fix(webapp): count a profile that is still starting as busy for idle exit

An auto-started gateway whose built ledgers were empty could idle-exit while hot-serve was still building a profile: the registry walk skips a reserved slot, so busy_reason saw nothing and the stop cancelled the start before that profile's queued admissions were recovered. busy_reason now reports a pending start (SessionAuthorities.starting_homes); the hold ends when the start is filled or fails.

gateway/run_idle_exit.py

@@ -138,6 +138,15 @@ def _ledger_busy(runner) -> str | None:
     return None
 
 
+def _profile_start_busy(runner) -> str | None:
+    """A profile hot-serve is still building has no authority to walk yet, but its queued admissions
+    are recovered once it starts; exiting now would cancel that start. A filled or failed start
+    leaves the registry's starting set, so the hold ends with it."""
+    registry = getattr(runner, "session_authorities", None)
+    starting = registry.starting_homes() if registry is not None else ()
+    return f"profile starting in {starting[0]}" if starting else None
+
+
 def _store_gates_busy(homes) -> str | None:
     from gateway.run_idle_gates import (
         profile_has_active_heartbeat, profile_has_active_loop, profile_has_pending_handoff)
@@ -186,8 +195,8 @@ def busy_reason(runner, *, window: float, count_clients: bool = True) -> str | N
         if runner._scale_to_zero_has_live_background_work():
             return "background work in flight"
         homes = _served_homes(runner)
-        return (_messaging_busy(runner) or _ledger_busy(runner) or _cron_busy(homes) or _kanban_busy()
-                or _store_gates_busy(homes))
+        return (_messaging_busy(runner) or _ledger_busy(runner) or _profile_start_busy(runner)
+                or _cron_busy(homes) or _kanban_busy() or _store_gates_busy(homes))
     except Exception as exc:
         logger.debug("idle-exit probe failed; staying up", exc_info=True)
         return f"idle probe failed ({type(exc).__name__})"

gateway/session_authorities.py

@@ -75,6 +75,10 @@ class SessionAuthorities:
         return next(((key, started) for key, started in list(self._starting.items())
                      if profile_matches_home(profile, Path(key))), None)
 
+    def starting_homes(self) -> list[str]:
+        """Keys of every slot whose authority is still being built (a snapshot, as in ``serving``)."""
+        return list(self._starting)
+
     def profile_name(self, authority):
         """Served profile name for *authority*; None for the launch profile (its adapters are
         ``runner.adapters``, its session keys the historical ``agent:main`` namespace)."""

tests/gateway/test_unmanaged_idle_exit.py

@@ -108,6 +108,30 @@ def test_a_profile_still_starting_leaves_the_served_ledgers_readable(tmp_path, m
         db.close()
 
 
+def test_a_profile_still_starting_keeps_an_otherwise_idle_gateway_up(tmp_path, monkeypatch):
+    """With every built ledger empty, a profile hot-serve is still building holds the gateway: its
+    queued admissions are recovered only once it starts. The hold ends with the start, filled or failed."""
+    runner, _home, db, _stops = _runner(tmp_path, monkeypatch)
+    registry = runner.session_authorities
+    starting = tmp_path / "starting"
+    starting.mkdir()
+    try:
+        assert run_idle_exit.busy_reason(runner, window=0.2) is None
+        registry.add(starting, None, name="starting")  # as serve_profile_runtime does
+        assert "profile starting" in run_idle_exit.busy_reason(runner, window=0.2)
+        registry.remove(starting)  # the build failed
+        assert run_idle_exit.busy_reason(runner, window=0.2) is None
+        registry.add(starting, None, name="starting")
+        starting_db = SessionDB(db_path=starting / "state.db")
+        registry.replace(starting, SimpleNamespace(profile_id=str(starting), db=starting_db))
+        try:
+            assert run_idle_exit.busy_reason(runner, window=0.2) is None
+        finally:
+            starting_db.close()
+    finally:
+        db.close()
+
+
 def test_secondary_local_session_adapter_does_not_count_as_messaging(tmp_path, monkeypatch):
     """A secondary local session leaves an adapter map behind after the client disconnects."""
     runner, _home, db, _stops = _runner(tmp_path, monkeypatch)