Add a /tdd skill

CLAUDE.md

@@ -18,7 +18,7 @@ Current version: **2.2.0** (see [CHANGELOG.md](./CHANGELOG.md)).
 │   ├── .claude-plugin/
 │   │   └── plugin.json
 │   ├── agents/         # 21 agent definitions (.md with frontmatter)
-│   ├── skills/         # 15 skill directories, each with SKILL.md + references/
+│   ├── skills/         # 17 skill directories, each with SKILL.md + references/
 │   └── references/     # Cross-skill reference files (e.g. yagni-rule.md)
 ├── docs/               # Operator-facing documentation
 │   ├── writing-voice.md   # Voice profile every doc follows
@@ -27,7 +27,7 @@ Current version: **2.2.0** (see [CHANGELOG.md](./CHANGELOG.md)).
 │   ├── sizing.md
 │   ├── yagni.md
 │   ├── agents/         # Long-form docs for all 21 agents, plus README
-│   ├── skills/         # Long-form docs for all 15 skills, plus README
+│   ├── skills/         # Long-form docs for all 17 skills, plus README
 │   ├── guidance/       # Contributor-facing authoring guidance
 │   └── templates/      # Templates and coverage rule for long-form docs
 └── images/             # Banner and graphics for README
@@ -56,11 +56,13 @@ The plugin is shipped from `plugin/`; documentation lives in `docs/`. Long-form
 
 ### Skill catalog (`docs/skills/`)
 
-- **[docs/skills/README.md](./docs/skills/README.md).** Index of all 15 skills grouped by purpose (planning, investigation, review, discovery, conventions, reporting). Start here when looking for the right slash command.
+- **[docs/skills/README.md](./docs/skills/README.md).** Index of all 17 skills grouped by purpose (planning, building, investigation, review, discovery, conventions, reporting). Start here when looking for the right slash command.
 - **[docs/skills/plan-a-feature.md](./docs/skills/plan-a-feature.md).** Spec a feature from scratch through an evidence-based interview that walks the design tree and dispatches specialist reviewers.
 - **[docs/skills/plan-implementation.md](./docs/skills/plan-implementation.md).** Turn a feature specification into an implementation plan through a project-manager-led team conversation.
 - **[docs/skills/plan-a-phased-build.md](./docs/skills/plan-a-phased-build.md).** Split a body of context (gap analysis, PRD, design doc) into a numbered sequence of vertical-slice phases, each independently demoable.
 - **[docs/skills/iterative-plan-review.md](./docs/skills/iterative-plan-review.md).** Stress-test an existing plan through multiple codebase-grounded review passes. Edits the plan in place and records every finding.
+- **[docs/skills/tdd.md](./docs/skills/tdd.md).** Drive a feature or behavior through a BDD-framed red-green-refactor loop with an enforced observed-failure gate. The plugin's only execution skill: it writes code, applying coding standards and ADRs in green and refactor.
+- **[docs/skills/issue-triage.md](./docs/skills/issue-triage.md).** Classify a vague issue or bug report, identify missing information, assess severity and reproducibility, and recommend the right next skill.
 - **[docs/skills/investigate.md](./docs/skills/investigate.md).** Evidence-based investigation of bugs, failures, and unexpected behavior, with adversarial validation of the proposed fix.
 - **[docs/skills/code-review.md](./docs/skills/code-review.md).** Comprehensive code review of the current branch or specified files. Dispatches a domain-aware roster that scales with sizing.
 - **[docs/skills/gh-pr-review.md](./docs/skills/gh-pr-review.md).** Run `/code-review` against a GitHub PR and post the review as comments after a clarity check.
@@ -123,4 +125,4 @@ Subdirectories:
 - **Every long-form doc links up.** The first bullet of the "Related Documentation" section always points back to the README at the repo root.
 - **Voice is uniform.** Every doc follows [docs/writing-voice.md](./docs/writing-voice.md). No em-dashes, direct second person, no flattery or hype.
 - **YAGNI applies to docs too.** Don't add speculative sections, for-future-flexibility warnings, or examples for behavior the skill doesn't have. The same evidence rule that gates plan steps gates docs.
-- **Counts to verify when editing indexes.** 21 agents in `plugin/agents/`; 15 skills in `plugin/skills/`; 21 long-form agent docs in `docs/agents/`; 15 long-form skill docs in `docs/skills/`.
+- **Counts to verify when editing indexes.** 21 agents in `plugin/agents/`; 17 skills in `plugin/skills/`; 21 long-form agent docs in `docs/agents/`; 17 long-form skill docs in `docs/skills/`.

