fix(drone): broker start_background blocks until listening — kill connect-before-bind race

CHANGELOG.md

@@ -38,6 +38,15 @@ and this project uses [Calendar Versioning](https://calver.org/) in the format
   (method-level, so the graceful no-broker paths still run on Windows). All skip on
   Windows and run unchanged on Linux. windows-setup was green pre-sandbox-merge
   (`00edd8b`) and red since (`0b4ba63`); this closes it.
+- **Broker `start_background` connect-before-bind race.** `drone`'s out-of-sandbox
+  broker daemon started via `start_background()`, which returned *before* the
+  `AF_UNIX` socket was bound — callers then raced the bind, and on a slower machine
+  `create_identified_connection()` hit `FileNotFoundError` (socket not yet present).
+  Deterministic locally (`test_delete_nested_file` 0/5), green in CI only by timing
+  luck — latent flakiness. Fixed with a `threading.Event` set right after `listen()`;
+  `start_background(timeout=5.0)` now blocks on it and **raises** if the socket never
+  binds, so callers never guess a `sleep`. Removed the 4 blind `time.sleep(0.15)`
+  waits from the broker tests. Verified 55/55 broker tests, formerly-failing test 10/10.
 
 ### Added
 

src/aipass/drone/.seedgo/bypass.json

@@ -270,7 +270,7 @@
     {
       "file": "apps/handlers/broker/daemon.py",
       "standard": "unused_function",
-      "lines": [420],
+      "lines": [422],
       "reason": "Threaded broker entrypoint, exercised by tests/test_broker.py; production uses blocking start(); intentionally not called in shipped non-test code."
     }
   ],

src/aipass/drone/apps/handlers/broker/daemon.py

@@ -125,6 +125,7 @@ class BrokerDaemon:
         self._secret: bytes = b""
         self._server: socket.socket | None = None
         self._running = False
+        self._listening = threading.Event()
         self._lock = threading.Lock()
         json_handler.log_operation(
             "broker_init",
@@ -400,6 +401,7 @@ class BrokerDaemon:
         self._server.listen(5)
         self._server.settimeout(1.0)
         self._running = True
+        self._listening.set()
 
         logger.info("broker: listening on %s", self.socket_path)
         json_handler.log_operation("broker_start", {"socket": str(self.socket_path)})
@@ -417,10 +419,13 @@ class BrokerDaemon:
                     logger.error("broker: accept error: %s", exc)
                 break
 
-    def start_background(self) -> threading.Thread:
-        """Start the broker in a background thread. Returns the thread."""
+    def start_background(self, timeout: float = 5.0) -> threading.Thread:
+        """Start the broker in a background thread, blocking until listening."""
+        self._listening.clear()
         t = threading.Thread(target=self.start, daemon=True, name="drone-broker")
         t.start()
+        if not self._listening.wait(timeout):
+            raise RuntimeError(f"broker failed to start listening within {timeout}s")
         return t
 
     def stop(self) -> None:

src/aipass/drone/tests/test_broker.py

@@ -23,7 +23,6 @@ import json
 import socket
 import os
 import stat
-import time
 from pathlib import Path
 
 import pytest
@@ -125,7 +124,6 @@ def broker(tmp_path: Path, repo_root: Path) -> BrokerDaemon:
 def running_broker(broker: BrokerDaemon):
     """Start a broker in background, yield it, stop on teardown."""
     t = broker.start_background()
-    time.sleep(0.15)
     yield broker
     broker.stop()
     t.join(timeout=3)
@@ -367,7 +365,6 @@ class TestBrokerDaemon:
     def test_stop_cleans_socket(self, broker: BrokerDaemon) -> None:
         """Stopping the broker removes the socket file."""
         t = broker.start_background()
-        time.sleep(0.15)
         assert broker.socket_path.exists()
         broker.stop()
         t.join(timeout=3)
@@ -574,7 +571,6 @@ class TestIdentity:
             secret_path=secret_path,
         )
         t1 = d1.start_background()
-        time.sleep(0.15)
         secret1 = secret_path.read_bytes()
         d1.stop()
         t1.join(timeout=3)
@@ -586,7 +582,6 @@ class TestIdentity:
             secret_path=secret_path,
         )
         t2 = d2.start_background()
-        time.sleep(0.15)
         secret2 = secret_path.read_bytes()
         d2.stop()
         t2.join(timeout=3)