Stage 3 · Implementation Specs
Stage 3 turns your approved PRD and tech spec into a numbered suite of implementation specs — the buildable blueprint for your feature, with real type definitions instead of pseudocode.
What it does
Section titled “What it does”Generates numbered implementation spec documents containing everything needed to build the feature: complete type definitions in the project language (not pseudocode), error handling, examples, and cross-references between docs.
The 00- and 01- foundation docs are written first; the remaining domain docs are then fanned out in parallel (via forge-spec-writer subagents) for speed.
Command
Section titled “Command”/feature-forge:forge-3-specs <feature-name>Inputs it consumes
Section titled “Inputs it consumes”- A completed
PRD.mdandtech-spec.md(both prerequisites) - Existing codebase patterns
- The project’s stack profile
Artifacts it produces
Section titled “Artifacts it produces”- Sequentially numbered spec docs:
00-core-definitions.md,01-architecture-layout.md,02-*.md… up to a testing-strategy doc TRACEABILITY.md— maps everyREQ-XXX-NNto the spec section that covers it- Updates
.pipeline-state.json - Auto-commits if enabled
What you review & approve
Section titled “What you review & approve”You review the document plan (the titles and descriptions of the planned docs) and the depth/detail of the resulting suite.
What comes next
Section titled “What comes next”/feature-forge:forge-verify <feature>— strongly recommended before moving on. Specs feed every downstream stage, so this is a prime candidate forautoVerify: true, which runs it for you automatically. See Verify & Fix./feature-forge:forge-4-backlog <feature>— see Stage 4 · Backlog.
Notes & gotchas
Section titled “Notes & gotchas”- Stages forge-1 (PRD) and forge-2 (tech spec) must be complete before this runs.
- Every PRD requirement must be covered by at least one spec — traceability is validated, so gaps are caught here rather than during implementation.