CONTRIBUTING.md

@@ -29,7 +29,8 @@ Read these once:
    - Body: numbered steps, `${CLAUDE_SKILL_DIR}` paths for script references, extracted references under `references/`.
 3. Copy [the skill template](./docs/templates/skill-long-form-template.md) into `docs/skills/{name}.md` and fill it in. Every skill gets a long-form doc.
 4. Add the skill to the [Skills Index](./docs/skills/README.md) with a one-sentence scent line and a link.
-5. Update the marketplace registry at [`.claude-plugin/marketplace.json`](./.claude-plugin/marketplace.json) if needed.
+5. Update the skill counts and catalog so they stay accurate: the skill catalog and "Counts to verify when editing indexes" line in [Root CLAUDE.md](./CLAUDE.md), the count in [Concepts](./docs/concepts.md) ("What does the plugin include?"), and the counts in the [README](./README.md). If the skill belongs to a new category, add it to the category lists too.
+6. Update the marketplace registry at [`.claude-plugin/marketplace.json`](./.claude-plugin/marketplace.json) if needed.
 
 ## Adding an agent
 

README.md

@@ -2,28 +2,28 @@
 
 <img src="images/han-banner.png">
 
-Han is a suite of AI skills and agents for solo (or small-team) product engineers. It combines evidence-based planning, full documentation maintenance, deep code review, and architectural analysis into a team of specialists you can dispatch from Claude Code.
+Han is a suite of AI skills and agents for solo (or small-team) product engineers. It combines evidence-based planning, test-driven implementation, full documentation maintenance, deep code review, and architectural analysis into a team of specialists you can dispatch from Claude Code.
 
 ## What this plugin does
 
-Han turns planning, review, and documentation work that would normally take a team into a set of deterministic skills you run from Claude Code. Each skill dispatches specialist agents (project managers, adversarial reviewers, investigators, architectural analysts, testing and security specialists) to do the judgment-heavy work, then folds their findings into an artifact you can trust.
+Han turns planning, implementation, review, and documentation work that would normally take a team into a set of deterministic skills you run from Claude Code. Each skill dispatches specialist agents (project managers, adversarial reviewers, investigators, architectural analysts, testing and security specialists) to do the judgment-heavy work, then folds their findings into an artifact you can trust.
 
-The skills are designed to compose. You can plan a feature, then plan its implementation, then iterate on the plan, then review the resulting code, then write the PR description. All through named skills that hand off to each other cleanly.
+The skills are designed to compose. You can plan a feature, then plan its implementation, then iterate on the plan, then build it test-first, then review the resulting code, then write the PR description. All through named skills that hand off to each other cleanly.
 
 Read [Concepts](./docs/concepts.md) for the skill-and-agent model that runs through the whole plugin.
 
 ## Which path are you on?
 
 - **New to han?** → Start with [Concepts](./docs/concepts.md), then the [Quickstart](./docs/quickstart.md).
-- **Looking for a specific skill?** → [Skills Index](./docs/skills/README.md). 16 skills grouped by purpose.
+- **Looking for a specific skill?** → [Skills Index](./docs/skills/README.md). 17 skills grouped by purpose.
 - **Looking for a specific agent?** → [Agents Index](./docs/agents/README.md). 21 agents grouped by role.
-- **Wondering how the agent swarms scale?** → [Sizing](./docs/sizing.md). The small / medium / large dispatch model used by `/code-review`, `/gap-analysis`, `/iterative-plan-review`, `/plan-a-feature`, and `/plan-implementation`.
+- **Wondering how the agent swarms scale?** → [Sizing](./docs/sizing.md). The small / medium / large dispatch model used by `/architectural-analysis`, `/code-review`, `/gap-analysis`, `/iterative-plan-review`, `/plan-a-feature`, and `/plan-implementation`.
 - **Wondering why a skill said "YAGNI"?** → [YAGNI](./docs/yagni.md). The evidence-based rule every planning, review, and architecture skill applies before committing items to an artifact.
 - **Writing or editing a skill or agent?** → [Contributing](./CONTRIBUTING.md).
 
 ## Skills
 
-Sixteen skills, grouped by the moment you reach for them. Each category links to the full long-form docs through the [Skills Index](./docs/skills/README.md).
+Seventeen skills, grouped by the moment you reach for them. Each category links to the full long-form docs through the [Skills Index](./docs/skills/README.md).
 
 ### Planning
 
@@ -34,11 +34,17 @@ Spec what to build, plan how to build it, sequence it into phases, and stress-te
 - **[`/plan-a-phased-build`](./docs/skills/plan-a-phased-build.md).** Split a body of work into a numbered sequence of vertical-slice phases, each independently demoable.
 - **[`/iterative-plan-review`](./docs/skills/iterative-plan-review.md).** Stress-test an existing plan through multiple codebase-grounded review passes.
 
+### Building
+
+Write the code, test-first, through a disciplined red-green-refactor loop.
+
+- **[`/tdd`](./docs/skills/tdd.md).** Drive a feature or behavior through a BDD-framed red-green-refactor loop with an enforced observed-failure gate, applying coding standards and ADRs in green and refactor.
+
 ### Investigation & root cause
 
 Find out *why* something is broken, with evidence to back it.
 
