Summary

• Reuse the Linux test binaries and Playwright binary produced by compile_and_lint instead of recompiling sqlpage in the database and browser-test jobs.
• Keep Windows incremental/local sqlpage artifacts in a PR/ref-scoped cache so source edits can reuse incremental compilation state without allowing PRs to write a trusted main cache.
• Make Docker cache scopes explicit: PR caches write to PR-scoped BuildKit GHA scopes, while trusted main remains a restore-only Docker Hub fallback for PRs.
• Move .cargo/config.toml into the Docker dependency warmup layer so the warmup and final build use the same LIBSQLITE3_FLAGS.
• Use BuildKit's Git context for Docker builds so dependency layers are keyed by committed source rather than by a per-job local runner context stream.

Current findings

• The Rust job deduplication works. In CI run 26915251134, the DB matrix and Playwright jobs used uploaded binaries and did not run Cargo builds.
• The Docker final-build warmup gap is fixed. In 26892512893, amd64-minimal build-project.sh compiled only sqlpage; the previous repeat compiles of libsqlite3-sys, sqlx-core-oldapi, sqlx-macros-oldapi, and sqlx-oldapi disappeared after copying .cargo/ before build-dependencies.sh.
• The remaining Docker dependency-cache miss came from using context: .. Same-commit reruns had identical Docker frontend args and checkout SHA, but different BuildKit local-context vertex digests, which invalidated every downstream COPY and therefore build-dependencies.sh.
• Switching Docker builds to context: "{{defaultContext}}" fixes that instability. The first Git-context build is cold once per platform because the old path-context cache keys are not reusable. After that warmup, same-commit reruns hit: amd64-minimal rerun job 79405292019 completed in 23 seconds, and armv7-minimal rerun job 79406759422 completed in 24 seconds, with build-dependencies.sh and build-project.sh both CACHED.

Validation

• git diff --check
• actionlint -ignore 'SC2046' .github/workflows/ci.yml
• docker buildx build --check --target builder .
• CI run 26915251134: full workflow passed.
• CI run 26915251134, rerun jobs 79405292019 and 79406759422: same-commit amd64-minimal and armv7-minimal reruns proved the Docker GHA cache hits the dependency layer after the first Git-context warmup for that platform.

Reverted experiments

• BuildKit Cargo cache mounts were tested and reverted earlier. On same-SHA rerun they still downloaded hundreds of crates and compiled hundreds of units, worse than plain layer caching.
• A dummy lib-target warmup was tested and removed. It did not stop SQLx recompilation; copying .cargo/config.toml before dependency warmup did.