Motivation and Context

Using the example code from README:

// Legacy message endpoint for older clients
app.post('/messages', async (req, res) => {
  const sessionId = req.query.sessionId as string;
  const transport = transports.sse[sessionId];
  if (transport) {
    await transport.handlePostMessage(req, res, req.body);
  } else {
    res.status(400).send('No transport found for sessionId');
  }
});

I notice that "await" is not respected

    await transport.handlePostMessage(req, res, req.body);

The reason is a missing await in handlePostMessage 

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• [ x] I have read the MCP Documentation
• [ x] My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed