Self-delegation deadlocks: the sending turn holds `_run_lock`, the receive
handler waits for the same lock, the A2A request 30s-times-out, and the
whole cycle is wasted (the Dev Lead system prompt warns agents off this by
hand — "Never delegate_task to your own workspace ID … there is no peer who
is also you"). The platform/runtime had no guard. Now both
`tool_delegate_task` and `tool_delegate_task_async` early-return an
actionable error when `workspace_id == effective_source` (`source_workspace_id
or _peer_to_source[target] or WORKSPACE_ID`) — before `discover_peer`, so no
network round-trip is wasted either. A genuinely different target (incl.
another of a multi-workspace agent's own registered workspaces) is
unaffected.
Tests: tests/test_a2a_tools_delegation.py — new TestSelfDelegationGuard (4
cases: rejects own ID; rejects when source_workspace_id explicitly == target;
async path rejects; a different target passes the guard through to
discover_peer). `pytest tests/test_a2a_tools_delegation.py` → 12 passed.
(tests/test_a2a_tools_impl.py's TestToolDelegateTask* suite is red on this
PC2/Windows checkout — same on `main` without this change; httpx-mock infra,
not this PR — CI validates on Linux.)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
