resolves `ITaskActivity` instances from `IServiceProvider`, if available there.
-- `DurableTaskClient` methods have been touched up to ensure `CancellationToken` is included, as well as is the last parameter.
-- Removed obsolete/unimplemented local lambda activity calls from `TaskOrchestrationContext`
-- Input is now an optional parameter on `TaskOrchestrationContext.ContinueAsNew`
-- Multi-target gRPC projects to now use `Grpc.Net.Client` when appropriate (.NET6.0 and up)
-
-*Note: `Microsoft.DurableTask.Generators` is remaining as `preview.1`.*
-
-## v1.0.0-rc.1
-
-### Included Packages
-
-Microsoft.DurableTask.Abstractions \
-Microsoft.DurableTask.Client \
-Microsoft.DurableTask.Client.Grpc \
-Microsoft.DurableTask.Worker \
-Microsoft.DurableTask.Worker.Grpc \
-
-_see v1.0.0-preview.1 for `Microsoft.DurableTask.Generators`_
-
-### Updates
-
-- Refactors and splits assemblies.
-  - `Microsoft.DurableTask.Abstractions`
-  - `Microsoft.DurableTask.Generators`
-  - `Microsoft.DurableTask.Client`
-  - `Microsoft.DurableTask.Client.Grpc`
-  - `Microsoft.DurableTask.Worker`
-  - `Microsoft.DurableTask.Worker.Grpc`
-- Added more API documentation
-- Adds ability to perform multi-instance query
-- Adds `PurgeInstancesMetadataAsync` and `PurgeInstancesAsync` support and implementation to `GrpcDurableTaskClient`
-- Fix issue with mixed Newtonsoft.Json and System.Text.Json serialization.
-- `IDurableTaskClientProvider` added to support multiple named clients.
-- Added new options pattern for starting new and sub orchestrations.
-- Overhauled builder API built on top of .NET generic host.
-  - Now relies on dependency injection.
-  - Integrates into options pattern, giving a variety of ways for user configuration.
-  - Builder is now re-enterable. Multiple calls to `.AddDurableTask{Worker|Client}` with the same name will yield the exact same builder instance.
-
-### Breaking Changes
-
-- `Microsoft.DurableTask.Generators` reference removed.
-- Added new abstract property `TaskOrchestrationContext.ParentInstance`.
-- Added new abstract method `DurableTaskClient.PurgeInstancesAsync`.
-- Renamed `TaskOrchestratorBase` to `TaskOrchestrator`
-  - `OnRunAsync` -> `RunAsync`, forced-nullability removed.
-  - Nullability can be done in generic params, ie: `MyOrchestrator : TaskOrchestrator<string?, string?>`
-  - Nullability is not verified at runtime by the base class, it is up to the individual orchestrator implementations to verify their own nullability.
-- Renamed `TaskActivityBase` to `TaskActivity`
-  - `OnRun` removed. With both `OnRun` and `OnRunAsync`, there was no compiler error when you did not implement one. The remaining method is now marked `abstract` to force an implementation. Synchronous implementation can still be done via `Task.FromResult`.
-  - `OnRunAsync` -> `RunAsync`, forced-nullability removed.
-  - Nullability can be done in generic params, ie: `MyActivity : TaskActivity<string?, string?>`
-  - Nullability is not verified at runtime by the base class, it is up to the individual activity implementations to verify their own nullability.
-- `TaskOrchestrationContext.StartSubOrchestrationAsync` refactored:
-  - `instanceId` parameter removed. Can now specify it via supplying `SubOrchestrationOptions` for `TaskOptions`.
-- `TaskOptions` refactored to be a record type.
-  - Builder removed.
-  - Retry provided via a property `TaskRetryOptions`, which is a pseudo union-type which can be either a `RetryPolicy` or `AsyncRetryHandler`.
-  - `SubOrchestrationOptions` is a derived type that can be used to specific a sub-orchestrations instanceId.
-  - Helper method `.WithInstanceId(string? instanceId)` added.
-- `DurableTaskClient.ScheduleNewOrchestrationInstanceAsync` refactored:
-  - `instanceId` and `startAfter` wrapped into `StartOrchestrationOptions` object.
-- Builder API completely overhauled. Now built entirely on top of the .NET generic host.
-  - See samples for how the new API works.
-  - Supports multiple workers and named-clients.
-- Ability to set `TaskName.Version` removed for now. Will be added when we address versioning.
-- `IDurableTaskRegistry` removed, only `DurableTaskRegistry` concrete type.
-  - All lambda-methods renamed to `AddActivityFunc` and `AddOrchestratorFunc`. This was to avoid ambiguous or incorrect overload resolution with the factory methods.
-
-## v1.0.0-preview.1
-
-### Included Packages
-
-Microsoft.DurableTask.Generators
-
-### Breaking Changes
-
-- `Microsoft.DurableTask.Generators` is now an optional package.
-  - no longer automatically brought in when referencing other packages.
-  - To get code generation, add `<PackageReference Include="Microsoft.DurableTask.Generators" Version="1.0.0-preview.1" PrivateAssets="All" />` to your csproj.
-- `GeneratedDurableTaskExtensions.AddAllGeneratedTasks` made `internal` (from `public`)
-  - This is also to avoid conflicts when multiple files have this method generated. When wanting to expose to external consumes, a new extension method can be manually authored in the desired namespace and with an appropriate name which calls this method.
-
-## v0.4.1-beta
-
-Initial public release
-
-
-
-
-
+# Changelog
+
+## Unreleased
+
+- Split private preview on-demand sandbox APIs into opt-in `Microsoft.DurableTask.Client.AzureManaged.Sandboxes` and `Microsoft.DurableTask.Worker.AzureManaged.Sandboxes` packages.
+- Updated private preview on-demand sandbox worker profile declarations to use `SandboxWorkerProfileOptions.AddActivity(...)`, and updated the on-demand sandbox sample to share activity name constants between the main app and remote worker.
+- Added SDK-side validation for private preview on-demand sandbox CPU and memory resource quantities.
+
+
+## v1.25.0-preview.1
+- Implement per-orchestration and per-activity versioning ([#695](https://github.com/microsoft/durabletask-dotnet/pull/695))
+- Add es-metadata.yml to schema 1.0.0 ([#722](https://github.com/microsoft/durabletask-dotnet/pull/722))
+- Release v1.24.2 ([#724](https://github.com/microsoft/durabletask-dotnet/pull/724))
+- Add per-task versioning via `[DurableTask(Version = "...")]`, `TaskOptions.Version`, and `StartOrchestrationOptions.Version` ([#695](https://github.com/microsoft/durabletask-dotnet/pull/695))
+
+
+## v1.24.2
+- Bump DI.Abstractions and Bcl.AsyncInterfaces to 9.0.1 ([#3433](https://github.com/microsoft/durabletask-dotnet/pull/3433)) (#723)
+- Validate UseWorkItemFilters names against registered tasks at worker build time ([#719](https://github.com/microsoft/durabletask-dotnet/pull/719))
+- Bump `Microsoft.Extensions.DependencyInjection.Abstractions` from 8.0.2 to 9.0.1 (and `Microsoft.Bcl.AsyncInterfaces` from 8.0.0 to 9.0.1, which the former transitively floors at 9.0.1) to align with the floor declared by `Microsoft.Azure.WebJobs 3.0.45 -> Microsoft.Extensions.Logging.Abstractions 9.0.1`. Fixes NU1605 in downstream Azure Functions Worker isolated apps consuming `Microsoft.DurableTask.Extensions.AzureBlobPayloads` ([Azure/azure-functions-durable-extension#3433](https://github.com/Azure/azure-functions-durable-extension/issues/3433)).
+- Validate explicit `UseWorkItemFilters(filters)` filter names against the worker's `DurableTaskRegistry`. Filters that reference an orchestration, activity, or entity name not registered with the worker now throw `OptionsValidationException` at worker startup instead of silently waiting for work items that will never arrive. No customer-side validation call is required. ([#719](https://github.com/microsoft/durabletask-dotnet/pull/719))
+
+## 1.24.1
+- Add retry to grpc calls that failed due to transient errors by @sophiatev ([#714](https://github.com/microsoft/durabletask-dotnet/pull/714))
+
+## v1.24.0
+- Harden grpc worker and client against silent disconnects by @berndverst ([#708](https://github.com/microsoft/durabletask-dotnet/pull/708))
+- Preserve late events after continue-as-new by @berndverst ([#711](https://github.com/microsoft/durabletask-dotnet/pull/711))
+- Fix inprocesstesthost continueasnew stuck-instance race condition by @bachuv ([#707](https://github.com/microsoft/durabletask-dotnet/pull/707))
+- Fix continue-as-new race condition at inprocesstesthost by @nytian ([#703](https://github.com/microsoft/durabletask-dotnet/pull/703))
+- Add opt-in timeout to purgeinstancesfilter for partial purge by @yunchuwang ([#680](https://github.com/microsoft/durabletask-dotnet/pull/680))
+
+## v1.23.3
+- fix: revert shared framework packages to 8.x for net8 Functions host compatibility ([#698](https://github.com/microsoft/durabletask-dotnet/pull/698))
+- Release v1.23.2 ([#693](https://github.com/microsoft/durabletask-dotnet/pull/693))
+
+## v1.23.2
+- fix: improve large payload error handling — better error message and prevent infinite retry and fix conflict with auto chunking ([#691](https://github.com/microsoft/durabletask-dotnet/pull/691))
+- Bump dotnet-sdk from 10.0.103 to 10.0.201 ([#673](https://github.com/microsoft/durabletask-dotnet/pull/673))
+- Bump Microsoft.Azure.DurableTask.Core from 3.7.0 to 3.7.1 ([#685](https://github.com/microsoft/durabletask-dotnet/pull/685))
+- feat(copilot): add evidence-based Copilot customizations ([#690](https://github.com/microsoft/durabletask-dotnet/pull/690))
+
+## v1.23.1
+- Fix CHANGELOG line ending preservation in Prepare Release workflow ([#687](https://github.com/microsoft/durabletask-dotnet/pull/687))
+- Add Prepare Release GitHub Action for automated release kickoff ([#686](https://github.com/microsoft/durabletask-dotnet/pull/686))
+- Add ContinueAsNewOptions with NewVersion support ([#682](https://github.com/microsoft/durabletask-dotnet/pull/682))
+- Fix concurrent timer race condition in InMemoryOrchestrationService ([#678](https://github.com/microsoft/durabletask-dotnet/pull/678))
+
+## v1.23.0
+- Generate extension methods in task namespace instead of Microsoft.DurableTask ([#538](https://github.com/microsoft/durabletask-dotnet/pull/538))
+- Fix #668: Change work item filters from auto opt-in to explicit opt-in ([#669](https://github.com/microsoft/durabletask-dotnet/pull/669))
+- Add `ReplaySafeLoggerFactory` for context wrappers ([#670](https://github.com/microsoft/durabletask-dotnet/pull/670))
+- Add NuGet publish job for Microsoft.DurableTask.Analyzers ([#662](https://github.com/microsoft/durabletask-dotnet/pull/662))
+- Bump Azure.Identity from 1.17.1 to 1.18.0 ([#656](https://github.com/microsoft/durabletask-dotnet/pull/656))
+- Bump Microsoft.Azure.Functions.Worker.Extensions.DurableTask from 1.12.1 to 1.15.0 ([#658](https://github.com/microsoft/durabletask-dotnet/pull/658))
+- Add missing input validation to SuspendInstanceAsync and ResumeInstanceAsync ([#652](https://github.com/microsoft/durabletask-dotnet/pull/652))
+- Add ExportHistory package to NuGet publish pipeline ([#651](https://github.com/microsoft/durabletask-dotnet/pull/651))
+- Add OpenTelemetry sample and update deps ([#637](https://github.com/microsoft/durabletask-dotnet/pull/637))
+- Fix build warnings and clean up exception message ([#647](https://github.com/microsoft/durabletask-dotnet/pull/647))
+
+## v1.22.0
+- Changing the default dedupe statuses behavior by sophiatev ([#622](https://github.com/microsoft/durabletask-dotnet/pull/622))
+- Bump Analyzers package version to 1.22.0 stable release (from 0.3.0)
+- Add DURABLE0011: ContinueAsNew warning for unbounded orchestration loops ([#660](https://github.com/microsoft/durabletask-dotnet/pull/660))
+
+## 1.21.0
+- Introduce WorkItemFilters into worker flow by halspang ([#616](https://github.com/microsoft/durabletask-dotnet/pull/616))
+- Fix Analyzers treating passed in variable argument name as null by wangbill ([#640](https://github.com/microsoft/durabletask-dotnet/pull/640))
+- Move DURABLE0009/0010 from Unshipped to Shipped for v0.3.0 by cgillum ([#641](https://github.com/microsoft/durabletask-dotnet/pull/641))
+
+## 1.20.1
+- Fix GrpcChannel handle leak in AzureManaged backendby nytian ([#629](https://github.com/microsoft/durabletask-dotnet/pull/629))
+
+## 1.20.0
+- Partial orchestration workitem completion support (merge after next dts dp release) by wangbill ([#514](https://github.com/microsoft/durabletask-dotnet/pull/514))
+- Export history job by wangbill ([#494](https://github.com/microsoft/durabletask-dotnet/pull/494))
+- Add dependency injection support to durabletasktesthost by Naiyuan Tian ([#613](https://github.com/microsoft/durabletask-dotnet/pull/613))
+
+## v1.19.1
+- Throw an `InvalidOperationException` for purge requests on running orchestrations by sophiatev ([#611](https://github.com/microsoft/durabletask-dotnet/pull/611))
+- Validate c# identifiers in durabletask source generator by Copilot ([#578](https://github.com/microsoft/durabletask-dotnet/pull/578))
+- Document orchestration discovery and method probing behavior in analyzers by Copilot ([#594](https://github.com/microsoft/durabletask-dotnet/pull/594))
+
+## v1.19.0
+- Extended sessions for entities in .net isolated by sophiatev ([#507](https://github.com/microsoft/durabletask-dotnet/pull/507))
+- Adding the ability to specify tags and a retry policy for suborchestrations by sophiatev ([#603](https://github.com/microsoft/durabletask-dotnet/pull/603))
+- Improve durabletask source generator detection and add optional project type configuration by Copilot ([#575](https://github.com/microsoft/durabletask-dotnet/pull/575))
+- Add timeprovider support to orchestration analyzer by Copilot ([#573](https://github.com/microsoft/durabletask-dotnet/pull/573))
+- Expand azure functions smoke tests to cover source generator scenarios by Copilot ([#604](https://github.com/microsoft/durabletask-dotnet/pull/604))
+- Fix "syntaxtree is not part of the compilation" exception in orchestration analyzers by Copilot ([#588](https://github.com/microsoft/durabletask-dotnet/pull/588))
+- Add waitforexternalevent overload with timeout and cancellation token by Copilot ([#555](https://github.com/microsoft/durabletask-dotnet/pull/555))
+- Fix source generator for void-returning activity functions by Copilot ([#554](https://github.com/microsoft/durabletask-dotnet/pull/554))
+
+## v1.18.2
+- Add copy constructors to TaskOptions and sub-classes by halspang ([#587](https://github.com/microsoft/durabletask-dotnet/pull/587))
+- Change FunctionNotFound analyzer severity to Info for cross-assembly scenarios by Copilot ([#584](https://github.com/microsoft/durabletask-dotnet/pull/584))
+- Add Roslyn analyzer for non-contextual logger usage in orchestrations (DURABLE0010) by Copilot ([#553](https://github.com/microsoft/durabletask-dotnet/pull/553))
+- Add specific logging categories for Worker.Grpc and orchestration logs with backward-compatible opt-in by Copilot ([#583](https://github.com/microsoft/durabletask-dotnet/pull/583))
+- Fix flaky integration test race condition in dedup status check by Copilot ([#579](https://github.com/microsoft/durabletask-dotnet/pull/579))
+- Add analyzer to suggest input parameter binding over GetInput() by Copilot ([#550](https://github.com/microsoft/durabletask-dotnet/pull/550))
+- Add strongly-typed external events with DurableEventAttribute by Copilot ([#549](https://github.com/microsoft/durabletask-dotnet/pull/549))
+- Fix orchestration analyzer to detect non-function orchestrations correctly by Copilot ([#572](https://github.com/microsoft/durabletask-dotnet/pull/572))
+- Fix race condition in WaitForInstanceAsync causing intermittent test failures by Copilot ([#574](https://github.com/microsoft/durabletask-dotnet/pull/574))
+- Add HelpLinkUri to Roslyn analyzer diagnostics by Copilot ([#548](https://github.com/microsoft/durabletask-dotnet/pull/548))
+- Add DateTimeOffset.Now and DateTimeOffset.UtcNow detection to Roslyn analyzer by Copilot ([#547](https://github.com/microsoft/durabletask-dotnet/pull/547))
+- Bump Google.Protobuf from 3.33.1 to 3.33.2 by dependabot[bot] ([#569](https://github.com/microsoft/durabletask-dotnet/pull/569))
+- Add integration test coverage for Suspend/Resume operations by Copilot ([#546](https://github.com/microsoft/durabletask-dotnet/pull/546))
+- Bump coverlet.collector from 6.0.2 to 6.0.4 by dependabot[bot] ([#527](https://github.com/microsoft/durabletask-dotnet/pull/527))
+- Bump FluentAssertions from 6.12.1 to 6.12.2 by dependabot[bot] ([#528](https://github.com/microsoft/durabletask-dotnet/pull/528))
+- Add Azure Functions smoke tests with Docker CI automation by Copilot ([#545](https://github.com/microsoft/durabletask-dotnet/pull/545))
+- Bump dotnet-sdk from 10.0.100 to 10.0.101 by dependabot[bot] ([#568](https://github.com/microsoft/durabletask-dotnet/pull/568))
+- Add scheduled auto-closure for stale "Needs Author Feedback" issues by Copilot ([#566](https://github.com/microsoft/durabletask-dotnet/pull/566))
+
+## v1.18.1
+- Support dedup status when starting orchestration by wangbill ([#542](https://github.com/microsoft/durabletask-dotnet/pull/542))
+- Add 404 exception handling in blobpayloadstore.downloadasync by Copilot ([#534](https://github.com/microsoft/durabletask-dotnet/pull/534))
+- Bump analyzers version to 0.2.0 by Copilot ([#552](https://github.com/microsoft/durabletask-dotnet/pull/552))
+- Add integration tests for exception type handling by Copilot ([#544](https://github.com/microsoft/durabletask-dotnet/pull/544))
+- Add roslyn analyzer to detect calls to non-existent functions (name mismatch) by Copilot ([#530](https://github.com/microsoft/durabletask-dotnet/pull/530))
+- Remove preview suffix by Copilot ([#541](https://github.com/microsoft/durabletask-dotnet/pull/541))
+- Add xml documentation with see cref links to generated code for better ide navigation by Copilot ([#535](https://github.com/microsoft/durabletask-dotnet/pull/535))
+- Add entity source generation support for durable functions by Copilot ([#533](https://github.com/microsoft/durabletask-dotnet/pull/533))
+
+## v1.18.0
+- Add taskentity support to durabletasksourcegenerator by Copilot ([#517](https://github.com/microsoft/durabletask-dotnet/pull/517))
+- Bump azure.identity by dependabot[bot] ([#525](https://github.com/microsoft/durabletask-dotnet/pull/525))
+- Bump google.protobuf by dependabot[bot] ([#529](https://github.com/microsoft/durabletask-dotnet/pull/529))
+- Configure dependabot for dotnet-sdk updates by Tomer Rosenthal ([#524](https://github.com/microsoft/durabletask-dotnet/pull/524))
+- Add code review guidelines to copilot-instructions.md by Copilot ([#522](https://github.com/microsoft/durabletask-dotnet/pull/522))
+- Remove webapi sample by sophiatev ([#520](https://github.com/microsoft/durabletask-dotnet/pull/520))
+- Fix functioncontext check and polymorphic type conversions in activity analyzer by Naiyuan Tian ([#506](https://github.com/microsoft/durabletask-dotnet/pull/506))
+- Align waitforexternalevent waiter picking order to lifo by wangbill ([#509](https://github.com/microsoft/durabletask-dotnet/pull/509))
+- Update project to support .net 6.0 alongside .net 8.0 and .net 10 by Tomer Rosenthal ([#512](https://github.com/microsoft/durabletask-dotnet/pull/512))
+- Update project to target .net 8.0 and .net 10 and upgrade dependencies by Tomer Rosenthal ([#510](https://github.com/microsoft/durabletask-dotnet/pull/510))
+- Support worker features announcement by wangbill ([#502](https://github.com/microsoft/durabletask-dotnet/pull/502))
+- Introduce custom copilot review instructions by halspang ([#503](https://github.com/microsoft/durabletask-dotnet/pull/503))
+- Add API to get orchestration history ([#516](https://github.com/microsoft/durabletask-dotnet/pull/516))
+
+## v1.17.1
+- Fix Worker Registry and Add Documentation Notes by nytian in [#462](https://github.com/microsoft/durabletask-dotnet/pull/495)
+- Initial attempt to fix carryover events issue on continue-as-new by cgillum in [#496](https://github.com/microsoft/durabletask-dotnet/pull/496)
+- Fix encoding of entity unlock events by sebastianburckhardt in [#462](https://github.com/microsoft/durabletask-dotnet/pull/462)
+
+## v1.17.0
+-Add Microsoft.DurableTask.Extensions.AzureBlobPayloads to nuget publish by YunchuWang in [#488](https://github.com/microsoft/durabletask-dotnet/pull/488)
+-Add API for In-process Testing and Add Class-Syntax Integration Tests by nytian in [#476](https://github.com/microsoft/durabletask-dotnet/pull/476)
+-Fix Purge Instance Comments by sophiatev in [#489](https://github.com/microsoft/durabletask-dotnet/pull/489)
+-Fix ServiceCollectionExtensions.AddDurableTaskClient by sophiatev in [#490](https://github.com/microsoft/durabletask-dotnet/pull/490)
+-Update zuremanaged sdks to official version by YunchuWang in [#493](https://github.com/microsoft/durabletask-dotnet/pull/493)
+-Add Rewind to .NET isolated by sophiatev in [#479](https://github.com/microsoft/durabletask-dotnet/pull/479)
+-Add tags field to CompleteOrchestratorAction by sophiatev in [#492](https://github.com/microsoft/durabletask-dotnet/pull/492)
+
+## v1.16.2
+- Generate changelog script + update changelog for v1.16.1 by wangbill ([#486](https://github.com/microsoft/durabletask-dotnet/pull/486))
+- Remove unnecessary project reference to grpc.azuremanagedbackend in azureblobpayloads.csproj by wangbill ([#485](https://github.com/microsoft/durabletask-dotnet/pull/485))
+- Large payload azure blob externalization support by wangbill ([#468](https://github.com/microsoft/durabletask-dotnet/pull/468))
+
+## v1.16.1
+- Include exception properties in failure details when orchestration throws directly by Naiyuan Tian ([#482](https://github.com/microsoft/durabletask-dotnet/pull/482))
+- Set low priority for scheduled runs by Daniel Castro ([#477](https://github.com/microsoft/durabletask-dotnet/pull/477))
+
+## v1.16.0
+- Include Exception Properties at FailureDetails by nytian in([#474](https://github.com/microsoft/durabletask-dotnet/pull/474))
+
+## v1.15.1
+- Add version check to activities by @halspang in ([#472](https://github.com/microsoft/durabletask-dotnet/pull/472))
+
+## v1.15.0
+- Abandon workitem if processing workitem failed by @YunchuWang in ([#467](https://github.com/microsoft/durabletask-dotnet/pull/467))
+- Extended Sessions for Isolated (Orchestrations) by @sophiatev in ([#449](https://github.com/microsoft/durabletask-dotnet/pull/449))
+
+## v1.14.0
+- Add RestartAsync API Support at DurableTaskClient ([#456](https://github.com/microsoft/durabletask-dotnet/pull/456))
+
+## v1.13.0
+- Add orchestration execution tracing ([#441](https://github.com/microsoft/durabletask-dotnet/pull/441))
+
+## v1.12.0
+
+- Activity tag support ([#426](https://github.com/microsoft/durabletask-dotnet/pull/426))
+- Adding Analyzer to build and release ([#444](https://github.com/microsoft/durabletask-dotnet/pull/444))
+- Add ability to filter orchestrations at worker ([#443](https://github.com/microsoft/durabletask-dotnet/pull/443))
+- Removing breaking change for TaskOptions ([#446](https://github.com/microsoft/durabletask-dotnet/pull/446))
+- Expose gRPC retry options in Azure Managed extensions ([#447](https://github.com/microsoft/durabletask-dotnet/pull/447))
+
+## v1.11.0
+
+- Add New Property Properties to TaskOrchestrationContext ([#415](https://github.com/microsoft/durabletask-dotnet/pull/415))
+- Add automatic retry on gateway timeout in `GrpcDurableTaskClient.WaitForInstanceCompletionAsync` ([#412](https://github.com/microsoft/durabletask-dotnet/pull/412))
+- Add specific logging for NotFound error on worker connection ([#413](https://github.com/microsoft/durabletask-dotnet/pull/413))
+- Add user agent header to gRPC called ([#417](https://github.com/microsoft/durabletask-dotnet/pull/417))
+- Enrich User-Agent Header in gRPC Metadata to indicate Client or Worker as caller ([#421](https://github.com/microsoft/durabletask-dotnet/pull/421))
+- Change DTS user agent metadata to avoid overlap with gRPC user agent ([#423](https://github.com/microsoft/durabletask-dotnet/pull/423))
+- Add extension methods for registering entities by type ([#427](https://github.com/microsoft/durabletask-dotnet/pull/427))
+- Add TaskVersion and utilize it for version overrides when starting orchestrations ([#416](https://github.com/microsoft/durabletask-dotnet/pull/416))
+- Update sub-orchestration default versioning ([#437](https://github.com/microsoft/durabletask-dotnet/pull/437))
+- Distributed Tracing for Entities (Isolated) ([#404](https://github.com/microsoft/durabletask-dotnet/pull/404))
+
+## v1.10.0
+
+- Update DurableTask.Core to v3.1.0 and Bump version to v1.10.0 by @nytian in ([#411](https://github.com/microsoft/durabletask-dotnet/pull/411))
+
+## v1.9.1
+
+- Add basic orchestration and activity execution logs by @cgillum in ([#405](https://github.com/microsoft/durabletask-dotnet/pull/405))
+- Add default version in `TaskOrchestrationContext` by @halspang in ([#408](https://github.com/microsoft/durabletask-dotnet/pull/408))
+
+## v1.9.0
+
+- Fix schedule sample logging setup by @YunchuWang in ([#392](https://github.com/microsoft/durabletask-dotnet/pull/392))
+- Introduce versioning to the DurableTaskClient by @halspang in ([#393](https://github.com/microsoft/durabletask-dotnet/pull/393))
+- Support for local credential types for DTS by @cgillum in ([#396](https://github.com/microsoft/durabletask-dotnet/pull/396))
+- Add utilities for easier versioning usage by @halspang in ([#394](https://github.com/microsoft/durabletask-dotnet/pull/394))
+- Add tags to CreateInstanceRequest by @torosent in ([#397](https://github.com/microsoft/durabletask-dotnet/pull/397))
+- Partial Purge Support by @YunchuWang in ([#400](https://github.com/microsoft/durabletask-dotnet/pull/400))
+- Dts Grpc client retry support by @YunchuWang in ([#403](https://github.com/microsoft/durabletask-dotnet/pull/403))
+- Introduce orchestration versioning into worker by @halspang in ([#401](https://github.com/microsoft/durabletask-dotnet/pull/401))
+
+## v1.8.1
+
+- Add timeout to gRPC workitem streaming ([#390](https://github.com/microsoft/durabletask-dotnet/pull/390))
+
+## v1.8.0
+
+- Add Schedule Support for Durable Task Framework ([#368](https://github.com/microsoft/durabletask-dotnet/pull/368))
+- Fixes and improvements
+
+## v1.7.0
+
+- Add parent trace context information when scheduling an orchestration ([#358](https://github.com/microsoft/durabletask-dotnet/pull/358))
+
+## v1.6.0
+
+- Added new preview packages, `Microsoft.DurableTask.Client.AzureManaged` and `Microsoft.DurableTask.Worker.AzureManaged`
+- Move to Central Package Management ([#373](https://github.com/microsoft/durabletask-dotnet/pull/373))
+
+### Microsoft.DurableTask.Client
+
+- Add new `IDurableTaskClientBuilder AddDurableTaskClient(IServiceCollection, string?)` API
+
+### Microsoft.DurableTask.Worker
+
+- Add new `IDurableTaskWorkerBuilder AddDurableTaskWorker(IServiceCollection, string?)` API
+- Add support for work item history streaming
+
+### Microsoft.DurableTask.Worker.Grpc
+
+- Provide entity support for direct grpc connections to DTS ([#369](https://github.com/microsoft/durabletask-dotnet/pull/369))
+
+### Microsoft.DurableTask.Grpc
+
+- Replace submodule for proto files with download script for easier maintenance
+- Update to latest proto files
+
+## v1.5.0
+
+- Implement work item completion tokens for standalone worker scenarios ([#359](https://github.com/microsoft/durabletask-dotnet/pull/359))
+- Support for worker concurrency configuration ([#359](https://github.com/microsoft/durabletask-dotnet/pull/359))
+- Bump System.Text.Json to 6.0.10
+- Initial support for the Azure-managed [Durable Task Scheduler](https://techcommunity.microsoft.com/blog/appsonazureblog/announcing-limited-early-access-of-the-durable-task-scheduler-for-azure-durable-/4286526) preview.
+
+## v1.4.0
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `3.0.0`
+
+## v1.3.0
+
+### Microsoft.DurableTask.Abstractions
+
+- Add `RetryPolicy.Handle` property to allow for exception filtering on retries ([#314](https://github.com/microsoft/durabletask-dotnet/pull/314))
+
+## v1.2.4
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.17.1`
+
+## v1.2.3
+
+### Microsoft.DurableTask.Client
+
+- Fix filter not being passed along in `PurgeAllInstancesAsync` (https://github.com/microsoft/durabletask-dotnet/pull/289)
+
+### Microsoft.DurableTask.Abstractions
+
+- Enable inner exception detail propagation in `TaskFailureDetails` ([#290](https://github.com/microsoft/durabletask-dotnet/pull/290))
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.17.0`
+
+## v1.2.2
+
+### Microsoft.DurableTask.Abstractions
+
+- Fix `TaskFailureDetails.IsCausedBy` to support custom exceptions and 3rd party exceptions ([#273](https://github.com/microsoft/durabletask-dotnet/pull/273))
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.2`
+
+### Microsoft.DurableTask.Client
+
+- Fix typo in `PurgeInstanceAsync`  in `DurableTaskClient` (https://github.com/microsoft/durabletask-dotnet/pull/264)
+
+## v1.2.0
+
+- Adds support to recursively terminate/purge sub-orchestrations in `GrpcDurableTaskClient` (https://github.com/microsoft/durabletask-dotnet/pull/262)
+
+## v1.1.1
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.1`
+
+## v1.1.0
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.0`
+
+## v1.1.0-preview.2
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.0-preview.2`
+
+## v1.1.0-preview.1
+
+Adds support for durable entities. Learn more [here](https://learn.microsoft.com/azure/azure-functions/durable/durable-functions-entities?tabs=csharp).
+
+### Microsoft.DurableTask.Abstractions
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.16.0-preview.1`
+
+## v1.0.5
+
+### Microsoft.DurableTask.Abstractions
+
+- Microsoft.Azure.DurableTask.Core dependency increased to `2.15.0` (https://github.com/microsoft/durabletask-dotnet/pull/212)
+
+### Microsoft.DurableTask.Worker
+
+- Fix re-encoding of events when using `TaskOrchestrationContext.ContinueAsNew(preserveUnprocessedEvents: true)` (https://github.com/microsoft/durabletask-dotnet/pull/212)
+
+## v1.0.4
+
+### Microsoft.DurableTask.Worker
+
+- Fix handling of concurrent external events with the same name (https://github.com/microsoft/durabletask-dotnet/pull/194)
+
+## v1.0.3
+
+### Microsoft.DurableTask.Worker
+
+- Fix instance ID not being passed in when using retry policy (https://github.com/microsoft/durabletask-dotnet/issues/174)
+
+### Microsoft.DurableTask.Worker.Grpc
+
+- Add `GrpcDurableTaskWorkerOptions.CallInvoker` as an alternative to `GrpcDurableTaskWorkerOptions.Channel`
+
+### Microsoft.DurableTask.Client.Grpc
+
+- Add `GrpcDurableTaskClientOptions.CallInvoker` as an alternative to `GrpcDurableTaskClientOptions.Channel`
+
+## v1.0.2
+
+### Microsoft.DurableTask.Worker
+
+- Fix issue with `TaskOrchestrationContext.Parent` not being set.
+
+## v1.0.1
+
+### Microsoft.DurableTask.Client
+
+- Fix incorrect bounds check on `PurgeResult`
+- Address typo for `DurableTaskClient.GetInstancesAsync` (incorrectly pluralized)
+    - Added `GetInstanceAsync`
+    - Hide `GetInstancesAsync` from editor
+
+## v1.0.0
+
+- Added `SuspendInstanceAsync` and `ResumeInstanceAsync` to `DurableTaskClient`.
+- Rename `DurableTaskClient` methods
+    - `TerminateAsync` -> `TerminateInstanceAsync`
+    - `PurgeInstanceMetadataAsync` -> `PurgeInstanceAsync`
+    - `PurgeInstances` -> `PurgeAllInstancesAsync`
+    - `GetInstanceMetadataAsync` -> `GetInstanceAsync`
+    - `GetInstances` -> `GetAllInstancesAsync`
+- `TaskOrchestrationContext.CreateReplaySafeLogger` now creates `ILogger` directly (as opposed to wrapping an existing `ILogger`).
+- Durable Functions class-based syntax now resolves `ITaskActivity` instances from `IServiceProvider`, if available there.
+- `DurableTaskClient` methods have been touched up to ensure `CancellationToken` is included, as well as is the last parameter.
+- Removed obsolete/unimplemented local lambda activity calls from `TaskOrchestrationContext`
+- Input is now an optional parameter on `TaskOrchestrationContext.ContinueAsNew`
+- Multi-target gRPC projects to now use `Grpc.Net.Client` when appropriate (.NET6.0 and up)
+
+*Note: `Microsoft.DurableTask.Generators` is remaining as `preview.1`.*
+
+## v1.0.0-rc.1
+
+### Included Packages
+
+Microsoft.DurableTask.Abstractions \
+Microsoft.DurableTask.Client \
+Microsoft.DurableTask.Client.Grpc \
+Microsoft.DurableTask.Worker \
+Microsoft.DurableTask.Worker.Grpc \
+
+_see v1.0.0-preview.1 for `Microsoft.DurableTask.Generators`_
+
+### Updates
+
+- Refactors and splits assemblies.
+  - `Microsoft.DurableTask.Abstractions`
+  - `Microsoft.DurableTask.Generators`
+  - `Microsoft.DurableTask.Client`
+  - `Microsoft.DurableTask.Client.Grpc`
+  - `Microsoft.DurableTask.Worker`
+  - `Microsoft.DurableTask.Worker.Grpc`
+- Added more API documentation
+- Adds ability to perform multi-instance query
+- Adds `PurgeInstancesMetadataAsync` and `PurgeInstancesAsync` support and implementation to `GrpcDurableTaskClient`
+- Fix issue with mixed Newtonsoft.Json and System.Text.Json serialization.
+- `IDurableTaskClientProvider` added to support multiple named clients.
+- Added new options pattern for starting new and sub orchestrations.
+- Overhauled builder API built on top of .NET generic host.
+  - Now relies on dependency injection.
+  - Integrates into options pattern, giving a variety of ways for user configuration.
+  - Builder is now re-enterable. Multiple calls to `.AddDurableTask{Worker|Client}` with the same name will yield the exact same builder instance.
+
+### Breaking Changes
+
+- `Microsoft.DurableTask.Generators` reference removed.
+- Added new abstract property `TaskOrchestrationContext.ParentInstance`.
+- Added new abstract method `DurableTaskClient.PurgeInstancesAsync`.
+- Renamed `TaskOrchestratorBase` to `TaskOrchestrator`
+  - `OnRunAsync` -> `RunAsync`, forced-nullability removed.
+  - Nullability can be done in generic params, ie: `MyOrchestrator : TaskOrchestrator<string?, string?>`
+  - Nullability is not verified at runtime by the base class, it is up to the individual orchestrator implementations to verify their own nullability.
+- Renamed `TaskActivityBase` to `TaskActivity`
+  - `OnRun` removed. With both `OnRun` and `OnRunAsync`, there was no compiler error when you did not implement one. The remaining method is now marked `abstract` to force an implementation. Synchronous implementation can still be done via `Task.FromResult`.
+  - `OnRunAsync` -> `RunAsync`, forced-nullability removed.
+  - Nullability can be done in generic params, ie: `MyActivity : TaskActivity<string?, string?>`
+  - Nullability is not verified at runtime by the base class, it is up to the individual activity implementations to verify their own nullability.
+- `TaskOrchestrationContext.StartSubOrchestrationAsync` refactored:
+  - `instanceId` parameter removed. Can now specify it via supplying `SubOrchestrationOptions` for `TaskOptions`.
+- `TaskOptions` refactored to be a record type.
+  - Builder removed.
+  - Retry provided via a property `TaskRetryOptions`, which is a pseudo union-type which can be either a `RetryPolicy` or `AsyncRetryHandler`.
+  - `SubOrchestrationOptions` is a derived type that can be used to specific a sub-orchestrations instanceId.
+  - Helper method `.WithInstanceId(string? instanceId)` added.
+- `DurableTaskClient.ScheduleNewOrchestrationInstanceAsync` refactored:
+  - `instanceId` and `startAfter` wrapped into `StartOrchestrationOptions` object.
+- Builder API completely overhauled. Now built entirely on top of the .NET generic host.
+  - See samples for how the new API works.
+  - Supports multiple workers and named-clients.
+- Ability to set `TaskName.Version` removed for now. Will be added when we address versioning.
+- `IDurableTaskRegistry` removed, only `DurableTaskRegistry` concrete type.
+  - All lambda-methods renamed to `AddActivityFunc` and `AddOrchestratorFunc`. This was to avoid ambiguous or incorrect overload resolution with the factory methods.
+
+## v1.0.0-preview.1
+
+### Included Packages
+
+Microsoft.DurableTask.Generators
+
+### Breaking Changes
+
+- `Microsoft.DurableTask.Generators` is now an optional package.
+  - no longer automatically brought in when referencing other packages.
+  - To get code generation, add `<PackageReference Include="Microsoft.DurableTask.Generators" Version="1.0.0-preview.1" PrivateAssets="All" />` to your csproj.
+- `GeneratedDurableTaskExtensions.AddAllGeneratedTasks` made `internal` (from `public`)
+  - This is also to avoid conflicts when multiple files have this method generated. When wanting to expose to external consumes, a new extension method can be manually authored in the desired namespace and with an appropriate name which calls this method.
+
+## v0.4.1-beta
+
+Initial public release
+
+
+
+
+
diff --git a/Microsoft.DurableTask.sln b/Microsoft.DurableTask.sln
index 0b05c418..3c6d4539 100644
--- a/Microsoft.DurableTask.sln
+++ b/Microsoft.DurableTask.sln
@@ -1,4 +1,4 @@
-
+
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.3.32901.215
@@ -117,16 +117,34 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ReplaySafeLoggerFactorySamp
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "WorkerVersioningSample", "samples\WorkerVersioningSample\WorkerVersioningSample.csproj", "{26988639-D204-4E0B-80BE-F4E11952DFF8}"
 EndProject
-Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "AzureManaged", "AzureManaged", "{D4587EC0-1B16-8420-7502-A967139249D4}"
-EndProject
-Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "AzureManaged", "AzureManaged", "{53193780-CD18-2643-6953-C26F59EAEDF5}"
-EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EternalOrchestrationVersionMigrationSample", "samples\EternalOrchestrationVersionMigrationSample\EternalOrchestrationVersionMigrationSample.csproj", "{1E30F09F-1ADA-4375-81CC-F0FBC74D5621}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ActivityVersioningSample", "samples\ActivityVersioningSample\ActivityVersioningSample.csproj", "{3FBCFDBA-F547-4FD5-B8C6-0B645EF73E3A}"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EntityWithVersionedOrchestrationSample", "samples\EntityWithVersionedOrchestrationSample\EntityWithVersionedOrchestrationSample.csproj", "{8E0D27B3-2B5D-4B6F-A4E6-5C8E7B0F7DD2}"
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "on-demand-sandbox", "on-demand-sandbox", "{D422B5FD-8E3C-6588-ACD1-DEFAB429269C}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "shared", "samples\on-demand-sandbox\shared\shared.csproj", "{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "main-app", "samples\on-demand-sandbox\main-app\main-app.csproj", "{0CB44F0A-3483-4052-A49F-D4E6F140741C}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "remote-worker", "samples\on-demand-sandbox\remote-worker\remote-worker.csproj", "{B7069604-DD97-4115-8B30-FC1D4C0E6D43}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "AzureManaged.Sandboxes", "AzureManaged.Sandboxes", "{28648169-70E4-D0BA-4357-338A556A7DA8}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Client.AzureManaged.Sandboxes", "src\Client\AzureManaged.Sandboxes\Client.AzureManaged.Sandboxes.csproj", "{A7C6DF09-1AD3-42F6-BCF1-D40E011D1056}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "AzureManaged", "AzureManaged", "{D4587EC0-1B16-8420-7502-A967139249D4}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "AzureManaged.Sandboxes", "AzureManaged.Sandboxes", "{9686B8F9-2644-6C9B-E567-55B0471E4584}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Worker.AzureManaged.Sandboxes", "src\Worker\AzureManaged.Sandboxes\Worker.AzureManaged.Sandboxes.csproj", "{C1995163-1DCE-405D-BE82-8B4B2584893E}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "AzureManaged", "AzureManaged", "{53193780-CD18-2643-6953-C26F59EAEDF5}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Grpc", "Grpc", "{3B8F957E-7773-4C0C-ACD7-91A1591D9312}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -761,6 +779,66 @@ Global
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+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}.Debug|x64.Build.0 = Debug|Any CPU
+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279}.Debug|x86.Build.0 = Debug|Any CPU
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+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Debug|x86.Build.0 = Debug|Any CPU
+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Release|x64.ActiveCfg = Release|Any CPU
+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Release|x64.Build.0 = Release|Any CPU
+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Release|x86.ActiveCfg = Release|Any CPU
+		{C1995163-1DCE-405D-BE82-8B4B2584893E}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -819,11 +897,20 @@ Global
 		{5A69FD28-D814-490E-A76B-B0A5F88C25B2} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
 		{8E7BECBC-7226-4778-B8F2-8EBDFF0D3BA4} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
 		{26988639-D204-4E0B-80BE-F4E11952DFF8} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
-		{D4587EC0-1B16-8420-7502-A967139249D4} = {1C217BB2-CE16-41CC-9D47-0FC0DB60BDB3}
-		{53193780-CD18-2643-6953-C26F59EAEDF5} = {5B448FF6-EC42-491D-A22E-1DC8B618E6D5}
 		{1E30F09F-1ADA-4375-81CC-F0FBC74D5621} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
 		{3FBCFDBA-F547-4FD5-B8C6-0B645EF73E3A} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
 		{8E0D27B3-2B5D-4B6F-A4E6-5C8E7B0F7DD2} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
+		{D422B5FD-8E3C-6588-ACD1-DEFAB429269C} = {EFF7632B-821E-4CFC-B4A0-ED4B24296B17}
+		{F0DC6D16-C9BC-4804-BBAF-84C050D5E279} = {D422B5FD-8E3C-6588-ACD1-DEFAB429269C}
+		{0CB44F0A-3483-4052-A49F-D4E6F140741C} = {D422B5FD-8E3C-6588-ACD1-DEFAB429269C}
+		{B7069604-DD97-4115-8B30-FC1D4C0E6D43} = {D422B5FD-8E3C-6588-ACD1-DEFAB429269C}
+		{28648169-70E4-D0BA-4357-338A556A7DA8} = {1C217BB2-CE16-41CC-9D47-0FC0DB60BDB3}
+		{A7C6DF09-1AD3-42F6-BCF1-D40E011D1056} = {28648169-70E4-D0BA-4357-338A556A7DA8}
+		{D4587EC0-1B16-8420-7502-A967139249D4} = {1C217BB2-CE16-41CC-9D47-0FC0DB60BDB3}
+		{9686B8F9-2644-6C9B-E567-55B0471E4584} = {5B448FF6-EC42-491D-A22E-1DC8B618E6D5}
+		{C1995163-1DCE-405D-BE82-8B4B2584893E} = {9686B8F9-2644-6C9B-E567-55B0471E4584}
+		{53193780-CD18-2643-6953-C26F59EAEDF5} = {5B448FF6-EC42-491D-A22E-1DC8B618E6D5}
+		{3B8F957E-7773-4C0C-ACD7-91A1591D9312} = {5B448FF6-EC42-491D-A22E-1DC8B618E6D5}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {AB41CB55-35EA-4986-A522-387AB3402E71}
diff --git a/README.md b/README.md
index 84686d37..2fc37547 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Durable Task .NET Client SDK
+# Durable Task .NET Client SDK
 
