v0.3.0 — A2A AgentCard + DNS TXT, four-language parity

.github/workflows/go.yml

@@ -0,0 +1,34 @@
+name: Go CI
+on:
+  push:
+    branches: [main, dev]
+    paths: ['go/**', '.github/workflows/go.yml']
+  pull_request:
+    paths: ['go/**', '.github/workflows/go.yml']
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        go-version: ['1.21', '1.22']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: ${{ matrix.go-version }}
+      - name: gofmt
+        working-directory: go
+        run: |
+          out=$(gofmt -l .)
+          if [ -n "$out" ]; then
+            echo "::error::gofmt would reformat the following files:"
+            echo "$out"
+            exit 1
+          fi
+      - name: go vet
+        working-directory: go
+        run: go vet ./...
+      - name: go test
+        working-directory: go
+        run: go test ./...

.github/workflows/javascript.yml

@@ -0,0 +1,27 @@
+name: JavaScript CI
+on:
+  push:
+    branches: [main]
+    paths: ['javascript/**']
+  pull_request:
+    paths: ['javascript/**']
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: ['18', '20']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: ${{ matrix.node-version }}
+      - working-directory: javascript
+        # The JS SDK has no runtime deps and intentionally does not commit a
+        # lockfile (it is in .gitignore), so use `npm install` instead of
+        # `npm ci`. Lock-free installs are fine here since devDependencies are
+        # only used for tests/lint, not anything that ships.
+        run: |
+          npm install --no-audit --no-fund
+          npm test

.github/workflows/python.yml

@@ -0,0 +1,23 @@
+name: Python CI
+on:
+  push:
+    branches: [main]
+    paths: ['python/**']
+  pull_request:
+    paths: ['python/**']
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ['3.9', '3.12']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - working-directory: python
+        run: |
+          pip install -e ".[dev]"
+          python -m pytest tests/ -v

.github/workflows/release.yml

@@ -0,0 +1,26 @@
+name: Release Check
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  version-consistency:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Check version consistency
+        run: |
+          RUST_VER=$(grep '^version' crates/agentpin/Cargo.toml | head -1 | sed 's/.*"\(.*\)"/\1/')
+          PY_VER=$(grep 'version' python/pyproject.toml | head -1 | sed 's/.*"\(.*\)"/\1/')
+          JS_VER=$(node -e "console.log(require('./javascript/package.json').version)")
+          GO_VER=$(grep -E '^const Version' go/internal/version/version.go | sed 's/.*"\(.*\)".*/\1/')
+          echo "Rust: $RUST_VER"
+          echo "Python: $PY_VER"
+          echo "JavaScript: $JS_VER"
+          echo "Go: $GO_VER"
+          if [ "$RUST_VER" != "$PY_VER" ] || [ "$RUST_VER" != "$JS_VER" ] || [ "$RUST_VER" != "$GO_VER" ]; then
+            echo "::error::Version mismatch! Rust=$RUST_VER Python=$PY_VER JavaScript=$JS_VER Go=$GO_VER"
+            exit 1
+          fi
+          echo "All versions match: $RUST_VER"

.github/workflows/rust.yml

@@ -0,0 +1,26 @@
+name: Rust CI
+on:
+  push:
+    branches: [main]
+    paths: ['crates/**', 'Cargo.toml', 'Cargo.lock']
+  pull_request:
+    paths: ['crates/**', 'Cargo.toml', 'Cargo.lock']
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust: [stable, '1.86']
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+          components: clippy, rustfmt
+      - run: cargo fmt --check
+        if: matrix.rust == 'stable'
+      - run: cargo clippy --workspace -j2 -- -D warnings
+        if: matrix.rust == 'stable'
+      - run: cargo test --workspace -j2
+      - run: cargo test --workspace -j2 --features fetch

.gitignore

@@ -5,6 +5,10 @@ Cargo.lock
 # Private keys — NEVER commit these
 *.private.pem
 *.private.jwk.json
+# Exception: cross-language interop test fixtures under testdata/ ARE
+# deliberately committed throwaway keypairs used only for SDK interop tests.
+# They are NOT used to sign anything in production.
+!go/pkg/verification/testdata/*.private.pem
 
