workflow web crashes on unmatched routes (e.g. /robots.txt, /favicon.ico)

[lamualfa]

Bug Description

When running workflow web, the process crashes (exits with code 1) when any request hits a URL that doesn't match a React Router route (e.g. /robots.txt, /favicon.ico, /sitemap.xml).

Root Cause

The oclif Web command class has a catch handler that calls process.exit(1) on any error:

https://github.com/vercel/workflow/blob/main/packages/cli/src/commands/web.ts#L29

When a browser or bot requests a static file like /robots.txt, the React Router SSR handler (via @react-router/express) encounters a "No route matches" error. This error gets logged and can propagate through the error handling chain, eventually triggering the oclif catch handler which calls process.exit(1).

Error Output

Error: No route matches URL "/robots.txt"
    at getInternalRouterError (...)
    at Object.query (...)
    at handleDocumentRequest (...)
    at requestHandler (...)
    at requestHandler (...)
No routes matched location "/robots.txt"
ErrorResponseImpl {
  status: 404,
  statusText: 'Not Found',
  internal: true,
  data: 'Error: No route matches URL "/robots.txt"',
  error: Error: No route matches URL "/robots.txt"
}

Expected Behavior

The server should handle unmatched routes gracefully by returning a 404 response without crashing.

Possible Fixes

1. Don't use process.exit(1) in the catch handler for request-level errors - The catch handler should only call process.exit(1) for startup errors, not for errors that occur during request handling.

2. Add error handling middleware to the Express app in @workflow/web/server - Add an Express error handler that catches ErrorResponseImpl with internal: true and returns a proper 404 response instead of letting the error propagate.

3. Add a catch-all route or static file fallback before the React Router handler to serve common static files like /robots.txt and /favicon.ico.

Environment

• workflow: 4.2.0-beta.67
• @workflow/web: 4.1.0-beta.39
• @workflow/cli: 4.2.0-beta.73
• Node.js: 24
• OS: Linux