recipe-reverse-engineer

name	recipe-reverse-engineer
description	Generate PRD and Design Docs from existing codebase through discovery, generation, verification, and review workflow
disable-model-invocation	true

Execute the llm-friendly-context skill (/skill:llm-friendly-context) before writing subagent prompts, handoffs, or generated artifacts. Execute the subagents-orchestration-guide skill (/skill:subagents-orchestration-guide) before making workflow decisions, invoking agents, or resolving findings.

Context: Reverse engineering workflow to create documentation from existing code

Target: the skill invocation arguments

Orchestrator Definition

Core Identity: "I am an orchestrator."

Local authority gate: Make this recipe's workflow decisions and validate each returned result directly; delegate semantic deliverable production to the named specialist.

Review Resolution Gate [MANDATORY]: Resolve every actionable deliverable-review finding through subagents-orchestration-guide Review Resolution before correction or progression. Before the first finding disposition, read references/review-resolution.md from the loaded subagents-orchestration-guide skill.

Execution Protocol:

1. Invoke named specialists for deliverable production — pass deliverable paths between them and validate their results (see subagents-orchestration-guide "Orchestrator Execution Boundary")
2. Process one step at a time: Execute steps sequentially within each unit (2 → 3 → 4 → 5). Each step's output is the required input for the next step. Complete all steps for one unit before starting the next
3. Preserve evidence while bridging outputs — copy the fields required by the next specialist in their declared form; apply Review Resolution before routing any correction

At each subagent invocation below, build the prompt as a mechanical extraction: copy the named source values into the exact fields, apply only the declared serialization, then invoke immediately.

Task Registration: Register phases first using todo_list, then steps within each phase as you enter it. Update status using todo_list.

Step 0: Initial Configuration

0.1 Scope Confirmation

Use ask_question to confirm:

1. Target path: Which directory/module to document
2. Depth: PRD only, or PRD + Design Docs
3. Reference Architecture: layered / mvc / clean / hexagonal / none
4. Human review: Yes (recommended) / No (fully autonomous)
5. Fullstack design: Yes / No
   • Yes: For each functional unit, generate backend + frontend Design Docs
   • Note: Requires both agents (technical-designer, technical-designer-frontend)

0.2 Output Configuration

• PRD output: docs/prd/ or existing PRD directory
• Design Doc output: docs/design/ or existing design directory
• Verify directories exist, create if needed

Workflow Overview

Phase 1: PRD Generation
  Step 1: Scope Discovery (unified, single pass → group into PRD units → human review)
  Step 2-5: Per-unit loop (Generation → Verification → Review → Revision)

Phase 2: Design Doc Generation (if requested)
  Step 6: Design Doc Scope Mapping (reuse Step 1 results, no re-discovery)
  Step 7-10: Per-unit loop (Generation → Verification → Review → Revision)
  ※ fullstack=Yes: each unit produces backend + frontend Design Docs

Phase 1: PRD Generation

Register using todo_list:

• Step 1: PRD Scope Discovery
• Per-unit processing (Steps 2-5 for each unit)

Step 1: PRD Scope Discovery

subagent tool invocation:

agent: scope-discoverer
description: "Discover functional scope"
prompt: |
  Discover functional scope targets in the codebase.

  target_path: $USER_TARGET_PATH
  reference_architecture: $USER_RA_CHOICE
  focus_area: [user-confirmed focus area verbatim, if specified]

Store output as: $STEP_1_OUTPUT

Quality Gate:

• At least one unit discovered → proceed
• No units discovered → ask user for hints
• $STEP_1_OUTPUT.prdUnits exists
• All sourceUnits across prdUnits (flattened, deduplicated) match the set of discoveredUnits IDs — no unit missing, no unit duplicated
• Each discovered unit's unitInventory has at least one non-empty category (routes, testFiles, or publicExports). Units with all three empty indicate incomplete discovery — re-run scope-discoverer with focus on that unit's relatedFiles

Human Review Point (if enabled): Present $STEP_1_OUTPUT.prdUnits with their source unit mapping. The user confirms, adjusts grouping, or excludes units from scope. This is the most important review point — incorrect grouping cascades into all downstream documents.

Step 2-5: Per-Unit Processing

FOR each unit in $STEP_1_OUTPUT.prdUnits (sequential, one unit at a time):

Step 2: PRD Generation

subagent tool invocation:

agent: prd-creator
description: "Generate PRD"
prompt: |
  Create reverse-engineered PRD for the following feature.

  Operation Mode: reverse-engineer
  External Scope Provided: true

  Feature: $PRD_UNIT_NAME (current Step 1 PRD unit name unchanged)
  Description: $PRD_UNIT_DESCRIPTION (current Step 1 PRD unit description unchanged)
  Related Files: $PRD_UNIT_COMBINED_RELATED_FILES
  Entry Points: $PRD_UNIT_COMBINED_ENTRY_POINTS

  Use provided scope as investigation starting point.
  If tracing entry points reveals files outside this scope, include them.
  Create final version PRD based on thorough code investigation.

Store output as: $STEP_2_OUTPUT (PRD path)

Step 3: Code Verification

Prerequisite: $STEP_2_OUTPUT (PRD path from Step 2)

subagent tool invocation:

agent: code-verifier
description: "Verify PRD consistency"
prompt: |
  Verify consistency between PRD and code implementation.

  doc_type: prd
  document_path: $STEP_2_OUTPUT
  unit_inventory: [the current unit's Step 1 unitInventory]
  verbose: false

unit_inventory supplies the completeness baseline while repository evidence supplies the search scope.

Store output as: $STEP_3_OUTPUT

Quality Gate:

• summary.status is blocked, inventory coverage is missing, or counts do not balance → re-run or escalate with the exact unusable input or evidence
• Any balanced non-blocked result → proceed to review with the complete verifier output; needs_review / inconsistent and any unaccounted items become explicit review evidence

Step 4: Review

Required Input: $STEP_3_OUTPUT (verification JSON from Step 3)

subagent tool invocation:

agent: document-reviewer
description: "Review PRD"
prompt: |
  Review the following PRD considering code verification findings.

  doc_type: PRD
  target: $STEP_2_OUTPUT
  review_context: reverse-engineer
  verification_evidence: $STEP_3_OUTPUT

Store output as: $STEP_4_OUTPUT

Step 5: Revision (conditional)

Pass $STEP_3_OUTPUT to document-reviewer as verification evidence, then apply the Review Resolution Gate to $STEP_4_OUTPUT. Run revision only when at least one finding is apply; a decline-only result completes the review, and unresolved user_decision_required stops for user input.

subagent tool invocation:

agent: prd-creator
description: "Revise PRD"
prompt: |
  Update PRD based on review feedback and code verification results.

  Operation Mode: update
  Existing PRD: $STEP_2_OUTPUT

  ## Adjudicated Findings
  [complete reviewer finding objects verbatim, with only their orchestrator dispositions added]

  Treat these findings as the complete revision scope and preserve adjacent content.

Re-validation: After each revision, re-run code-verifier on the revised document, then re-run document-reviewer with the latest verification_evidence and prior_feedback.

Unit Completion

• No apply findings remain; every other review finding has a disposition and every user_decision_required item has a recorded user decision
• Human review passed (if enabled in Step 0)

Next: Proceed to next unit. After all units → Phase 2.

Phase 2: Design Doc Generation

Execute only if Design Docs were requested in Step 0

Register using todo_list:

• Step 6: Design Doc Scope Mapping
• Per-unit processing (Steps 7-10 for each unit)

Step 6: Design Doc Scope Mapping

No additional discovery required. Use $STEP_1_OUTPUT.discoveredUnits (implementation-granularity units) for technical profiles. Use $STEP_1_OUTPUT.prdUnits[].sourceUnits to trace which discovered units belong to each PRD unit.

Each PRD unit from Phase 1 maps to Design Doc unit(s):

• Standard mode (fullstack=No): 1 PRD unit → 1 Design Doc (using technical-designer)
• Fullstack mode (fullstack=Yes): 1 PRD unit → 2 Design Docs (technical-designer + technical-designer-frontend)

Map $STEP_1_OUTPUT units to Design Doc generation targets, carrying forward:

• technicalProfile.primaryModules → Primary Files
• technicalProfile.publicInterfaces → Public Interfaces
• dependencies → Dependencies
• relatedFiles → Scope boundary
• unitInventory → Unit Inventory (routes, test files, public exports)

In fullstack mode, partition each unit inventory by the owning path into backend and frontend target inventories. Assign a shared entry to each Design Doc whose public contract must account for it and record that shared reason; otherwise assign it once. Each Step 7 and Step 8 invocation receives its target's inventory, not the unpartitioned combined unit.

Store output as: $STEP_6_OUTPUT

Step 7-10: Per-Unit Processing

FOR each unit in $STEP_6_OUTPUT (sequential, one unit at a time):

Step 7: Design Doc Generation

Scope: Document the current architecture exactly as implemented in code.

Standard mode (fullstack=No):

subagent tool invocation:

agent: technical-designer
description: "Generate Design Doc"
prompt: |
  Create Design Doc for the following feature based on existing code.

  Operation Mode: reverse-engineer

  Feature: $UNIT_NAME (current Step 6 target name unchanged)
  Description: $UNIT_DESCRIPTION (current Step 6 target description unchanged)
  Primary Files: $UNIT_PRIMARY_MODULES
  Public Interfaces: $UNIT_PUBLIC_INTERFACES
  Dependencies: $UNIT_DEPENDENCIES
  Unit Inventory: $DESIGN_DOC_UNIT_INVENTORY

  Parent PRD: $APPROVED_PRD_PATH

  Document current architecture as-is. Use Unit Inventory as a completeness baseline — all routes and exports should be accounted for in the Design Doc.

Store output as: $STEP_7_OUTPUT

Fullstack mode (fullstack=Yes):

For each unit, invoke 7a then 7b sequentially (7b depends on 7a output):

7a. Backend Design Doc:

agent: technical-designer
description: "Generate backend Design Doc"
prompt: |
  Create a backend Design Doc for the following feature based on existing code.

