plan-authoring

name	plan-authoring
description	Creates implementation plans with technical context, architecture decisions, data models, API contracts, and project instructions alignment checks. Use when designing a technical approach for a feature, choosing technologies, defining data structures, or when resolving NEEDS CLARIFICATION markers in plans.

Plan Authoring Guide

Agent-First Format Rule

Every plan.md section MUST use tables, key-value pairs, or tagged lists as primary format. Prose is limited to the Summary section (max 3 key-value lines). The primary consumer is an AI agent — optimize for parseability over readability.

Plan Writing Process

Phase 0: Research

1. HAS_TECH_CONTEXT_DOC = true → read as baseline; pre-fill Technical Context values, require only confirmation.
2. Extract unknowns (anything marked NEEDS CLARIFICATION) → research task per unknown.
3. Consolidate in research.md using structured format below. Merge by topic, rewrite full file.
4. Budget: ≤4KB. Existing >3KB → consolidate before adding.

research.md Format

Prohibited: code blocks, implementation snippets, comparison tables, narrative paragraphs, duplicate summary sections.

Per-topic: 4 structured fields, max 2 sources. Global budget: ≤4KB.

Consolidation: merge overlapping topics, normalize names, remove stale details.

Structure:

# Research: [Feature Name]
> Feature | Date | Purpose

## [Topic N]
- **Decision**: [what was chosen]
- **Rationale**: [why — max 1 sentence]
- **Rejected**: [alternatives and why — max 1 sentence]
- **Pitfalls**: [anti-patterns to avoid — max 1 sentence]
- **Sources**: [URL1], [URL2]

## Summary
| Topic | Decision | Rationale |
|-------|----------|-----------|

## Sources Index
| URL | Topic | Fetched |
|-----|-------|---------|

Phase 1: Design & Contracts

Prerequisites: research.md complete

Items 1–2 are conditional — auto-detect signals from spec; fall back to interactive prompt when ambiguous.

1. Data Model → data-model.md (conditional):

   • Generate when: non-empty "Key Entities", terms database/storage/persist/CRUD/entity/etc., or Storage ≠ N/A
   • Skip → replace Data Model Summary table with N/A — no persistent data
   • Include: entity names, fields, relationships, validation rules, state transitions
   • Populate ## Data Model Summary table in plan.md with entity overview

2. API Contracts → contracts/ (conditional):

   • Generate when: terms API/endpoint/route/REST/GraphQL/HTTP/webhook/etc., or Project Type = web/mobile
   • Skip → replace API Surface Summary table with N/A — no API surface
   • Map user actions → endpoints; use REST/GraphQL patterns; output OpenAPI/GraphQL schemas
   • Populate ## API Surface Summary table in plan.md with endpoint overview

Instructions Check

• Read project-instructions.md
• Validate every plan decision against project instructions principles
• If violations exist that must be justified, add a "## Complexity Tracking" section to plan.md with a table: | Violation | Why Needed | Simpler Alternative Rejected Because |. If no violations exist, omit the section entirely.
• GATE: Must pass before research. Re-check after design.
• Auditor outputs are transient gate checks; report status/decisions in plan.md without pasting full Auditor reports.

Artifact Conventions

Full rules: .github/skills/artifact-conventions/SKILL.md (read during edit/remediation phases).

• plan.md ≤ 10KB — Mermaid ≤20 nodes (component-level)
• Conditional sections: populate table OR replace with N/A — [reason]. Never leave template placeholders.
• Mermaid: C4 syntax, Container/Component views, <br> for breaks (never \n)
• Do NOT remove Instructions Check, Technical Context, or Requirement Coverage Map sections
• Do NOT change Architecture Decision IDs (AD-###) — they may be referenced by tasks
• [NEEDS CLARIFICATION] → resolve only with user-approved answers
• Preserve all cross-referenced IDs (AD-###, HINT-###)

Technical Context Fields

The plan template captures these metadata fields:

Field	Example	Notes
Language/Version	Python 3.11	Or "NEEDS CLARIFICATION"
Primary Dependencies	FastAPI	Frameworks, libraries
Storage	PostgreSQL	Or "N/A" if no persistence
Testing	pytest	Test framework
Target Platform	Linux server	Or iOS 15+, WASM, etc.
Project Type	single/web/mobile	Determines source structure
Project Mode	greenfield/brownfield/mixed	Determines structure approach
Performance Goals	1000 req/s	Domain-specific
Constraints	<200ms p95	Domain-specific
Scale/Scope	10k users	Domain-specific

These same fields should also appear in the project-level Technical Context Document when one is maintained.