 [![Build status](https://github.com/microsoft/durabletask-dotnet/workflows/Validate%20Build/badge.svg)](https://github.com/microsoft/durabletask-dotnet/actions?workflow=Validate+Build)
 [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://opensource.org/licenses/MIT)
@@ -198,6 +198,8 @@ This SDK can also be used with the Durable Task Scheduler directly, without any
 
 For runnable DTS emulator examples that demonstrate versioning, see the [WorkerVersioningSample](samples/WorkerVersioningSample/README.md) (deployment-based versioning), the [EternalOrchestrationVersionMigrationSample](samples/EternalOrchestrationVersionMigrationSample/README.md) (multi-version routing with `[DurableTask(Version = "...")]`), the [ActivityVersioningSample](samples/ActivityVersioningSample/README.md) (activity versioning with inherited defaults and explicit override support), and the [EntityWithVersionedOrchestrationSample](samples/EntityWithVersionedOrchestrationSample/README.md) (a single instance migrating v1→v2 via `ContinueAsNew(NewVersion)` while preserving entity-held state).
 
+The [on-demand sandbox activities sample](samples/on-demand-sandbox/README.md) shows how to declare selected activities for Durable Task Scheduler (DTS)-managed on-demand sandbox execution and build the remote worker container image separately from the declarer app.
+
 ## Obtaining the Protobuf definitions
 
 This project utilizes protobuf definitions from [durabletask-protobuf](https://github.com/microsoft/durabletask-protobuf), which are copied (vendored) into this repository under the `src/Grpc` directory. See the corresponding [README.md](./src/Grpc/README.md) for more information about how to update the protobuf definitions.
diff --git a/eng/publish/publish.yml b/eng/publish/publish.yml
index b77ead2d..a3009469 100644
--- a/eng/publish/publish.yml
+++ b/eng/publish/publish.yml
@@ -137,7 +137,7 @@ extends:
             # the packages to push pattern explicitly excludes:
             # - 'Microsoft.DurableTask.Client.Grpc'
             # - 'Microsoft.DurableTask.Client.OrchestrationServiceClientShim'
-            # - 'Microsoft.DurableTask.Client.AzureManaged'
+            # - 'Microsoft.DurableTask.Client.AzureManaged.*'
             # which are pushed by their respective jobs
             packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.*.nupkg;!$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.Grpc.*.nupkg;!$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.OrchestrationServiceClientShim.*.nupkg;!$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.AzureManaged.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
             packageParentPath: $(System.DefaultWorkingDirectory) # This needs to be set to some prefix of the `packagesToPush` parameter. Apparently it helps with SDL tooling
@@ -324,7 +324,30 @@ extends:
             command: push
             nuGetFeedType: external
             publishFeedCredentials: 'DurableTask org NuGet API Key'
-            packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.AzureManaged.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
+            packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.AzureManaged.*.nupkg;!$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.AzureManaged.Sandboxes.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
+            packageParentPath: $(System.DefaultWorkingDirectory) # This needs to be set to some prefix of the `packagesToPush` parameter. Apparently it helps with SDL tooling
+
+      # NuGet release (Microsoft.DurableTask.Client.AzureManaged.Sandboxes)
+      - job: nugetRelease_Microsoft_DurableTask_Client_AzureManaged_Sandboxes
+        displayName: NuGet Release (Microsoft.DurableTask.Client.AzureManaged.Sandboxes)
+        dependsOn: nugetApproval
+        condition: succeeded('nugetApproval') # nuget packages need to be on ADO first
+        templateContext:
+          type: releaseJob
+          isProduction: true
+          inputs:
+          - input: pipelineArtifact
+            pipeline: officialPipeline  # Pipeline reference as defined in the resources section
+            artifactName: drop
+            targetPath: $(System.DefaultWorkingDirectory)/drop
+        steps:
+        - task: 1ES.PublishNuget@1
+          displayName: 'NuGet push (Microsoft.DurableTask.Client.AzureManaged.Sandboxes)'
+          inputs:
+            command: push
+            nuGetFeedType: external
+            publishFeedCredentials: 'DurableTask org NuGet API Key'
+            packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Client.AzureManaged.Sandboxes.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
             packageParentPath: $(System.DefaultWorkingDirectory) # This needs to be set to some prefix of the `packagesToPush` parameter. Apparently it helps with SDL tooling
 
       # NuGet release (Microsoft.DurableTask.Worker.AzureManaged)
@@ -347,7 +370,30 @@ extends:
             command: push
             nuGetFeedType: external
             publishFeedCredentials: 'DurableTask org NuGet API Key'
-            packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Worker.AzureManaged.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
+            packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Worker.AzureManaged.*.nupkg;!$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Worker.AzureManaged.Sandboxes.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
+            packageParentPath: $(System.DefaultWorkingDirectory) # This needs to be set to some prefix of the `packagesToPush` parameter. Apparently it helps with SDL tooling
+
+      # NuGet release (Microsoft.DurableTask.Worker.AzureManaged.Sandboxes)
+      - job: nugetRelease_Microsoft_DurableTask_Worker_AzureManaged_Sandboxes
+        displayName: NuGet Release (Microsoft.DurableTask.Worker.AzureManaged.Sandboxes)
+        dependsOn: nugetApproval
+        condition: succeeded('nugetApproval') # nuget packages need to be on ADO first
+        templateContext:
+          type: releaseJob
+          isProduction: true
+          inputs:
+          - input: pipelineArtifact
+            pipeline: officialPipeline  # Pipeline reference as defined in the resources section
+            artifactName: drop
+            targetPath: $(System.DefaultWorkingDirectory)/drop
+        steps:
+        - task: 1ES.PublishNuget@1
+          displayName: 'NuGet push (Microsoft.DurableTask.Worker.AzureManaged.Sandboxes)'
+          inputs:
+            command: push
+            nuGetFeedType: external
+            publishFeedCredentials: 'DurableTask org NuGet API Key'
+            packagesToPush: '$(System.DefaultWorkingDirectory)/drop/Microsoft.DurableTask.Worker.AzureManaged.Sandboxes.*.nupkg;!$(System.DefaultWorkingDirectory)/**/*.symbols.nupkg' # Despite this being a custom command, we need to keep this for 1ES validation
             packageParentPath: $(System.DefaultWorkingDirectory) # This needs to be set to some prefix of the `packagesToPush` parameter. Apparently it helps with SDL tooling
 
