Long workstreams land phase by phase on `edge` and reach `main` as a single
cutover. With `branches: [main]` alone, every one of those phase PRs merges
with no checks at all -- no server tests, no client build, no bot install --
and the whole workstream runs blind until the cutover, where the breakage
arrives all at once and un-bisected.
This is not hypothetical: it is what happened to all nine Android M12 phase
PRs in the Android-app repo, whose pr-checks.yml carries the same trigger.
It matters for the module system specifically because Phase 2's exit
criterion IS a CI result -- a zero-line routes.manifest.json diff and a
passing suite -- and that manifest is the frozen URL surface protecting
three shipped clients. A branch accumulating work for weeks needs the gate
more than main does, not less.
Landing before the module-system edge branch is cut, so the first phase PR
is checked. build-images.yml is deliberately untouched: it triggers on push
to main, so images publish and production rolls at the cutover and never
before.
Co-Authored-By: Claude <noreply@anthropic.com>
