Rust SDK: add typed per-session capability controls by Morabbin · Pull Request #1455 · github/copilot-sdk

Morabbin · 2026-05-27T14:47:12Z

Summary

Adds typed SessionConfig / ResumeSessionConfig fields and builder methods backed by the generated SessionCapability enum, so callers can express per-session capability opt-in / opt-out without stringly-typed flags.

This is a per-session API: the capability fields are sent as JSON-RPC wire parameters on session.create and session.resume, so it works for every transport including Transport::External.

Experimental. The new capability enable/disable surface is part of an experimental wire-protocol API. The Rust SDK marks the new fields and builders with the repository's <div class="warning">**Experimental.**</div> rustdoc block (the convention used in rust/src/generated/); there is no #[experimental] attribute, so the marker is documentation-only.

Why

Some SDK consumers use Transport::External, so spawn-time CLI flags have no effect. A per-session wire API is the correct approach for session-scoped runtime capabilities.

What

`SessionCapability` enum

Reuses the generated protocol enum and re-exports it from the crate root as github_copilot_sdk::SessionCapability.
Includes generated typed variants such as Memory, PlanMode, CanvasRenderer, Elicitation, McpApps, SessionStore, TuiHints, CliDocumentation, AskUser, InteractiveMode, and SystemNotifications.
Preserves generated per-variant rustdoc and serde wire names.
Rejects SessionCapability::Unknown as invalid outbound create/resume configuration, since that variant is only a deserialization fallback.

`SessionConfig` and `ResumeSessionConfig` (`rust/src/types.rs`)

New fields:

enabled_capabilities: Vec<SessionCapability> -- opt this session into additional capabilities.
disabled_capabilities: Vec<SessionCapability> -- opt this session out of capabilities; disable wins over enable on overlap.

Four builders on each config type:

with_enable_capability, with_disable_capability
with_enabled_capabilities, with_disabled_capabilities

Wire serialization (`rust/src/wire.rs`)

SessionCreateWire and SessionResumeWire gain:

enabledCapabilities?: SessionCapability[]
disabledCapabilities?: SessionCapability[]

Both fields are omitted from the wire when empty. The generated enum serde emits the protocol strings such as memory, plan-mode, and canvas-renderer.

Runtime dependency

Requires a runtime version that supports enabledCapabilities and disabledCapabilities. On older runtimes the fields are silently ignored.

Validation

cargo +nightly fmt --check
cargo clippy --lib --tests -- -D warnings
cargo test --lib (154 passed)
cargo test --doc (20 passed, 30 ignored)
cargo build

Adds a typed `SessionCapability` enum and matching `SessionConfig` / `ResumeSessionConfig` fields plus builder methods, so callers can express "enable memory", "disable plan-mode", etc. as a per-session wire parameter rather than a spawn-time CLI flag. - `SessionCapability` is `#[non_exhaustive]`, kebab-case-serialized (via `Display` / `FromStr` / `From<&str>` / `From<String>`), and carries an `Other(String)` escape hatch for forward compatibility with capabilities the runtime adds without requiring an SDK rebuild. - `SessionConfig` and `ResumeSessionConfig` each gain `enabled_capabilities` / `disabled_capabilities` vectors and four builders: `with_enable_capability`, `with_disable_capability`, `with_enabled_capabilities`, `with_disabled_capabilities`. - `SessionConfig::into_wire` and `ResumeSessionConfig::into_wire` convert the vecs to `Option<Vec<String>>` and emit them as `enabledCapabilities` / `disabledCapabilities` in the `session.create` and `session.resume` JSON-RPC payloads. Empty vecs are serialised as `None` (field omitted). Disable wins over enable on conflict (the runtime applies enable first, then disable). - Works for every transport -- including `Transport::External` (Desktop app / shared CLI server) -- because it does not rely on CLI spawn arguments. Pairs with github/copilot-agent-runtime#8918 (per-session capability API) and github/agents#981 (Desktop missing memory capability). 10 new unit tests: 3 enum-level tests (Display / FromStr / From conversions) and 7 wire-serialisation tests in a dedicated `capability_tests` module in `types.rs` (empty omitted, single enable, single disable, bulk-replace, Other round-trip, resume empty, resume enable+disable). Pre-existing test breakage: rust/tests/session_test.rs and rust/tests/protocol_version_test.rs reference removed API methods on main and are unrelated to this change. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Make `with_enabled_capabilities` / `with_disabled_capabilities` append to the existing list (via `extend`) instead of replacing it, so the plural builders are consistent with the singular `with_enable_capability` / `with_disable_capability`. Update the builder docs and the round-trip test accordingly. Trim the README capability section to drop implementation details and the hand-maintained variants table, deferring to the enum's own documentation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings May 27, 2026 14:47

Morabbin requested a review from a team as a code owner May 27, 2026 14:47

Morabbin marked this pull request as draft May 27, 2026 15:06

Morabbin changed the title ~~rust: add typed SessionCapability enum and ClientOptions builders~~ Rust SDK: add typed SessionCapability enum and ClientOptions builders May 27, 2026

Morabbin changed the title ~~Rust SDK: add typed SessionCapability enum and ClientOptions builders~~ Rust SDK: add typed per-session capability controls May 27, 2026

Morabbin force-pushed the morabbin/rust-typed-session-capabilities branch 6 times, most recently from 8899958 to cb93071 Compare June 3, 2026 11:48

Morabbin force-pushed the morabbin/rust-typed-session-capabilities branch 2 times, most recently from e59f4d0 to e205d4c Compare June 9, 2026 07:20