       # NuGet release (Microsoft.DurableTask.ScheduledTasks)
diff --git a/samples/on-demand-sandbox/README.md b/samples/on-demand-sandbox/README.md
new file mode 100644
index 00000000..134182df
--- /dev/null
+++ b/samples/on-demand-sandbox/README.md
@@ -0,0 +1,74 @@
+# On-demand sandbox activities sample
+
+This sample shows how to run selected Durable Task activities in DTS-managed on-demand sandboxes.
+
+The sample is intentionally split into two projects:
+
+| Path | Purpose |
+| --- | --- |
+| `shared/` | Defines activity identity constants shared by the main app and remote worker. |
+| `main-app/` | Runs locally or in a normal app host. It declares the on-demand sandbox activity and starts one hello orchestration. |
+| `remote-worker/` | Builds the container image that DTS starts inside a sandbox. It contains the remote hello activity. |
+
+## Build
+
+```powershell
+dotnet build .\samples\on-demand-sandbox\main-app\main-app.csproj
+dotnet build .\samples\on-demand-sandbox\remote-worker\remote-worker.csproj
+```
+
+## Build the remote worker image
+
+Run from the repository root:
+
+```powershell
+$image = "<acr-name>.azurecr.io/dts-ondemand-sandbox-sample:<tag>"
+docker build -f .\samples\on-demand-sandbox\remote-worker\Containerfile -t $image .
+docker push $image
+```
+
+## Run a hello orchestration
+
+The main app uses `DefaultAzureCredential`; sign in with Azure CLI or configure another supported Azure identity before running it.
+After pushing the remote worker image, set these environment variables:
+
+```powershell
+$env:DTS_SANDBOX_CONTAINER_IMAGE = "<container image reference>"
+$env:DTS_SANDBOX_IMAGE_PULL_UMI_CLIENT_ID = "<image-pull UMI client ID>"
+$env:DTS_SANDBOX_SCHEDULER_UMI_CLIENT_ID = "<scheduler UMI client ID>"
+```
+
+The worker profile class declares the image, CPU, memory, max concurrency, and on-demand sandbox activity identities with `options.AddActivity(name, version)`. The main app and remote worker both use the `shared/SandboxActivities.cs` constants so the workerProfile and worker registration stay in sync.
+
+Update `main-app/appsettings.json` with your scheduler endpoint and task hub:
+
+```json
+{
+  "OnDemandSandboxSample": {
+    "EndpointAddress": "https://<scheduler-endpoint>",
+    "TaskHubName": "<task-hub-name>"
+  }
+}
+```
+
+Then run the main app:
+
+```powershell
+Push-Location .\samples\on-demand-sandbox\main-app
+dotnet run
+Pop-Location
+```
+
+Expected output includes the on-demand sandbox activity result:
+
+```text
+Runtime status: Completed
+Output: "hello locally: on-demand-sandbox-sample; hello remotely from <sandbox> pid=<pid>: on-demand-sandbox-sample"
+```
+
+Use the Durable Task Scheduler dashboard's On-demand sandbox preview tab to inspect sandboxes and stream runtime logs.
+
+The remote worker image does not need customer-provided DTS runtime settings.
+DTS injects the scheduler endpoint, task hub, worker profile, capacity, sandbox provider,
+and sandbox identifier when it starts the sandbox. The worker reports the
+activity identities registered in the image when it connects.
diff --git a/samples/on-demand-sandbox/main-app/Activities.cs b/samples/on-demand-sandbox/main-app/Activities.cs
new file mode 100644
index 00000000..4048e3ea
--- /dev/null
+++ b/samples/on-demand-sandbox/main-app/Activities.cs
@@ -0,0 +1,20 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask;
+
+namespace Microsoft.DurableTask.Samples.OnDemandSandbox.MainApp;
+
+internal static class OnDemandSandboxTaskNames
+{
+    public const string LocalHello = "LocalHello";
+    public const string HelloOrchestrator = nameof(HelloOrchestrator);
+}
+
+[DurableTask(OnDemandSandboxTaskNames.LocalHello)]
+internal sealed class LocalHelloActivity : TaskActivity<string, string>
+{
+    public override Task<string> RunAsync(TaskActivityContext context, string input)
+        => Task.FromResult($"hello locally: {input}");
+}
+
diff --git a/samples/on-demand-sandbox/main-app/Orchestrators.cs b/samples/on-demand-sandbox/main-app/Orchestrators.cs
new file mode 100644
index 00000000..332a69b0
--- /dev/null
+++ b/samples/on-demand-sandbox/main-app/Orchestrators.cs
@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask;
+using Microsoft.DurableTask.Samples.OnDemandSandbox.Shared;
+
+namespace Microsoft.DurableTask.Samples.OnDemandSandbox.MainApp;
+
+[DurableTask(nameof(HelloOrchestrator))]
+internal sealed class HelloOrchestrator : TaskOrchestrator<string, string>
+{
+    public override async Task<string> RunAsync(TaskOrchestrationContext context, string input)
+    {
+        string localResult = await context.CallActivityAsync<string>(OnDemandSandboxTaskNames.LocalHello, input);
+        string remoteResult = await context.CallActivityAsync<string>(
+            SandboxActivities.RemoteHelloName,
+            input,
+            new TaskOptions { Version = new TaskVersion(SandboxActivities.RemoteHelloVersion) });
+        return $"{localResult}; {remoteResult}";
+    }
+}
diff --git a/samples/on-demand-sandbox/main-app/Program.cs b/samples/on-demand-sandbox/main-app/Program.cs
new file mode 100644
index 00000000..1e9d92e2
--- /dev/null
+++ b/samples/on-demand-sandbox/main-app/Program.cs
@@ -0,0 +1,82 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Azure.Core;
+using Azure.Identity;
+using Microsoft.DurableTask;
+using Microsoft.DurableTask.Client;
+using Microsoft.DurableTask.Client.AzureManaged;
+using Microsoft.DurableTask.Samples.OnDemandSandbox.MainApp;
+using Microsoft.DurableTask.Worker;
+using Microsoft.DurableTask.Worker.AzureManaged;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+const string Input = "on-demand-sandbox-sample";
+
+HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
+string endpoint = GetRequiredConfigurationValue("OnDemandSandboxSample:EndpointAddress");
+string taskHub = GetRequiredConfigurationValue("OnDemandSandboxSample:TaskHubName");
+TokenCredential credential = new DefaultAzureCredential();
+builder.Logging.AddSimpleConsole(options =>
+{
+    options.SingleLine = true;
+    options.UseUtcTimestamp = true;
+    options.TimestampFormat = "yyyy-MM-ddTHH:mm:ss.fffZ ";
+});
+
+builder.Services.AddDurableTaskWorker(workerBuilder =>
+{
+    workerBuilder.AddTasks(tasks => tasks.AddAllGeneratedTasks());
+    workerBuilder.UseWorkItemFilters();
+    workerBuilder.UseDurableTaskScheduler(options =>
+    {
+        options.EndpointAddress = endpoint;
+        options.TaskHubName = taskHub;
+        options.Credential = credential;
+    });
+});
+
+builder.Services.AddDurableTaskClient(clientBuilder =>
+{
+    clientBuilder.UseDurableTaskScheduler(options =>
+    {
+        options.EndpointAddress = endpoint;
+        options.TaskHubName = taskHub;
+        options.Credential = credential;
+    });
+});
+builder.Services.AddDurableTaskSchedulerSandboxActivitiesClient();
+
+using IHost host = builder.Build();
+
+await host.StartAsync();
+
+SandboxActivitiesClient sandboxActivitiesClient = host.Services.GetRequiredService<SandboxActivitiesClient>();
+await sandboxActivitiesClient.EnableSandboxActivitiesAsync();
+
+DurableTaskClient client = host.Services.GetRequiredService<DurableTaskClient>();
+string instanceId = await client.ScheduleNewOrchestrationInstanceAsync(
+    OnDemandSandboxTaskNames.HelloOrchestrator,
+    input: Input);
+Console.WriteLine($"Started orchestration: {instanceId}");
+
+OrchestrationMetadata result = await client.WaitForInstanceCompletionAsync(
+    instanceId,
+    getInputsAndOutputs: true);
+Console.WriteLine($"Runtime status: {result.RuntimeStatus}");
+Console.WriteLine($"Output: {result.SerializedOutput ?? "<null>"}");
+
+await host.StopAsync();
+
+string GetRequiredConfigurationValue(string key)
+{
+    string? value = builder.Configuration[key];
+    if (string.IsNullOrWhiteSpace(value))
+    {
+        throw new InvalidOperationException($"Configuration value '{key}' must be set.");
+    }
+
+    return value.Trim();
+}
diff --git a/samples/on-demand-sandbox/main-app/WorkerProfiles.cs b/samples/on-demand-sandbox/main-app/WorkerProfiles.cs
new file mode 100644
index 00000000..1a7d96c8
--- /dev/null
+++ b/samples/on-demand-sandbox/main-app/WorkerProfiles.cs
@@ -0,0 +1,44 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask.Client.AzureManaged;
+using Microsoft.DurableTask.Samples.OnDemandSandbox.Shared;
+
+namespace Microsoft.DurableTask.Samples.OnDemandSandbox.MainApp;
+
+[SandboxWorkerProfile("remote-hello-profile")]
+internal sealed class RemoteHelloSandboxWorkerProfile : ISandboxWorkerProfile
+{
+    public void Configure(SandboxWorkerProfileOptions options)
+    {
+        options.ContainerImage = GetRequiredEnvironmentVariable("DTS_SANDBOX_CONTAINER_IMAGE");
+        options.ImagePullManagedIdentityClientId = GetRequiredEnvironmentVariable("DTS_SANDBOX_IMAGE_PULL_UMI_CLIENT_ID");
+        options.SchedulerManagedIdentityClientId = GetRequiredEnvironmentVariable("DTS_SANDBOX_SCHEDULER_UMI_CLIENT_ID");
+        options.Cpu = "1000m";
+        options.Memory = "2048Mi";
+        options.MaxConcurrentActivities = 1;
+        AddEnvironmentVariable(options, "SAMPLE_REMOTE_MARKER");
+        AddEnvironmentVariable(options, "SAMPLE_REMOTE_DELAY_MS");
+        options.AddActivity(SandboxActivities.RemoteHelloName, SandboxActivities.RemoteHelloVersion);
+    }
+
+    static void AddEnvironmentVariable(SandboxWorkerProfileOptions options, string name)
+    {
+        string? value = Environment.GetEnvironmentVariable(name);
+        if (!string.IsNullOrWhiteSpace(value))
+        {
+            options.EnvironmentVariables[name] = value;
+        }
+    }
+
+    static string GetRequiredEnvironmentVariable(string name)
+    {
+        string? value = Environment.GetEnvironmentVariable(name);
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            throw new InvalidOperationException($"{name} must be set.");
+        }
+
+        return value.Trim();
+    }
+}
diff --git a/samples/on-demand-sandbox/main-app/appsettings.json b/samples/on-demand-sandbox/main-app/appsettings.json
new file mode 100644
index 00000000..89e35344
--- /dev/null
+++ b/samples/on-demand-sandbox/main-app/appsettings.json
@@ -0,0 +1,6 @@
+{
+  "OnDemandSandboxSample": {
+    "EndpointAddress": "https://<scheduler-endpoint>",
+    "TaskHubName": "<task-hub-name>"
+  }
+}
diff --git a/samples/on-demand-sandbox/main-app/main-app.csproj b/samples/on-demand-sandbox/main-app/main-app.csproj
new file mode 100644
index 00000000..86df35d7
--- /dev/null
+++ b/samples/on-demand-sandbox/main-app/main-app.csproj
@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <AssemblyName>OnDemandSandboxMainApp</AssemblyName>
+    <RootNamespace>Microsoft.DurableTask.Samples.OnDemandSandbox.MainApp</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="$(SrcRoot)Client/AzureManaged/Client.AzureManaged.csproj" />
+    <ProjectReference Include="$(SrcRoot)Client/AzureManaged.Sandboxes/Client.AzureManaged.Sandboxes.csproj" />
+    <ProjectReference Include="$(SrcRoot)Worker/AzureManaged/Worker.AzureManaged.csproj" />
+    <ProjectReference Include="$(SrcRoot)Worker/AzureManaged.Sandboxes/Worker.AzureManaged.Sandboxes.csproj" />
+    <ProjectReference Include="..\shared\shared.csproj" />
+    <ProjectReference Include="$(SrcRoot)Analyzers/Analyzers.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+    <ProjectReference Include="$(SrcRoot)Generators/Generators.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+  </ItemGroup>
+
+</Project>
diff --git a/samples/on-demand-sandbox/remote-worker/Activities.cs b/samples/on-demand-sandbox/remote-worker/Activities.cs
new file mode 100644
index 00000000..5ac7dcf4
--- /dev/null
+++ b/samples/on-demand-sandbox/remote-worker/Activities.cs
@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask;
+using Microsoft.DurableTask.Samples.OnDemandSandbox.Shared;
+
+namespace Microsoft.DurableTask.Samples.OnDemandSandbox.RemoteWorker;
+
+[DurableTask(SandboxActivities.RemoteHelloName, Version = SandboxActivities.RemoteHelloVersion)]
+internal sealed class RemoteHelloActivity : TaskActivity<string, string>
+{
+    public override Task<string> RunAsync(TaskActivityContext context, string input)
+    {
+        return Task.FromResult($"hello remotely from {Environment.MachineName} pid={Environment.ProcessId}: {input}");
+    }
+}
diff --git a/samples/on-demand-sandbox/remote-worker/Containerfile b/samples/on-demand-sandbox/remote-worker/Containerfile
new file mode 100644
index 00000000..99267aa4
--- /dev/null
+++ b/samples/on-demand-sandbox/remote-worker/Containerfile
@@ -0,0 +1,30 @@
+# syntax=docker/dockerfile:1.7
+
+FROM --platform=$TARGETPLATFORM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+ARG TARGETARCH
+
+COPY . /src/durabletask-dotnet
+
+WORKDIR /src/durabletask-dotnet/samples/on-demand-sandbox/remote-worker
+RUN case "$TARGETARCH" in \
+        amd64) runtime_identifier=linux-x64 ;; \
+        arm64) runtime_identifier=linux-arm64 ;; \
+        *) echo "Unsupported target architecture: $TARGETARCH" >&2; exit 1 ;; \
+    esac \
+    && dotnet publish remote-worker.csproj \
+    -c Release \
+    -r "$runtime_identifier" \
+    --self-contained false \
+    -o /app/publish \
+    --configfile /src/durabletask-dotnet/nuget.config \
+    /p:DebugSymbols=false \
+    /p:DebugType=None \
+    && find /app/publish -type f \( -name '*.xml' -o -name '*.pdb' \) -delete
+
+FROM mcr.microsoft.com/dotnet/runtime:10.0 AS runtime
+WORKDIR /app
+
+COPY --from=build /app/publish ./
+
+ENTRYPOINT ["dotnet", "OnDemandSandboxRemoteWorker.dll"]
diff --git a/samples/on-demand-sandbox/remote-worker/Containerfile.dockerignore b/samples/on-demand-sandbox/remote-worker/Containerfile.dockerignore
new file mode 100644
index 00000000..7def663b
--- /dev/null
+++ b/samples/on-demand-sandbox/remote-worker/Containerfile.dockerignore
@@ -0,0 +1,20 @@
+**
+!Directory.Build.props
+!Directory.Build.targets
+!Directory.Packages.props
+!global.json
+!nuget.config
+!stylecop.json
+!eng/
+!eng/**
+!src/
+!src/**
+!samples/
+!samples/Directory.Build.props
+!samples/Directory.Packages.props
+!samples/on-demand-sandbox/
+!samples/on-demand-sandbox/**
+**/bin/
+**/obj/
+**/.git/
+**/.tunnel-url
\ No newline at end of file
diff --git a/samples/on-demand-sandbox/remote-worker/Program.cs b/samples/on-demand-sandbox/remote-worker/Program.cs
new file mode 100644
index 00000000..ef12fa29
--- /dev/null
+++ b/samples/on-demand-sandbox/remote-worker/Program.cs
@@ -0,0 +1,28 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask.Samples.OnDemandSandbox.RemoteWorker;
+using Microsoft.DurableTask.Worker;
+using Microsoft.DurableTask.Worker.AzureManaged;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
+builder.Logging.AddSimpleConsole(options =>
+{
+    options.SingleLine = true;
+    options.UseUtcTimestamp = true;
+    options.TimestampFormat = "yyyy-MM-ddTHH:mm:ss.fffZ ";
+});
+
+builder.Services.AddDurableTaskWorker(workerBuilder =>
+{
+    workerBuilder.AddTasks(tasks =>
+    {
+        tasks.AddActivity<RemoteHelloActivity>();
+    });
+    workerBuilder.UseSandboxWorker();
+});
+
+await builder.Build().RunAsync();
diff --git a/samples/on-demand-sandbox/remote-worker/remote-worker.csproj b/samples/on-demand-sandbox/remote-worker/remote-worker.csproj
new file mode 100644
index 00000000..9a9a6aca
--- /dev/null
+++ b/samples/on-demand-sandbox/remote-worker/remote-worker.csproj
@@ -0,0 +1,22 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <AssemblyName>OnDemandSandboxRemoteWorker</AssemblyName>
+    <RootNamespace>Microsoft.DurableTask.Samples.OnDemandSandbox.RemoteWorker</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="$(SrcRoot)Worker/AzureManaged/Worker.AzureManaged.csproj" />
+    <ProjectReference Include="$(SrcRoot)Worker/AzureManaged.Sandboxes/Worker.AzureManaged.Sandboxes.csproj" />
+    <ProjectReference Include="..\shared\shared.csproj" />
+    <ProjectReference Include="$(SrcRoot)Analyzers/Analyzers.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+  </ItemGroup>
+
+</Project>
diff --git a/samples/on-demand-sandbox/shared/SandboxActivities.cs b/samples/on-demand-sandbox/shared/SandboxActivities.cs
new file mode 100644
index 00000000..a073967f
--- /dev/null
+++ b/samples/on-demand-sandbox/shared/SandboxActivities.cs
@@ -0,0 +1,11 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.DurableTask.Samples.OnDemandSandbox.Shared;
+
+public static class SandboxActivities
+{
+    public const string RemoteHelloName = "RemoteHello";
+
+    public const string RemoteHelloVersion = "";
+}
\ No newline at end of file
diff --git a/samples/on-demand-sandbox/shared/shared.csproj b/samples/on-demand-sandbox/shared/shared.csproj
new file mode 100644
index 00000000..4767e89c
--- /dev/null
+++ b/samples/on-demand-sandbox/shared/shared.csproj
@@ -0,0 +1,10 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <AssemblyName>OnDemandSandboxShared</AssemblyName>
+    <RootNamespace>Microsoft.DurableTask.Samples.OnDemandSandbox.Shared</RootNamespace>
+  </PropertyGroup>
+
+</Project>
diff --git a/src/Client/AzureManaged.Sandboxes/Client.AzureManaged.Sandboxes.csproj b/src/Client/AzureManaged.Sandboxes/Client.AzureManaged.Sandboxes.csproj
new file mode 100644
index 00000000..d25d0412
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/Client.AzureManaged.Sandboxes.csproj
@@ -0,0 +1,28 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <PackageDescription>Azure Managed on-demand sandbox activity management extensions for the Durable Task Framework client.</PackageDescription>
+    <AssemblyName>Microsoft.DurableTask.Client.AzureManaged.Sandboxes</AssemblyName>
+    <EnableStyleCop>true</EnableStyleCop>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Grpc.Net.Client" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\AzureManaged\Client.AzureManaged.csproj" />
+    <ProjectReference Include="..\..\Grpc\Grpc.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <SharedSection Include="AzureManaged.Sandboxes" />
+    <SharedSection Include="Core" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="Microsoft.DurableTask.Client.AzureManaged.Tests" Key="$(StrongNamePublicKey)" />
+  </ItemGroup>
+
+</Project>
diff --git a/src/Client/AzureManaged.Sandboxes/ISandboxWorkerProfile.cs b/src/Client/AzureManaged.Sandboxes/ISandboxWorkerProfile.cs
new file mode 100644
index 00000000..aabd9d9a
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/ISandboxWorkerProfile.cs
@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Configures an on-demand sandbox worker profile workerProfile.
+/// </summary>
+public interface ISandboxWorkerProfile
+{
+    /// <summary>
+    /// Configures the on-demand sandbox worker profile workerProfile options.
+    /// </summary>
+    /// <param name="options">The workerProfile options to configure.</param>
+    void Configure(SandboxWorkerProfileOptions options);
+}
diff --git a/src/Client/AzureManaged.Sandboxes/SandboxActivitiesClient.cs b/src/Client/AzureManaged.Sandboxes/SandboxActivitiesClient.cs
new file mode 100644
index 00000000..0432dc52
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/SandboxActivitiesClient.cs
@@ -0,0 +1,81 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Client for DTS on-demand sandbox activity management operations.
+/// </summary>
+public sealed class SandboxActivitiesClient
+{
+    readonly ISandboxActivitiesTransport transport;
+    readonly SandboxWorkerProfileProvider workerProfileProvider;
+    readonly string taskHub;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SandboxActivitiesClient"/> class.
+    /// </summary>
+    /// <param name="transport">The transport used to call DTS on-demand sandbox management operations.</param>
+    /// <param name="taskHub">The task hub whose workerProfiles should be sent to DTS.</param>
+    /// <param name="workerProfileProvider">The workerProfile provider.</param>
+    internal SandboxActivitiesClient(
+        ISandboxActivitiesTransport transport,
+        string taskHub,
+        SandboxWorkerProfileProvider workerProfileProvider)
+    {
+        this.transport = Check.NotNull(transport);
+        this.workerProfileProvider = Check.NotNull(workerProfileProvider);
+        this.taskHub = string.IsNullOrWhiteSpace(taskHub)
+            ? throw new ArgumentException("Task hub name is required.", nameof(taskHub))
+            : taskHub.Trim();
+    }
+
+    /// <summary>
+    /// Enables on-demand sandbox activities declared by worker profiles for the configured task hub.
+    /// </summary>
+    /// <param name="cancellation">The cancellation token used to cancel the request.</param>
+    /// <returns>A task that completes when DTS accepts all workerProfiles.</returns>
+    public async Task EnableSandboxActivitiesAsync(CancellationToken cancellation = default)
+    {
+        IReadOnlyList<SandboxWorkerProfileOptions> workerProfiles = this.workerProfileProvider.ResolveWorkerProfiles(this.taskHub);
+        foreach (SandboxWorkerProfileOptions options in workerProfiles)
+        {
+            SandboxActivityMetadata.Activity[] activities = SandboxWorkerProfileBuilder.ResolveActivities(options.Activities);
+            if (activities.Length == 0)
+            {
+                continue;
+            }
+
+            Proto.SandboxWorkerProfile workerProfile =
+                SandboxWorkerProfileBuilder.BuildWorkerProfile(options, activities);
+            await this.transport.DeclareSandboxWorkerProfileAsync(
+                    workerProfile,
+                    this.taskHub,
+                    cancellation)
+                .ConfigureAwait(false);
+        }
+    }
+
+    /// <summary>
+    /// Removes an on-demand sandbox activity workerProfile for a worker profile.
+    /// </summary>
+    /// <param name="workerProfileId">The worker profile ID whose workerProfile should be removed.</param>
+    /// <param name="cancellation">The cancellation token used to cancel the request.</param>
+    /// <returns>A task that completes when DTS removes the workerProfile.</returns>
+    public Task RemoveSandboxWorkerProfileAsync(
+        string workerProfileId,
+        CancellationToken cancellation = default)
+    {
+        string normalizedWorkerProfileId = string.IsNullOrWhiteSpace(workerProfileId)
+            ? throw new ArgumentException("Worker profile ID is required.", nameof(workerProfileId))
+            : workerProfileId.Trim();
+
+        return this.transport.RemoveSandboxWorkerProfileAsync(
+            normalizedWorkerProfileId,
+            this.taskHub,
+            cancellation);
+    }
+}
diff --git a/src/Client/AzureManaged.Sandboxes/SandboxActivitiesClientServiceCollectionExtensions.cs b/src/Client/AzureManaged.Sandboxes/SandboxActivitiesClientServiceCollectionExtensions.cs
new file mode 100644
index 00000000..138e37f1
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/SandboxActivitiesClientServiceCollectionExtensions.cs
@@ -0,0 +1,74 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Grpc.Net.Client;
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Microsoft.DurableTask.Client.Grpc;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Extensions.Options;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Extension methods for registering DTS on-demand sandbox activity management clients.
+/// </summary>
+public static class SandboxActivitiesClientServiceCollectionExtensions
+{
+    /// <summary>
+    /// Adds a DTS on-demand sandbox activity management client using the default Durable Task client configuration.
+    /// </summary>
+    /// <param name="services">The service collection to configure.</param>
+    /// <returns>The original service collection, for call chaining.</returns>
+    public static IServiceCollection AddDurableTaskSchedulerSandboxActivitiesClient(this IServiceCollection services)
+        => AddDurableTaskSchedulerSandboxActivitiesClient(services, Options.DefaultName);
+
+    /// <summary>
+    /// Adds a DTS on-demand sandbox activity management client using a named Durable Task client configuration.
+    /// </summary>
+    /// <param name="services">The service collection to configure.</param>
+    /// <param name="clientName">The Durable Task client name whose scheduler channel should be reused.</param>
+    /// <returns>The original service collection, for call chaining.</returns>
+    public static IServiceCollection AddDurableTaskSchedulerSandboxActivitiesClient(
+        this IServiceCollection services,
+        string clientName)
+    {
+        ArgumentNullException.ThrowIfNull(services);
+        ArgumentNullException.ThrowIfNull(clientName);
+
+        services.TryAddSingleton<SandboxWorkerProfileProvider>();
+
+        services.AddSingleton(provider =>
+        {
+            DurableTaskSchedulerClientOptions schedulerOptions = provider
+                .GetRequiredService<IOptionsMonitor<DurableTaskSchedulerClientOptions>>()
+                .Get(clientName);
+            GrpcDurableTaskClientOptions options = provider
+                .GetRequiredService<IOptionsMonitor<GrpcDurableTaskClientOptions>>()
+                .Get(clientName);
+            SandboxWorkerProfileProvider workerProfileProvider = provider.GetRequiredService<SandboxWorkerProfileProvider>();
+
+            if (options.CallInvoker is { } callInvoker)
+            {
+                return new SandboxActivitiesClient(
+                    new SandboxActivitiesGrpcTransport(new Proto.SandboxActivities.SandboxActivitiesClient(callInvoker)),
+                    schedulerOptions.TaskHubName,
+                    workerProfileProvider);
+            }
+
+            if (options.Channel is GrpcChannel channel)
+            {
+                return new SandboxActivitiesClient(
+                    new SandboxActivitiesGrpcTransport(
+                        new Proto.SandboxActivities.SandboxActivitiesClient(channel.CreateCallInvoker()),
+                        attachTaskHubMetadata: false),
+                    schedulerOptions.TaskHubName,
+                    workerProfileProvider);
+            }
+
+            throw new InvalidOperationException("DTS on-demand sandbox activity management requires a configured Durable Task Scheduler client.");
+        });
+        return services;
+    }
+}
diff --git a/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileAttribute.cs b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileAttribute.cs
new file mode 100644
index 00000000..30844afa
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileAttribute.cs
@@ -0,0 +1,27 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Declares an on-demand sandbox worker profile that DTS can start for activities declared by the profile.
+/// </summary>
+[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
+public sealed class SandboxWorkerProfileAttribute : Attribute
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SandboxWorkerProfileAttribute"/> class.
+    /// </summary>
+    /// <param name="workerProfileId">The worker profile ID.</param>
+    public SandboxWorkerProfileAttribute(string workerProfileId)
+    {
+        this.WorkerProfileId = string.IsNullOrWhiteSpace(workerProfileId)
+            ? throw new ArgumentException("On-demand sandbox worker profile ID cannot be empty.", nameof(workerProfileId))
+            : workerProfileId.Trim();
+    }
+
+    /// <summary>
+    /// Gets the worker profile ID.
+    /// </summary>
+    public string WorkerProfileId { get; }
+}
diff --git a/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileBuilder.cs b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileBuilder.cs
new file mode 100644
index 00000000..465d75b8
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileBuilder.cs
@@ -0,0 +1,217 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Globalization;
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Builds and normalizes on-demand sandbox activity workerProfile protocol messages.
+/// </summary>
+static class SandboxWorkerProfileBuilder
+{
+    /// <summary>
+    /// Resolves configured activity identities for on-demand sandbox activity execution.
+    /// </summary>
+    /// <param name="configuredActivities">The configured activity identities.</param>
+    /// <returns>The normalized activity identities.</returns>
+    public static SandboxActivityMetadata.Activity[] ResolveActivities(IEnumerable<SandboxActivityMetadata.Activity> configuredActivities)
+    {
+        return SandboxActivityMetadata.ResolveActivities(configuredActivities);
+    }
+
+    /// <summary>
+    /// Builds an on-demand sandbox activity workerProfile protocol message.
+    /// </summary>
+    /// <param name="options">The on-demand sandbox options.</param>
+    /// <param name="activities">The activity identities included in the workerProfile.</param>
+    /// <returns>The workerProfile protocol message.</returns>
+    public static Proto.SandboxWorkerProfile BuildWorkerProfile(
+        SandboxWorkerProfileOptions options,
+        IReadOnlyCollection<SandboxActivityMetadata.Activity> activities)
+    {
+        Check.NotNull(options);
+        Check.NotNull(activities);
+
+        _ = NormalizeRequired(options.TaskHub, "On-demand sandbox activity workerProfile requires a task hub name.");
+        if (activities.Count == 0)
+        {
+            throw new InvalidOperationException("On-demand sandbox activity workerProfile requires at least one activity.");
+        }
+
+        string workerProfileId = NormalizeWorkerProfileId(
+            options.WorkerProfileId,
+            "On-demand sandbox activity workerProfile requires a worker profile ID.");
+        if (options.MaxConcurrentActivities <= 0)
+        {
+            throw new InvalidOperationException("On-demand sandbox activity max concurrent activities must be greater than zero.");
+        }
+
+        string schedulerManagedIdentityClientId = NormalizeRequired(
+            options.SchedulerManagedIdentityClientId ?? string.Empty,
+            "On-demand sandbox activity workerProfile requires the managed identity client ID workers use to connect to the DTS scheduler.");
+
+        Proto.SandboxWorkerProfile workerProfile = new()
+        {
+            WorkerProfileId = workerProfileId,
+            Image = BuildImage(options),
+            Resources = BuildResources(options),
+            MaxConcurrentActivities = options.MaxConcurrentActivities,
+            SchedulerManagedIdentityClientId = schedulerManagedIdentityClientId,
+        };
+
+        workerProfile.Activities.AddRange(activities.Select(ToProtoActivity));
+        workerProfile.EnvironmentVariables.Add(options.EnvironmentVariables);
+        workerProfile.Image.Entrypoint.AddRange(NormalizeOptionalStrings(options.Entrypoint));
+        workerProfile.Image.Cmd.AddRange(NormalizeOptionalStrings(options.Cmd));
+        return workerProfile;
+    }
+
+    /// <summary>
+    /// Normalizes a worker profile ID and throws with the supplied message if it is missing.
+    /// </summary>
+    /// <param name="value">The worker profile ID value.</param>
+    /// <param name="errorMessage">The error message to use when the value is missing.</param>
+    /// <returns>The normalized worker profile ID.</returns>
+    internal static string NormalizeWorkerProfileId(string value, string errorMessage)
+    {
+        return SandboxActivityMetadata.NormalizeRequired(value, errorMessage);
+    }
+
+    /// <summary>
+    /// Normalizes a required string and throws with the supplied message if it is missing.
+    /// </summary>
+    /// <param name="value">The value.</param>
+    /// <param name="errorMessage">The error message to use when the value is missing.</param>
+    /// <returns>The normalized value.</returns>
+    internal static string NormalizeRequired(string value, string errorMessage)
+    {
+        return SandboxActivityMetadata.NormalizeRequired(value, errorMessage);
+    }
+
+    static Proto.SandboxActivityImage BuildImage(SandboxWorkerProfileOptions options)
+    {
+        string imageRef = NormalizeRequired(
+            options.ContainerImage ?? string.Empty,
+            "On-demand sandbox activity image metadata requires a container image reference like 'myregistry.azurecr.io/workers/hello:1.0' or 'myregistry.azurecr.io/workers/hello@sha256:...'.");
+
+        Proto.SandboxActivityImage image = new()
+        {
+            ImageRef = imageRef,
+            ManagedIdentityClientId = NormalizeRequired(
+                options.ImagePullManagedIdentityClientId ?? string.Empty,
+                "On-demand sandbox activity workerProfile requires the managed identity client ID ADC uses to pull the worker image."),
+        };
+
+        return image;
+    }
+
+    static Proto.SandboxActivity ToProtoActivity(SandboxActivityMetadata.Activity activity) => new()
+    {
+        Name = activity.Name,
+        Version = activity.Version ?? string.Empty,
+    };
+
+    static Proto.SandboxActivityResources BuildResources(SandboxWorkerProfileOptions options)
+    {
+        string cpu = NormalizeCpu(options.Cpu);
+        string memory = NormalizeMemory(options.Memory);
+
+        return new Proto.SandboxActivityResources
+        {
+            Cpu = cpu,
+            Memory = memory,
+        };
+    }
+
+    static string NormalizeCpu(string value)
+    {
+        string normalized = NormalizeRequired(value, "On-demand sandbox activity workerProfile requires CPU resources.");
+        if (TryParseCpuMillicores(normalized) is not { } milliCpu || milliCpu <= 0)
+        {
+            throw new InvalidOperationException(
+                "On-demand sandbox activity CPU resources must be a positive Kubernetes-style CPU quantity. " +
+                "Use formats like '500m', '2', or '0.5'.");
+        }
+
+        return normalized;
+    }
+
+    static string NormalizeMemory(string value)
+    {
+        string normalized = NormalizeRequired(value, "On-demand sandbox activity workerProfile requires memory resources.");
+        if (TryParseMemoryMiB(normalized) is not { } memoryMiB || memoryMiB <= 0)
+        {
+            throw new InvalidOperationException(
+                "On-demand sandbox activity memory resources must be a positive Kubernetes-style memory quantity. " +
+                "Use formats like '256Mi', '1Gi', or '2048'.");
+        }
+
+        return normalized;
+    }
+
+    static long? TryParseCpuMillicores(string value)
+    {
+        if (value.EndsWith('m') || value.EndsWith('M'))
+        {
+            return long.TryParse(
+                value[..^1],
+                NumberStyles.Integer,
+                CultureInfo.InvariantCulture,
+                out long milliCpu)
+                ? milliCpu
+                : null;
+        }
+
+        return decimal.TryParse(
+            value,
+            NumberStyles.Number,
+            CultureInfo.InvariantCulture,
+            out decimal cores)
+            ? (long)(cores * 1000)
+            : null;
+    }
+
+    static long? TryParseMemoryMiB(string value)
+    {
+        if (value.EndsWith("Gi", StringComparison.OrdinalIgnoreCase))
+        {
+            return decimal.TryParse(
+                value[..^2],
+                NumberStyles.Number,
+                CultureInfo.InvariantCulture,
+                out decimal gib)
+                ? (long)(gib * 1024)
+                : null;
+        }
+
+        if (value.EndsWith("Mi", StringComparison.OrdinalIgnoreCase))
+        {
+            return decimal.TryParse(
+                value[..^2],
+                NumberStyles.Number,
+                CultureInfo.InvariantCulture,
+                out decimal mib)
+                ? (long)mib
+                : null;
+        }
+
+        return decimal.TryParse(
+            value,
+            NumberStyles.Number,
+            CultureInfo.InvariantCulture,
+            out decimal parsed)
+            ? (long)parsed
+            : null;
+    }
+
+    static string[] NormalizeOptionalStrings(IEnumerable<string> values)
+    {
+        return values
+            .Where(static value => !string.IsNullOrWhiteSpace(value))
+            .Select(static value => value.Trim())
+            .ToArray();
+    }
+}
diff --git a/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileOptions.cs b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileOptions.cs
new file mode 100644
index 00000000..c5ecac6f
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileOptions.cs
@@ -0,0 +1,111 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Reflection;
+using Microsoft.DurableTask;
+using Microsoft.DurableTask.AzureManaged.Internal;
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Options for declaring on-demand sandbox activities and the worker image DTS should start for them.
+/// </summary>
+public sealed class SandboxWorkerProfileOptions
+{
+    /// <summary>
+    /// Gets or sets the task hub where the on-demand sandbox activity workerProfile is stored.
+    /// </summary>
+    public string TaskHub { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the worker profile ID used for the on-demand sandbox activity pool.
+    /// This value must be set explicitly.
+    /// </summary>
+    public string WorkerProfileId { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the full OCI container image reference for on-demand sandbox workers.
+    /// Examples: <c>myregistry.azurecr.io/workers/hello:1.0</c> or
+    /// <c>myregistry.azurecr.io/workers/hello@sha256:0123456789abcdef...</c>.
+    /// </summary>
+    public string? ContainerImage { get; set; }
+
+    /// <summary>
+    /// Gets or sets the user-assigned managed identity client ID ADC uses to pull the on-demand sandbox worker image.
+    /// </summary>
+    public string? ImagePullManagedIdentityClientId { get; set; }
+
+    /// <summary>
+    /// Gets or sets the user-assigned managed identity client ID workers use to authenticate to the DTS scheduler.
+    /// </summary>
+    public string? SchedulerManagedIdentityClientId { get; set; }
+
+    /// <summary>
+    /// Gets or sets the CPU quantity declared for each sandbox. Supported formats include <c>500m</c>, <c>2</c>, and <c>0.5</c>.
+    /// </summary>
+    public string Cpu { get; set; } = "1000m";
+
+    /// <summary>
+    /// Gets or sets the memory quantity declared for each sandbox. Supported formats include <c>256Mi</c>, <c>1Gi</c>, and <c>2048</c>.
+    /// </summary>
+    public string Memory { get; set; } = "2048Mi";
+
+    /// <summary>
+    /// Gets custom environment variables DTS should provide to on-demand sandbox workers created from this workerProfile.
+    /// DTS-owned runtime variables such as <c>DTS_ENDPOINT</c>, <c>DTS_TASK_HUB</c>, and
+    /// <c>DTS_SANDBOX_ID</c> are injected by the backend and should not be supplied here.
+    /// </summary>
+    public IDictionary<string, string> EnvironmentVariables { get; } = new Dictionary<string, string>(StringComparer.Ordinal);
+
+    /// <summary>
+    /// Gets the sandbox entrypoint declared for on-demand sandbox workers.
+    /// </summary>
+    public IList<string> Entrypoint { get; } = new List<string>();
+
+    /// <summary>
+    /// Gets the sandbox command declared for on-demand sandbox workers.
+    /// </summary>
+    public IList<string> Cmd { get; } = new List<string>();
+
+    /// <summary>
+    /// Gets or sets the maximum number of concurrent activities expected from each on-demand sandbox worker.
+    /// </summary>
+    public int MaxConcurrentActivities { get; set; } = 100;
+
+    /// <summary>
+    /// Gets the on-demand sandbox activity identities to declare. Remote workers report their
+    /// registered activities separately when they connect.
+    /// </summary>
+    internal IList<SandboxActivityMetadata.Activity> Activities { get; } = new List<SandboxActivityMetadata.Activity>();
+
+    /// <summary>
+    /// Adds an activity name and version to the on-demand sandbox worker profile workerProfile.
+    /// </summary>
+    /// <param name="activityName">The activity name.</param>
+    /// <param name="version">The activity version, or <see langword="null" /> for unversioned/wildcard activity execution.</param>
+    public void AddActivity(string activityName, string? version)
+    {
+        if (string.IsNullOrWhiteSpace(activityName))
+        {
+            throw new ArgumentException("On-demand sandbox activity name cannot be empty.", nameof(activityName));
+        }
+
+        this.Activities.Add(new SandboxActivityMetadata.Activity(
+            activityName.Trim(),
+            SandboxActivityMetadata.NormalizeOptional(version)));
+    }
+
+    /// <summary>
+    /// Adds an activity to the on-demand sandbox worker profile workerProfile using its durable task name.
+    /// </summary>
+    /// <typeparam name="TActivity">The activity type.</typeparam>
+    public void AddActivity<TActivity>() where TActivity : class, ITaskActivity
+    {
+        Type activityType = typeof(TActivity);
+        DurableTaskAttribute? attribute = activityType.GetCustomAttribute<DurableTaskAttribute>();
+        string? activityName = attribute?.Name.Name;
+        this.AddActivity(
+            string.IsNullOrWhiteSpace(activityName) ? activityType.Name : activityName,
+            attribute?.Version);
+    }
+}
diff --git a/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileProvider.cs b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileProvider.cs
new file mode 100644
index 00000000..10cbb0f5
--- /dev/null
+++ b/src/Client/AzureManaged.Sandboxes/SandboxWorkerProfileProvider.cs
@@ -0,0 +1,154 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Reflection;
+using System.Threading;
+using Microsoft.DurableTask.AzureManaged.Internal;
+
+namespace Microsoft.DurableTask.Client.AzureManaged;
+
+/// <summary>
+/// Provides on-demand sandbox activity workerProfiles from worker profile configuration.
+/// </summary>
+sealed class SandboxWorkerProfileProvider
+{
+    readonly Lazy<ProfileMetadata[]> profiles;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SandboxWorkerProfileProvider"/> class.
+    /// </summary>
+    public SandboxWorkerProfileProvider()
+    {
+        this.profiles = new Lazy<ProfileMetadata[]>(ScanProfiles, LazyThreadSafetyMode.ExecutionAndPublication);
+    }
+
+    /// <summary>
+    /// Resolves on-demand sandbox workerProfiles for the specified task hub.
+    /// </summary>
+    /// <param name="taskHub">The task hub name.</param>
+    /// <returns>The resolved on-demand sandbox workerProfile options.</returns>
+    public IReadOnlyList<SandboxWorkerProfileOptions> ResolveWorkerProfiles(string taskHub)
+    {
+        string normalizedTaskHub = string.IsNullOrWhiteSpace(taskHub)
+            ? throw new InvalidOperationException("On-demand sandbox activity workerProfile requires a task hub name.")
+            : taskHub.Trim();
+
+        SandboxWorkerProfileOptions[] workerProfiles = this.profiles.Value
+            .Select(profile => CreateOptions(normalizedTaskHub, profile))
+            .Where(static options => SandboxWorkerProfileBuilder.ResolveActivities(options.Activities).Length > 0)
+            .ToArray();
+
+        ValidateActivityOwnership(workerProfiles);
+        return workerProfiles;
+    }
+
+    /// <summary>
+    /// Validates that a profile type can configure on-demand sandbox workerProfiles.
+    /// </summary>
+    /// <param name="profileType">The profile type.</param>
+    internal static void ValidateProfileType(Type profileType)
+    {
+        if (!typeof(ISandboxWorkerProfile).IsAssignableFrom(profileType))
+        {
+            throw new InvalidOperationException(
+                $"On-demand sandbox worker profile '{profileType.FullName}' must implement {nameof(ISandboxWorkerProfile)}.");
+        }
+    }
+
+    static ProfileMetadata[] ScanProfiles()
+    {
+        Dictionary<string, ProfileMetadata> profiles = new(StringComparer.Ordinal);
+        foreach (Type type in GetCandidateTypes())
+        {
+            if (type.GetCustomAttribute<SandboxWorkerProfileAttribute>() is not { } profile)
+            {
+                continue;
+            }
+
+            ValidateProfileType(type);
+
+            if (profiles.ContainsKey(profile.WorkerProfileId))
+            {
+                throw new InvalidOperationException($"On-demand sandbox worker profile '{profile.WorkerProfileId}' is declared more than once.");
+            }
+
+            profiles.Add(profile.WorkerProfileId, new ProfileMetadata(profile.WorkerProfileId, type));
+        }
+
+        return profiles.Values.ToArray();
+    }
+
+    static SandboxWorkerProfileOptions CreateOptions(
+        string taskHub,
+        ProfileMetadata profile)
+    {
+        SandboxWorkerProfileOptions options = new()
+        {
+            TaskHub = taskHub,
+            WorkerProfileId = profile.WorkerProfileId,
+        };
+
+        ConfigureProfile(profile.Type, options);
+        return options;
+    }
+
+    static void ConfigureProfile(Type profileType, SandboxWorkerProfileOptions options)
+    {
+        ValidateProfileType(profileType);
+
+        object? instance = Activator.CreateInstance(profileType, nonPublic: true)
+            ?? throw new InvalidOperationException($"On-demand sandbox worker profile '{profileType.FullName}' could not be created.");
+        ((ISandboxWorkerProfile)instance).Configure(options);
+    }
+
+    static IEnumerable<Type> GetCandidateTypes()
+    {
+        foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies())
+        {
+            if (assembly.IsDynamic)
+            {
+                continue;
+            }
+
+            Type[] types;
+            try
+            {
+                types = assembly.GetTypes();
+            }
+            catch (ReflectionTypeLoadException ex)
+            {
+                types = ex.Types.Where(static type => type is not null).Cast<Type>().ToArray();
+            }
+
+            foreach (Type type in types)
+            {
+                yield return type;
+            }
+        }
+    }
+
+    static void ValidateActivityOwnership(IEnumerable<SandboxWorkerProfileOptions> workerProfiles)
+    {
+        List<(SandboxActivityMetadata.Activity Activity, string WorkerProfileId)> activityOwners = [];
+        foreach (SandboxWorkerProfileOptions workerProfile in workerProfiles)
+        {
+            foreach (SandboxActivityMetadata.Activity activity in SandboxWorkerProfileBuilder.ResolveActivities(workerProfile.Activities))
+            {
+                string? existingProfile = activityOwners
+                    .Where(owner => SandboxActivityMetadata.ActivitiesOverlap(owner.Activity, activity))
+                    .Select(static owner => owner.WorkerProfileId)
+                    .FirstOrDefault(profileId => !string.Equals(profileId, workerProfile.WorkerProfileId, StringComparison.Ordinal));
+                if (existingProfile is not null)
+                {
+                    throw new InvalidOperationException($"On-demand sandbox activity '{SandboxActivityMetadata.FormatActivity(activity)}' is assigned to both worker profile '{existingProfile}' and '{workerProfile.WorkerProfileId}'.");
+                }
+
+                activityOwners.Add((activity, workerProfile.WorkerProfileId));
+            }
+        }
+    }
+
+    sealed record ProfileMetadata(
+        string WorkerProfileId,
+        Type Type);
+}
diff --git a/src/Grpc/orchestrator_service.proto b/src/Grpc/orchestrator_service.proto
index 3d7c8eb4..3d9194ac 100644
--- a/src/Grpc/orchestrator_service.proto
+++ b/src/Grpc/orchestrator_service.proto
@@ -370,12 +370,14 @@ message OrchestratorResponse {
     // Whether or not a history is required to complete the original OrchestratorRequest and none was provided.
     bool requiresHistory = 7;
 
