refactor(model-routing): centralize explicit foreground fallback policy (#6020)

* refactor(model-routing): centralize explicit foreground fallback policy Make foreground fallback an explicit per-user, availability-only policy shared by streaming Chat, non-stream Chat, and Agent runs. Preserve strict defaults, owner/model and credential boundaries, pinned Agent routes, and truthful per-round provenance/accounting. Carry provider-reported model identifiers through native streaming adapters, non-stream responses, and caches, and keep legacy default_model_fallbacks as tombstoned raw storage that generic settings APIs and agent tools cannot expose or mutate. * fix(agent-loop): restore rebase-dropped qwen routing, workspace prompt, and temperature clamp * fix(model-routing): thread selected endpoint identity, fix cost classification and fallback eligibility * fix(chat): restore stream helpers and harden run stop lifecycle * fix(model-routing): let numeric provider codes win over symbolic rate-limit statuses * fix(agent-loop): apply qwen temperature and notes-tool clamps per fallback candidate * fix(chat): honor queued stop across resend and reload canonical terminal on EOF * fix(chat): track stop queue and cleanup ownership by per-send generation * fix(agent-loop): preserve requested temperature for non-qwen fallback candidates * fix(chat): reserve send ownership before any await and scope stop to the current send * fix(chat): clear the previous run identity at send reservation --------- Co-authored-by: RaresKeY <158580472+RaresKeY@users.noreply.github.com> Co-authored-by: StressTestor <212606152+StressTestor@users.noreply.github.com>
2026-10-29 01:02:25 +01:00 · 2026-08-14 08:10:30 +01:00
parent b52296471b
commit c4369305f0
46 changed files with 11418 additions and 1006 deletions
@@ -81,6 +81,13 @@ def _make_stream_with_save(sink, chunks, *, hang_after=None):
    return gen()


+async def _collect_subscription(session_id, expected_run=None):
+    return [
+        event
+        async for event in agent_runs.subscribe(session_id, expected_run)
+    ]
+
+
 # --------------------------------------------------------------------------- #
 # agent_runs: detached-run semantics (what NORMAL chat/agent streams use)
 # --------------------------------------------------------------------------- #
@@ -136,7 +143,7 @@ async def test_stop_cancels_detached_run_and_saves_partial_exactly_once():
            break
    await sub.aclose()

-    stopped = agent_runs.stop(session_id)
+    stopped = agent_runs.stop(session_id, run.run_id)
    assert stopped is True

    await run.task  # propagates promptly — not stuck on the hung await
@@ -165,6 +172,172 @@ async def test_normal_completion_saves_exactly_once_not_partial():
    assert sink.saves == []