Testing Strategy Configuration

Populate ## Testing Strategy table in plan.md. Each row maps a testing tier to its tool, scope, mock boundary, and install command.

Tiers to cover

Tier	Purpose
Unit	Isolated logic tests
Integration	Cross-component / API tests
Security	Vulnerability scanning (code + dependencies)
Coverage	Code coverage measurement

Rules

1. Delegate to Technical Researcher during planning Step 4.5 for detected tech stack.
2. Consider: language/version, framework, dependency manager, existing tool configs.
3. Prefer: widely adopted, actively maintained, single-command install.
4. Existing config → Install column = configured.
5. N/A tier → include row with rationale in Scope column (e.g., N/A — no external dependencies).
6. Include ready-to-run install commands for tools not yet present.

Error Handling Strategy

Populate ## Error Handling Strategy table when the feature has API endpoints, external service calls, or user-facing error states. Skip (replace with N/A) for pure libraries, CLI tools with simple exit codes, or infrastructure-only features.

Columns

Column	Content
Error Category	Domain grouping (Validation, Auth, Downstream, Internal)
Pattern	Strategy (fail-fast, circuit breaker, retry, fallback)
Response	What the caller sees (status code + body shape, log level, alert)
Retry	yes/no + policy (exponential, fixed, none)

Architecture Decisions

Populate ## Architecture Decisions table during Phase 0 (Research) and Phase 1 (Design). One row per non-trivial technical choice.

Rules

1. ID format: AD-### (sequential, zero-padded 3 digits).
2. Every row: question asked, options evaluated, choice made, rationale.
3. Tasks may reference decisions via {AD-###} tag (optional, not required).
4. Do NOT duplicate decisions already captured in Technical Context Document — reference them instead.

Requirement Coverage Map

Populate ## Requirement Coverage Map table after design. Every FR-###, TR-###, OR-###, and RR-### from spec.md must have a row.

Rules

1. Map each requirement to the component(s) and file path(s) that will implement it.
2. This table is the primary input for /sddp-tasks — task generation should consume it directly rather than re-deriving from prose.
3. Missing requirement → flag as gap during Plan Readiness Check.

Risk Mitigation

Populate ## Risk Mitigation table by mapping each risk from spec.md Assumptions & Risks to a concrete technical mitigation.

Rules

1. One row per risk from spec. Preserve spec wording in Risk column.
2. Mitigation = specific technical action (not "monitor" or "be careful").
3. Owner = component or team responsible for the mitigation.

Implementation Hints

Populate ## Implementation Hints with max 5 tagged items. Each captures a non-obvious constraint, gotcha, or order-sensitive operation that the implementing agent needs.

Format

- **[HINT-###]** Category: detail

Categories: Order, Gotcha, Constraint, Compatibility, Performance.

Project Structure Options

By Project Type (greenfield)

• Single project (default): src/, tests/ at root
• Web application (frontend + backend detected): backend/, frontend/
• Mobile + API (iOS/Android detected): api/, ios/ or android/

Brownfield / Mixed Mode

When Project Mode = brownfield or mixed:

1. Scan existing project layout — do NOT impose a template structure.
2. Show only new/modified paths: prefix + (new file) or ~ (modified file).
3. Include Brownfield Notes block in template:
   • Patterns to reuse: existing patterns relevant to this feature
   • Tests to extend: existing test files/suites to add cases to
   • Naming conventions: observed conventions to follow
4. Omit generic project initialization tasks.

Delete unused options from the template. The delivered plan must not include "Option" labels.

Template

Use the template at assets/plan-template.md.