+    /* Chunking logic has since been deprecated and fields related to it are marked as such */
+
     // True if this is a partial (chunked) completion. The backend must keep the work item open until the final chunk (isPartial=false).
-    bool isPartial = 8;
+    bool isPartial = 8 [deprecated=true];
 
     // Zero-based position of the current chunk within a chunked completion sequence.
     // This field is omitted for non-chunked completions.
-    google.protobuf.Int32Value chunkIndex = 9;
+    google.protobuf.Int32Value chunkIndex = 9 [deprecated=true];
 }
 
 message CreateInstanceRequest {
diff --git a/src/Grpc/refresh-protos.ps1 b/src/Grpc/refresh-protos.ps1
index a91393a4..8458d10c 100644
--- a/src/Grpc/refresh-protos.ps1
+++ b/src/Grpc/refresh-protos.ps1
@@ -17,14 +17,23 @@ $commitDetails = Invoke-RestMethod -Uri "https://api.github.com/repos/microsoft/
 $commitId = $commitDetails.sha
 
 # These are the proto files we need to download from the durabletask-protobuf repository.
-$protoFileNames = @(
-    "orchestrator_service.proto"
+$protoFiles = @(
+    @{
+        SourcePath = "orchestrator_service.proto"
+        OutputFileName = "orchestrator_service.proto"
+    },
+    @{
+        SourcePath = "durable-task-scheduler/sandbox_service.proto"
+        OutputFileName = "sandbox_service.proto"
+    }
 )
 
 # Download each proto file to the local directory using the above commit ID
-foreach ($protoFileName in $protoFileNames) {
-    $url = "https://raw.githubusercontent.com/microsoft/durabletask-protobuf/$commitId/protos/$protoFileName"
-    $outputFile = "$PSScriptRoot\$protoFileName"
+foreach ($protoFile in $protoFiles) {
+    $sourcePath = $protoFile.SourcePath
+    $outputFileName = $protoFile.OutputFileName
+    $url = "https://raw.githubusercontent.com/microsoft/durabletask-protobuf/$commitId/protos/$sourcePath"
+    $outputFile = "$PSScriptRoot\$outputFileName"
 
     try {
         Invoke-WebRequest -Uri $url -OutFile $outputFile        
@@ -46,10 +55,11 @@ Add-Content `
     -Path $versionsFile `
     -Value "# The following files were downloaded from branch $branch at $(Get-Date -Format "yyyy-MM-dd HH:mm:ss" -AsUTC) UTC"
 
-foreach ($protoFileName in $protoFileNames) {
+foreach ($protoFile in $protoFiles) {
+    $sourcePath = $protoFile.SourcePath
     Add-Content `
         -Path $versionsFile `
-        -Value "https://raw.githubusercontent.com/microsoft/durabletask-protobuf/$commitId/protos/$protoFileName"
+        -Value "https://raw.githubusercontent.com/microsoft/durabletask-protobuf/$commitId/protos/$sourcePath"
 }
 