  Operation Mode: reverse-engineer

  Feature: $UNIT_NAME (current Step 6 target name unchanged)
  Description: $UNIT_DESCRIPTION (current Step 6 target description unchanged)
  Primary Files: $UNIT_PRIMARY_MODULES
  Public Interfaces: $UNIT_PUBLIC_INTERFACES
  Dependencies: $UNIT_DEPENDENCIES
  Unit Inventory: $BACKEND_UNIT_INVENTORY

  Parent PRD: $APPROVED_PRD_PATH

  Focus on: API contracts, data layer, business logic, service architecture.
  Document current architecture as-is. Use Unit Inventory as completeness baseline.

Store output as: $STEP_7a_OUTPUT

7b. Frontend Design Doc:

agent: technical-designer-frontend
description: "Generate frontend Design Doc"
prompt: |
  Create a frontend Design Doc for the following feature based on existing code.

  Operation Mode: reverse-engineer

  Feature: $UNIT_NAME (current Step 6 target name unchanged)
  Description: $UNIT_DESCRIPTION (current Step 6 target description unchanged)
  Primary Files: $UNIT_PRIMARY_MODULES
  Public Interfaces: $UNIT_PUBLIC_INTERFACES
  Dependencies: $UNIT_DEPENDENCIES
  Unit Inventory: $FRONTEND_UNIT_INVENTORY

  Parent PRD: $APPROVED_PRD_PATH
  Backend Design Doc: $STEP_7a_OUTPUT

  Reference backend Design Doc for API contracts.
  Focus on: component hierarchy, state management, UI interactions, data fetching.
  Document current architecture as-is. Use Unit Inventory as completeness baseline.

Store output as: $STEP_7b_OUTPUT

Step 8: Code Verification

Standard mode: Verify $STEP_7_OUTPUT.

Fullstack mode: Verify each Design Doc separately.

subagent tool invocation (per Design Doc):

agent: code-verifier
description: "Verify Design Doc consistency"
prompt: |
  Verify consistency between Design Doc and code implementation.

  doc_type: design-doc
  document_path: $STEP_7_OUTPUT (or $STEP_7a_OUTPUT / $STEP_7b_OUTPUT)
  unit_inventory: [the current Design Doc target's Step 6 unitInventory]
  verbose: false

Store output as: $STEP_8_OUTPUT

Verification gate (per Design Doc):

• blocked, missing inventoryCoverage, or unbalanced category counts → correct the invocation/input and rerun; stop for the user only when repository evidence cannot resolve the input defect.
• Any balanced non-blocked result proceeds to document review. Carry needs_review, inconsistent, and every unaccounted item as explicit verifier evidence.

Step 9: Review

Required Input: $STEP_8_OUTPUT (verification JSON from Step 8)

subagent tool invocation (per Design Doc):

agent: document-reviewer
description: "Review Design Doc"
prompt: |
  Review the following Design Doc considering code verification findings.

  doc_type: DesignDoc
  target: $STEP_7_OUTPUT (or $STEP_7a_OUTPUT / $STEP_7b_OUTPUT)
  review_context: reverse-engineer
  verification_evidence: $STEP_8_OUTPUT

  ## Parent PRD
  $APPROVED_PRD_PATH

  ## Additional Review Focus
  - Technical accuracy of documented interfaces
  - Consistency with parent PRD scope
  - Completeness of unit boundary definitions

Store output as: $STEP_9_OUTPUT

Step 10: Revision (conditional)

Pass $STEP_8_OUTPUT to document-reviewer as verification evidence, then apply the Review Resolution Gate to $STEP_9_OUTPUT. Run revision only when at least one finding is apply; a decline-only result completes the review, and unresolved user_decision_required stops for user input.

subagent tool invocation (per Design Doc):

agent: technical-designer (or technical-designer-frontend for frontend Design Docs)
description: "Revise Design Doc"
prompt: |
  Update Design Doc based on review feedback and code verification results.

  Operation Mode: update
  Existing Design Doc: $STEP_7_OUTPUT (or $STEP_7a_OUTPUT / $STEP_7b_OUTPUT)

  ## Adjudicated Findings
  [complete reviewer finding objects verbatim, with only their orchestrator dispositions added]

  Treat these findings as the complete revision scope and preserve adjacent content.

Re-validation: After each revision, re-run code-verifier on the revised document, then re-run document-reviewer with the latest verification_evidence and prior_feedback.

Unit Completion

• No apply findings remain; every other review finding has a disposition and every user_decision_required item has a recorded user decision
• Human review passed (if enabled in Step 0)

Next: Proceed to next unit. After all units → Final Report.

Final Report

Output summary including:

• Generated documents table (Type, Name, Verification Status, Review Status)
• Action items (undocumented features, flagged items)
• Declined actionable findings with ID, governing reason, and evidence, when any occurred
• Next steps checklist

Error Handling

Error	Action
Discovery finds nothing	Ask user for project structure hints
Generation fails	Log failure, continue with other units, report in summary
Verification is inconsistent or inventory remains unaccounted after correction	Flag for mandatory human review — require explicit human approval