Spec Dev Skill

Overview

Develop unambiguous, testable specifications before implementation. Structured 4-phase process producing EARS-notation requirements, architecture diagrams, and a beads epic.

Scale formality to risk: skip for trivial (<1h), lightweight (EARS + epic) for small, full 4-phase for medium+. Use AskUserQuestion early to gauge scope.

Methodology: 4-Phase Spec Development

Phase 1: Explore

Goal: Map the problem domain before narrowing.

1. Ask "why" before "how" -- understand the real need
2. Search memory: ca search for past features, constraints, decisions
3. Search knowledge: ca knowledge "relevant terms"
4. Spawn subagents for research (.claude/agents/compound/repo-analyst.md, memory-analyst.md, or subagent_type: Explore)
5. For deep domain knowledge, consider /get-a-phd
6. Build a discovery mindmap (Mermaid mindmap) -- makes implicit assumptions visible
7. Use AskUserQuestion to clarify scope and preferences

Iteration trigger: If research reveals the problem is fundamentally different, restart Explore.

Phase 2: Understand

Goal: Crystallize requirements through Socratic dialogue.

1. For each capability, ask: triggers? edge cases? constraints? acceptance criteria?
2. Use Mermaid diagrams (sequenceDiagram, stateDiagram-v2) to expose hidden structure
3. Detect ambiguities: vague adjectives, unclear pronouns, passive voice, compound requirements. See references/spec-guide.md for full checklist
4. Build a domain glossary for ambiguous terms
5. Use AskUserQuestion to resolve each ambiguity

Iteration trigger: If specifying reveals missing knowledge, loop back to Explore.

Phase 3: Specify

Goal: Produce formal, testable requirements.

1. Write each requirement using EARS notation:

   • Ubiquitous: The system shall <action>.
   • Event-driven: When <trigger>, the system shall <action>.
   • State-driven: While <state>, the system shall <action>.
   • Unwanted behavior: If <condition>, then the system shall <action>.
   • Optional: Where <feature>, the system shall <action>.
   • Combined ordering: Where > While > When > If/then > shall

2. Verify each requirement: no vague adjectives, edge cases covered, quantities specified, testable

3. Document trade-offs when requirements conflict (see references/spec-guide.md)

4. Produce architecture diagrams (erDiagram, C4Context, flowchart)

5. Create ADRs in docs/decisions/ for significant decisions

6. Generate scenario table from EARS requirements and Mermaid diagrams:

   • For each EARS requirement: at least one happy scenario + one error scenario
   • For quantified parameters: boundary scenarios (min, max, just-beyond)
   • From sequence diagrams: one scenario per message path including alt/opt fragments
   • From state diagrams: each transition + at least one invalid transition (adversarial)
   • For multi-parameter requirements: combinatorial scenarios using pairwise (2-way) coverage
   • For external interfaces: adversarial scenarios per applicable STRIDE category (Spoofing, Tampering, Repudiation, Information Disclosure, DoS, Elevation of Privilege)
   • Use sequential IDs (S1, S2...) and this table format:

   ID	Source	Category	Precondition	Trigger	Expected Outcome
   S1	R1	happy	precondition	action	assertion

   Categories: happy, error, boundary, combinatorial, adversarial

Iteration trigger: If contradictions or gaps emerge, loop back to Understand.

Phase 4: Hand off

1. Create beads epic if needed (bd create --title="..." --type=epic --priority=<N>)
2. Store spec in the epic description (bd update <epic-id> --description="...") -- single source of truth, including both EARS requirements and scenario table
3. Note on downstream contracts: The EARS requirements you write here are the source material for both the Acceptance Criteria table and the Verification Contract. The plan phase will extract testable AC rows and derive the epic-local proof of done from the product profile, touched surfaces, and risks. Write EARS requirements with testability in mind, and call out user-visible surfaces, public APIs, persistence changes, packaging concerns, and operational risks explicitly.
4. Flag open questions for plan phase
5. Capture lessons: ca learn

Memory Integration

• ca search before generating approaches
• ca knowledge for indexed project docs
• ca learn after corrections or discoveries

Reference Material

Read .claude/skills/compound/spec-dev/references/spec-guide.md on demand for EARS patterns, Mermaid templates, ambiguity checklists, and trade-off frameworks.

Common Pitfalls

• Jumping to solutions before exploring the problem
• Skipping diagrams -- they reveal hidden assumptions
• Vague requirements without EARS patterns
• Not searching memory for past patterns and pitfalls
• Over-specifying trivial tasks
• Ignoring iteration signals when gaps emerge
• Not creating the beads epic
• Specifying implementation instead of requirements
• Skipping scenario table generation after EARS requirements
• Writing EARS requirements that cannot be mapped to testable acceptance criteria
• Hiding important surfaces or risks in prose so plan cannot derive a clean Verification Contract

Quality Criteria

• Requirements use EARS notation
• Ambiguities detected and resolved via dialogue
• Mermaid diagrams used as thinking tools
• Memory searched (ca search)
• Trade-offs documented with rationale
• User engaged via AskUserQuestion at decisions
• Scenario table generated from EARS requirements and diagrams
• Spec and scenario table stored in beads epic description
• ADRs created for significant decisions
• EARS requirements are testable and can map to acceptance criteria
• Important surfaces and risks are explicit enough for plan to derive a Verification Contract