 Write-Host "Wrote commit ID $commitId to $versionsFile" -ForegroundColor Green
diff --git a/src/Grpc/sandbox_service.proto b/src/Grpc/sandbox_service.proto
new file mode 100644
index 00000000..1d52ed7d
--- /dev/null
+++ b/src/Grpc/sandbox_service.proto
@@ -0,0 +1,101 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+syntax = "proto3";
+
+package microsoft.durabletask.sandboxes;
+
+option csharp_namespace = "Microsoft.DurableTask.Protobuf.Sandboxes";
+
+service SandboxActivities {
+  // Opens a live sandbox activity worker session. The first message
+  // must be a start message with static worker metadata. Heartbeats carry
+  // dynamic state only. Closing the stream deregisters the worker.
+  rpc ConnectSandboxActivityWorker(stream SandboxActivityWorkerMessage) returns (SandboxActivityWorkerSessionResult);
+
+  // Creates or updates a sandbox worker profile before any live worker stream exists.
+  // This is a configuration contract and does not advertise active worker
+  // capacity.
+  rpc DeclareSandboxWorkerProfile(SandboxWorkerProfile) returns (DeclareSandboxWorkerProfileResult);
+
+  // Removes a sandbox worker profile so the backend stops
+  // waking new sandbox workers for the specified worker profile. Existing
+  // workers are not terminated by this RPC.
+  rpc RemoveSandboxWorkerProfile(RemoveSandboxWorkerProfileRequest) returns (RemoveSandboxWorkerProfileResult);
+}
+
+message SandboxActivityWorkerMessage {
+  oneof message {
+    SandboxActivityWorkerStart start = 1;
+    SandboxActivityWorkerHeartbeat heartbeat = 2;
+  }
+}
+
+message SandboxActivityWorkerStart {
+  string task_hub = 1;
+  int32 max_activities_count = 2;
+  // Sandbox provider the worker is running in. UNSPECIFIED = legacy
+  // (pre-provider-aware) workers.
+  SandboxProviderKind sandbox_provider = 3;
+  // DTS-generated sandbox identifier injected as DTS_SANDBOX_ID. This is not
+  // the ADC provider sandbox resource id.
+  string dts_sandbox_identifier = 4;
+  // Caller-defined profile/catalog ID shared by worker profiles and live worker registration.
+  string worker_profile_id = 5;
+  // Activity handlers registered by the worker process. DTS validates this
+  // matches the worker profile before advertising worker capacity.
+  repeated SandboxActivity activities = 6;
+}
+
+message SandboxActivityWorkerHeartbeat {
+  int32 active_activities_count = 1;
+}
+
+message SandboxActivityWorkerSessionResult {
+  string message = 1;
+}
+
+message SandboxWorkerProfile {
+  // Caller-defined profile/catalog ID shared by worker profiles and live worker registration.
+  string worker_profile_id = 1;
+  repeated SandboxActivity activities = 2;
+  SandboxActivityImage image = 3;
+  map<string, string> environment_variables = 4;
+  int32 max_concurrent_activities = 5;
+  SandboxActivityResources resources = 6;
+  string scheduler_managed_identity_client_id = 7;
+}
+
+message SandboxActivity {
+  string name = 1;
+  string version = 2;
+}
+
+message SandboxActivityImage {
+  string image_ref = 1;
+  string managed_identity_client_id = 2;
+  repeated string entrypoint = 3;
+  repeated string cmd = 4;
+}
+
+message SandboxActivityResources {
+  string cpu = 1;
+  string memory = 2;
+}
+
+message DeclareSandboxWorkerProfileResult {
+}
+
+message RemoveSandboxWorkerProfileRequest {
+  string worker_profile_id = 1;
+}
+
+message RemoveSandboxWorkerProfileResult {
+}
+
+// Sandbox provider executing the activity worker.
+enum SandboxProviderKind {
+  SANDBOX_PROVIDER_KIND_UNSPECIFIED = 0;
+  SANDBOX_PROVIDER_KIND_ACA_SESSION_POOL = 1;
+  SANDBOX_PROVIDER_KIND_SANDBOX = 2;
+}
diff --git a/src/Grpc/versions.txt b/src/Grpc/versions.txt
index b781a390..8ce5f427 100644
--- a/src/Grpc/versions.txt
+++ b/src/Grpc/versions.txt
@@ -1,2 +1,3 @@
-# The following files were downloaded from branch main at 2026-04-06 16:10:08 UTC
-https://raw.githubusercontent.com/microsoft/durabletask-protobuf/bcf5af6a22caa70601bfc909918ba5937484279f/protos/orchestrator_service.proto
+# The following files were downloaded from branch main at 2026-06-15 21:35:22 UTC
+https://raw.githubusercontent.com/microsoft/durabletask-protobuf/67a2f1d3b9ea8a210eb86addb636a5d8a6484dbc/protos/orchestrator_service.proto
+https://raw.githubusercontent.com/microsoft/durabletask-protobuf/67a2f1d3b9ea8a210eb86addb636a5d8a6484dbc/protos/durable-task-scheduler/sandbox_service.proto
diff --git a/src/Shared/AzureManaged.Sandboxes/SandboxActivitiesGrpcTransport.cs b/src/Shared/AzureManaged.Sandboxes/SandboxActivitiesGrpcTransport.cs
new file mode 100644
index 00000000..33246284
--- /dev/null
+++ b/src/Shared/AzureManaged.Sandboxes/SandboxActivitiesGrpcTransport.cs
@@ -0,0 +1,178 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Grpc.Core;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.AzureManaged.Internal;
+
+/// <summary>
+/// Transport abstraction for the on-demand sandbox activities gRPC service.
+/// </summary>
+interface ISandboxActivitiesTransport
+{
+    /// <summary>
+    /// Declares on-demand sandbox activities to DTS.
+    /// </summary>
+    /// <param name="workerProfile">The workerProfile message.</param>
+    /// <param name="taskHub">The task hub that owns the workerProfile.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>The workerProfile result.</returns>
+    Task<Proto.DeclareSandboxWorkerProfileResult> DeclareSandboxWorkerProfileAsync(
+        Proto.SandboxWorkerProfile workerProfile,
+        string taskHub,
+        CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Removes an on-demand sandbox activity workerProfile from DTS.
+    /// </summary>
+    /// <param name="workerProfileId">The worker profile ID whose workerProfile should be removed.</param>
+    /// <param name="taskHub">The task hub that owns the workerProfile.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>The removal result.</returns>
+    Task<Proto.RemoveSandboxWorkerProfileResult> RemoveSandboxWorkerProfileAsync(
+        string workerProfileId,
+        string taskHub,
+        CancellationToken cancellationToken);
+
+    /// <summary>
+    /// Opens an on-demand sandbox activity worker registration session.
+    /// </summary>
+    /// <param name="taskHub">The task hub that owns the worker session.</param>
+    /// <param name="cancellationToken">The cancellation token.</param>
+    /// <returns>The worker registration session.</returns>
+    ISandboxActivityWorkerSession OpenSandboxActivityWorkerSession(string taskHub, CancellationToken cancellationToken);
+}
+
+/// <summary>
+/// Client-streaming session used by an on-demand sandbox activity worker registration.
+/// </summary>
+interface ISandboxActivityWorkerSession : IAsyncDisposable
+{
+    /// <summary>
+    /// Writes a worker registration message to the stream.
+    /// </summary>
+    /// <param name="message">The message to write.</param>
+    /// <returns>A task that completes when the message is written.</returns>
+    Task WriteMessageAsync(Proto.SandboxActivityWorkerMessage message);
+
+    /// <summary>
+    /// Waits for the server to complete the worker registration session.
+    /// </summary>
+    /// <returns>The worker session result.</returns>
+    Task<Proto.SandboxActivityWorkerSessionResult> WaitForCompletionAsync();
+
+    /// <summary>
+    /// Completes the request stream and waits for the server response.
+    /// </summary>
+    /// <returns>A task that completes when the server response is observed.</returns>
+    Task CompleteAsync();
+}
+
+/// <summary>
+/// gRPC-backed implementation of <see cref="ISandboxActivitiesTransport"/>.
+/// </summary>
+sealed class SandboxActivitiesGrpcTransport : ISandboxActivitiesTransport
+{
+    readonly Proto.SandboxActivities.SandboxActivitiesClient client;
+    readonly bool attachTaskHubMetadata;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SandboxActivitiesGrpcTransport"/> class.
+    /// </summary>
+    /// <param name="client">The generated on-demand sandbox activities gRPC client.</param>
+    /// <param name="attachTaskHubMetadata">True to add per-call task hub metadata when the underlying channel does not already do so.</param>
+    public SandboxActivitiesGrpcTransport(
+        Proto.SandboxActivities.SandboxActivitiesClient client,
+        bool attachTaskHubMetadata = true)
+    {
+        this.client = Check.NotNull(client);
+        this.attachTaskHubMetadata = attachTaskHubMetadata;
+    }
+
+    /// <inheritdoc/>
+    public async Task<Proto.DeclareSandboxWorkerProfileResult> DeclareSandboxWorkerProfileAsync(
+        Proto.SandboxWorkerProfile workerProfile,
+        string taskHub,
+        CancellationToken cancellationToken)
+    {
+        using AsyncUnaryCall<Proto.DeclareSandboxWorkerProfileResult> call =
+            this.client.DeclareSandboxWorkerProfileAsync(
+                workerProfile,
+                headers: this.CreateTaskHubHeaders(taskHub),
+                cancellationToken: cancellationToken);
+        return await call.ResponseAsync.ConfigureAwait(false);
+    }
+
+    /// <inheritdoc/>
+    public async Task<Proto.RemoveSandboxWorkerProfileResult> RemoveSandboxWorkerProfileAsync(
+        string workerProfileId,
+        string taskHub,
+        CancellationToken cancellationToken)
+    {
+        Proto.RemoveSandboxWorkerProfileRequest request = new()
+        {
+            WorkerProfileId = workerProfileId,
+        };
+
+        using AsyncUnaryCall<Proto.RemoveSandboxWorkerProfileResult> call =
+            this.client.RemoveSandboxWorkerProfileAsync(
+                request,
+                headers: this.CreateTaskHubHeaders(taskHub),
+                cancellationToken: cancellationToken);
+        return await call.ResponseAsync.ConfigureAwait(false);
+    }
+
+    /// <inheritdoc/>
+    public ISandboxActivityWorkerSession OpenSandboxActivityWorkerSession(string taskHub, CancellationToken cancellationToken)
+    {
+        AsyncClientStreamingCall<Proto.SandboxActivityWorkerMessage, Proto.SandboxActivityWorkerSessionResult> call =
+            this.client.ConnectSandboxActivityWorker(
+                headers: this.CreateTaskHubHeaders(taskHub),
+                cancellationToken: cancellationToken);
+        return new GrpcSandboxActivityWorkerSession(call);
+    }
+
+    Metadata? CreateTaskHubHeaders(string taskHub) => this.attachTaskHubMetadata
+        ? new Metadata { { "taskhub", taskHub }, }
+        : null;
+
+    /// <summary>
+    /// gRPC-backed on-demand sandbox activity worker registration session.
+    /// </summary>
+    sealed class GrpcSandboxActivityWorkerSession : ISandboxActivityWorkerSession
+    {
+        readonly AsyncClientStreamingCall<Proto.SandboxActivityWorkerMessage, Proto.SandboxActivityWorkerSessionResult> call;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="GrpcSandboxActivityWorkerSession"/> class.
+        /// </summary>
+        /// <param name="call">The active gRPC client-streaming call.</param>
+        public GrpcSandboxActivityWorkerSession(AsyncClientStreamingCall<Proto.SandboxActivityWorkerMessage, Proto.SandboxActivityWorkerSessionResult> call)
+        {
+            this.call = call;
+        }
+
+        /// <inheritdoc/>
+        public Task WriteMessageAsync(Proto.SandboxActivityWorkerMessage message) =>
+            this.call.RequestStream.WriteAsync(message);
+
+        /// <inheritdoc/>
+        public async Task<Proto.SandboxActivityWorkerSessionResult> WaitForCompletionAsync() =>
+            await this.call.ResponseAsync.ConfigureAwait(false);
+
+        /// <inheritdoc/>
+        public async Task CompleteAsync()
+        {
+            await this.call.RequestStream.CompleteAsync().ConfigureAwait(false);
+            await this.WaitForCompletionAsync().ConfigureAwait(false);
+        }
+
+        /// <inheritdoc/>
+        public ValueTask DisposeAsync()
+        {
+            this.call.Dispose();
+            return default;
+        }
+    }
+}
diff --git a/src/Shared/AzureManaged.Sandboxes/SandboxActivityMetadata.cs b/src/Shared/AzureManaged.Sandboxes/SandboxActivityMetadata.cs
new file mode 100644
index 00000000..4fabf25e
--- /dev/null
+++ b/src/Shared/AzureManaged.Sandboxes/SandboxActivityMetadata.cs
@@ -0,0 +1,109 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.DurableTask.AzureManaged.Internal;
+
+/// <summary>
+/// Shared normalization helpers for on-demand sandbox activity metadata.
+/// </summary>
+static class SandboxActivityMetadata
+{
+    /// <summary>
+    /// Resolves configured activities for on-demand sandbox activity execution.
+    /// </summary>
+    /// <param name="configuredActivities">The configured activities.</param>
+    /// <returns>The normalized activities.</returns>
+    public static Activity[] ResolveActivities(IEnumerable<Activity> configuredActivities)
+    {
+        List<Activity> activities = [];
+        foreach (Activity activity in configuredActivities)
+        {
+            if (string.IsNullOrWhiteSpace(activity.Name))
+            {
+                continue;
+            }
+
+            Activity normalized = new(
+                activity.Name.Trim(),
+                NormalizeOptional(activity.Version));
+            if (!activities.Any(existing => ActivityEquals(existing, normalized)))
+            {
+                activities.Add(normalized);
+            }
+        }
+
+        return activities.ToArray();
+    }
+
+    /// <summary>
+    /// Normalizes an optional string.
+    /// </summary>
+    /// <param name="value">The value to normalize.</param>
+    /// <returns>The trimmed value, or <see langword="null" /> if it is empty.</returns>
+    public static string? NormalizeOptional(string? value) =>
+        string.IsNullOrWhiteSpace(value) ? null : value.Trim();
+
+    /// <summary>
+    /// Determines whether two activities represent the same activity identity.
+    /// </summary>
+    /// <param name="left">The left activity.</param>
+    /// <param name="right">The right activity.</param>
+    /// <returns><see langword="true" /> if the activities are equal; otherwise, <see langword="false" />.</returns>
+    public static bool ActivityEquals(Activity left, Activity right) =>
+        string.Equals(left.Name, right.Name, StringComparison.OrdinalIgnoreCase)
+        && string.Equals(left.Version, right.Version, StringComparison.Ordinal);
+
+    /// <summary>
+    /// Determines whether two activity filters can match overlapping work.
+    /// </summary>
+    /// <param name="left">The left activity.</param>
+    /// <param name="right">The right activity.</param>
+    /// <returns><see langword="true" /> if the activities overlap; otherwise, <see langword="false" />.</returns>
+    public static bool ActivitiesOverlap(Activity left, Activity right) =>
+        string.Equals(left.Name, right.Name, StringComparison.OrdinalIgnoreCase)
+        && (left.Version is null
+            || right.Version is null
+            || string.Equals(left.Version, right.Version, StringComparison.Ordinal));
+
+    /// <summary>
+    /// Formats an activity identity for messages.
+    /// </summary>
+    /// <param name="activity">The activity identity.</param>
+    /// <returns>The formatted activity identity.</returns>
+    public static string FormatActivity(Activity activity) =>
+        activity.Version is null ? activity.Name : $"{activity.Name}@{activity.Version}";
+
+    /// <summary>
+    /// Normalizes a worker profile ID.
+    /// </summary>
+    /// <param name="value">The worker profile ID.</param>
+    /// <param name="errorMessage">The exception message to use when the value is empty.</param>
+    /// <returns>The normalized worker profile ID.</returns>
+    public static string NormalizeWorkerProfileId(string value, string errorMessage)
+    {
+        return NormalizeRequired(value, errorMessage);
+    }
+
+    /// <summary>
+    /// Normalizes a required string.
+    /// </summary>
+    /// <param name="value">The value to normalize.</param>
+    /// <param name="errorMessage">The exception message to use when the value is empty.</param>
+    /// <returns>The normalized value.</returns>
+    public static string NormalizeRequired(string value, string errorMessage)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            throw new InvalidOperationException(errorMessage);
+        }
+
+        return value.Trim();
+    }
+
+    /// <summary>
+    /// Represents a sandbox activity identity.
+    /// </summary>
+    /// <param name="Name">The activity name.</param>
+    /// <param name="Version">The activity version, or <see langword="null" /> for wildcard/unversioned execution.</param>
+    public readonly record struct Activity(string Name, string? Version);
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/DurableTaskSchedulerSandboxWorkerExtensions.cs b/src/Worker/AzureManaged.Sandboxes/DurableTaskSchedulerSandboxWorkerExtensions.cs
new file mode 100644
index 00000000..45a251f6
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/DurableTaskSchedulerSandboxWorkerExtensions.cs
@@ -0,0 +1,219 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Collections.Generic;
+using System.Linq;
+using Azure.Core;
+using Azure.Identity;
+using Grpc.Net.Client;
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Microsoft.DurableTask.Protobuf.Sandboxes;
+using Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+using Microsoft.DurableTask.Worker.Grpc;
+using Microsoft.DurableTask.Worker.Grpc.Internal;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+
+namespace Microsoft.DurableTask.Worker.AzureManaged;
+
+/// <summary>
+/// Extension methods for configuring Azure Managed Durable Task workers with on-demand sandbox activity support.
+/// </summary>
+public static class DurableTaskSchedulerSandboxWorkerExtensions
+{
+    const string UseSandboxWorkerNoActivitiesErrorMessage =
+        "On-demand sandbox workers require at least one registered activity. " +
+        "Register an activity on this worker before starting the sandbox worker.";
+
+    const string ManagedIdentityAuthentication = "ManagedIdentity";
+
+    /// <summary>
+    /// Configures this worker as an on-demand sandbox activity worker that connects to DTS to receive and execute
+    /// on-demand sandbox activities. Use this on a dedicated worker binary that runs inside sandbox infrastructure.
+    /// Runtime configuration is read from environment variables injected by DTS.
+    /// </summary>
+    /// <param name="builder">The Durable Task worker builder to configure.</param>
+    /// <returns>The original builder, for call chaining.</returns>
+    public static IDurableTaskWorkerBuilder UseSandboxWorker(this IDurableTaskWorkerBuilder builder)
+    {
+        Check.NotNull(builder);
+
+        ConfigureDurableTaskSchedulerFromEnvironment(builder);
+        builder.UseWorkItemFilters();
+
+        builder.Services.AddOptions<SandboxWorkerRuntimeOptions>(builder.Name)
+            .PostConfigure<IOptionsMonitor<DurableTaskSchedulerWorkerOptions>>((options, schedulerOptions) =>
+            {
+                ApplyRuntimeTaskHubDefault(options, schedulerOptions.Get(builder.Name).TaskHubName);
+                ApplyWorkerEnvironmentOverrides(options);
+            });
+
+        builder.Services.AddOptions<DurableTaskWorkerOptions>(builder.Name)
+            .PostConfigure<IOptionsMonitor<SandboxWorkerRuntimeOptions>>((options, runtimeOptions) =>
+                ConfigureSandboxWorkerConcurrency(options, runtimeOptions.Get(builder.Name)));
+
+        builder.Services.AddOptions<DurableTaskWorkerWorkItemFilters>(builder.Name)
+            .PostConfigure(IncludeOnlyRegisteredActivities);
+
+        builder.Services.AddSingleton<SandboxActivityTracker>();
+        builder.Services.AddOptions<GrpcDurableTaskWorkerOptions>(builder.Name)
+            .Configure<SandboxActivityTracker>((options, activityTracker) =>
+                options.ConfigureActivityNotification(phase =>
+                {
+                    if (phase == ActivityNotificationPhase.Started)
+                    {
+                        activityTracker.NotifyActivityStarted();
+                    }
+                    else if (phase == ActivityNotificationPhase.Completed)
+                    {
+                        activityTracker.NotifyActivityCompleted();
+                    }
+                }));
+
+        builder.Services.AddSingleton<IHostedService>(sp => CreateSandboxActivityWorkerRegistrationHostedService(sp, builder.Name));
+        return builder;
+    }
+
+    static void IncludeOnlyRegisteredActivities(DurableTaskWorkerWorkItemFilters filters)
+    {
+        if (filters.Activities.Count == 0)
+        {
+            throw new InvalidOperationException(UseSandboxWorkerNoActivitiesErrorMessage);
+        }
+
+        filters.Orchestrations = [];
+        filters.Entities = [];
+    }
+
+    static void ConfigureSandboxWorkerConcurrency(
+        DurableTaskWorkerOptions options,
+        SandboxWorkerRuntimeOptions runtimeOptions)
+    {
+        options.Concurrency.MaximumConcurrentActivityWorkItems = runtimeOptions.MaxConcurrentActivities;
+        options.Concurrency.MaximumConcurrentOrchestrationWorkItems = 0;
+        options.Concurrency.MaximumConcurrentEntityWorkItems = 0;
+    }
+
+    static SandboxActivityWorkerRegistrationHostedService CreateSandboxActivityWorkerRegistrationHostedService(
+        IServiceProvider services,
+        string builderName)
+    {
+        SandboxWorkerRuntimeOptions options = services.GetRequiredService<IOptionsMonitor<SandboxWorkerRuntimeOptions>>().Get(builderName);
+        ILoggerFactory loggerFactory = services.GetRequiredService<ILoggerFactory>();
+        IHostApplicationLifetime? lifetime = services.GetService<IHostApplicationLifetime>();
+        SandboxActivityTracker activityTracker = services.GetRequiredService<SandboxActivityTracker>();
+        DurableTaskWorkerWorkItemFilters filters = services.GetRequiredService<IOptionsMonitor<DurableTaskWorkerWorkItemFilters>>().Get(builderName);
+
+        return new SandboxActivityWorkerRegistrationHostedService(
+            CreateSandboxActivitiesTransport(services, builderName),
+            options,
+            ResolveActivityFilters(filters.Activities),
+            loggerFactory.CreateLogger<SandboxActivityWorkerRegistrationHostedService>(),
+            lifetime,
+            activityTracker);
+    }
+
+    static SandboxActivitiesGrpcTransport CreateSandboxActivitiesTransport(IServiceProvider services, string builderName)
+    {
+        GrpcDurableTaskWorkerOptions options = services.GetRequiredService<IOptionsMonitor<GrpcDurableTaskWorkerOptions>>().Get(builderName);
+        if (options.CallInvoker is { } callInvoker)
+        {
+            return new SandboxActivitiesGrpcTransport(new SandboxActivities.SandboxActivitiesClient(callInvoker));
+        }
+
+        if (options.Channel is { } channel)
+        {
+            return new SandboxActivitiesGrpcTransport(
+                new SandboxActivities.SandboxActivitiesClient(channel.CreateCallInvoker()),
+                attachTaskHubMetadata: false);
+        }
+
+        throw new InvalidOperationException("Azure Managed on-demand sandbox activities require a configured gRPC channel or call invoker.");
+    }
+
+    static void ApplyRuntimeTaskHubDefault(SandboxWorkerRuntimeOptions options, string taskHubName)
+    {
+        if (string.IsNullOrWhiteSpace(options.TaskHub) && !string.IsNullOrWhiteSpace(taskHubName))
+        {
+            options.TaskHub = taskHubName;
+        }
+    }
+
+    static void ConfigureDurableTaskSchedulerFromEnvironment(IDurableTaskWorkerBuilder builder)
+    {
+        string endpoint = GetRequiredEnvironmentVariable("DTS_ENDPOINT");
+        string taskHub = GetRequiredEnvironmentVariable("DTS_TASK_HUB");
+        string authentication = GetRequiredEnvironmentVariable("DTS_AUTHENTICATION");
+
+        builder.UseDurableTaskScheduler(options =>
+        {
+            options.EndpointAddress = endpoint;
+            options.TaskHubName = taskHub;
+            if (UsesManagedIdentityAuthentication(authentication))
+            {
+                options.Credential = CreateManagedIdentityCredential();
+                options.AllowInsecureCredentials = false;
+            }
+            else
+            {
+                throw new InvalidOperationException(
+                    $"DTS_AUTHENTICATION must be '{ManagedIdentityAuthentication}' for on-demand sandbox workers.");
+            }
+        });
+    }
+
+    static bool UsesManagedIdentityAuthentication(string authentication) =>
+        string.Equals(authentication, ManagedIdentityAuthentication, StringComparison.OrdinalIgnoreCase);
+
+    static ManagedIdentityCredential CreateManagedIdentityCredential() =>
+        new ManagedIdentityCredential(ManagedIdentityId.FromUserAssignedClientId(GetRequiredEnvironmentVariable("DTS_UMI_CLIENT_ID")));
+
+    static string GetRequiredEnvironmentVariable(string name)
+    {
+        string? value = Environment.GetEnvironmentVariable(name);
+        return string.IsNullOrWhiteSpace(value)
+            ? throw new InvalidOperationException($"{name} must be injected by DTS for on-demand sandbox workers.")
+            : value.Trim();
+    }
+
+    static void ApplyWorkerEnvironmentOverrides(SandboxWorkerRuntimeOptions options)
+    {
+        ValidateSandboxWorkerSandboxProvider(GetRequiredEnvironmentVariable("DTS_SANDBOX_PROVIDER"));
+
+        options.WorkerProfileId = GetRequiredEnvironmentVariable("DTS_WORKER_PROFILE_ID");
+
+        string? maxActivitiesValue = Environment.GetEnvironmentVariable("DTS_SANDBOX_MAX_ACTIVITIES");
+        if (maxActivitiesValue is null)
+        {
+            return;
+        }
+
+        if (!int.TryParse(maxActivitiesValue.Trim(), out int maxActivities) || maxActivities <= 0)
+        {
+            throw new InvalidOperationException(
+                "DTS_SANDBOX_MAX_ACTIVITIES must be a positive integer when injected by DTS for on-demand sandbox workers.");
+        }
+
+        options.MaxConcurrentActivities = maxActivities;
+    }
+
+    static void ValidateSandboxWorkerSandboxProvider(string sandboxProvider)
+    {
+        if (!string.Equals(sandboxProvider, "Sandbox", StringComparison.OrdinalIgnoreCase)
+            && !string.Equals(sandboxProvider, "AcaSessionPool", StringComparison.OrdinalIgnoreCase))
+        {
+            throw new InvalidOperationException(
+                "DTS_SANDBOX_PROVIDER must be 'Sandbox' or 'AcaSessionPool' for on-demand sandbox workers.");
+        }
+    }
+
+    static SandboxActivityMetadata.Activity[] ResolveActivityFilters(IReadOnlyList<DurableTaskWorkerWorkItemFilters.ActivityFilter> activityFilters)
+    {
+        return SandboxActivityMetadata.ResolveActivities(activityFilters.SelectMany(static filter =>
+            filter.Versions.Count == 0
+                ? [new SandboxActivityMetadata.Activity(filter.Name, Version: null)]
+                : filter.Versions.Select(version => new SandboxActivityMetadata.Activity(filter.Name, version))));
+    }
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/Logs.cs b/src/Worker/AzureManaged.Sandboxes/Logs.cs
new file mode 100644
index 00000000..0a0d8153
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/Logs.cs
@@ -0,0 +1,68 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.Extensions.Logging;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+
+/// <summary>
+/// Log messages for on-demand sandbox activity services.
+/// </summary>
+static partial class Logs
+{
+    [LoggerMessage(
+        EventId = 701,
+        Level = LogLevel.Information,
+        Message = "On-demand sandbox activity worker registered hub={Hub} count={Count} sandboxProvider={SandboxProvider} sandboxId={SandboxId}")]
+    public static partial void SandboxActivityWorkerRegistered(
+        ILogger logger, string hub, int count, Proto.SandboxProviderKind sandboxProvider, string sandboxId);
+
+    [LoggerMessage(
+        EventId = 702,
+        Level = LogLevel.Error,
+        Message = "On-demand sandbox activity worker registration stream failed hub={Hub}")]
+    public static partial void SandboxActivityWorkerRegistrationFailed(ILogger logger, Exception exception, string hub);
+
+    [LoggerMessage(
+        EventId = 703,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox worker session completion failure during shutdown.")]
+    public static partial void SandboxWorkerSessionCompletionFailureIgnored(ILogger logger, Exception exception);
+
+    [LoggerMessage(
+        EventId = 704,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox worker registration pump cancellation during shutdown.")]
+    public static partial void SandboxWorkerRegistrationPumpCancellationIgnored(ILogger logger, Exception exception);
+
+    [LoggerMessage(
+        EventId = 705,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox worker registration pump failure during shutdown.")]
+    public static partial void SandboxWorkerRegistrationPumpFailureIgnored(ILogger logger, Exception exception);
+
+    [LoggerMessage(
+        EventId = 706,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox worker session dispose failure during shutdown.")]
+    public static partial void SandboxWorkerSessionDisposeFailureIgnored(ILogger logger, Exception exception);
+
+    [LoggerMessage(
+        EventId = 707,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox heartbeat pump cancellation after registration session completion.")]
+    public static partial void SandboxHeartbeatPumpCancellationIgnored(ILogger logger, Exception exception);
+
+    [LoggerMessage(
+        EventId = 708,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox heartbeat pump failure after registration session completion.")]
+    public static partial void SandboxHeartbeatPumpFailureIgnored(ILogger logger, Exception exception);
+
+    [LoggerMessage(
+        EventId = 709,
+        Level = LogLevel.Debug,
+        Message = "Ignoring on-demand sandbox worker session completion failure after heartbeat pump failure.")]
+    public static partial void SandboxWorkerSessionCompletionAfterHeartbeatFailureIgnored(ILogger logger, Exception exception);
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/SandboxActivityTracker.cs b/src/Worker/AzureManaged.Sandboxes/SandboxActivityTracker.cs
new file mode 100644
index 00000000..610a45fa
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/SandboxActivityTracker.cs
@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+
+/// <summary>
+/// Tracks activity execution state for an on-demand sandbox worker process.
+/// </summary>
+sealed class SandboxActivityTracker
+{
+    int activeActivityCount;
+
+    /// <summary>
+    /// Gets the number of activities currently in flight on this worker.
+    /// </summary>
+    public int InFlightCount => Volatile.Read(ref this.activeActivityCount);
+
+    /// <summary>
+    /// Records the start of an in-flight activity.
+    /// </summary>
+    internal void NotifyActivityStarted() => Interlocked.Increment(ref this.activeActivityCount);
+
+    /// <summary>
+    /// Records the completion of an activity.
+    /// </summary>
+    internal void NotifyActivityCompleted()
+    {
+        while (true)
+        {
+            int currentCount = Volatile.Read(ref this.activeActivityCount);
+            if (currentCount == 0)
+            {
+                return;
+            }
+
+            if (Interlocked.CompareExchange(ref this.activeActivityCount, currentCount - 1, currentCount) == currentCount)
+            {
+                return;
+            }
+        }
+    }
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/SandboxActivityWorkerRegistrationHostedService.cs b/src/Worker/AzureManaged.Sandboxes/SandboxActivityWorkerRegistrationHostedService.cs
new file mode 100644
index 00000000..efc862f7
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/SandboxActivityWorkerRegistrationHostedService.cs
@@ -0,0 +1,443 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.IO;
+using Grpc.Core;
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+
+/// <summary>
+/// Hosted service that registers a running process as an on-demand sandbox activity worker with DTS.
+/// </summary>
+sealed class SandboxActivityWorkerRegistrationHostedService : IHostedService, IAsyncDisposable
+{
+    readonly object sync = new();
+    readonly ISandboxActivitiesTransport transport;
+    readonly SandboxWorkerRuntimeOptions options;
+    readonly IReadOnlyCollection<SandboxActivityMetadata.Activity> registeredActivities;
+    readonly ILogger<SandboxActivityWorkerRegistrationHostedService> logger;
+    readonly IHostApplicationLifetime? lifetime;
+    readonly SandboxActivityTracker? activityTracker;
+    readonly Random reconnectJitter;
+    readonly SemaphoreSlim streamSync = new(1, 1);
+    CancellationTokenSource? cts;
+    ISandboxActivityWorkerSession? session;
+    Task? pump;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SandboxActivityWorkerRegistrationHostedService"/> class.
+    /// </summary>
+    /// <param name="transport">The on-demand sandbox activities transport.</param>
+    /// <param name="options">The on-demand sandbox worker runtime options.</param>
+    /// <param name="registeredActivities">The activity handlers registered by this worker process.</param>
+    /// <param name="logger">The logger.</param>
+    /// <param name="lifetime">The optional application lifetime used to stop the host when a non-retriable registration stream failure occurs.</param>
+    /// <param name="activityTracker">The optional activity tracker used to report live in-flight activity count.</param>
+    /// <param name="reconnectJitter">The optional random source used to jitter reconnect delays.</param>
+    public SandboxActivityWorkerRegistrationHostedService(
+        ISandboxActivitiesTransport transport,
+        SandboxWorkerRuntimeOptions options,
+        IReadOnlyCollection<SandboxActivityMetadata.Activity> registeredActivities,
+        ILogger<SandboxActivityWorkerRegistrationHostedService> logger,
+        IHostApplicationLifetime? lifetime = null,
+        SandboxActivityTracker? activityTracker = null,
+        Random? reconnectJitter = null)
+    {
+        this.transport = Check.NotNull(transport);
+        this.options = Check.NotNull(options);
+        this.registeredActivities = Check.NotNull(registeredActivities);
+        this.logger = Check.NotNull(logger);
+        this.lifetime = lifetime;
+        this.activityTracker = activityTracker;
+        this.reconnectJitter = reconnectJitter ?? Random.Shared;
+    }
+
+    /// <inheritdoc/>
+    public Task StartAsync(CancellationToken cancellationToken)
+    {
+        SandboxActivityMetadata.Activity[] activities = SandboxActivityMetadata.ResolveActivities(this.registeredActivities);
+        CancellationTokenSource registrationCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        Task registrationPump = Task.Run(
+            () => this.RunRegistrationLoopAsync(activities.Length, registrationCts.Token),
+            CancellationToken.None);
+        lock (this.sync)
+        {
+            this.cts = registrationCts;
+            this.pump = registrationPump;
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public async Task StopAsync(CancellationToken cancellationToken)
+    {
+        CancellationTokenSource? localCts;
+        ISandboxActivityWorkerSession? localSession;
+        Task? localPump;
+        lock (this.sync)
+        {
+            localCts = this.cts;
+            localSession = this.session;
+            localPump = this.pump;
+        }
+
+        localCts?.Cancel();
+
+        if (localSession is not null)
+        {
+            try
+            {
+                await this.CompleteSessionAsync(localSession, cancellationToken).ConfigureAwait(false);
+            }
+            catch (Exception ex) when (ex is OperationCanceledException or ObjectDisposedException or RpcException)
+            {
+                Logs.SandboxWorkerSessionCompletionFailureIgnored(this.logger, ex);
+            }
+        }
+
+        if (localPump is not null)
+        {
+            try
+            {
+                await localPump.WaitAsync(cancellationToken).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException ex) when (cancellationToken.IsCancellationRequested)
+            {
+                Logs.SandboxWorkerRegistrationPumpCancellationIgnored(this.logger, ex);
+            }
+            catch (Exception ex) when (ex is OperationCanceledException or ObjectDisposedException or RpcException)
+            {
+                Logs.SandboxWorkerRegistrationPumpFailureIgnored(this.logger, ex);
+            }
+        }
+
+        lock (this.sync)
+        {
+            if (ReferenceEquals(this.cts, localCts))
+            {
+                this.cts = null;
+            }
+
+            if (ReferenceEquals(this.session, localSession))
+            {
+                this.session = null;
+            }
+
+            if (ReferenceEquals(this.pump, localPump))
+            {
+                this.pump = Task.CompletedTask;
+            }
+        }
+
+        localCts?.Dispose();
+    }
+
+    /// <inheritdoc/>
+    public async ValueTask DisposeAsync()
+    {
+        await this.StopAsync(CancellationToken.None).ConfigureAwait(false);
+        this.streamSync.Dispose();
+    }
+
+    /// <summary>
+    /// Computes a full-jitter reconnect delay in the range <c>[0, retryDelay)</c>.
+    /// </summary>
+    /// <param name="retryDelay">The current exponential retry delay.</param>
+    /// <param name="random">The random source used for jitter.</param>
+    /// <returns>The jittered reconnect delay.</returns>
+    internal static TimeSpan ComputeJitteredReconnectDelay(TimeSpan retryDelay, Random random)
+    {
+        Check.NotNull(random);
+        if (retryDelay <= TimeSpan.Zero)
+        {
+            return TimeSpan.Zero;
+        }
+
+        long jitteredTicks = (long)(random.NextDouble() * retryDelay.Ticks);
+        return TimeSpan.FromTicks(jitteredTicks);
+    }
+
+    /// <summary>
+    /// Computes the next exponential retry delay, capped at the configured maximum delay.
+    /// </summary>
+    /// <param name="retryDelay">The current retry delay.</param>
+    /// <param name="maxDelay">The maximum retry delay.</param>
+    /// <returns>The next retry delay.</returns>
+    internal static TimeSpan ComputeNextRetryDelay(TimeSpan retryDelay, TimeSpan maxDelay)
+    {
+        if (retryDelay <= TimeSpan.Zero)
+        {
+            return retryDelay;
+        }
+
+        if (retryDelay >= maxDelay || retryDelay.Ticks > maxDelay.Ticks / 2)
+        {
+            return maxDelay;
+        }
+
+        return TimeSpan.FromTicks(retryDelay.Ticks * 2);
+    }
+
+    static async ValueTask DisposeSessionAsync(
+        ISandboxActivityWorkerSession registrationSession,
+        ILogger logger)
+    {
+        try
+        {
+            await registrationSession.DisposeAsync().ConfigureAwait(false);
+        }
+        catch (Exception ex) when (ex is OperationCanceledException or ObjectDisposedException or RpcException)
+        {
+            Logs.SandboxWorkerSessionDisposeFailureIgnored(logger, ex);
+        }
+    }
+
+    static bool IsRetriableRegistrationFailure(Exception exception) =>
+        (exception is OperationCanceledException or ObjectDisposedException or IOException)
+        || (exception is RpcException rpcException
+            && rpcException.StatusCode is StatusCode.Cancelled
+                or StatusCode.DeadlineExceeded
+                or StatusCode.Internal
+                or StatusCode.ResourceExhausted
+                or StatusCode.Unavailable
+                or StatusCode.Unknown);
+
+    static bool IsFatalException(Exception ex) => ex is OutOfMemoryException
+        or StackOverflowException
+        or AccessViolationException
+        or ThreadAbortException;
+
+    static async Task ObserveCompletionFailureAfterHeartbeatFailureAsync(
+        Task<Proto.SandboxActivityWorkerSessionResult> completionTask,
+        ILogger logger)
+    {
+        try
+        {
+            await completionTask.ConfigureAwait(false);
+        }
+        catch (Exception ex) when (!IsFatalException(ex))
+        {
+            Logs.SandboxWorkerSessionCompletionAfterHeartbeatFailureIgnored(logger, ex);
+        }
+    }
+
+    async Task RunRegistrationLoopAsync(int activityCount, CancellationToken cancellationToken)
+    {
+        TimeSpan retryDelay = this.GetInitialRetryDelay();
+        while (!cancellationToken.IsCancellationRequested)
+        {
+            ISandboxActivityWorkerSession? registrationSession = null;
+            try
+            {
+                Proto.SandboxActivityWorkerMessage startMessage = SandboxWorkerMessageBuilder.BuildWorkerStart(this.options, this.registeredActivities);
+                registrationSession = this.transport.OpenSandboxActivityWorkerSession(startMessage.Start.TaskHub, cancellationToken);
+                this.SetCurrentSession(registrationSession);
+
+                await this.WriteSessionMessageAsync(registrationSession, startMessage, cancellationToken).ConfigureAwait(false);
+                Logs.SandboxActivityWorkerRegistered(
+                    this.logger,
+                    startMessage.Start.TaskHub,
+                    activityCount,
+                    startMessage.Start.SandboxProvider,
+                    startMessage.Start.DtsSandboxIdentifier);
+
+                await this.RunRegistrationSessionAsync(registrationSession, cancellationToken).ConfigureAwait(false);
+                retryDelay = this.GetInitialRetryDelay();
+            }
+            catch (OperationCanceledException) when (cancellationToken.IsCancellationRequested)
+            {
+                break;
+            }
+            catch (RpcException ex) when (IsRetriableRegistrationFailure(ex))
+            {
+                retryDelay = await this.HandleRetriableRegistrationFailureAsync(
+                    ex,
+                    retryDelay,
+                    cancellationToken).ConfigureAwait(false);
+            }
+            catch (IOException ex) when (IsRetriableRegistrationFailure(ex))
+            {
+                retryDelay = await this.HandleRetriableRegistrationFailureAsync(
+                    ex,
+                    retryDelay,
+                    cancellationToken).ConfigureAwait(false);
+            }
+            catch (ObjectDisposedException ex) when (IsRetriableRegistrationFailure(ex))
+            {
+                retryDelay = await this.HandleRetriableRegistrationFailureAsync(
+                    ex,
+                    retryDelay,
+                    cancellationToken).ConfigureAwait(false);
+            }
+            catch (OperationCanceledException ex) when (IsRetriableRegistrationFailure(ex))
+            {
+                retryDelay = await this.HandleRetriableRegistrationFailureAsync(
+                    ex,
+                    retryDelay,
+                    cancellationToken).ConfigureAwait(false);
+            }
+            catch (Exception ex) when (!IsFatalException(ex))
+            {
+                Logs.SandboxActivityWorkerRegistrationFailed(this.logger, ex, this.options.TaskHub);
+                this.lifetime?.StopApplication();
+                break;
+            }
+            finally
+            {
+                if (registrationSession is not null)
+                {
+                    this.ClearCurrentSession(registrationSession);
+                    await DisposeSessionAsync(registrationSession, this.logger).ConfigureAwait(false);
+                }
+            }
+        }
+    }
+
+    async Task<TimeSpan> HandleRetriableRegistrationFailureAsync(
+        Exception exception,
+        TimeSpan retryDelay,
+        CancellationToken cancellationToken)
+    {
+        Logs.SandboxActivityWorkerRegistrationFailed(this.logger, exception, this.options.TaskHub);
+        await this.DelayBeforeReconnectAsync(retryDelay, cancellationToken).ConfigureAwait(false);
+        return this.GetNextRetryDelay(retryDelay);
+    }
+
+    async Task RunRegistrationSessionAsync(
+        ISandboxActivityWorkerSession registrationSession,
+        CancellationToken cancellationToken)
+    {
+        using CancellationTokenSource heartbeatCts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        Task heartbeatTask = this.PumpHeartbeatsAsync(registrationSession, heartbeatCts.Token);
+        Task<Proto.SandboxActivityWorkerSessionResult> completionTask = registrationSession.WaitForCompletionAsync();
+        Task completedTask = await Task.WhenAny(heartbeatTask, completionTask).ConfigureAwait(false);
+
+        if (ReferenceEquals(completedTask, completionTask))
+        {
+            heartbeatCts.Cancel();
+            try
+            {
+                await heartbeatTask.ConfigureAwait(false);
+            }
+            catch (OperationCanceledException ex) when (heartbeatCts.IsCancellationRequested)
+            {
+                Logs.SandboxHeartbeatPumpCancellationIgnored(this.logger, ex);
+            }
+            catch (RpcException ex)
+            {
+                // The server response is authoritative once the response task wins the race.
+                Logs.SandboxHeartbeatPumpFailureIgnored(this.logger, ex);
+            }
+            catch (IOException ex)
+            {
+                // The server response is authoritative once the response task wins the race.
+                Logs.SandboxHeartbeatPumpFailureIgnored(this.logger, ex);
+            }
+            catch (ObjectDisposedException ex)
+            {
+                // The server response is authoritative once the response task wins the race.
+                Logs.SandboxHeartbeatPumpFailureIgnored(this.logger, ex);
+            }
+
+            await completionTask.ConfigureAwait(false);
+            return;
+        }
+
+        try
+        {
+            await heartbeatTask.ConfigureAwait(false);
+        }
+        finally
+        {
+            _ = ObserveCompletionFailureAfterHeartbeatFailureAsync(completionTask, this.logger);
+        }
+    }
+
+    async Task PumpHeartbeatsAsync(
+        ISandboxActivityWorkerSession registrationSession,
+        CancellationToken cancellationToken)
+    {
+        using PeriodicTimer timer = new(this.options.HeartbeatInterval);
+        while (await timer.WaitForNextTickAsync(cancellationToken).ConfigureAwait(false))
+        {
+            int activeActivitiesCount = this.activityTracker?.InFlightCount ?? 0;
+            await this.WriteSessionMessageAsync(
+                registrationSession,
+                SandboxWorkerMessageBuilder.BuildWorkerHeartbeat(activeActivitiesCount),
+                cancellationToken).ConfigureAwait(false);
+        }
+    }
+
+    async Task WriteSessionMessageAsync(
+        ISandboxActivityWorkerSession registrationSession,
+        Proto.SandboxActivityWorkerMessage message,
+        CancellationToken cancellationToken)
+    {
+        await this.streamSync.WaitAsync(cancellationToken).ConfigureAwait(false);
+        try
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+            await registrationSession.WriteMessageAsync(message).ConfigureAwait(false);
+        }
+        finally
+        {
+            this.streamSync.Release();
+        }
+    }
+
+    async Task CompleteSessionAsync(
+        ISandboxActivityWorkerSession registrationSession,
+        CancellationToken cancellationToken)
+    {
+        await this.streamSync.WaitAsync(cancellationToken).ConfigureAwait(false);
+        try
+        {
+            await registrationSession.CompleteAsync().WaitAsync(cancellationToken).ConfigureAwait(false);
+        }
+        finally
+        {
+            this.streamSync.Release();
+        }
+    }
+
+    void SetCurrentSession(ISandboxActivityWorkerSession registrationSession)
+    {
+        lock (this.sync)
+        {
+            this.session = registrationSession;
+        }
+    }
+
+    void ClearCurrentSession(ISandboxActivityWorkerSession registrationSession)
+    {
+        lock (this.sync)
+        {
+            if (ReferenceEquals(this.session, registrationSession))
+            {
+                this.session = null;
+            }
+        }
+    }
+
+    TimeSpan GetInitialRetryDelay() =>
+        this.options.WorkerRegistrationRetryInitialDelay <= this.options.WorkerRegistrationRetryMaxDelay
+            ? this.options.WorkerRegistrationRetryInitialDelay
+            : this.options.WorkerRegistrationRetryMaxDelay;
+
+    TimeSpan GetNextRetryDelay(TimeSpan retryDelay) =>
+        ComputeNextRetryDelay(retryDelay, this.options.WorkerRegistrationRetryMaxDelay);
+
+    async Task DelayBeforeReconnectAsync(TimeSpan retryDelay, CancellationToken cancellationToken)
+    {
+        TimeSpan jitteredDelay = ComputeJitteredReconnectDelay(retryDelay, this.reconnectJitter);
+        if (jitteredDelay > TimeSpan.Zero)
+        {
+            await Task.Delay(jitteredDelay, cancellationToken).ConfigureAwait(false);
+        }
+    }
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/SandboxWorkerMessageBuilder.cs b/src/Worker/AzureManaged.Sandboxes/SandboxWorkerMessageBuilder.cs
new file mode 100644
index 00000000..6593adad
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/SandboxWorkerMessageBuilder.cs
@@ -0,0 +1,108 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Proto = Microsoft.DurableTask.Protobuf.Sandboxes;
+
+namespace Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+
+/// <summary>
+/// Builds on-demand sandbox activity worker registration protocol messages.
+/// </summary>
+static class SandboxWorkerMessageBuilder
+{
+    /// <summary>
+    /// Builds the initial on-demand sandbox activity worker registration message.
+    /// </summary>
+    /// <param name="options">The on-demand sandbox options.</param>
+    /// <param name="registeredActivities">The activity handlers registered by the worker process.</param>
+    /// <returns>The worker start protocol message.</returns>
+    public static Proto.SandboxActivityWorkerMessage BuildWorkerStart(
+        SandboxWorkerRuntimeOptions options,
+        IReadOnlyCollection<SandboxActivityMetadata.Activity> registeredActivities)
+    {
+        Check.NotNull(options);
+        Check.NotNull(registeredActivities);
+
+        string taskHub = SandboxActivityMetadata.NormalizeRequired(
+            options.TaskHub,
+            "On-demand sandbox activity worker registration requires a task hub name.");
+        SandboxActivityMetadata.Activity[] activities = SandboxActivityMetadata.ResolveActivities(registeredActivities);
+        if (activities.Length == 0)
+        {
+            throw new InvalidOperationException("On-demand sandbox activity worker registration requires at least one registered activity.");
+        }
+
+        if (options.MaxConcurrentActivities <= 0)
+        {
+            throw new InvalidOperationException("On-demand sandbox activity worker max activity count must be greater than zero.");
+        }
+
+        string workerProfileId = SandboxActivityMetadata.NormalizeWorkerProfileId(
+            options.WorkerProfileId,
+            "On-demand sandbox activity worker registration requires a worker profile ID.");
+        string dtsSandboxIdentifier = SandboxActivityMetadata.NormalizeRequired(
+            Environment.GetEnvironmentVariable("DTS_SANDBOX_ID") ?? string.Empty,
+            "On-demand sandbox activity worker registration requires a DTS sandbox ID.");
+
+        Proto.SandboxActivityWorkerStart start = new()
+        {
+            TaskHub = taskHub,
+            WorkerProfileId = workerProfileId,
+            MaxActivitiesCount = options.MaxConcurrentActivities,
+            SandboxProvider = GetSandboxProviderFromEnvironment(),
+            DtsSandboxIdentifier = dtsSandboxIdentifier,
+        };
+        start.Activities.AddRange(activities.Select(ToProtoActivity));
+
+        return new Proto.SandboxActivityWorkerMessage { Start = start };
+    }
+
+    /// <summary>
+    /// Builds an on-demand sandbox activity worker heartbeat message.
+    /// </summary>
+    /// <param name="activeActivitiesCount">The number of activities currently executing.</param>
+    /// <returns>The heartbeat protocol message.</returns>
+    public static Proto.SandboxActivityWorkerMessage BuildWorkerHeartbeat(int activeActivitiesCount)
+    {
+        if (activeActivitiesCount < 0)
+        {
+            throw new InvalidOperationException("On-demand sandbox activity worker active activity count cannot be negative.");
+        }
+
+        return new Proto.SandboxActivityWorkerMessage
+        {
+            Heartbeat = new Proto.SandboxActivityWorkerHeartbeat
+            {
+                ActiveActivitiesCount = activeActivitiesCount,
+            },
+        };
+    }
+
+    static Proto.SandboxActivity ToProtoActivity(SandboxActivityMetadata.Activity activity) => new()
+    {
+        Name = activity.Name,
+        Version = activity.Version ?? string.Empty,
+    };
+
+    static Proto.SandboxProviderKind GetSandboxProviderFromEnvironment()
+    {
+        string? sandboxProvider = Environment.GetEnvironmentVariable("DTS_SANDBOX_PROVIDER");
+        if (sandboxProvider is null)
+        {
+            return Proto.SandboxProviderKind.Unspecified;
+        }
+
+        if (sandboxProvider.Equals("Sandbox", StringComparison.OrdinalIgnoreCase))
+        {
+            return Proto.SandboxProviderKind.Sandbox;
+        }
+
+        if (sandboxProvider.Equals("AcaSessionPool", StringComparison.OrdinalIgnoreCase))
+        {
+            return Proto.SandboxProviderKind.AcaSessionPool;
+        }
+
+        return Proto.SandboxProviderKind.Unspecified;
+    }
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/SandboxWorkerRuntimeOptions.cs b/src/Worker/AzureManaged.Sandboxes/SandboxWorkerRuntimeOptions.cs
new file mode 100644
index 00000000..e3a82e46
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/SandboxWorkerRuntimeOptions.cs
@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+
+/// <summary>
+/// Internal runtime settings for an on-demand sandbox worker process.
+/// </summary>
+internal sealed class SandboxWorkerRuntimeOptions
+{
+    /// <summary>
+    /// Gets or sets the task hub used by on-demand sandbox worker registration.
+    /// </summary>
+    public string TaskHub { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the worker profile ID used by on-demand sandbox worker registration.
+    /// </summary>
+    public string WorkerProfileId { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the maximum number of concurrent activities expected from this on-demand sandbox worker.
+    /// </summary>
+    public int MaxConcurrentActivities { get; set; } = 100;
+
+    /// <summary>
+    /// Gets or sets the interval used to refresh live worker capacity while the registration stream is open.
+    /// </summary>
+    public TimeSpan HeartbeatInterval { get; set; } = TimeSpan.FromSeconds(2);
+
+    /// <summary>
+    /// Gets or sets the initial delay before retrying a failed worker registration stream.
+    /// </summary>
+    public TimeSpan WorkerRegistrationRetryInitialDelay { get; set; } = TimeSpan.FromSeconds(1);
+
+    /// <summary>
+    /// Gets or sets the maximum delay before retrying a failed worker registration stream.
+    /// </summary>
+    public TimeSpan WorkerRegistrationRetryMaxDelay { get; set; } = TimeSpan.FromSeconds(30);
+}
diff --git a/src/Worker/AzureManaged.Sandboxes/Worker.AzureManaged.Sandboxes.csproj b/src/Worker/AzureManaged.Sandboxes/Worker.AzureManaged.Sandboxes.csproj
new file mode 100644
index 00000000..6fbe8aec
--- /dev/null
+++ b/src/Worker/AzureManaged.Sandboxes/Worker.AzureManaged.Sandboxes.csproj
@@ -0,0 +1,30 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <PackageDescription>Azure Managed on-demand sandbox activity worker extensions for the Durable Task Framework worker.</PackageDescription>
+    <AssemblyName>Microsoft.DurableTask.Worker.AzureManaged.Sandboxes</AssemblyName>
+    <EnableStyleCop>true</EnableStyleCop>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Grpc.Net.Client" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\AzureManaged\Worker.AzureManaged.csproj" />
+    <ProjectReference Include="..\Grpc\Worker.Grpc.csproj" />
+    <ProjectReference Include="..\..\Grpc\Grpc.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <SharedSection Include="AzureManaged.Sandboxes" />
+    <SharedSection Include="Core" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <InternalsVisibleTo Include="Microsoft.DurableTask.Worker.AzureManaged.Tests" Key="$(StrongNamePublicKey)" />
+  </ItemGroup>
+
+</Project>
diff --git a/src/Worker/AzureManaged/DurableTaskSchedulerWorkerExtensions.cs b/src/Worker/AzureManaged/DurableTaskSchedulerWorkerExtensions.cs
index 3b9d4e55..2b832a54 100644
--- a/src/Worker/AzureManaged/DurableTaskSchedulerWorkerExtensions.cs
+++ b/src/Worker/AzureManaged/DurableTaskSchedulerWorkerExtensions.cs
@@ -300,6 +300,7 @@ and not AccessViolationException
                     }
                 }
             }
+
             GC.SuppressFinalize(this);
         }
 
