From 8b3149cb7eb0da0c10d94a4e474d9fbec6205088 Mon Sep 17 00:00:00 2001
From: pe1hvh <github@pe1hvh.nl>
Date: Mon, 9 Feb 2026 22:53:27 +0100
Subject: [PATCH] fix: subscribe before send to prevent event race condition

---
 src/meshcore/commands/base.py | 87 +++++++++++++++++++++++++++++++----
 1 file changed, 78 insertions(+), 9 deletions(-)

diff --git a/src/meshcore/commands/base.py b/src/meshcore/commands/base.py
index 4625473..6e89ab1 100644
--- a/src/meshcore/commands/base.py
+++ b/src/meshcore/commands/base.py
@@ -140,6 +140,10 @@ class CommandHandlerBase:
         """
         Send a command and wait for expected event responses.
 
+        Uses subscribe-before-send to avoid race conditions where the
+        device responds before the event listener is registered.  This
+        mirrors the pattern used by the companion apps (JS/iOS/Android).
+
         Args:
             data: The data to send
             expected_events: EventType or list of EventTypes to wait for
@@ -154,17 +158,82 @@ class CommandHandlerBase:
         # Use the provided timeout or fall back to default_timeout
         timeout = timeout if timeout is not None else self.default_timeout
 
-        if self._sender_func:
-            logger.debug(
-                f"Sending raw data: {data.hex() if isinstance(data, bytes) else data}"
-            )
-            await self._sender_func(data)
-
         if expected_events:
-        # For commands that don't expect events, return a success event
-            return await self.wait_for_events(expected_events, timeout)
+            # ── Subscribe BEFORE sending ──────────────────────────
+            # Register event listeners first so we never miss a fast
+            # device response, even on a busy mesh network where the
+            # asyncio event loop processes RX_LOG events in between.
+            if not isinstance(expected_events, list):
+                expected_events = [expected_events]
 
-        return Event(EventType.OK, {})
+            futures: List[asyncio.Future] = []
+            subscriptions = []
+
+            loop = asyncio.get_event_loop()
+            for event_type in expected_events:
+                future = loop.create_future()
+
+                def _handler(event: Event, f: asyncio.Future = future) -> None:
+                    if not f.done():
+                        f.set_result(event)
+
+                sub = self.dispatcher.subscribe(event_type, _handler)
+                futures.append(future)
+                subscriptions.append(sub)
+
+            try:
+                # ── Now send the command ──────────────────────────
+                if self._sender_func:
+                    logger.debug(
+                        f"Sending raw data: "
+                        f"{data.hex() if isinstance(data, bytes) else data}"
+                    )
+                    await self._sender_func(data)
+
+                # ── Wait for the first matching event ─────────────
+                done, pending = await asyncio.wait(
+                    futures,
+                    timeout=timeout,
+                    return_when=asyncio.FIRST_COMPLETED,
+                )
+
+                # Cancel futures we no longer need
+                for f in pending:
+                    f.cancel()
+
+                # Return the first successfully received event
+                for f in done:
+                    try:
+                        event = f.result()
+                        if event:
+                            return event
+                    except (asyncio.CancelledError, asyncio.InvalidStateError):
+                        pass
+
+                return Event(EventType.ERROR, {"reason": "no_event_received"})
+
+            except asyncio.TimeoutError:
+                logger.debug(
+                    f"Command timed out waiting for events {expected_events}"
+                )
+                return Event(EventType.ERROR, {"reason": "timeout"})
+            except Exception as e:
+                logger.debug(f"Command error: {e}")
+                return Event(EventType.ERROR, {"error": str(e)})
+            finally:
+                # Always clean up subscriptions
+                for sub in subscriptions:
+                    sub.unsubscribe()
+
+        else:
+            # Fire-and-forget commands (no expected response)
+            if self._sender_func:
+                logger.debug(
+                    f"Sending raw data: "
+                    f"{data.hex() if isinstance(data, bytes) else data}"
+                )
+                await self._sender_func(data)
+            return Event(EventType.OK, {})
 
     # attached at base because its a common method
     async def send_binary_req(self, dst: DestinationType, request_type: BinaryReqType, data: Optional[bytes] = None, context={}, timeout=None, min_timeout=0) -> Event: