Summary

• Adds assign as a new agent-layer action class (alongside merge/close/label/review_state_label/update_branch) that best-effort sets a PR's opening contributor as its GitHub assignee, gated by its own per-repo autonomy.assign dial (default observe/off).
• No new DB migration: autonomy is already a single JSON column (AutonomyPolicy), so a new action class is just a new literal in the shared AGENT_ACTION_CLASSES array — .gittensory.yml parsing, the dashboard dial, and the approval queue all pick it up for free.
• GitHub silently drops an assignee who lacks push/triage access to the repo instead of erroring (the common case for an external contributor) — the new ensurePullRequestAssignee (src/github/assignees.ts) detects this from the live response and the executor falls back to a per-login contributor:<login> label instead of a comment, so a repeated sweep never spams (the label GET is naturally idempotent).
• Closes feat(agent): auto-assign PR opener as GitHub assignee (config + wiring) #3182.

Scope

• The PR title follows type(scope): short summary Conventional Commit format, for example fix(api): restore profile access checks.
• This PR is focused and does not mix unrelated backend, UI, MCP, docs, dependency, and deploy changes.
• This follows CONTRIBUTING.md and does not reintroduce GitHub Pages, VitePress, site/, or CNAME.
• I linked an issue, or this is small enough that the summary explains why an issue is not needed.

Validation

• git diff --check
• npm run actionlint
• npm run typecheck
• npm run test:coverage locally; codecov/patch requires ≥99% coverage of the lines AND branches you changed (aim for 100% on your diff so CI variance does not fail near the threshold). Global coverage is a non-blocking trend with a loose 90% backstop, not the gate.
• npm run test:workers
• npm run build:mcp
• npm run test:mcp-pack
• npm run ui:openapi:check
• npm run ui:lint
• npm run ui:typecheck
• npm run ui:build
• npm audit --audit-level=moderate
• New or changed behavior has unit/integration tests for new branches, fallback paths, and sanitizer boundaries

If any required check was skipped, explain why:

• Ran targeted validation instead of the full local gate: typecheck, git diff --check, ui:openapi:check (regenerated + verified), and the specific affected suites (test/unit/agent-actions.test.ts, test/unit/agent-action-executor.test.ts, test/unit/github-assignees.test.ts, test/unit/autonomy.test.ts, test/unit/openapi.test.ts, test/unit/ci-openapi-settings-parity.test.ts, test/unit/selfhost-config-examples.test.ts) plus npm run test:changed (224 files / 5756 tests, all green — this touches src/queue/processors.ts so it covers test/unit/queue.test.ts too). No UI/MCP/workers files touched by this diff, so ui:*/test:workers/build:mcp/test:mcp-pack are out of scope. CI runs the full gate on push.

Safety

• No secrets, wallet details, hotkeys, coldkeys, user PATs, private keys, raw trust scores, private rankings, or private maintainer evidence are exposed.
• Public GitHub text stays sanitized, low-noise, and does not imply compensation guarantees or optimization tactics.
• Auth, cookie, CORS, GitHub App, Cloudflare, or session changes include negative-path tests. (N/A — no auth/CORS/session surface touched; new GitHub API call is covered by fetch-stub tests including the silent-drop path.)
• API/OpenAPI/MCP behavior is updated and tested where needed. (autonomy enum regenerated via npm run ui:openapi.)
• UI changes use live API data or real empty/error/loading states, not production mock/demo fallbacks. (N/A — no UI changes.)
• Visible UI changes include a UI Evidence section below... (N/A — backend-only change, no visible UI.)
• Public docs/changelogs are updated where needed... (N/A — no changelog edit per house rule.)

UI Evidence

N/A — backend-only change, no visible UI.

Notes

• Design note: the assignee slot itself is placed alongside review_state_label in the planner (src/settings/agent-actions.ts) as an independent, always-safe block — not folded into the merge/close disposition tree, since assignment has no bearing on CI/mergeability and shouldn't share failure modes with those higher-stakes actions.
• Follow-up work tracked under the parent epic roadmap(agent): auto-assign PR opener + auto-project/milestone matching #3180: milestone/project auto-matching (feat(agent): auto-match PRs to open GitHub Milestones (suggest-mode) #3183, feat(agent): auto-match PRs to open GitHub Projects v2 (suggest-mode) #3184), promotion to auto-apply (feat(agent): promote project/milestone matching to auto-apply mode #3185), and a Linear adapter (feat(agent): Linear adapter for project/milestone matching #3186).