Parallel Work Units in a background workflow

The SDLC pipeline's implement ⇄ review loop runs as a saved dynamic workflow (claude-plugins/chicio-labs-sdlc/workflows/), not inline in the main thread, so that an Approved Plan split into a Work Unit Graph can be built and reviewed Wave by Wave, with the Work Units of a Wave in parallel. This reverses the earlier rule that isolation is pipeline-level only and never per-agent: parallel implementers cannot share one working tree, because each one wipes .next, needs port 3000 for the dev server and Playwright, and commits on the same index. So a Wave with more than one Work Unit gives each its own worktree and branch, merged back into the feature branch before the next Wave; a Wave of one runs in the pipeline's shared worktree as before.

Consequences

• The mechanical checks are split. A Work Unit passes only the Unit Checks; the build, the end-to-end suite and knip run once, as Full Checks, on the combined result, run by a dedicated gate-runner. The reviewer no longer re-runs every check itself: it trusts the gate-runner and verifies specific claims.
• A workflow cannot ask anything. A stuck Work Unit (an escalated rebuttal or an exhausted round budget) does not pause the run: its dependents are skipped, independent Work Units finish, and the workflow returns a partial result. Fabrizio decides in the main thread, which resumes the run from cache.
• Conflicts are a planning error. Every file belongs to exactly one Work Unit, so the Human Gate, which approves the Work Unit Graph, is where overlap is caught; the merge agent resolves only trivial conflicts.

Considered Options

• Parallel Work Units in one shared tree, trusting disjoint file ownership: git commits from several agents on one branch still race, and every build collides on .next.
• Always isolate: a single-unit plan (every fix, many features) would pay npm install in a fresh worktree for no parallelism.