Default Error Handler

If you do not register a custom error handler, Volten's default error handler responds according to the error type and the client's Accept header.

Content Negotiation

• JSON Clients: If the request includes Accept: application/json, the response is automatically formatted as JSON:

  {
    "error": "Route Not Found",
    "code": 404
  }

• Standard Clients: Otherwise, it sends plain text:

  Route Not Found

• 405 Method Not Allowed: When the path exists but the HTTP method is not registered, the response includes an RFC Allow header listing the methods that are registered for that path (for example Allow: GET, POST). The MethodNotAllowedError instance also exposes those methods as allowedMethods for custom app.onError handlers.

Developer Experience (HTML Stack Traces)

To improve Developer Experience (DevEx), when an unhandled exception occurs (HTTP 500) and NODE_ENV is explicitly set to "development", the default error handler will generate a rich, syntax-highlighted HTML error page.

This page beautifully formats the stack trace and highlights the exact file, line, and column where the error originated, making it drastically easier to debug.

If NODE_ENV is unset or set to any other environment (such as "production"), the HTML page is disabled to prevent leaking sensitive stack traces and internal paths to users, falling back to a generic 500 Internal Server Error message.

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