diff --git a/app/main.py b/app/main.py
index 40b327c..833821c 100644
--- a/app/main.py
+++ b/app/main.py
@@ -180,6 +180,25 @@ async def radio_disconnected_handler(request: Request, exc: RadioDisconnectedErr
     return JSONResponse(status_code=503, content={"detail": "Radio not connected"})
 
 
+@app.middleware("http")
+async def log_server_errors(request: Request, call_next):
+    """Capture 5xx errors and unhandled exceptions into the log ring buffer.
+
+    Starlette writes unhandled-exception tracebacks to stderr, bypassing
+    Python logging, so they never reach the debug dump.  This middleware
+    catches them and logs via ``logger.exception()`` so the full traceback
+    is preserved in the ring buffer for the ``GET /api/debug`` snapshot.
+    """
+    try:
+        response = await call_next(request)
+    except Exception:
+        logger.exception("Unhandled exception on %s %s", request.method, request.url.path)
+        raise
+    if response.status_code >= 500:
+        logger.error("HTTP %d on %s %s", response.status_code, request.method, request.url.path)
+    return response
+
+
 # API routes - all prefixed with /api for production compatibility
 app.include_router(health.router, prefix="/api")
 app.include_router(debug.router, prefix="/api")
diff --git a/app/services/message_send.py b/app/services/message_send.py
index 6752b41..0789600 100644
--- a/app/services/message_send.py
+++ b/app/services/message_send.py
@@ -258,6 +258,12 @@ async def send_channel_message_with_effective_scope(
             )
             raise HTTPException(status_code=504, detail=NO_RADIO_RESPONSE_AFTER_SEND_DETAIL)
         if send_result.type == EventType.ERROR:
+            logger.error(
+                "Radio returned error during %s for channel %s: %s",
+                action_label,
+                channel.name,
+                send_result.payload,
+            )
             radio_manager.invalidate_cached_channel_slot(channel_key)
         else:
             radio_manager.note_channel_slot_used(channel_key)