diff --git a/src/Worker/Grpc/GrpcDurableTaskWorker.Processor.cs b/src/Worker/Grpc/GrpcDurableTaskWorker.Processor.cs
index 7b7c41c7..1ff3dc39 100644
--- a/src/Worker/Grpc/GrpcDurableTaskWorker.Processor.cs
+++ b/src/Worker/Grpc/GrpcDurableTaskWorker.Processor.cs
@@ -156,7 +156,7 @@ await this.ProcessWorkItemsAsync(
                         this.internalOptions.ReconnectBackoffBase,
                         this.internalOptions.ReconnectBackoffCap,
                         backoffRandom,
-                        fullJitter: true);
+                        fullJitter: true);
                     this.Logger.ReconnectBackoff(reconnectAttempt, (int)delay.TotalMilliseconds);
                     reconnectAttempt++;
                     await Task.Delay(delay, cancellation);
@@ -405,12 +405,23 @@ void DispatchWorkItem(P.WorkItem workItem, CancellationToken cancellation)
             }
             else if (workItem.RequestCase == P.WorkItem.RequestOneofCase.ActivityRequest)
             {
+                this.NotifyActivity(ActivityNotificationPhase.Started);
                 this.RunBackgroundTask(
                     workItem,
-                    () => this.OnRunActivityAsync(
-                        workItem.ActivityRequest,
-                        workItem.CompletionToken,
-                        cancellation),
+                    async () =>
+                    {
+                        try
+                        {
+                            await this.OnRunActivityAsync(
+                                workItem.ActivityRequest,
+                                workItem.CompletionToken,
+                                cancellation).ConfigureAwait(false);
+                        }
+                        finally
+                        {
+                            this.NotifyActivity(ActivityNotificationPhase.Completed);
+                        }
+                    },
                     cancellation);
             }
             else if (workItem.RequestCase == P.WorkItem.RequestOneofCase.EntityRequest)
@@ -449,6 +460,27 @@ void DispatchWorkItem(P.WorkItem workItem, CancellationToken cancellation)
             }
         }
 
+        void NotifyActivity(ActivityNotificationPhase phase)
+        {
+            Action<ActivityNotificationPhase>? callback = this.internalOptions.NotifyActivity;
+            if (callback is null)
+            {
+                return;
+            }
+
+            try
+            {
+                callback(phase);
+            }
+            catch (Exception ex) when (ex is not OutOfMemoryException
+                and not StackOverflowException
+                and not AccessViolationException
+                and not ThreadAbortException)
+            {
+                this.Logger.ActivityNotificationFailed(phase, ex);
+            }
+        }
+
         void RunBackgroundTask(P.WorkItem? workItem, Func<Task> handler, CancellationToken cancellation)
         {
             // TODO: is Task.Run appropriate here? Should we have finer control over the tasks and their threads?
diff --git a/src/Worker/Grpc/GrpcDurableTaskWorkerOptions.cs b/src/Worker/Grpc/GrpcDurableTaskWorkerOptions.cs
index 49bd6350..59c21a00 100644
--- a/src/Worker/Grpc/GrpcDurableTaskWorkerOptions.cs
+++ b/src/Worker/Grpc/GrpcDurableTaskWorkerOptions.cs
@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using Microsoft.DurableTask.Worker.Grpc.Internal;
 using P = Microsoft.DurableTask.Protobuf;
 
 namespace Microsoft.DurableTask.Worker.Grpc;
@@ -165,5 +166,10 @@ internal class InternalOptions
         /// deferring disposal of the old channel so in-flight RPCs already using it are not interrupted.
         /// </summary>
         public Func<GrpcChannel, CancellationToken, Task<GrpcChannel>>? ChannelRecreator { get; set; }
+
+        /// <summary>
+        /// Gets or sets a callback that is invoked when activity work items are received or finished.
+        /// </summary>
+        public Action<ActivityNotificationPhase>? NotifyActivity { get; set; }
     }
 }
diff --git a/src/Worker/Grpc/Internal/InternalOptionsExtensions.cs b/src/Worker/Grpc/Internal/InternalOptionsExtensions.cs
index b26b36cc..81ad09d5 100644
--- a/src/Worker/Grpc/Internal/InternalOptionsExtensions.cs
+++ b/src/Worker/Grpc/Internal/InternalOptionsExtensions.cs
@@ -2,11 +2,25 @@
 // Licensed under the MIT License.
 
 using System;
-using System.Collections.Generic;
-using System.Text;
 
 namespace Microsoft.DurableTask.Worker.Grpc.Internal;
 
+/// <summary>
+/// Identifies the phase of activity execution being reported to internal worker hooks.
+/// </summary>
+public enum ActivityNotificationPhase
+{
+    /// <summary>
+    /// The worker has received and started processing an activity work item.
+    /// </summary>
+    Started,
+
+    /// <summary>
+    /// The worker has finished processing an activity work item.
+    /// </summary>
+    Completed,
+}
+
 /// <summary>
 /// Provides access to configuring internal options for the gRPC worker.
 /// </summary>
@@ -28,6 +42,24 @@ public static void ConfigureForAzureManaged(this GrpcDurableTaskWorkerOptions op
         options.Internal.InsertEntityUnlocksOnCompletion = true;
     }
 
+    /// <summary>
+    /// Registers a callback invoked when activity work items start and finish execution.
+    /// </summary>
+    /// <param name="options">The gRPC worker options.</param>
+    /// <param name="notification">The activity notification callback.</param>
+    /// <remarks>
+    /// This is an internal API that supports the DurableTask infrastructure and not subject to
+    /// the same compatibility standards as public APIs. It may be changed or removed without notice in
+    /// any release. You should only use it directly in your code with extreme caution and knowing that
+    /// doing so can result in application failures when updating to a new DurableTask release.
+    /// </remarks>
+    public static void ConfigureActivityNotification(
+        this GrpcDurableTaskWorkerOptions options,
+        Action<ActivityNotificationPhase> notification)
+    {
+        options.Internal.NotifyActivity = notification ?? throw new ArgumentNullException(nameof(notification));
+    }
+
     /// <summary>
     /// Sets a callback that the worker invokes when the underlying gRPC channel needs to be recreated
     /// after repeated connect failures (e.g., because the backend was replaced and the existing channel
diff --git a/src/Worker/Grpc/Logs.cs b/src/Worker/Grpc/Logs.cs
index 878efe9c..f378a7fc 100644
--- a/src/Worker/Grpc/Logs.cs
+++ b/src/Worker/Grpc/Logs.cs
@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using Microsoft.DurableTask.Worker.Grpc.Internal;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.DurableTask.Worker.Grpc
@@ -99,9 +100,12 @@ static partial class Logs
         public static partial void ReceivedHealthPing(this ILogger logger);
 
         [LoggerMessage(EventId = 76, Level = LogLevel.Information, Message = "Work-item stream ended by the backend (graceful close). Will reconnect.")]
-        public static partial void StreamEndedByPeer(this ILogger logger);
-
+        public static partial void StreamEndedByPeer(this ILogger logger);
+
         [LoggerMessage(EventId = 77, Level = LogLevel.Warning, Message = "Transient gRPC error for '{OperationName}'. Attempt {Attempt} of {MaxAttempts}. Retrying in {BackoffMs} ms. StatusCode={StatusCode}")]
         public static partial void TransientGrpcRetry(this ILogger logger, string operationName, int attempt, int maxAttempts, double backoffMs, int statusCode, Exception exception);
+
+        [LoggerMessage(EventId = 78, Level = LogLevel.Warning, Message = "Activity notification callback failed for phase '{Phase}'.")]
+        public static partial void ActivityNotificationFailed(this ILogger logger, ActivityNotificationPhase phase, Exception exception);
     }
 }
diff --git a/test/Client/AzureManaged.Tests/Client.AzureManaged.Tests.csproj b/test/Client/AzureManaged.Tests/Client.AzureManaged.Tests.csproj
index ba569a77..b9b8cd70 100644
--- a/test/Client/AzureManaged.Tests/Client.AzureManaged.Tests.csproj
+++ b/test/Client/AzureManaged.Tests/Client.AzureManaged.Tests.csproj
@@ -4,10 +4,6 @@
     <TargetFramework>net10.0</TargetFramework>
   </PropertyGroup>
 
-  <ItemGroup>
-    <Compile Include="../../../src/Shared/AzureManaged/**/*.cs" />
-  </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
     <PackageReference Include="Grpc.Core" />
@@ -15,6 +11,7 @@
 
   <ItemGroup>
     <ProjectReference Include="../../../src/Client/AzureManaged/Client.AzureManaged.csproj" />
+    <ProjectReference Include="../../../src/Client/AzureManaged.Sandboxes/Client.AzureManaged.Sandboxes.csproj" />
     <ProjectReference Include="../../TestHelpers/TestHelpers.csproj" />
   </ItemGroup>
 