 # IDE
 .idea/

CHANGELOG.md

@@ -5,6 +5,127 @@ All notable changes to the AgentPin project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.3.0] - 2026-05-14
+
+### Added
+
+Four-language parity (Rust, JavaScript, Python, Go) for the A2A AgentCard
+extension surface and DNS TXT cross-verification. Cards signed in any of the
+four SDKs verify cleanly in the other three; signature canonicalisation is
+byte-identical across implementations.
+
+#### A2A AgentCard extension types, signed builder, and verifier
+
+- **`A2aAgentCard` + supporting types** — minimal A2A AgentCard subset
+  (`A2aAgentCard`, `A2aAgentCapabilities`, `A2aAgentSkill`) plus the
+  AgentPin-specific `AgentpinExtension` payload (`agentpin_endpoint`,
+  `public_key_jwk`, `signature`). Inline definition rather than depending on
+  the upstream `a2a-types` crate while the A2A spec is still draft.
+- **`A2aAgentCardBuilder`** (Rust) / `buildAndSignAgentCard` (JS) /
+  `build_and_sign_agent_card` (Python) / `a2a.BuildAndSignAgentCard` (Go) —
+  turns an AgentDeclaration into a signed `A2aAgentCard`. Maps capabilities
+  to skills via `capability_to_skill`; propagates `allowed_domains` from the
+  source constraints into `A2aAgentCapabilities.allowed_domains`. Detached
+  ECDSA P-256 signature covers the canonical bytes of the AgentCard with the
+  extension cleared.
+- **`verify_agentpin_extension(card)`** — verifies the AgentPin extension
+  signature against the JWK embedded in the extension. Sorted-key canonical
+  JSON shared across all four SDKs; mirrors the canonicalisation pattern
+  used by SchemaPin.
+- **`AllowedDomains` typed wrapper** — extracted from
+  `Constraints::allowed_domains` and exposed for cross-protocol use
+  (SchemaPin v1.4's `A2aVerificationContext` scopes tool verification to the
+  intersection of caller and provider domains). Empty list = no restriction
+  (all domains trusted) by convention; `intersect(unrestricted, X) = X`.
+- **`a2a_endpoint` field** on `DiscoveryDocument` — optional URL of the
+  entity's A2A AgentCard endpoint, enabling cross-protocol discovery.
+
+#### Discovery resolvers for A2A AgentCards
+
+- **`LocalAgentCardStore`** (all SDKs) — in-memory store of pre-registered
+  AgentCards keyed by their AgentPin discovery domain. Verifies the
+  AgentPin extension signature at registration time and pre-derives a
+  `DiscoveryDocument` so the rest of the AgentPin verification stack runs
+  unchanged. Supports Symbiont's push-based external-agent registration
+  flow where the coordinator receives AgentCard JSON inline rather than
+  fetching it from a `.well-known` endpoint.
+- **`A2aAgentCardResolver`** (all SDKs; gated on `fetch` in Rust) — fetches
+  `https://{domain}/.well-known/agent-card.json`, verifies the AgentPin
+  extension, cross-checks that the embedded `agentpin_endpoint` host
+  matches the fetched domain, and derives a `DiscoveryDocument`. Exposes
+  the original A2A representation alongside the derived doc for callers
+  that want both.
+
+#### DNS TXT cross-verification at `_agentpin.{domain}`
+
+- **`dns` module** (all SDKs) — `parse_txt_record`, `verify_dns_match`,
+  `txt_record_name`. Wire format mirrors SchemaPin's `_schemapin.{domain}`
+  record with the version tag changed:
+  `"v=agentpin1; kid=...; fp=sha256:<hex>"`. Whitespace-tolerant parser,
+  case-insensitive on `fp`, ignores unknown fields for forward
+  compatibility.
+- **`fetch_dns_txt(domain)`** — Rust: async lookup behind the new `dns`
+  Cargo feature (`hickory-resolver`, `tokio`, `async-trait`). JavaScript:
+  uses Node's built-in `dns/promises`. Python: uses the optional
+  `dnspython` package. Go: `dns.LookupTxt(ctx, resolver, domain)` over the
+  standard-library `net.Resolver`.
+- **Multi-key match semantics** — AgentPin discovery docs may carry several
+  keys for rotation; a published TXT record need only match one of them.
+  When the TXT carries an explicit `kid`, the matching key MUST also carry
+  the same `kid`.
+- **Fail-closed on mismatch** — a publisher who *intentionally* publishes a
+  TXT record has signaled DNS is part of their trust chain. Divergence
+  between DNS and `.well-known` indicates compromise of one channel and is
+  treated as a hard failure.
+
+#### Go SDK (fourth-language port)
+
+- **Initial `go/` SDK** — wire-compatible with Rust, JavaScript, and Python.
+  Mirrors the package layout of the SchemaPin Go SDK. Module path:
+  `github.com/ThirdKeyAi/agentpin/go`.
+- **Packages**: `crypto`, `jwk`, `jwt`, `types`, `discovery`, `credential`,
+  `verification`, `revocation`, `pinning`, `delegation`, `mutual`, `nonce`,
+  `bundle`, `resolver`, plus the new `a2a` and `dns` packages added in this
+  release.
+- **CLI**: `cmd/agentpin` with `keygen`, `issue`, `verify`, `bundle`
+  subcommands matching the Rust binary.
+- **ES256-only** enforcement implemented inline using `crypto/ecdsa`. The
+  JWT verifier rejects `none`, `HS256`, `RS256`, `ES384`, and any other
+  algorithm before any signature work. No third-party JWT dependency.
+- **CI**: `.github/workflows/go.yml` runs `go test`, `go vet`, and
+  `gofmt -l` on every PR touching `go/**`. The version-consistency check
+  in `.github/workflows/release.yml` validates the Go SDK's declared
+  version against the Rust/JavaScript/Python versions.
+
+### Changed
+
+- Cross-SDK version coordination — Rust, JavaScript, Python, and Go SDKs
+  all release as **0.3.0** together. The earlier `0.3.0-alpha.1` Rust
+  preview is superseded by this entry.
+- **Rust MSRV bumped from 1.70 to 1.86.** Downstream ecosystem crates
+  (`getrandom`, `clap_builder`, the `icu_*` family) have moved to edition
+  2024 and/or to declared rust-version 1.86, making the previously-
+  declared 1.70 floor unbuildable from scratch in practice. The CI
+  matrix's MSRV row now tests against 1.86.
+
+### Notes
+
+- This release is the unblock for **Symbiont v1.8.0 Phase 3** (AgentPin-
+  verified AgentCards, A2A auth middleware) and **SchemaPin v1.4.0**'s
+  `A2aVerificationContext` (which consumes `AllowedDomains` for tool-
+  verification scoping). Both downstream releases were waiting on this
+  surface.
+- DNS TXT defends against HTTPS-origin compromise (compromised hosting
+  account, expired domain not removed from CDN, ACME ownership-validation
+  bypass) and TLS cert mis-issuance — the DNS credential chain (registrar,
+  DNS provider, optionally DNSSEC) is independent of the HTTPS hosting
+  chain. Spec § 4.8.3 reserved this slot in v0.1; this release ships the
+  implementation across all SDKs.
+- All additions are purely additive — v0.2.0 callers are unaffected.
+  Discovery documents without `a2a_endpoint`, AgentCards without an
+  `agentpin` extension, and absent `_agentpin` TXT records all behave
+  exactly as before.
+
 ## [0.2.0] - 2026-02-12
 
 ### Added

README.md

@@ -16,7 +16,7 @@ AgentPin lets organizations publish verifiable identity for their AI agents. Iss
 - **Credential revocation** at credential, agent, and key level
 - **Mutual authentication** with challenge-response
 - **Trust bundles** for air-gapped and enterprise environments
-- **Cross-language** — Rust, JavaScript, and Python SDKs produce interoperable credentials
+- **Cross-language** — Rust, JavaScript, Python, and Go SDKs produce interoperable credentials
 
 ## Quick Start
 
@@ -43,7 +43,7 @@ agentpin verify --credential <jwt>
 
 ```toml
 [dependencies]
-agentpin = { version = "0.2", features = ["fetch"] }
+agentpin = { version = "0.3", features = ["fetch"] }
 ```
 
 ### JavaScript
@@ -58,6 +58,13 @@ npm install agentpin
 pip install agentpin
 ```
 
+### Go
+
+```bash
+go install github.com/ThirdKeyAi/agentpin/go/cmd/agentpin@latest
+go get github.com/ThirdKeyAi/agentpin/go
+```
+
 ## Documentation
 
 | Topic | Link |
@@ -80,6 +87,7 @@ crates/
 └── agentpin-server/   # HTTP server for .well-known endpoints
 javascript/            # JavaScript/Node.js SDK
 python/                # Python SDK
+go/                    # Go SDK
 ```
 
 ## License