Deno

Deno’s GitHub releases page is the operational changelog, and breaking changes live in the body text of each release entry rather than in a separate migration guide. The most substantial migration is documented across the Deno 2.0 release notes: the consolidation of the broad --unstable flag into per-feature flags such as --unstable-kv and --unstable-cron, the Node.js and npm compatibility layer that changed module resolution behaviour, and the narrowed surface of the Deno.* namespace APIs that had been quietly deprecated through the 1.x series.

Minor releases carry surprises too, particularly around the permissions model. When a script passes under one version and fails a permissions assertion under the next, the relevant release entry is usually the right first stop; the team tends to annotate those changes explicitly rather than letting them surface as undocumented behaviour shifts.