+@pytest.mark.asyncio
+async def test_detached_run_identity_is_stable_for_replay_and_unique_per_run():
+    session_id = "sess-detached-run-identity"
+    agent_runs._RUNS.pop(session_id, None)
+
+    first = agent_runs.start(session_id, _make_stream_with_save(_FakeSaveSink(), ["one"]))
+    first_id = first.run_id
+    assert agent_runs.get_run_id(session_id) == first_id
+    await first.task
+    assert agent_runs.get_run_id(session_id) == first_id
+
+    second = agent_runs.start(session_id, _make_stream_with_save(_FakeSaveSink(), ["two"]))
+    assert second.run_id != first_id
+    assert agent_runs.get_run_id(session_id) == second.run_id
+    await second.task
+
+
+@pytest.mark.asyncio
+async def test_lazy_subscription_stays_bound_to_header_run_after_replacement():
+    session_id = "sess-detached-lazy-subscription"
+    agent_runs._RUNS.pop(session_id, None)
+
+    async def stream(label):
+        yield f'data: {{"delta":"{label}"}}\n\n'
+
+    first = agent_runs.start(session_id, stream("first"))
+    await first.task
+    # StreamingResponse does not iterate its body until after construction.
+    # Capture the same exact run object used for its identity header.
+    lazy_body = agent_runs.subscribe(session_id, first)
+
+    second = agent_runs.start(session_id, stream("second"))
+    await second.task
+
+    replayed = [event async for event in lazy_body]
+    assert replayed == ['data: {"delta":"first"}\n\n']
+    assert agent_runs.get_run_id(session_id) == second.run_id
+
+
+@pytest.mark.asyncio
+async def test_stale_run_identity_cannot_stop_replacement_run():
+    session_id = "sess-detached-stale-stop"
+    agent_runs._RUNS.pop(session_id, None)
+    release = asyncio.Event()
+
+    async def finished():
+        yield 'data: {"delta":"old"}\n\n'
+
+    async def replacement():
+        yield 'data: {"delta":"new"}\n\n'
+        await release.wait()
+
+    first = agent_runs.start(session_id, finished())
+    await first.task
+    second = agent_runs.start(session_id, replacement())
+    await asyncio.sleep(0)
+
+    assert agent_runs.stop(session_id) is False
+    assert agent_runs.stop(session_id, first.run_id) is False
+    assert second.task is not None and not second.task.done()
+    assert agent_runs.stop(session_id, second.run_id) is True
+    await second.task
+
+
+@pytest.mark.asyncio
+async def test_triple_replacement_closes_middle_subscriber_and_preserves_save_order():
+    session_id = "sess-detached-triple-replacement"
+    agent_runs._RUNS.pop(session_id, None)
+    first_closing = asyncio.Event()
+    release_first = asyncio.Event()
+    third_started = asyncio.Event()
+
+    async def first_stream():
+        try:
+            yield 'data: {"delta":"first"}\n\n'
+            await asyncio.Event().wait()
+        finally:
+            first_closing.set()
+            await release_first.wait()
+
+    async def middle_stream():
+        yield 'data: {"delta":"middle"}\n\n'
+
+    async def third_stream():
+        third_started.set()
+        yield 'data: {"delta":"third"}\n\n'
+
+    first = agent_runs.start(session_id, first_stream())
+    while not first.buffer:
+        await asyncio.sleep(0)
+
+    middle = agent_runs.start(session_id, middle_stream())
+    await first_closing.wait()
+    assert middle.task is not None and not middle.task.done()
+
+    middle_events_task = asyncio.create_task(
+        _collect_subscription(session_id, middle)
+    )
+    while not middle.subscribers:
+        await asyncio.sleep(0)
+
+    third = agent_runs.start(session_id, third_stream())
+
+    # The superseded middle response closes immediately even though its task
+    # remains as the transitive barrier for the first run's partial save.
+    assert await asyncio.wait_for(middle_events_task, timeout=1) == []
+    assert middle.status == "stopped"
+    assert middle.task is not None and not middle.task.done()
+    assert not third_started.is_set()
+
+    release_first.set()
+    await asyncio.wait_for(first.task, timeout=1)
+    await asyncio.wait_for(middle.task, timeout=1)
+    await asyncio.wait_for(third.task, timeout=1)
+
+    assert first.status == "stopped"
+    assert middle.status == "stopped"
+    assert third.status == "done"
+    assert third_started.is_set()
+
+
+@pytest.mark.asyncio
+async def test_reconnect_replays_pinned_fallback_run_without_restarting_tools():
+    session_id = "sess-detached-fallback-resume"
+    agent_runs._RUNS.pop(session_id, None)
+    release = asyncio.Event()
+    tool_executions = 0
+    fallback = 'data: {"type":"fallback","answered_by":"backup","candidate_index":1}\n\n'
+    tool = 'data: {"type":"tool_output","tool":"bash","output":"ok"}\n\n'
+
+    async def pinned_run():
+        nonlocal tool_executions
+        yield fallback
+        tool_executions += 1
+        yield tool
+        await release.wait()
+        yield 'data: {"delta":"backup finished"}\n\n'
+        yield "data: [DONE]\n\n"
+
+    run = agent_runs.start(session_id, pinned_run())
+    first = agent_runs.subscribe(session_id)
+    first_events = []
+    async for event in first:
+        first_events.append(event)
+        if len(first_events) == 2:
+            break
+    await first.aclose()
+
+    assert run.status == "running"
+    assert tool_executions == 1
+    assert agent_runs._RUNS[session_id] is run
+
+    resumed_events = []
+    resumed = agent_runs.subscribe(session_id)
+    async for event in resumed:
+        resumed_events.append(event)
+        if len(resumed_events) == 2:
+            release.set()
+    await run.task
+
+    assert resumed_events[:2] == [fallback, tool]
+    assert resumed_events[-1] == "data: [DONE]\n\n"
+    assert tool_executions == 1
+    assert agent_runs._RUNS[session_id] is run
+
+
 # --------------------------------------------------------------------------- #
 # chat_stream: Compare panes must NOT be detached, so the Stop button (closing
 # the SSE) cancels the upstream generator promptly — exercising the same