Release Engineering

Release Engineering

Computing the bump

Pre-1.0 inverts this. Under 0.x, a breaking change bumps the minor, not the major. This is the classic release-automation bug, and it is not recoverable once published.

List commits that do not parse as conventional rather than ignoring them. A version computed from commits the tool could not read has an unknown bump.

Readiness gates

Default branch CI green at the release commit · no open release-blocker · no open reachable critical advisory · manifest versions match the computed tag · lockfile in sync · every breaking change has a migration note · the previous release is not still draft.

A failed gate stops the release and names the gate. There is no "mostly ready".

Breaking changes need sequencing, not just documentation

The safe pattern across releases is expand → migrate → contract:

1. Expand — add the new field/endpoint/column alongside the old. Nothing breaks.
2. Migrate — move consumers over. Both paths work.
3. Contract — remove the old path, in a later release.

A single release doing all three is a breaking change wearing a disguise. The same logic applies within a rolling deploy: old code and new schema coexist for minutes, so NOT NULL without a default breaks every insert in flight.

Changelog vs release notes

They are different documents for different moments.

Changelog — Keep a Changelog sections (Added Changed Deprecated Removed Fixed Security), written from user effect, not commit subject:

commit  fix(api): guard null user before id deref
entry   Fixed a 500 error when requesting a user id that does not exist;
        the API now returns 404.

Omit internal refactors with no observable effect. A changelog padded with chore: entries trains readers to skip it.

Release notes — read once, in a hurry: Highlights → Breaking changes with migrations → Fixed/Added → compare link.

Every breaking change carries the actual migration steps, not just the fact that it is breaking. A breaking change without migration instructions is an incident scheduled for whenever someone upgrades.

Rollback vs forward-fix

An irreversible migration flips the decision on its own — reverting code whose migration ran leaves the schema ahead of the code.

Check for a feature flag first. A flag flip has no code risk, cannot conflict with work merged since, does not touch history, and reverses in seconds. The best rollback is often not a git operation.

Reverting the code does not revert the data already written in the new shape. Ask that question every time.

Never

Never tag a commit whose CI is not green. Never move or rewrite a published tag — publish a new patch; a moved tag breaks every consumer that pinned it, invisibly. Never delete a published release; supersede it. Never git reset a shared branch.

See also

• ../commands/release.md · ../commands/rollback.md