"""Regression guard for PR #16660 (salvaged as PR #18027): ContextVar propagation into concurrent tool worker threads. Background ---------- Gateway adapters (Slack, Telegram, Discord, ...) set ``tools.approval._approval_session_key`` as a ContextVar before calling ``agent.run_conversation`` so that dangerous-command approval prompts route back to the channel/session that initiated the tool call. When the agent dispatches multiple tools in parallel, it uses ``concurrent.futures.ThreadPoolExecutor.submit(...)`` — and ``submit`` runs the callable in a *fresh* context, NOT the caller's context. Without an explicit ``contextvars.copy_context().run(...)`` wrapper, worker threads observe the ContextVar's default value, fall through to the ``os.environ`` legacy fallback (which the gateway overwrites at each agent step), and route the approval card to *whichever session stepped most recently* — not the one that raised the prompt. Confirmed in the wild on Slack with two concurrent channels: session A's `rm -rf` approval card was delivered to session B. The fix (4 LOC in ``run_agent.py``) snapshots the caller's context with ``copy_context()`` and submits ``ctx.run(_run_tool, …)`` instead of ``_run_tool`` directly. Mirrors ``asyncio.to_thread`` semantics. This suite follows the ``contextvar-run-in-executor-bridge`` skill's two-test pattern: one end-to-end test proves the fix works at the call-site level, one documents the Python contract that makes the fix necessary. If anyone ever reverts the wrapper, the call-site test fails while the contract test keeps passing — a clear diagnostic signal for *why* the call-site regressed. """ from __future__ import annotations import concurrent.futures import contextvars import threading def test_executor_submit_without_copy_context_does_not_propagate(): """Documents the Python contract the fix relies on. ``concurrent.futures.ThreadPoolExecutor.submit(fn)`` runs ``fn`` in a worker thread with a fresh, empty context. A ContextVar set by the caller is invisible inside ``fn``. This is the exact trap that made approval-session routing race in the gateway before #16660. If this test ever fails — i.e. submit() starts propagating ContextVars by default — the copy_context() wrapper in run_agent.py becomes redundant but not harmful, and the call-site test below should be updated accordingly. """ probe: contextvars.ContextVar[str] = contextvars.ContextVar( "probe_default_propagation", default="unset" ) def read_in_worker() -> str: return probe.get() probe.set("set-in-main") with concurrent.futures.ThreadPoolExecutor(max_workers=1) as ex: observed = ex.submit(read_in_worker).result(timeout=5) assert observed == "unset", ( "Unexpected: executor.submit propagated a ContextVar without " "copy_context(). If Python's behavior changed, update " "test_run_tool_worker_sees_parent_context below." ) def test_run_tool_worker_sees_parent_approval_session_key(): """End-to-end call-site guard. Mirrors the exact shape of the fixed call site in ``run_agent.py::_execute_tool_calls_concurrent`` — a ``ThreadPoolExecutor`` with ``executor.submit(ctx.run, fn, *args)``. Sets the real ``tools.approval._approval_session_key`` ContextVar in the caller and asserts the worker observes it via ``tools.approval.get_current_session_key()``. If the PR's ``copy_context().run`` wrapper is reverted, this test fails with ``Expected 'session-A' but worker saw 'default'``. """ from tools.approval import ( _approval_session_key, get_current_session_key, ) observed: dict = {} barrier = threading.Event() def worker_equivalent_to_run_tool() -> None: # Mirror what real _run_tool does early: read the session key. observed["session_key"] = get_current_session_key(default="FALLBACK") barrier.set() # Set the ContextVar the gateway would set before calling agent.run. token = _approval_session_key.set("session-A") try: with concurrent.futures.ThreadPoolExecutor(max_workers=1) as ex: ctx = contextvars.copy_context() fut = ex.submit(ctx.run, worker_equivalent_to_run_tool) fut.result(timeout=5) assert barrier.is_set(), "worker did not complete" finally: _approval_session_key.reset(token) assert observed.get("session_key") == "session-A", ( f"Worker thread did not inherit _approval_session_key from caller. " f"Expected 'session-A', got {observed.get('session_key')!r}. " "This is the bug that PR #16660 fixed — approval prompts route to " "the wrong session in concurrent gateway traffic. Check whether " "the copy_context().run wrapper in _execute_tool_calls_concurrent " "was removed." ) def test_two_concurrent_tool_batches_keep_session_keys_isolated(): """End-to-end guard: two callers each set a different session key and submit workers concurrently. Each worker must see its own caller's key, not the other's. Guards against a future "optimization" that reuses a single context snapshot across callers (which would collapse isolation the same way the unfixed ``submit`` does). """ from tools.approval import ( _approval_session_key, get_current_session_key, ) results: dict = {} def caller(label: str) -> None: token = _approval_session_key.set(f"session-{label}") try: with concurrent.futures.ThreadPoolExecutor(max_workers=1) as ex: ctx = contextvars.copy_context() fut = ex.submit( ctx.run, lambda: get_current_session_key(default="FALLBACK"), ) results[label] = fut.result(timeout=5) finally: _approval_session_key.reset(token) t_a = threading.Thread(target=caller, args=("A",)) t_b = threading.Thread(target=caller, args=("B",)) t_a.start() t_b.start() t_a.join(timeout=10) t_b.join(timeout=10) assert results.get("A") == "session-A", ( f"Session A worker saw {results.get('A')!r}, expected 'session-A'" ) assert results.get("B") == "session-B", ( f"Session B worker saw {results.get('B')!r}, expected 'session-B'" )