diff --git a/test/Client/AzureManaged.Tests/SandboxActivitiesClientTests.cs b/test/Client/AzureManaged.Tests/SandboxActivitiesClientTests.cs
new file mode 100644
index 00000000..9c7dc1e3
--- /dev/null
+++ b/test/Client/AzureManaged.Tests/SandboxActivitiesClientTests.cs
@@ -0,0 +1,448 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Reflection;
+using FluentAssertions;
+using Grpc.Core;
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Microsoft.DurableTask.Client.Grpc;
+using Microsoft.DurableTask.Protobuf.Sandboxes;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+using Xunit;
+
+namespace Microsoft.DurableTask.Client.AzureManaged.Tests;
+
+public class SandboxActivitiesClientTests
+{
+    const string TaskHub = "testhub";
+
+    [Fact]
+    public void OnDemandSandboxWorkerProfileContract_DoesNotExposeRemovedOptions()
+    {
+        typeof(SandboxWorkerProfileOptions).GetProperty("LaunchCommand").Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty("WorkerProfileRetryMaxAttempts").Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty("WorkerProfileRetryDelay").Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty(
+            "HeartbeatInterval",
+            BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic).Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty("WakeupPort").Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty(
+            "WorkerRegistrationRetryInitialDelay",
+            BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic).Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty(
+            "WorkerRegistrationRetryMaxDelay",
+            BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic).Should().BeNull();
+        typeof(SandboxWorkerProfileOptions).GetProperty(
+            "Mode",
+            BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic).Should().BeNull();
+        typeof(SandboxWorkerProfile).GetProperty("LaunchCommand").Should().BeNull();
+    }
+
+    [Fact]
+    public void OnDemandSandboxWorkerProfileContract_ExposesProfileAddActivityOnly()
+    {
+        // Arrange
+        Type optionsType = typeof(SandboxWorkerProfileOptions);
+        Type? activityAttributeType = typeof(SandboxWorkerProfileOptions).Assembly.GetType(
+            "Microsoft.DurableTask.Client.AzureManaged.SandboxesActivityAttribute");
+
+        // Act/Assert
+        optionsType.GetProperty("ActivityNames").Should().BeNull();
+        optionsType.GetMethod("AddActivity", [typeof(string)]).Should().BeNull();
+        optionsType.GetMethod("AddActivity", [typeof(string), typeof(string)]).Should().NotBeNull();
+        optionsType.GetMethods().Should().Contain(method =>
+            method.Name == "AddActivity" && method.IsGenericMethodDefinition);
+        activityAttributeType.Should().BeNull();
+    }
+
+    [Theory]
+    [InlineData("500m", "1024Mi")]
+    [InlineData("0.5", "1Gi")]
+    [InlineData("2", "2048")]
+    public void SandboxWorkerProfileBuilder_BuildWorkerProfile_AcceptsAdcResourceQuantities(
+        string cpu,
+        string memory)
+    {
+        // Arrange
+        SandboxWorkerProfileOptions options = CreateWorkerProfileOptions();
+        options.Cpu = cpu;
+        options.Memory = memory;
+
+        // Act
+        SandboxWorkerProfile workerProfile = SandboxWorkerProfileBuilder.BuildWorkerProfile(
+            options,
+            SandboxWorkerProfileBuilder.ResolveActivities(options.Activities));
+
+        // Assert
+        workerProfile.Resources.Cpu.Should().Be(cpu);
+        workerProfile.Resources.Memory.Should().Be(memory);
+    }
+
+    [Theory]
+    [InlineData("0", "1024Mi", "CPU")]
+    [InlineData("0m", "1024Mi", "CPU")]
+    [InlineData("500.5m", "1024Mi", "CPU")]
+    [InlineData("500Mi", "1024Mi", "CPU")]
+    [InlineData("500m", "0", "memory")]
+    [InlineData("500m", "0Mi", "memory")]
+    [InlineData("500m", "500m", "memory")]
+    public void SandboxWorkerProfileBuilder_BuildWorkerProfile_RejectsInvalidAdcResourceQuantities(
+        string cpu,
+        string memory,
+        string expectedMessage)
+    {
+        // Arrange
+        SandboxWorkerProfileOptions options = CreateWorkerProfileOptions();
+        options.Cpu = cpu;
+        options.Memory = memory;
+
+        // Act
+        Action action = () => SandboxWorkerProfileBuilder.BuildWorkerProfile(
+            options,
+            SandboxWorkerProfileBuilder.ResolveActivities(options.Activities));
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage($"*{expectedMessage}*");
+    }
+
+    [Fact]
+    public void SandboxWorkerProfileBuilder_ResolveActivities_DeduplicatesCaseInsensitively()
+    {
+        // Arrange
+        SandboxWorkerProfileOptions options = CreateWorkerProfileOptions();
+        options.AddActivity(" RemoteHello ", version: null);
+        options.AddActivity("remotehello", version: null);
+        options.AddActivity("Other", "v1");
+
+        // Act
+        SandboxActivityMetadata.Activity[] activities = SandboxWorkerProfileBuilder.ResolveActivities(options.Activities);
+
+        // Assert
+        activities.Should().Equal(
+            new SandboxActivityMetadata.Activity("RemoteHello", Version: null),
+            new SandboxActivityMetadata.Activity("Other", "v1"));
+    }
+
+    [Fact]
+    public void SandboxWorkerProfileBuilder_BuildWorkerProfile_RequiresSchedulerManagedIdentityClientId()
+    {
+        // Arrange
+        SandboxWorkerProfileOptions options = CreateWorkerProfileOptions();
+        options.SchedulerManagedIdentityClientId = " ";
+
+        // Act
+        Action action = () => SandboxWorkerProfileBuilder.BuildWorkerProfile(
+            options,
+            SandboxWorkerProfileBuilder.ResolveActivities(options.Activities));
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("*managed identity client ID*");
+    }
+
+    [Fact]
+    public void SandboxWorkerProfileBuilder_BuildWorkerProfile_RequiresImagePullManagedIdentityClientId()
+    {
+        // Arrange
+        SandboxWorkerProfileOptions options = CreateWorkerProfileOptions();
+        options.ImagePullManagedIdentityClientId = " ";
+
+        // Act
+        Action action = () => SandboxWorkerProfileBuilder.BuildWorkerProfile(
+            options,
+            SandboxWorkerProfileBuilder.ResolveActivities(options.Activities));
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("*managed identity client ID ADC uses to pull the worker image*");
+    }
+
+    [Fact]
+    public void SandboxWorkerProfileProvider_ResolveWorkerProfiles_UsesWorkerProfileConfigure()
+    {
+        // Arrange
+        using EnvironmentVariableScope image = new("DTS_ON_DEMAND_SANDBOX_ACTIVITY_IMAGE", "example.com/not-used:latest");
+        using EnvironmentVariableScope cpu = new("DTS_ON_DEMAND_SANDBOX_CPU", "2000m");
+        using EnvironmentVariableScope memory = new("DTS_ON_DEMAND_SANDBOX_MEMORY", "4096Mi");
+        using EnvironmentVariableScope maxActivities = new("DTS_SANDBOX_MAX_ACTIVITIES", "99");
+
+        SandboxWorkerProfileProvider provider = new();
+
+        // Act
+        SandboxWorkerProfileOptions options = provider.ResolveWorkerProfiles(TaskHub)
+            .Single(options => options.WorkerProfileId == "annotated-profile");
+        SandboxWorkerProfile workerProfile = SandboxWorkerProfileBuilder.BuildWorkerProfile(
+            options,
+            SandboxWorkerProfileBuilder.ResolveActivities(options.Activities));
+
+        // Assert
+        workerProfile.WorkerProfileId.Should().Be("annotated-profile");
+        workerProfile.Activities.Select(static activity => activity.Name).Should().Equal("ConfiguredRemoteHello");
+        workerProfile.Activities.Select(static activity => activity.Version).Should().Equal("v1");
+        workerProfile.Image.ImageRef.Should().Be("example.com/repo/annotated-worker:latest");
+        workerProfile.Image.ManagedIdentityClientId.Should().Be("image-pull-client-id");
+        workerProfile.SchedulerManagedIdentityClientId.Should().Be("scheduler-client-id");
+        workerProfile.Resources.Cpu.Should().Be("500m");
+        workerProfile.Resources.Memory.Should().Be("1024Mi");
+        workerProfile.MaxConcurrentActivities.Should().Be(4);
+        workerProfile.EnvironmentVariables.Should().ContainKey("CUSTOM_ENV").WhoseValue.Should().Be("configured-value");
+        workerProfile.Image.Entrypoint.Should().BeEmpty();
+        workerProfile.Image.Cmd.Should().BeEmpty();
+    }
+
+    [Fact]
+    public void SandboxWorkerProfileProvider_ValidateProfileType_RequiresProfileInterface()
+    {
+        // Arrange
+        // Act
+        Action action = () => SandboxWorkerProfileProvider.ValidateProfileType(typeof(ProfileWithoutInterface));
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage($"*{nameof(ISandboxWorkerProfile)}*");
+    }
+
+    [Fact]
+    public void SandboxWorkerProfileProvider_ResolveWorkerProfiles_DetectsCaseInsensitiveActivityOwnership()
+    {
+        // Arrange
+        using EnvironmentVariableScope enableDuplicateCaseProfiles = new(
+            "DTS_TEST_ENABLE_CASE_DUPLICATE_SANDBOX_PROFILES",
+            "true");
+        SandboxWorkerProfileProvider provider = new();
+
+        // Act
+        Action action = () => provider.ResolveWorkerProfiles(TaskHub);
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .Where(ex => ex.Message.Contains("CaseActivity", StringComparison.OrdinalIgnoreCase)
+                && ex.Message.Contains("case-profile-a", StringComparison.Ordinal)
+                && ex.Message.Contains("case-profile-b", StringComparison.Ordinal));
+    }
+
+    [Fact]
+    public async Task AddDurableTaskSchedulerSandboxActivitiesClient_UsesConfiguredDurableTaskClientInvoker()
+    {
+        // Arrange
+        RecordingOnDemandSandboxLogCallInvoker callInvoker = new();
+        ServiceCollection services = new();
+        services.AddOptions<DurableTaskSchedulerClientOptions>(Options.DefaultName)
+            .Configure(options => options.TaskHubName = "client-test-taskhub");
+        services.AddOptions<GrpcDurableTaskClientOptions>(Options.DefaultName)
+            .Configure(options => options.CallInvoker = callInvoker);
+        services.AddDurableTaskSchedulerSandboxActivitiesClient();
+
+        using ServiceProvider provider = services.BuildServiceProvider();
+        SandboxActivitiesClient client = provider.GetRequiredService<SandboxActivitiesClient>();
+
+        // Act
+        await client.RemoveSandboxWorkerProfileAsync("profile-a");
+
+        // Assert
+        callInvoker.RemoveRequest.Should().NotBeNull();
+        callInvoker.RemoveRequest!.WorkerProfileId.Should().Be("profile-a");
+        callInvoker.RemoveHeaders.Should().Contain(header => header.Key == "taskhub" && header.Value == "client-test-taskhub");
+    }
+
+    [Fact]
+    public async Task EnableSandboxActivitiesAsync_SendsWorkerProfileWorkerProfiles()
+    {
+        // Arrange
+        RecordingOnDemandSandboxLogCallInvoker callInvoker = new();
+        SandboxActivitiesClient client = new(
+            new SandboxActivitiesGrpcTransport(new SandboxActivities.SandboxActivitiesClient(callInvoker)),
+            "client-test-taskhub",
+            new SandboxWorkerProfileProvider());
+
+        // Act
+        await client.EnableSandboxActivitiesAsync();
+
+        // Assert
+        SandboxWorkerProfile workerProfile = callInvoker.DeclareRequests
+            .Should()
+            .ContainSingle(request => request.WorkerProfileId == "client-test-profile")
+            .Subject;
+        workerProfile.Activities.Select(static activity => activity.Name).Should().Equal("ClientTestRemoteActivity");
+        workerProfile.Activities.Select(static activity => activity.Version).Should().Equal("v1");
+        workerProfile.Image.ImageRef.Should().Be("example.com/client-test-worker:latest");
+        callInvoker.DeclareHeaders.Should().Contain(header => header.Key == "taskhub" && header.Value == "client-test-taskhub");
+        callInvoker.UnaryDisposeCount.Should().BeGreaterThan(0);
+    }
+
+    sealed class RecordingOnDemandSandboxLogCallInvoker : CallInvoker
+    {
+        public List<SandboxWorkerProfile> DeclareRequests { get; } = [];
+
+        public Metadata DeclareHeaders { get; private set; } = [];
+
+        public RemoveSandboxWorkerProfileRequest? RemoveRequest { get; private set; }
+
+        public Metadata RemoveHeaders { get; private set; } = [];
+
+        public int UnaryDisposeCount { get; private set; }
+
+        public override TResponse BlockingUnaryCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options,
+            TRequest request)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options,
+            TRequest request)
+        {
+            if (method.FullName.EndsWith("/DeclareSandboxWorkerProfile", StringComparison.Ordinal))
+            {
+                this.DeclareRequests.Add(((SandboxWorkerProfile)(object)request).Clone());
+                this.DeclareHeaders = options.Headers ?? [];
+                return CreateUnaryCall((TResponse)(object)new DeclareSandboxWorkerProfileResult());
+            }
+
+            if (method.FullName.EndsWith("/RemoveSandboxWorkerProfile", StringComparison.Ordinal))
+            {
+                this.RemoveRequest = (RemoveSandboxWorkerProfileRequest)(object)request;
+                this.RemoveHeaders = options.Headers ?? [];
+                return CreateUnaryCall((TResponse)(object)new RemoveSandboxWorkerProfileResult());
+            }
+
+            throw new NotSupportedException(method.FullName);
+        }
+
+        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options,
+            TRequest request)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options)
+        {
+            throw new NotSupportedException();
+        }
+
+        AsyncUnaryCall<TResponse> CreateUnaryCall<TResponse>(TResponse response)
+        {
+            return new AsyncUnaryCall<TResponse>(
+                Task.FromResult(response),
+                Task.FromResult(new Metadata()),
+                () => new Status(StatusCode.OK, string.Empty),
+                () => new Metadata(),
+                () => this.UnaryDisposeCount++);
+        }
+    }
+
+    static SandboxWorkerProfileOptions CreateWorkerProfileOptions()
+    {
+        SandboxWorkerProfileOptions options = new()
+        {
+            TaskHub = TaskHub,
+            WorkerProfileId = "profile-a",
+            ContainerImage = "mcr.microsoft.com/durabletask/demo-worker:1.0",
+            ImagePullManagedIdentityClientId = "image-pull-client-id",
+            SchedulerManagedIdentityClientId = "scheduler-client-id",
+            Cpu = "500m",
+            Memory = "1024Mi",
+            MaxConcurrentActivities = 7,
+        };
+        options.AddActivity("RemoteHello", version: null);
+        return options;
+    }
+
+    [SandboxWorkerProfile("client-test-profile")]
+    sealed class ClientTestWorkerProfile : ISandboxWorkerProfile
+    {
+        public void Configure(SandboxWorkerProfileOptions options)
+        {
+            options.ContainerImage = "example.com/client-test-worker:latest";
+            options.ImagePullManagedIdentityClientId = "image-pull-client-id";
+            options.SchedulerManagedIdentityClientId = "scheduler-client-id";
+            options.Cpu = "500m";
+            options.Memory = "1024Mi";
+            options.MaxConcurrentActivities = 4;
+            options.AddActivity("ClientTestRemoteActivity", "v1");
+        }
+    }
+
+    [SandboxWorkerProfile("annotated-profile")]
+    sealed class AnnotatedWorkerProfile : ISandboxWorkerProfile
+    {
+        public static int ConfigureCallCount { get; private set; }
+
+        public void Configure(SandboxWorkerProfileOptions options)
+        {
+            ConfigureCallCount++;
+            options.ContainerImage = "example.com/repo/annotated-worker:latest";
+            options.ImagePullManagedIdentityClientId = "image-pull-client-id";
+            options.SchedulerManagedIdentityClientId = "scheduler-client-id";
+            options.Cpu = "500m";
+            options.Memory = "1024Mi";
+            options.MaxConcurrentActivities = 4;
+            options.EnvironmentVariables["CUSTOM_ENV"] = "configured-value";
+            options.AddActivity("ConfiguredRemoteHello", "v1");
+        }
+    }
+
+    [SandboxWorkerProfile("case-profile-a")]
+    sealed class CaseDuplicateWorkerProfileA : ISandboxWorkerProfile
+    {
+        public void Configure(SandboxWorkerProfileOptions options)
+        {
+            if (Environment.GetEnvironmentVariable("DTS_TEST_ENABLE_CASE_DUPLICATE_SANDBOX_PROFILES") == "true")
+            {
+                options.AddActivity("CaseActivity", version: null);
+            }
+        }
+    }
+
+    [SandboxWorkerProfile("case-profile-b")]
+    sealed class CaseDuplicateWorkerProfileB : ISandboxWorkerProfile
+    {
+        public void Configure(SandboxWorkerProfileOptions options)
+        {
+            if (Environment.GetEnvironmentVariable("DTS_TEST_ENABLE_CASE_DUPLICATE_SANDBOX_PROFILES") == "true")
+            {
+                options.AddActivity("caseactivity", version: null);
+            }
+        }
+    }
+
+    sealed class ProfileWithoutInterface
+    {
+    }
+
+    sealed class EnvironmentVariableScope : IDisposable
+    {
+        readonly string name;
+        readonly string? originalValue;
+
+        public EnvironmentVariableScope(string name, string? value)
+        {
+            this.name = name;
+            this.originalValue = Environment.GetEnvironmentVariable(name);
+            Environment.SetEnvironmentVariable(name, value);
+        }
+
+        public void Dispose() => Environment.SetEnvironmentVariable(this.name, this.originalValue);
+    }
+}
diff --git a/test/Shared/AzureManaged.Tests/Shared.AzureManaged.Tests.csproj b/test/Shared/AzureManaged.Tests/Shared.AzureManaged.Tests.csproj
index 4599449b..5d7f0abd 100644
--- a/test/Shared/AzureManaged.Tests/Shared.AzureManaged.Tests.csproj
+++ b/test/Shared/AzureManaged.Tests/Shared.AzureManaged.Tests.csproj
@@ -17,6 +17,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ProjectReference Include="..\..\..\src\Grpc\Grpc.csproj" />
     <ProjectReference Include="..\..\TestHelpers\TestHelpers.csproj" />
   </ItemGroup>
 </Project>
diff --git a/test/Worker/AzureManaged.Tests/SandboxActivitiesTests.cs b/test/Worker/AzureManaged.Tests/SandboxActivitiesTests.cs
new file mode 100644
index 00000000..146d142b
--- /dev/null
+++ b/test/Worker/AzureManaged.Tests/SandboxActivitiesTests.cs
@@ -0,0 +1,1131 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Azure.Identity;
+using FluentAssertions;
+using Grpc.Core;
+using Microsoft.DurableTask.AzureManaged.Internal;
+using Microsoft.DurableTask.Protobuf.Sandboxes;
+using Microsoft.DurableTask.Worker.AzureManaged;
+using Microsoft.DurableTask.Worker.AzureManaged.Sandboxes;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+using Moq;
+using Xunit;
+
+namespace Microsoft.DurableTask.Worker.AzureManaged.Tests;
+
+public class SandboxActivitiesTests
+{
+    const string TaskHub = "testhub";
+
+    [Fact]
+    public async Task SandboxActivitiesGrpcTransport_SendsTaskHubMetadata()
+    {
+        // Arrange
+        RecordingSandboxActivitiesCallInvoker callInvoker = new();
+        SandboxActivitiesGrpcTransport transport = new(new SandboxActivities.SandboxActivitiesClient(callInvoker));
+        SandboxWorkerProfile workerProfile = new()
+        {
+            WorkerProfileId = "profile-a",
+            Image = new SandboxActivityImage
+            {
+                ImageRef = "example.com/repo/worker:latest",
+            },
+            Resources = new SandboxActivityResources
+            {
+                Cpu = "500m",
+                Memory = "1024Mi",
+            },
+            MaxConcurrentActivities = 7,
+        };
+        workerProfile.Activities.Add(new SandboxActivity { Name = "RemoteHello" });
+
+        // Act
+        await transport.DeclareSandboxWorkerProfileAsync(workerProfile, TaskHub, CancellationToken.None);
+        await using ISandboxActivityWorkerSession session = transport.OpenSandboxActivityWorkerSession(
+            TaskHub,
+            CancellationToken.None);
+
+        // Assert
+        callInvoker.WorkerProfileHeaders.Should().Contain(header => header.Key == "taskhub" && header.Value == TaskHub);
+        callInvoker.WorkerSessionHeaders.Should().Contain(header => header.Key == "taskhub" && header.Value == TaskHub);
+    }
+
+    [Fact]
+    public async Task SandboxActivitiesGrpcTransport_CanRelyOnChannelTaskHubMetadata()
+    {
+        // Arrange
+        RecordingSandboxActivitiesCallInvoker callInvoker = new();
+        SandboxActivitiesGrpcTransport transport = new(
+            new SandboxActivities.SandboxActivitiesClient(callInvoker),
+            attachTaskHubMetadata: false);
+        SandboxWorkerProfile workerProfile = new()
+        {
+            WorkerProfileId = "profile-a",
+            Image = new SandboxActivityImage
+            {
+                ImageRef = "example.com/repo/worker:latest",
+            },
+            Resources = new SandboxActivityResources
+            {
+                Cpu = "500m",
+                Memory = "1024Mi",
+            },
+            MaxConcurrentActivities = 7,
+        };
+        workerProfile.Activities.Add(new SandboxActivity { Name = "RemoteHello" });
+
+        // Act
+        await transport.DeclareSandboxWorkerProfileAsync(workerProfile, TaskHub, CancellationToken.None);
+        await using ISandboxActivityWorkerSession session = transport.OpenSandboxActivityWorkerSession(
+            TaskHub,
+            CancellationToken.None);
+
+        // Assert
+        callInvoker.WorkerProfileHeaders.Should().NotContain(header => header.Key == "taskhub");
+        callInvoker.WorkerSessionHeaders.Should().NotContain(header => header.Key == "taskhub");
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_SendsLiveWorkerMetadataWithRegisteredActivities()
+    {
+        // Arrange
+        string? originalSandboxProvider = Environment.GetEnvironmentVariable("DTS_SANDBOX_PROVIDER");
+        string? originalSandboxId = Environment.GetEnvironmentVariable("DTS_SANDBOX_ID");
+        Environment.SetEnvironmentVariable("DTS_SANDBOX_PROVIDER", "Sandbox");
+        Environment.SetEnvironmentVariable("DTS_SANDBOX_ID", "sandbox-1");
+
+        try
+        {
+            SandboxWorkerRuntimeOptions options = new()
+            {
+                TaskHub = TaskHub,
+                WorkerProfileId = "profile-a",
+                MaxConcurrentActivities = 3,
+                HeartbeatInterval = TimeSpan.FromDays(1),
+            };
+            FakeSandboxActivitiesTransport client = new();
+            SandboxActivityWorkerRegistrationHostedService service = new(
+                client,
+                options,
+                Activities("RemoteHello"),
+                NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance);
+
+            // Act
+            await service.StartAsync(CancellationToken.None);
+            await client.Session.WaitForMessageAsync(message => message.Start != null);
+            await service.StopAsync(CancellationToken.None);
+
+            // Assert
+            client.SessionTaskHubs.Should().Equal(TaskHub);
+            SandboxActivityWorkerMessage message = client.Session.Messages.Should().ContainSingle().Subject;
+            SandboxActivityWorkerStart start = message.Start;
+            start.TaskHub.Should().Be(TaskHub);
+            start.WorkerProfileId.Should().Be("profile-a");
+            start.MaxActivitiesCount.Should().Be(3);
+            start.SandboxProvider.Should().Be(SandboxProviderKind.Sandbox);
+            start.DtsSandboxIdentifier.Should().Be("sandbox-1");
+            start.Activities.Select(static activity => activity.Name).Should().Equal("RemoteHello");
+            start.Activities.Select(static activity => activity.Version).Should().Equal(string.Empty);
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("DTS_SANDBOX_PROVIDER", originalSandboxProvider);
+            Environment.SetEnvironmentVariable("DTS_SANDBOX_ID", originalSandboxId);
+        }
+    }
+
+    [Fact]
+    public void SandboxWorkerMessageBuilder_NormalizesTaskHubAndSandboxId()
+    {
+        // Arrange
+        string? originalSandboxId = Environment.GetEnvironmentVariable("DTS_SANDBOX_ID");
+        Environment.SetEnvironmentVariable("DTS_SANDBOX_ID", " sandbox-1 ");
+
+        try
+        {
+            SandboxWorkerRuntimeOptions options = new()
+            {
+                TaskHub = " testhub ",
+                WorkerProfileId = "profile-a",
+                MaxConcurrentActivities = 3,
+            };
+
+            // Act
+            SandboxActivityWorkerMessage message = SandboxWorkerMessageBuilder.BuildWorkerStart(
+                options,
+                Activities("RemoteHello"));
+
+            // Assert
+            SandboxActivityWorkerStart start = message.Start;
+            start.TaskHub.Should().Be(TaskHub);
+            start.DtsSandboxIdentifier.Should().Be("sandbox-1");
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("DTS_SANDBOX_ID", originalSandboxId);
+        }
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("   ")]
+    public void SandboxWorkerMessageBuilder_MissingSandboxId_Throws(string? sandboxId)
+    {
+        // Arrange
+        string? originalSandboxId = Environment.GetEnvironmentVariable("DTS_SANDBOX_ID");
+        Environment.SetEnvironmentVariable("DTS_SANDBOX_ID", sandboxId);
+
+        try
+        {
+            SandboxWorkerRuntimeOptions options = new()
+            {
+                TaskHub = TaskHub,
+                WorkerProfileId = "profile-a",
+                MaxConcurrentActivities = 3,
+            };
+
+            // Act
+            Action action = () => SandboxWorkerMessageBuilder.BuildWorkerStart(
+                options,
+                Activities("RemoteHello"));
+
+            // Assert
+            action.Should().Throw<InvalidOperationException>()
+                .WithMessage("On-demand sandbox activity worker registration requires a DTS sandbox ID.");
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("DTS_SANDBOX_ID", originalSandboxId);
+        }
+    }
+
+    [Fact]
+    public void SandboxActivityTracker_TracksInFlightActivityCount()
+    {
+        // Arrange
+        SandboxActivityTracker activityTracker = new();
+
+        // Act
+        activityTracker.NotifyActivityStarted();
+        activityTracker.NotifyActivityStarted();
+
+        // Assert
+        activityTracker.InFlightCount.Should().Be(2);
+
+        // Act
+        activityTracker.NotifyActivityCompleted();
+
+        // Assert
+        activityTracker.InFlightCount.Should().Be(1);
+
+        // Act
+        activityTracker.NotifyActivityCompleted();
+        activityTracker.NotifyActivityCompleted();
+
+        // Assert
+        activityTracker.InFlightCount.Should().Be(0);
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_SendsHeartbeatWithCurrentInFlightCount()
+    {
+        // Arrange
+        using EnvironmentVariableScope sandboxId = new("DTS_SANDBOX_ID", "sandbox-1");
+        SandboxWorkerRuntimeOptions options = new()
+        {
+            TaskHub = TaskHub,
+            WorkerProfileId = "profile-a",
+            MaxConcurrentActivities = 3,
+            HeartbeatInterval = TimeSpan.FromMilliseconds(10),
+        };
+
+        FakeSandboxActivitiesTransport client = new();
+        SandboxActivityTracker activityTracker = new();
+        activityTracker.NotifyActivityStarted();
+        activityTracker.NotifyActivityStarted();
+
+        SandboxActivityWorkerRegistrationHostedService service = new(
+            client,
+            options,
+            Activities("RemoteHello"),
+            NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance,
+            activityTracker: activityTracker);
+
+        // Act
+        await service.StartAsync(CancellationToken.None);
+        await client.Session.WaitForMessageAsync(message => message.Heartbeat?.ActiveActivitiesCount == 2);
+        activityTracker.NotifyActivityCompleted();
+        await client.Session.WaitForMessageAsync(message => message.Heartbeat?.ActiveActivitiesCount == 1);
+        await service.StopAsync(CancellationToken.None);
+
+        // Assert
+        client.Session.Messages.Should().Contain(message => message.Heartbeat != null && message.Heartbeat.ActiveActivitiesCount == 2);
+        client.Session.Messages.Should().Contain(message => message.Heartbeat != null && message.Heartbeat.ActiveActivitiesCount == 1);
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_ReopensSessionAfterTransientStreamFailure()
+    {
+        // Arrange
+        using EnvironmentVariableScope sandboxId = new("DTS_SANDBOX_ID", "sandbox-1");
+        SandboxWorkerRuntimeOptions options = new()
+        {
+            TaskHub = TaskHub,
+            WorkerProfileId = "profile-a",
+            MaxConcurrentActivities = 3,
+            HeartbeatInterval = TimeSpan.FromMilliseconds(10),
+            WorkerRegistrationRetryInitialDelay = TimeSpan.FromMilliseconds(10),
+            WorkerRegistrationRetryMaxDelay = TimeSpan.FromMilliseconds(10),
+        };
+
+        FakeSandboxActivityWorkerSession failedSession = new() { ThrowOnWriteAttempt = 2 };
+        FakeSandboxActivityWorkerSession recoveredSession = new();
+        FakeSandboxActivitiesTransport client = new();
+        client.QueueSession(failedSession);
+        client.QueueSession(recoveredSession);
+
+        SandboxActivityWorkerRegistrationHostedService service = new(
+            client,
+            options,
+            Activities("RemoteHello"),
+            NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance);
+
+        // Act
+        await service.StartAsync(CancellationToken.None);
+        await failedSession.WaitForMessageAsync(message => message.Start != null);
+        await recoveredSession.WaitForMessageAsync(message => message.Start != null);
+        await service.StopAsync(CancellationToken.None);
+
+        // Assert
+        client.SessionTaskHubs.Should().Equal(TaskHub, TaskHub);
+        failedSession.Messages.Should().ContainSingle(message => message.Start != null);
+        recoveredSession.Messages.Should().ContainSingle(message => message.Start != null);
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_ReopensSessionAfterTerminalServerFailure()
+    {
+        // Arrange
+        using EnvironmentVariableScope sandboxId = new("DTS_SANDBOX_ID", "sandbox-1");
+        SandboxWorkerRuntimeOptions options = new()
+        {
+            TaskHub = $" {TaskHub} ",
+            WorkerProfileId = "profile-a",
+            MaxConcurrentActivities = 3,
+            HeartbeatInterval = TimeSpan.FromDays(1),
+            WorkerRegistrationRetryInitialDelay = TimeSpan.FromMilliseconds(10),
+            WorkerRegistrationRetryMaxDelay = TimeSpan.FromMilliseconds(10),
+        };
+
+        FakeSandboxActivityWorkerSession failedSession = new();
+        FakeSandboxActivityWorkerSession recoveredSession = new();
+        FakeSandboxActivitiesTransport client = new();
+        client.QueueSession(failedSession);
+        client.QueueSession(recoveredSession);
+
+        SandboxActivityWorkerRegistrationHostedService service = new(
+            client,
+            options,
+            Activities("RemoteHello"),
+            NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance);
+
+        // Act
+        await service.StartAsync(CancellationToken.None);
+        await failedSession.WaitForMessageAsync(message => message.Start != null);
+        failedSession.FailCompletion(new RpcException(new Status(StatusCode.Unavailable, "terminal")));
+        await recoveredSession.WaitForMessageAsync(message => message.Start != null);
+        await service.StopAsync(CancellationToken.None);
+
+        // Assert
+        client.SessionTaskHubs.Should().Equal(TaskHub, TaskHub);
+        failedSession.Messages.Should().ContainSingle(message => message.Start != null);
+        recoveredSession.Messages.Should().ContainSingle(message => message.Start != null);
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_DoesNotResetBackoffAfterStartMessageOnly()
+    {
+        // Arrange
+        using EnvironmentVariableScope sandboxId = new("DTS_SANDBOX_ID", "sandbox-1");
+        SandboxWorkerRuntimeOptions options = new()
+        {
+            TaskHub = TaskHub,
+            WorkerProfileId = "profile-a",
+            MaxConcurrentActivities = 3,
+            HeartbeatInterval = TimeSpan.FromDays(1),
+            WorkerRegistrationRetryInitialDelay = TimeSpan.FromMilliseconds(250),
+            WorkerRegistrationRetryMaxDelay = TimeSpan.FromSeconds(1),
+        };
+
+        FakeSandboxActivityWorkerSession firstFailedSession = new();
+        FakeSandboxActivityWorkerSession secondFailedSession = new();
+        FakeSandboxActivityWorkerSession recoveredSession = new();
+        FakeSandboxActivitiesTransport client = new();
+        client.QueueSession(firstFailedSession);
+        client.QueueSession(secondFailedSession);
+        client.QueueSession(recoveredSession);
+
+        SandboxActivityWorkerRegistrationHostedService service = new(
+            client,
+            options,
+            Activities("RemoteHello"),
+            NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance,
+            reconnectJitter: new DeterministicRandom(0.999999));
+
+        // Act
+        await service.StartAsync(CancellationToken.None);
+        await firstFailedSession.WaitForMessageAsync(message => message.Start != null);
+        firstFailedSession.FailCompletion(new RpcException(new Status(StatusCode.Unavailable, "terminal-1")));
+        await secondFailedSession.WaitForMessageAsync(message => message.Start != null);
+        secondFailedSession.FailCompletion(new RpcException(new Status(StatusCode.Unavailable, "terminal-2")));
+        Task recoveredStartTask = recoveredSession.WaitForMessageAsync(message => message.Start != null);
+        Task completedTooEarly = await Task.WhenAny(
+            recoveredStartTask,
+            Task.Delay(TimeSpan.FromMilliseconds(375)));
+        await recoveredStartTask.WaitAsync(TimeSpan.FromSeconds(5));
+        await service.StopAsync(CancellationToken.None);
+
+        // Assert
+        completedTooEarly.Should().NotBe(recoveredStartTask);
+        client.SessionTaskHubs.Should().Equal(TaskHub, TaskHub, TaskHub);
+    }
+
+    [Fact]
+    public void SandboxActivityWorkerRegistrationHostedService_ComputeJitteredReconnectDelay_UsesFullJitterWindow()
+    {
+        // Arrange
+        TimeSpan retryDelay = TimeSpan.FromSeconds(10);
+
+        // Act
+        TimeSpan zero = SandboxActivityWorkerRegistrationHostedService.ComputeJitteredReconnectDelay(
+            TimeSpan.Zero,
+            new DeterministicRandom(0.5));
+        TimeSpan low = SandboxActivityWorkerRegistrationHostedService.ComputeJitteredReconnectDelay(
+            retryDelay,
+            new DeterministicRandom(0.0));
+        TimeSpan mid = SandboxActivityWorkerRegistrationHostedService.ComputeJitteredReconnectDelay(
+            retryDelay,
+            new DeterministicRandom(0.5));
+        TimeSpan high = SandboxActivityWorkerRegistrationHostedService.ComputeJitteredReconnectDelay(
+            retryDelay,
+            new DeterministicRandom(0.999999));
+
+        // Assert
+        zero.Should().Be(TimeSpan.Zero);
+        low.Should().Be(TimeSpan.Zero);
+        mid.Should().Be(TimeSpan.FromSeconds(5));
+        high.Should().BeGreaterThan(TimeSpan.FromSeconds(9));
+        high.Should().BeLessThan(retryDelay);
+    }
+
+    [Fact]
+    public void SandboxActivityWorkerRegistrationHostedService_GetNextRetryDelay_SaturatesBeforeTickOverflow()
+    {
+        // Arrange
+        // Act
+        TimeSpan nextRetryDelay = SandboxActivityWorkerRegistrationHostedService.ComputeNextRetryDelay(
+            TimeSpan.FromTicks((TimeSpan.MaxValue.Ticks / 2) + 1),
+            TimeSpan.MaxValue);
+
+        // Assert
+        nextRetryDelay.Should().Be(TimeSpan.MaxValue);
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_AppliesJitterToReconnectDelay()
+    {
+        // Arrange
+        using EnvironmentVariableScope sandboxId = new("DTS_SANDBOX_ID", "sandbox-1");
+        SandboxWorkerRuntimeOptions options = new()
+        {
+            TaskHub = TaskHub,
+            WorkerProfileId = "profile-a",
+            MaxConcurrentActivities = 3,
+            HeartbeatInterval = TimeSpan.FromMilliseconds(10),
+            WorkerRegistrationRetryInitialDelay = TimeSpan.FromDays(1),
+            WorkerRegistrationRetryMaxDelay = TimeSpan.FromDays(1),
+        };
+
+        FakeSandboxActivityWorkerSession failedSession = new() { ThrowOnWriteAttempt = 2 };
+        FakeSandboxActivityWorkerSession recoveredSession = new();
+        FakeSandboxActivitiesTransport client = new();
+        client.QueueSession(failedSession);
+        client.QueueSession(recoveredSession);
+
+        SandboxActivityWorkerRegistrationHostedService service = new(
+            client,
+            options,
+            Activities("RemoteHello"),
+            NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance,
+            reconnectJitter: new DeterministicRandom(0.0));
+
+        // Act
+        await service.StartAsync(CancellationToken.None);
+        await failedSession.WaitForMessageAsync(message => message.Start != null);
+        await recoveredSession.WaitForMessageAsync(message => message.Start != null);
+        await service.StopAsync(CancellationToken.None);
+
+        // Assert
+        client.SessionTaskHubs.Should().Equal(TaskHub, TaskHub);
+    }
+
+    [Fact]
+    public async Task SandboxActivityWorkerRegistrationHostedService_StopAsync_DoesNotCompleteStreamWhileWriteIsInFlight()
+    {
+        // Arrange
+        using EnvironmentVariableScope sandboxId = new("DTS_SANDBOX_ID", "sandbox-1");
+        SandboxWorkerRuntimeOptions options = new()
+        {
+            TaskHub = TaskHub,
+            WorkerProfileId = "profile-a",
+            MaxConcurrentActivities = 3,
+            HeartbeatInterval = TimeSpan.FromMilliseconds(10),
+        };
+
+        FakeSandboxActivityWorkerSession session = new() { BlockWriteAttempt = 2 };
+        FakeSandboxActivitiesTransport client = new();
+        client.QueueSession(session);
+
+        SandboxActivityWorkerRegistrationHostedService service = new(
+            client,
+            options,
+            Activities("RemoteHello"),
+            NullLogger<SandboxActivityWorkerRegistrationHostedService>.Instance);
+
+        // Act
+        await service.StartAsync(CancellationToken.None);
+        await session.WaitForBlockedWriteAsync();
+        Task stopTask = service.StopAsync(CancellationToken.None);
+        Task completeAttempt = session.WaitForCompleteAsync();
+        Task completeBeforeWriteReleased = await Task.WhenAny(
+            completeAttempt,
+            Task.Delay(TimeSpan.FromMilliseconds(100)));
+        session.ReleaseBlockedWrite();
+        await stopTask.WaitAsync(TimeSpan.FromSeconds(5));
+
+        // Assert
+        completeBeforeWriteReleased.Should().NotBe(completeAttempt);
+        session.CompleteCalled.Should().BeTrue();
+        session.CompleteCalledWhileWriteActive.Should().BeFalse();
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_ConfiguresRegisteredActivityWorkerFilter()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        using EnvironmentVariableScope sandboxProvider = new("DTS_SANDBOX_PROVIDER", "Sandbox");
+        using EnvironmentVariableScope maxActivities = new("DTS_SANDBOX_MAX_ACTIVITIES", "3");
+        ServiceCollection services = new();
+        services.Configure<DurableTaskRegistry>(
+            Options.DefaultName,
+            registry => registry.AddActivityFunc<string, string>(new TaskName("RemoteHello"), (_, input) => input));
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        mockBuilder.Object.UseSandboxWorker();
+
+        await using ServiceProvider provider = services.BuildServiceProvider();
+        DurableTaskWorkerWorkItemFilters filters = provider.GetRequiredService<IOptionsMonitor<DurableTaskWorkerWorkItemFilters>>().Get(Options.DefaultName);
+        DurableTaskWorkerOptions workerOptions = provider.GetRequiredService<IOptionsMonitor<DurableTaskWorkerOptions>>().Get(Options.DefaultName);
+
+        // Assert
+        filters.Activities.Select(filter => filter.Name).Should().Equal("RemoteHello");
+        filters.Orchestrations.Should().BeEmpty();
+        filters.Entities.Should().BeEmpty();
+        workerOptions.Concurrency.MaximumConcurrentActivityWorkItems.Should().Be(3);
+        workerOptions.Concurrency.MaximumConcurrentOrchestrationWorkItems.Should().Be(0);
+        workerOptions.Concurrency.MaximumConcurrentEntityWorkItems.Should().Be(0);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("0")]
+    [InlineData("-1")]
+    [InlineData("many")]
+    public async Task UseSandboxWorker_InvalidMaxActivities_ThrowsWhenWorkerOptionsAreResolved(string maxActivitiesValue)
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        using EnvironmentVariableScope sandboxProvider = new("DTS_SANDBOX_PROVIDER", "Sandbox");
+        using EnvironmentVariableScope maxActivities = new("DTS_SANDBOX_MAX_ACTIVITIES", maxActivitiesValue);
+        ServiceCollection services = new();
+        services.Configure<DurableTaskRegistry>(
+            Options.DefaultName,
+            registry => registry.AddActivityFunc<string, string>(new TaskName("RemoteHello"), (_, input) => input));
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        mockBuilder.Object.UseSandboxWorker();
+        await using ServiceProvider provider = services.BuildServiceProvider();
+
+        // Act
+        Action action = () => provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_SANDBOX_MAX_ACTIVITIES must be a positive integer when injected by DTS for on-demand sandbox workers.");
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_WithNoRegisteredActivities_FailsWhenWorkerFiltersAreResolved()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        using EnvironmentVariableScope sandboxProvider = new("DTS_SANDBOX_PROVIDER", "Sandbox");
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        mockBuilder.Object.UseSandboxWorker();
+
+        await using ServiceProvider provider = services.BuildServiceProvider();
+
+        // Act
+        Action act = () => provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskWorkerWorkItemFilters>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        act.Should().Throw<InvalidOperationException>()
+            .WithMessage("On-demand sandbox workers require at least one registered activity*");
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_ConfiguresSchedulerWithManagedIdentityCredential()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        mockBuilder.Object.UseSandboxWorker();
+
+        await using ServiceProvider provider = services.BuildServiceProvider();
+        DurableTaskSchedulerWorkerOptions options = provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskSchedulerWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        options.EndpointAddress.Should().Be("https://example.scheduler");
+        options.TaskHubName.Should().Be(TaskHub);
+        options.Credential.Should().BeOfType<ManagedIdentityCredential>();
+        options.AllowInsecureCredentials.Should().BeFalse();
+    }
+
+    [Fact]
+    public void UseSandboxWorker_MissingAuthentication_Throws()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", null);
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        Action action = () => mockBuilder.Object.UseSandboxWorker();
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_AUTHENTICATION must be injected by DTS for on-demand sandbox workers.");
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_InvalidAuthentication_ThrowsWhenSchedulerOptionsAreResolved()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentty");
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        mockBuilder.Object.UseSandboxWorker();
+        await using ServiceProvider provider = services.BuildServiceProvider();
+
+        // Act
+        Action action = () => provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskSchedulerWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_AUTHENTICATION must be 'ManagedIdentity' for on-demand sandbox workers.");
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_WithManagedIdentityAuth_ConfiguresSchedulerCredential()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        mockBuilder.Object.UseSandboxWorker();
+
+        await using ServiceProvider provider = services.BuildServiceProvider();
+        DurableTaskSchedulerWorkerOptions options = provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskSchedulerWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        options.EndpointAddress.Should().Be("https://example.scheduler");
+        options.TaskHubName.Should().Be(TaskHub);
+        options.Credential.Should().BeOfType<ManagedIdentityCredential>();
+        options.AllowInsecureCredentials.Should().BeFalse();
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_WithManagedIdentityAuthAndMissingClientId_Throws()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", null);
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        mockBuilder.Object.UseSandboxWorker();
+        await using ServiceProvider provider = services.BuildServiceProvider();
+        Action getOptions = () => provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskSchedulerWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        getOptions.Should().Throw<InvalidOperationException>()
+            .WithMessage("*DTS_UMI_CLIENT_ID*");
+    }
+
+    [Fact]
+    public void UseSandboxWorker_DoesNotRegisterWakeupServerHostedService()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        mockBuilder.Object.UseSandboxWorker();
+
+        // Assert
+        services.Count(descriptor => descriptor.ServiceType == typeof(IHostedService)).Should().Be(1);
+    }
+
+    [Fact]
+    public void UseSandboxWorker_MissingInjectedEndpoint_Throws()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", null);
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        Action action = () => mockBuilder.Object.UseSandboxWorker();
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_ENDPOINT must be injected by DTS for on-demand sandbox workers.");
+    }
+
+    [Fact]
+    public void UseSandboxWorker_MissingInjectedTaskHub_Throws()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", null);
+        ServiceCollection services = new();
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        // Act
+        Action action = () => mockBuilder.Object.UseSandboxWorker();
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_TASK_HUB must be injected by DTS for on-demand sandbox workers.");
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_MissingInjectedSandboxProvider_ThrowsWhenWorkerOptionsAreResolved()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        using EnvironmentVariableScope sandboxProvider = new("DTS_SANDBOX_PROVIDER", null);
+        ServiceCollection services = new();
+        services.Configure<DurableTaskRegistry>(
+            Options.DefaultName,
+            registry => registry.AddActivityFunc<string, string>(new TaskName("RemoteHello"), (_, input) => input));
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        mockBuilder.Object.UseSandboxWorker();
+        await using ServiceProvider provider = services.BuildServiceProvider();
+
+        // Act
+        Action action = () => provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_SANDBOX_PROVIDER must be injected by DTS for on-demand sandbox workers.");
+    }
+
+    [Fact]
+    public async Task UseSandboxWorker_InvalidInjectedSandboxProvider_ThrowsWhenWorkerOptionsAreResolved()
+    {
+        // Arrange
+        using EnvironmentVariableScope endpoint = new("DTS_ENDPOINT", "https://example.scheduler");
+        using EnvironmentVariableScope taskHub = new("DTS_TASK_HUB", TaskHub);
+        using EnvironmentVariableScope workerProfile = new("DTS_WORKER_PROFILE_ID", "profile-a");
+        using EnvironmentVariableScope auth = new("DTS_AUTHENTICATION", "ManagedIdentity");
+        using EnvironmentVariableScope clientId = new("DTS_UMI_CLIENT_ID", "worker-client-id");
+        using EnvironmentVariableScope sandboxProvider = new("DTS_SANDBOX_PROVIDER", "ContainerApp");
+        ServiceCollection services = new();
+        services.Configure<DurableTaskRegistry>(
+            Options.DefaultName,
+            registry => registry.AddActivityFunc<string, string>(new TaskName("RemoteHello"), (_, input) => input));
+        Mock<IDurableTaskWorkerBuilder> mockBuilder = new();
+        mockBuilder.Setup(builder => builder.Services).Returns(services);
+        mockBuilder.Setup(builder => builder.Name).Returns(Options.DefaultName);
+
+        mockBuilder.Object.UseSandboxWorker();
+        await using ServiceProvider provider = services.BuildServiceProvider();
+
+        // Act
+        Action action = () => provider
+            .GetRequiredService<IOptionsMonitor<DurableTaskWorkerOptions>>()
+            .Get(Options.DefaultName);
+
+        // Assert
+        action.Should().Throw<InvalidOperationException>()
+            .WithMessage("DTS_SANDBOX_PROVIDER must be 'Sandbox' or 'AcaSessionPool' for on-demand sandbox workers.");
+    }
+
+    static IReadOnlyCollection<SandboxActivityMetadata.Activity> Activities(params string[] names) =>
+        names.Select(static name => new SandboxActivityMetadata.Activity(name, Version: null)).ToArray();
+
+    sealed class FakeSandboxActivitiesTransport : ISandboxActivitiesTransport
+    {
+        readonly Queue<FakeSandboxActivityWorkerSession> queuedSessions = new();
+
+        public List<string> SessionTaskHubs { get; } = [];
+
+        public List<FakeSandboxActivityWorkerSession> Sessions { get; } = [];
+
+        public FakeSandboxActivityWorkerSession Session { get; } = new();
+
+        public void QueueSession(FakeSandboxActivityWorkerSession session) => this.queuedSessions.Enqueue(session);
+
+        public Task<DeclareSandboxWorkerProfileResult> DeclareSandboxWorkerProfileAsync(
+            SandboxWorkerProfile workerProfile,
+            string taskHub,
+            CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public Task<RemoveSandboxWorkerProfileResult> RemoveSandboxWorkerProfileAsync(
+            string workerProfileId,
+            string taskHub,
+            CancellationToken cancellationToken)
+        {
+            throw new NotSupportedException();
+        }
+
+        public ISandboxActivityWorkerSession OpenSandboxActivityWorkerSession(string taskHub, CancellationToken cancellationToken)
+        {
+            this.SessionTaskHubs.Add(taskHub);
+            FakeSandboxActivityWorkerSession session = this.queuedSessions.Count > 0
+                ? this.queuedSessions.Dequeue()
+                : this.Session;
+            this.Sessions.Add(session);
+            return session;
+        }
+    }
+
+    sealed class RecordingSandboxActivitiesCallInvoker : CallInvoker
+    {
+        public Metadata WorkerProfileHeaders { get; private set; } = [];
+
+        public Metadata WorkerSessionHeaders { get; private set; } = [];
+
+        public override TResponse BlockingUnaryCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options,
+            TRequest request)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options,
+            TRequest request)
+        {
+            method.FullName.Should().EndWith("/DeclareSandboxWorkerProfile");
+            this.WorkerProfileHeaders = options.Headers ?? [];
+
+            return new AsyncUnaryCall<TResponse>(
+                Task.FromResult((TResponse)(object)new DeclareSandboxWorkerProfileResult()),
+                Task.FromResult(new Metadata()),
+                () => new Status(StatusCode.OK, string.Empty),
+                () => [],
+                () => { });
+        }
+
+        public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options,
+            TRequest request)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options)
+        {
+            method.FullName.Should().EndWith("/ConnectSandboxActivityWorker");
+            this.WorkerSessionHeaders = options.Headers ?? [];
+
+            return new AsyncClientStreamingCall<TRequest, TResponse>(
+                new RecordingClientStreamWriter<TRequest>(),
+                Task.FromResult((TResponse)(object)new SandboxActivityWorkerSessionResult()),
+                Task.FromResult(new Metadata()),
+                () => new Status(StatusCode.OK, string.Empty),
+                () => [],
+                () => { });
+        }
+
+        public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(
+            Method<TRequest, TResponse> method,
+            string? host,
+            CallOptions options)
+        {
+            throw new NotSupportedException();
+        }
+    }
+
+    sealed class RecordingClientStreamWriter<T> : IClientStreamWriter<T>
+    {
+        public WriteOptions? WriteOptions { get; set; }
+
+        public Task WriteAsync(T message) => Task.CompletedTask;
+
+        public Task CompleteAsync() => Task.CompletedTask;
+    }
+
+    sealed class FakeSandboxActivityWorkerSession : ISandboxActivityWorkerSession
+    {
+        readonly object sync = new();
+        readonly TaskCompletionSource<SandboxActivityWorkerSessionResult> completion =
+            new(TaskCreationOptions.RunContinuationsAsynchronously);
+        readonly TaskCompletionSource blockedWriteStarted =
+            new(TaskCreationOptions.RunContinuationsAsynchronously);
+        readonly TaskCompletionSource releaseBlockedWrite =
+            new(TaskCreationOptions.RunContinuationsAsynchronously);
+        int writeAttempts;
+        int activeWrites;
+
+        public List<SandboxActivityWorkerMessage> Messages { get; } = [];
+
+        public int? ThrowOnWriteAttempt { get; init; }
+
+        public int? BlockWriteAttempt { get; init; }
+
+        public bool CompleteCalled { get; private set; }
+
+        public bool CompleteCalledWhileWriteActive { get; private set; }
+
+        public void FailCompletion(Exception exception) => this.completion.TrySetException(exception);
+
+        public Task WaitForBlockedWriteAsync() => this.blockedWriteStarted.Task.WaitAsync(TimeSpan.FromSeconds(5));
+
+        public Task WaitForCompleteAsync()
+        {
+            lock (this.sync)
+            {
+                return this.CompleteCalled ? Task.CompletedTask : this.completion.Task;
+            }
+        }
+
+        public void ReleaseBlockedWrite() => this.releaseBlockedWrite.TrySetResult();
+
+        public async Task WaitForMessageAsync(Func<SandboxActivityWorkerMessage, bool> predicate)
+        {
+            using CancellationTokenSource timeout = new(TimeSpan.FromSeconds(5));
+            while (!timeout.IsCancellationRequested)
+            {
+                lock (this.sync)
+                {
+                    if (this.Messages.Any(predicate))
+                    {
+                        return;
+                    }
+                }
+
+                await Task.Delay(TimeSpan.FromMilliseconds(10));
+            }
+
+            throw new TimeoutException("Timed out waiting for on-demand sandbox worker message.");
+        }
+
+        public Task WriteMessageAsync(SandboxActivityWorkerMessage message)
+        {
+            int attempt;
+            bool blockWrite;
+            lock (this.sync)
+            {
+                attempt = ++this.writeAttempts;
+                if (this.ThrowOnWriteAttempt == attempt)
+                {
+                    throw new RpcException(new Status(StatusCode.Unavailable, "transient"));
+                }
+
+                this.activeWrites++;
+                blockWrite = this.BlockWriteAttempt == attempt;
+                if (blockWrite)
+                {
+                    this.blockedWriteStarted.TrySetResult();
+                }
+            }
+
+            return this.WriteMessageCoreAsync(message, blockWrite);
+        }
+
+        public Task<SandboxActivityWorkerSessionResult> WaitForCompletionAsync() => this.completion.Task;
+
+        public async Task CompleteAsync()
+        {
+            lock (this.sync)
+            {
+                this.CompleteCalled = true;
+                this.CompleteCalledWhileWriteActive = this.activeWrites > 0;
+            }
+
+            this.completion.TrySetResult(new SandboxActivityWorkerSessionResult());
+            await this.completion.Task.ConfigureAwait(false);
+        }
+
+        public ValueTask DisposeAsync() => default;
+
+        async Task WriteMessageCoreAsync(SandboxActivityWorkerMessage message, bool blockWrite)
+        {
+            try
+            {
+                if (blockWrite)
+                {
+                    await this.releaseBlockedWrite.Task.ConfigureAwait(false);
+                }
+
+                lock (this.sync)
+                {
+                    this.Messages.Add(message.Clone());
+                }
+            }
+            finally
+            {
+                lock (this.sync)
+                {
+                    this.activeWrites--;
+                }
+            }
+        }
+    }
+
+    sealed class DeterministicRandom : Random
+    {
+        readonly double value;
+
+        public DeterministicRandom(double value)
+        {
+            this.value = value;
+        }
+
+        protected override double Sample() => this.value;
+    }
+
+    sealed class EnvironmentVariableScope : IDisposable
+    {
+        readonly string name;
+        readonly string? originalValue;
+
+        public EnvironmentVariableScope(string name, string? value)
+        {
+            this.name = name;
+            this.originalValue = Environment.GetEnvironmentVariable(name);
+            Environment.SetEnvironmentVariable(name, value);
+        }
+
+        public void Dispose() => Environment.SetEnvironmentVariable(this.name, this.originalValue);
+    }
+}
diff --git a/test/Worker/AzureManaged.Tests/Worker.AzureManaged.Tests.csproj b/test/Worker/AzureManaged.Tests/Worker.AzureManaged.Tests.csproj
index 9aab6f15..fe1183c3 100644
--- a/test/Worker/AzureManaged.Tests/Worker.AzureManaged.Tests.csproj
+++ b/test/Worker/AzureManaged.Tests/Worker.AzureManaged.Tests.csproj
@@ -5,11 +5,13 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Grpc.Core" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" />
   </ItemGroup>
 
