# CRC validation failed The message `validation failed on the message sent to STDOUT, RR docs: https://docs.roadrunner.dev/docs, invalid message: ...` means that you or some application sent an invalid raw message to `STDOUT`. The `STDOUT` stream is reserved for RR communication with the PHP process via the `goridge` protocol (`v3`). How to fix that? 1. Check your application. All dependencies should send their messages to `STDERR` instead of `STDOUT`. You may see the output after the `invalid message`. It might be truncated on Windows. 2. Check any `dd` or `echo` statements you inserted. PHP workers can redirect `echo` automatically from `STDOUT` to `STDERR`, but only after the worker is fully initialized. 3. A worker from RR v1 was used. To update, see: [link](/docs/integrations/migration.md) 4. OPcache is enabled with JIT, but some extensions don't support it, which leads to warnings. Adjust the `error_reporting` configuration (use only errors): [issue](https://github.com/roadrunner-server/roadrunner/issues/1306) 5. If you use a Symfony runtime, add `APP_RUNTIME` to the server environment variables, as described here: . --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.roadrunner.dev/docs/error-codes/stdout-crc.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.