Stale package versions persist after editing replit.nix in Replit

Does editing replit.nix automatically invalidate the Nix store?

Replit’s build system watches replit.nix for changes. When you save a modification, the platform schedules a rebuild of the environment for that repl. The rebuild is not instantaneous; it runs the next time you press Run or Restart. If the rebuild completes successfully, the old derivations are replaced and the new package versions are used.

How to guarantee a fresh environment

1. Edit replit.nix and commit the change.
2. Open the Replit sidebar (the gear icon on the left).
3. Click Rebuild environment. This forces the Nix store to discard the cached derivation for the current repl and rebuild the entire environment from the updated expression.
4. Wait for the status bar to show building… and finally success. The console will display the build log.
5. Verify the new version by running a command that reports the package’s version, e.g. python -m pip show requests or node -v, depending on the package.

If you prefer the command line, you can trigger garbage collection to clean unused derivations:

nix-store --gc

but this only removes unused items; it does not replace the current environment.

What if the new version still appears stale?

• Check the console for any build errors. If the rebuild was interrupted, the old derivation may still be in use.
• Confirm that the build log contains the expected package name and hash in the path, e.g. /nix/store/abcd1234-python3-requests-2.28.1.
• Ensure you are not using a custom overlay that might cache a different derivation.

Undocumented cache clearing

Deleting the hidden .replit-nix-cache directory is an unsupported workaround and may break future builds. Stick to the UI Rebuild environment button for predictable results.

Quick sanity check

After a rebuild, run:

nix-env -qaP <package>

to see the derivation hash and verify that it matches the new version you specified.

Missing diagnostic detail

Did the rebuild log show a success message, or were there any errors? Knowing this will determine whether the stale package is due to an incomplete rebuild or a different issue.