   <ItemGroup>
     <ProjectReference Include="../../../src/Worker/AzureManaged/Worker.AzureManaged.csproj" />
+    <ProjectReference Include="../../../src/Worker/AzureManaged.Sandboxes/Worker.AzureManaged.Sandboxes.csproj" />
     <ProjectReference Include="../../TestHelpers/TestHelpers.csproj" />
   </ItemGroup>
 
diff --git a/test/Worker/Grpc.Tests/GrpcDurableTaskWorkerTests.cs b/test/Worker/Grpc.Tests/GrpcDurableTaskWorkerTests.cs
index 4c78aac0..ff641f0a 100644
--- a/test/Worker/Grpc.Tests/GrpcDurableTaskWorkerTests.cs
+++ b/test/Worker/Grpc.Tests/GrpcDurableTaskWorkerTests.cs
@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System.Collections.Concurrent;
 using System.IO;
 using System.Reflection;
 using Google.Protobuf.WellKnownTypes;
@@ -9,6 +10,7 @@
 using Microsoft.DurableTask.Tests.Logging;
 using Microsoft.DurableTask.Worker;
 using Microsoft.DurableTask.Worker.Grpc.Internal;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 using P = Microsoft.DurableTask.Protobuf;
@@ -28,6 +30,9 @@ public class GrpcDurableTaskWorkerTests
     static readonly MethodInfo ProcessorConnectAsyncMethod = typeof(GrpcDurableTaskWorker)
         .GetNestedType("Processor", BindingFlags.NonPublic)!
         .GetMethod("ConnectAsync", BindingFlags.Instance | BindingFlags.NonPublic)!;
+    static readonly MethodInfo DispatchWorkItemMethod = typeof(GrpcDurableTaskWorker)
+        .GetNestedType("Processor", BindingFlags.NonPublic)!
+        .GetMethod("DispatchWorkItem", BindingFlags.Instance | BindingFlags.NonPublic)!;
     static readonly MethodInfo TryRecreateChannelAsyncMethod = typeof(GrpcDurableTaskWorker)
         .GetMethod("TryRecreateChannelAsync", BindingFlags.Instance | BindingFlags.NonPublic)!;
 
@@ -250,6 +255,111 @@ public async Task ProcessorExecuteAsync_GracefulDrainAfterFirstMessage_Reconnect
         logs.Should().NotContain(log => log.Message.Contains("Recreating gRPC channel to backend"));
     }
 
+    [Fact]
+    public async Task DispatchWorkItem_ActivityRequest_NotifiesActivityStartAndCompletion()
+    {
+        // Arrange
+        ConcurrentQueue<ActivityNotificationPhase> notifications = new();
+        TaskCompletionSource completed = new(TaskCreationOptions.RunContinuationsAsynchronously);
+        GrpcDurableTaskWorkerOptions grpcOptions = new();
+        grpcOptions.ConfigureActivityNotification(phase =>
+        {
+            notifications.Enqueue(phase);
+            if (phase == ActivityNotificationPhase.Completed)
+            {
+                completed.TrySetResult();
+            }
+        });
+
+        P.WorkItem activityWorkItem = new()
+        {
+            ActivityRequest = new P.ActivityRequest
+            {
+                Name = "MyActivity",
+                TaskId = 42,
+                OrchestrationInstance = new P.OrchestrationInstance
+                {
+                    InstanceId = "instance1",
+                    ExecutionId = "execution1",
+                },
+            },
+            CompletionToken = "completion1",
+        };
+
+        GrpcDurableTaskWorker worker = CreateActivityWorker(grpcOptions);
+        Mock<P.TaskHubSidecarService.TaskHubSidecarServiceClient> clientMock = new(
+            MockBehavior.Strict,
+            new object[] { Mock.Of<CallInvoker>() });
+        clientMock
+            .Setup(client => client.CompleteActivityTaskAsync(
+                It.IsAny<P.ActivityResponse>(),
+                It.IsAny<Metadata>(),
+                It.IsAny<DateTime?>(),
+                It.IsAny<CancellationToken>()))
+            .Returns(CreateUnaryCall(Task.FromResult(new P.CompleteTaskResponse())));
+        object processor = CreateProcessor(worker, clientMock.Object);
+
+        // Act
+        InvokeDispatchWorkItem(processor, activityWorkItem, CancellationToken.None);
+        await completed.Task.WaitAsync(TimeSpan.FromSeconds(5));
+
+        // Assert
+        notifications.Should().Equal(ActivityNotificationPhase.Started, ActivityNotificationPhase.Completed);
+    }
+
+    [Fact]
+    public async Task DispatchWorkItem_ActivityRequest_NotificationFailure_CompletesActivity()
+    {
+        // Arrange
+        TaskCompletionSource activityCompleted = new(TaskCreationOptions.RunContinuationsAsynchronously);
+        GrpcDurableTaskWorkerOptions grpcOptions = new();
+        grpcOptions.ConfigureActivityNotification(phase => throw new InvalidOperationException($"Notification failed: {phase}"));
+
+        P.WorkItem activityWorkItem = new()
+        {
+            ActivityRequest = new P.ActivityRequest
+            {
+                Name = "MyActivity",
+                TaskId = 42,
+                OrchestrationInstance = new P.OrchestrationInstance
+                {
+                    InstanceId = "instance1",
+                    ExecutionId = "execution1",
+                },
+            },
+            CompletionToken = "completion1",
+        };
+
+        DurableTaskWorkerOptions workerOptions = new()
+        {
+            Logging = { UseLegacyCategories = false },
+        };
+        TestLogProvider logProvider = new(new NullOutput());
+        GrpcDurableTaskWorker worker = CreateActivityWorker(grpcOptions, workerOptions, new SimpleLoggerFactory(logProvider));
+        Mock<P.TaskHubSidecarService.TaskHubSidecarServiceClient> clientMock = new(
+            MockBehavior.Strict,
+            new object[] { Mock.Of<CallInvoker>() });
+        clientMock
+            .Setup(client => client.CompleteActivityTaskAsync(
+                It.IsAny<P.ActivityResponse>(),
+                It.IsAny<Metadata>(),
+                It.IsAny<DateTime?>(),
+                It.IsAny<CancellationToken>()))
+            .Callback(() => activityCompleted.TrySetResult())
+            .Returns(CreateUnaryCall(Task.FromResult(new P.CompleteTaskResponse())));
+        object processor = CreateProcessor(worker, clientMock.Object);
+
+        // Act
+        InvokeDispatchWorkItem(processor, activityWorkItem, CancellationToken.None);
+        await activityCompleted.Task.WaitAsync(TimeSpan.FromSeconds(5));
+
+        // Assert
+        clientMock.VerifyAll();
+        logProvider.TryGetLogs(Category, out IReadOnlyCollection<LogEntry>? logs).Should().BeTrue();
+        logs!.Should().Contain(log => log.Message.Contains("Activity notification callback failed for phase 'Started'"));
+        logs.Should().Contain(log => log.Message.Contains("Activity notification callback failed for phase 'Completed'"));
+    }
+
     [Fact]
     public async Task ProcessorExecuteAsync_HelloDeadlineExceeded_ReturnsChannelRecreateRequested()
     {
@@ -570,19 +680,74 @@ static GrpcDurableTaskWorker CreateWorker(
         DurableTaskWorkerOptions workerOptions,
         ILoggerFactory loggerFactory,
         IDurableTaskFactory factory)
+    {
+        return CreateWorker(grpcOptions, workerOptions, loggerFactory, factory, Mock.Of<IServiceProvider>());
+    }
+
+    static GrpcDurableTaskWorker CreateActivityWorker(GrpcDurableTaskWorkerOptions grpcOptions)
+    {
+        return CreateActivityWorker(grpcOptions, new DurableTaskWorkerOptions(), NullLoggerFactory.Instance);
+    }
+
+    static GrpcDurableTaskWorker CreateActivityWorker(
+        GrpcDurableTaskWorkerOptions grpcOptions,
+        DurableTaskWorkerOptions workerOptions,
+        ILoggerFactory loggerFactory)
+    {
+        Mock<IDurableTaskFactory> factoryMock = new(MockBehavior.Strict);
+        factoryMock
+            .Setup(factory => factory.TryCreateActivity(
+                It.Is<TaskName>(name => name.Name == "MyActivity"),
+                It.IsAny<IServiceProvider>(),
+                out It.Ref<ITaskActivity?>.IsAny))
+            .Returns((TaskName name, IServiceProvider serviceProvider, out ITaskActivity? activity) =>
+            {
+                activity = new TestActivity();
+                return true;
+            });
+
+        factoryMock
+            .Setup(factory => factory.TryCreateOrchestrator(
+                It.IsAny<TaskName>(),
+                It.IsAny<IServiceProvider>(),
+                out It.Ref<ITaskOrchestrator?>.IsAny))
+            .Returns(false);
+
+        ServiceProvider services = new ServiceCollection().BuildServiceProvider();
+        return CreateWorker(grpcOptions, workerOptions, loggerFactory, factoryMock.Object, services);
+    }
+
+    static GrpcDurableTaskWorker CreateWorker(
+        GrpcDurableTaskWorkerOptions grpcOptions,
+        DurableTaskWorkerOptions workerOptions,
+        ILoggerFactory loggerFactory,
+        IDurableTaskFactory factory,
+        IServiceProvider services)
     {
         return new GrpcDurableTaskWorker(
             name: "Test",
             factory: factory,
             grpcOptions: new OptionsMonitorStub<GrpcDurableTaskWorkerOptions>(grpcOptions),
             workerOptions: new OptionsMonitorStub<DurableTaskWorkerOptions>(workerOptions),
-            services: Mock.Of<IServiceProvider>(),
+            services: services,
             loggerFactory: loggerFactory,
             orchestrationFilter: null,
             exceptionPropertiesProvider: null,
             workItemFiltersMonitor: null);
     }
 
+    sealed class TestActivity : ITaskActivity
+    {
+        public System.Type InputType => typeof(object);
+
+        public System.Type OutputType => typeof(object);
+
+        public Task<object?> RunAsync(TaskActivityContext context, object? input)
+        {
+            return Task.FromResult<object?>(input);
+        }
+    }
+
     static Task InvokeExecuteAsync(GrpcDurableTaskWorker worker, CancellationToken cancellationToken)
     {
         return (Task)ExecuteAsyncMethod.Invoke(worker, new object?[] { cancellationToken })!;
@@ -613,6 +778,11 @@ static async Task<ProcessorExitReason> InvokeProcessorExecuteAsync(object proces
         return (ProcessorExitReason)task.GetType().GetProperty("Result")!.GetValue(task)!;
     }
 
+    static void InvokeDispatchWorkItem(object processor, P.WorkItem workItem, CancellationToken cancellationToken)
+    {
+        DispatchWorkItemMethod.Invoke(processor, new object?[] { workItem, cancellationToken });
+    }
+
     static void InvokeApplySuccessfulRecreate(
         GrpcDurableTaskWorker worker,
         object result,