| name | prp-plan |
| description | Phase 2 of spec-driven development — turn spec.md into plan.md. Architecture, data model, contracts, layer placement in Morphic's 4-layer Clean Architecture. |
| when_to_use | After /prp-prd produces a spec.md. Before /prp-implement. |
| argument-hint | <feature-slug> |
| allowed-tools | ["Read","Write","Glob","Grep"] |
| model | opus |
PRP Phase 2 — Implementation Plan
You transform spec.md into plan.md — how to build, not what to build.
Input
$ARGUMENTS = <slug>. Reads specs/<slug>/spec.md.
Procedure
- Verify
specs/<slug>/spec.md exists. If not, abort with "run /prp-prd first".
- Delegate to
spec-writer subagent with phase=plan.
- The subagent:
- Loads the spec and
.specify/templates/plan.md.
- Maps each FR to a Clean Architecture layer:
- Business rule →
domain/entities/ or domain/services/
- Workflow →
application/use_cases/
- External system →
domain/ports/ + infrastructure/<subsystem>/
- HTTP/CLI surface →
interface/api/routes/ or interface/cli/commands/
- Proposes data model (Pydantic entities, SQLAlchemy if persisted).
- Proposes port interfaces (ABCs) when new external deps are needed.
- Flags constitution violations as
[CONSTITUTION WARNING].
- Writes
specs/<slug>/plan.md.
- Run
constitution-check skill as a gate — must pass before Phase 3.
Plan must contain
- Layer map: FR-01 →
domain/services/foo.py::Foo.bar()
- Data model: entities + relations, JSON schema for any persistence.
- Ports & adapters: new ABCs, new infra impls.
- Dependencies: what needs to be installed (trigger
/tool-scout if non-trivial).
- Migration: DB migrations, backfill strategy.
- Test strategy: unit / integration / E2E split.
- Rollout: feature flag? staged? fullauto-enabled by default?
- Risks: LAEE risk level of new actions, cost estimate.
Guardrails
- No code. Just structure and contracts.
- If a port already exists, reuse it — don't add a parallel one.
- If the feature requires >3 new infra impls, split into sub-features.
- Infrastructure must never appear in the domain layer map.
