## Context
Railway deploys via Railpack suddenly fail with `Failed to resolve version 1 of yarn` / `Failed to resolve version 1.22.22` even though nothing changed in the project, yarn 1.x detected via Corepack/mise, then version resolution fails.
## Verified resolution
Maintainer iloveitaly (maintains railpack): this was platform-side, the mise yarn backend (asdf) was broken/corrupted for a period of time; Railpack later moved to a different mise backend via PR #216, but the asdf backend had already been fixed, so builds recovered on their own (`deploy again and it should be fixed`). Workarounds that reporters used meanwhile: pin the builder to NIXPACKS in railway.json, or switch the service to a Dockerfile that installs yarn directly (`npm i -g yarn@1.22.22`).