Fix: Write directly to stdout.buffer to bypass TextIOWrapper issues

The TextIOWrapper may have buffering issues when stderr is redirected.
Writing directly to the binary buffer with encoded bytes ensures
immediate delivery of responses to Claude Code.

scripts/mcp/proxysql_mcp_stdio_bridge.py

@@ -271,17 +271,18 @@ class StdioMCPServer:
 
     async def _writeline(self, data: Any):
         """Write JSON data to stdout."""
-        loop = asyncio.get_event_loop()
         output = json.dumps(data, ensure_ascii=False) + "\n"
+        output_bytes = output.encode('utf-8')
 
-        debug_log(f"[_writeline] Writing {len(output)} bytes to stdout")
+        debug_log(f"[_writeline] Writing {len(output_bytes)} bytes to stdout")
         debug_log(f"[_writeline] sys.stdout: {sys.stdout}")
-        debug_log(f"[_writeline] sys.stdout.fileno(): {sys.stdout.fileno() if hasattr(sys.stdout, 'fileno') else 'N/A'}")
-
-        await loop.run_in_executor(None, sys.stdout.write, output)
+        debug_log(f"[_writeline] sys.stdout.buffer: {sys.stdout.buffer}")
 
-        debug_log(f"[_writeline] Data written, now flushing...")
-        await loop.run_in_executor(None, sys.stdout.flush)
+        # Write directly to the binary buffer to avoid any TextIOWrapper issues
+        # This bypasses Python's text encoding layer and writes raw bytes
+        loop = asyncio.get_event_loop()
+        await loop.run_in_executor(None, sys.stdout.buffer.write, output_bytes)
+        await loop.run_in_executor(None, sys.stdout.buffer.flush)
 
         debug_log(f"[_writeline] Flush complete")