fix(tui): preserve detached sessions with active work

tests/test_tui_gateway_server.py

@@ -1769,6 +1769,36 @@ def write(self, *a, **k):
     assert server._ws_session_is_orphaned(done) is False
 
 
+def test_ws_orphan_reap_spares_detached_session_still_in_progress(monkeypatch):
+    """A crashed desktop window must not reap work that can still resume."""
+
+    building_ready = threading.Event()
+    building = _session(
+        transport=server._detached_ws_transport,
+        running=False,
+        agent_ready=building_ready,
+        agent_build_started=True,
+    )
+    assert server._ws_session_is_orphaned(building, "building-sid") is False
+
+    inflight = _session(
+        transport=server._detached_ws_transport,
+        running=False,
+        inflight_turn={"user": "still streaming"},
+    )
+    assert server._ws_session_is_orphaned(inflight, "inflight-sid") is False
+
+    pending_event = threading.Event()
+    server._pending["approval-1"] = ("prompt-sid", pending_event)
+    server._pending_prompt_payloads["approval-1"] = ("approval.request", {})
+    try:
+        waiting = _session(transport=server._detached_ws_transport, running=False)
+        assert server._ws_session_is_orphaned(waiting, "prompt-sid") is False
+    finally:
+        server._pending.pop("approval-1", None)
+        server._pending_prompt_payloads.pop("approval-1", None)
+
+
 def test_ws_orphan_reap_disabled_when_grace_zero(monkeypatch):
     """Grace=0 disables the reaper entirely (pre-fix park-forever behaviour)."""
     fired = {"timer": False}

tui_gateway/server.py

@@ -493,17 +493,25 @@ def _close_session_by_id(sid: str, *, end_reason: str = "tui_close") -> bool:
 
 
 
-def _ws_session_is_orphaned(session: dict | None) -> bool:
+def _ws_session_is_orphaned(session: dict | None, sid: str | None = None) -> bool:
     """True if a WS session has no live transport and no in-flight turn.
 
     After ``handle_ws`` detaches a disconnected client it points the session at
     ``_detached_ws_transport``. A session left on that transport (and not
-    mid-turn) is genuinely orphaned and safe to reap.
+    mid-turn / mid-build / waiting on input) is genuinely orphaned and safe to
+    reap.
     """
     if not session or session.get("_finalized"):
         return False
     if session.get("running"):
         return False
+    if sid and _session_pending_kind(sid):
+        return False
+    if session.get("inflight_turn") is not None:
+        return False
+    ready = session.get("agent_ready")
+    if ready is not None and not ready.is_set() and session.get("agent_build_started"):
+        return False
     return session.get("transport") is _detached_ws_transport
 
 
@@ -528,7 +536,7 @@ def _reap() -> None:
         # guard with _sessions_lock). _sessions_lock is an RLock and the global
         # ordering is always resume_lock -> sessions_lock, so nesting is safe.
         with _session_resume_lock:
-            if not _ws_session_is_orphaned(_sessions.get(sid)):
+            if not _ws_session_is_orphaned(_sessions.get(sid), sid):
                 return
             _close_session_by_id(sid, end_reason="ws_orphan_reap")