fix: stop polling GET /api/tasks/runs/recent from cancelling running tasks

Two paths caused the scheduler to interrupt a running background task
when the frontend Activity view polled for status:

1. GET /api/tasks/runs/recent was not in _PASSIVE_EXACT_PATHS, so
   _InteractiveActivityMiddleware treated it as a foreground request
   and called stop_background_tasks_for_foreground, cancelling any
   in-flight scheduled task. Add it to _PASSIVE_EXACT_PATHS alongside
   the other read-only polling endpoints.

2. The /api/activity/heartbeat handler called
   stop_background_tasks_for_foreground unconditionally, ignoring
   BACKGROUND_TASK_FOREGROUND_GATE=false. Wrap the call in a
   _gate_enabled() guard so the env var fully disables heartbeat-
   triggered cancellations.

Fixes #5782

Signed-off-by: Christian Sidak <christian@sentineltech.eu>
Signed-off-by: Christian-Sidak <61099993+Christian-Sidak@users.noreply.github.com>

app.py

@@ -630,14 +630,15 @@ app.include_router(auth_router)
 
 @app.post("/api/activity/heartbeat")
 async def activity_heartbeat():
-    from src.interactive_gate import mark_browser_activity
+    from src.interactive_gate import mark_browser_activity, _enabled as _gate_enabled
     await mark_browser_activity()
-    async def _stop_background():
-        try:
-            await task_scheduler.stop_background_tasks_for_foreground(reason="browser heartbeat")
-        except Exception:
-            logging.getLogger("app.foreground_gate").debug("heartbeat task stop failed", exc_info=True)
-    asyncio.create_task(_stop_background())
+    if _gate_enabled():
+        async def _stop_background():
+            try:
+                await task_scheduler.stop_background_tasks_for_foreground(reason="browser heartbeat")
+            except Exception:
+                logging.getLogger("app.foreground_gate").debug("heartbeat task stop failed", exc_info=True)
+        asyncio.create_task(_stop_background())
     return {"ok": True}
 
 

src/interactive_gate.py

@@ -63,6 +63,7 @@ _PASSIVE_EXACT_PATHS = {
     "/api/activity/heartbeat",
     "/api/client-perf",
     "/api/tasks/notifications",
+    "/api/tasks/runs/recent",
     "/api/research/active",
     "/api/email/urgency-state",
 }

tests/test_poll_endpoint_no_task_interrupt.py

@@ -0,0 +1,54 @@
+"""Regression: read-only task-status polling must not interrupt running background tasks.
+
+GET /api/tasks/runs/recent is called by the Activity view while a scheduled
+task is executing. Before this fix, the _InteractiveActivityMiddleware treated
+it as a foreground request and called stop_background_tasks_for_foreground,
+which immediately cancelled the running task. The fix adds the endpoint to
+_PASSIVE_EXACT_PATHS so it is excluded from interactive tracking.
+
+Additionally, /api/activity/heartbeat called stop_background_tasks_for_foreground
+unconditionally, ignoring BACKGROUND_TASK_FOREGROUND_GATE=false. The fix wraps
+that call in a _gate_enabled() check so the env var fully disables interrupts.
+"""
+
+import importlib
+import os
+
+
+def _reload_gate():
+    import src.interactive_gate as ig
+    importlib.reload(ig)
+    return ig
+
+
+def test_tasks_runs_recent_is_passive():
+    ig = _reload_gate()
+    assert not ig.should_track_interactive_request("/api/tasks/runs/recent", "GET"), (
+        "GET /api/tasks/runs/recent must be treated as a passive endpoint so that "
+        "the Activity-view polling does not trigger stop_background_tasks_for_foreground "
+        "and cancel running scheduled tasks"
+    )
+
+
+def test_tasks_runs_recent_does_not_affect_other_task_paths():
+    ig = _reload_gate()
+    # Non-polling mutating task routes should still be interactive.
+    assert ig.should_track_interactive_request("/api/tasks/runs/recent/something", "POST")
+
+
+def test_heartbeat_respects_foreground_gate_disabled(monkeypatch):
+    """stop_background_tasks_for_foreground must NOT be called from the heartbeat
+    handler when BACKGROUND_TASK_FOREGROUND_GATE=false."""
+    monkeypatch.setenv("BACKGROUND_TASK_FOREGROUND_GATE", "false")
+    ig = _reload_gate()
+    assert not ig._enabled(), (
+        "_enabled() should return False when BACKGROUND_TASK_FOREGROUND_GATE=false"
+    )
+
+
+def test_heartbeat_gate_enabled_by_default(monkeypatch):
+    monkeypatch.delenv("BACKGROUND_TASK_FOREGROUND_GATE", raising=False)
+    ig = _reload_gate()
+    assert ig._enabled(), (
+        "_enabled() should return True by default (foreground gate on)"
+    )