fusion/docs/dag/milestone-b-implementation-checklist.md

Milestone B Implementation Checklist (Executor-Ready)

Related tasks: FN-4491, FN-4490, FN-4487, FN-4471, governance gate FN-4359.

See also: Schema migration plan · DagCoordinator design · ADR v1

Gate (must be first)

• FN-4359 freeze lifted or explicit carve-out granted for DAG prototype implementation. Until then, do not implement.
  • Policy quote (AGENTS.md): “Reliability mechanism changes are currently under freeze pending FN-4359 governance hardening; treat new reliability-layer behavior changes as blocked unless explicitly approved in task scope.”

Ordered milestones

ADR traceability: sequence follows ADR-0001 Decision (SQLite DAG + enqueue-only coordinator) and Consequences #1/#2/#4 (additive storage, non-blocking runtime, unchanged merge path).

1. Land additive migration(s) from plan

   • Outcome: dag_run, dag_node, dag_edge created via next schema version block.
   • File scope hints: packages/core/src/db.ts, packages/core/src/__tests__/db*.test.ts.
   • Verification: pnpm test, pnpm build.

2. Add DagCoordinator skeleton behind feature flag, no subscribers yet

   • Outcome: inert class and wiring seam exists but disabled by default.
   • File scope hints: packages/engine/src/dag-coordinator.ts, packages/engine/src/project-engine.ts (or equivalent bootstrap).
   • Verification: pnpm test, pnpm build.

3. Wire event subscriptions behind same flag

   • Outcome: listens to existing task:created|task:moved|task:updated and performs enqueue-only transitions.
   • File scope hints: packages/engine/src/dag-coordinator.ts, runtime registration surfaces.
   • Verification: pnpm test, pnpm build.

4. Add focused unit tests

   • Outcome: readiness evaluation, enqueue path, block/fail/complete event coverage.
   • File scope hints: packages/engine/src/__tests__/dag-coordinator.test.ts (new), helper fixtures.
   • Verification: pnpm test.

5. Add reliability interaction regression tests

   • Outcome: explicit interaction coverage in reliability backstop suite for scheduler/executor/self-healing/restart recovery adjacency.
   • File scope hints: packages/engine/src/__tests__/reliability-interactions/.
   • Verification: pnpm test.

6. Add opt-in integration test for 2-node DAG

   • Outcome: validates end-to-end enqueue-only orchestration with real SQLite state and mocked/controlled wakeups.
   • File scope hints: packages/engine/src/__tests__/dag-coordinator.integration.test.ts.
   • Verification: pnpm test, pnpm build.

7. Finalize docs + changeset when implementation lands

   • Outcome: update DAG docs and settings docs for shipped flag/behavior.
   • File scope hints: docs/dag/*.md, docs/settings-reference.md, .changeset/*.md.
   • Verification: pnpm test, pnpm build.

Config flag proposal

• Proposed setting: experimentalDagCoordinator: boolean (default false).
• Planned definition locations when implementation lands:
  • packages/core/src/types.ts (project settings type)
  • settings read/write plumbing
  • docs/settings-reference.md (documented only when implemented)

Changeset requirement for implementation task

When Milestone B implementation (code) lands, include a changeset for @runfusion/fusion because it introduces new user-facing functionality behind a flag.

• Acceptable bump: patch (if strictly bugfix-like/internal behavior) or minor (if introducing opt-in new capability surface).
• This current FN-4491 design-only task does not add a changeset.

Non-goals (self-contained)

• No scheduler replacement.
• No direct AgentSemaphore manipulation.
• No checkout-lease bypass.
• No merger/audit/file-scope invariant changes.
• No dashboard DAG UX/productization (Milestone C / FN-4492).
• No cross-project/cross-node DAG orchestration.
• No replay/time-travel/autoscaling orchestration engine.