-- **[`/issue-triage`](docs/skills/issue-triage.md).** Classify a vague issue or bug report, identify missing information, assess severity and reproducibility, and recommend the right next skill.
+- **[`/issue-triage`](./docs/skills/issue-triage.md).** Classify a vague issue or bug report, identify missing information, assess severity and reproducibility, and recommend the right next skill.
 - **[`/investigate`](./docs/skills/investigate.md).** Evidence-based investigation of bugs, failures, and unexpected behavior, with adversarial validation of the proposed fix.
 
 ### Review & analysis
@@ -86,7 +92,7 @@ Add the Test Double skills marketplace to Claude Code, then install the plugin:
 
 - [Concepts](./docs/concepts.md). Skill vs. agent, and how they compose. Read once before using the plugin.
 - [Quickstart](./docs/quickstart.md). Four paths for four common situations. Each path is a short sequence of skills.
-- [Skills Index](./docs/skills/README.md). All 16 skills, grouped by purpose.
+- [Skills Index](./docs/skills/README.md). All 17 skills, grouped by purpose.
 - [Agents Index](./docs/agents/README.md). All 21 agents, grouped by role.
 - [Sizing](./docs/sizing.md). The small / medium / large model that decides how many agents the swarming skills dispatch.
 - [YAGNI](./docs/yagni.md). The evidence-based "You Aren't Gonna Need It" rule every planning, review, and architecture skill applies.

docs/concepts.md

@@ -66,7 +66,7 @@ Every skill that dispatches an agent swarm classifies the work as **small**, **m
 
 - **Default is small.** Every sizing-aware skill starts the classification at small and only escalates when concrete signals require it.
 - **Auto-classified, with a `$size` override.** Skills read signals (file count, subsystems touched, security/data/infra surface) and announce the chosen size with a one-line justification. Pass `small`, `medium`, or `large` as the first positional argument to override (`/code-review medium`, `/plan-a-feature large "describe the feature"`).
-- **Five sizing-aware skills.** [`/code-review`](./skills/code-review.md), [`/gap-analysis`](./skills/gap-analysis.md), [`/iterative-plan-review`](./skills/iterative-plan-review.md), [`/plan-a-feature`](./skills/plan-a-feature.md), [`/plan-implementation`](./skills/plan-implementation.md).
+- **Six sizing-aware skills.** [`/architectural-analysis`](./skills/architectural-analysis.md), [`/code-review`](./skills/code-review.md), [`/gap-analysis`](./skills/gap-analysis.md), [`/iterative-plan-review`](./skills/iterative-plan-review.md), [`/plan-a-feature`](./skills/plan-a-feature.md), [`/plan-implementation`](./skills/plan-implementation.md).
 
 Read the full [Sizing](./sizing.md) reference for the bands, the auto-classification process, and the per-skill rules.
 
@@ -92,7 +92,7 @@ Direct invocation uses the `Agent` tool with `subagent_type: han:{agent-name}` (
 
 ## What does the plugin include?
 
-- **15 skills.** The [skills index](./skills/README.md) groups them by purpose (planning, investigation, review, discovery, conventions, reporting).
+- **17 skills.** The [skills index](./skills/README.md) groups them by purpose (planning, building, investigation, review, discovery, conventions, reporting).
 - **21 agents.** The [agents index](./agents/README.md) groups them by role (planning and facilitation, adversarial reviewers, investigation, architecture, testing, gap and content).
 
 Skim the indexes after you read this page. Pick the one skill you need right now. Come back later to learn the rest.
@@ -108,6 +108,6 @@ Skim the indexes after you read this page. Pick the one skill you need right now
 
 ## Related reading
 
-- [`docs/plugin-entity-taxonomy.md`](./guidance/plugin-entity-taxonomy.md). The taxonomy this plugin follows. Applies across all plugins in this repo.
+- [`docs/guidance/plugin-entity-taxonomy.md`](./guidance/plugin-entity-taxonomy.md). The taxonomy this plugin follows. Applies across all plugins in this repo.
 - [Claude Code Skills reference](https://code.claude.com/docs/en/skills). How skills are defined and invoked in Claude Code itself.
 - [Claude Code Subagents reference](https://code.claude.com/docs/en/sub-agents). How agents are dispatched from inside skills.

docs/quickstart.md

@@ -1,12 +1,12 @@
 # Quickstart
 
-New to the han plugin? Pick the path that matches what you are trying to do right now. Each path is a short sequence (two or three skills) that compose into a useful result. You can follow one path end to end, or jump off at any step.
+New to the han plugin? Pick the path that matches what you are trying to do right now. Each path is a short sequence (a few skills) that compose into a useful result. You can follow one path end to end, or jump off at any step.
 
 > See also: [Plugin landing page](../README.md) · [Concepts](./concepts.md) · [Skills](./skills/README.md) · [Agents](./agents/README.md) · [Sizing](./sizing.md) · [YAGNI](./yagni.md)
 
 ## Which path are you on?
 
-- **[Plan a new feature](#path-a--plan-a-new-feature).** You have an idea for a feature and need to figure out what it should do and how to build it.
+- **[Plan a new feature](#path-a--plan-a-new-feature).** You have an idea for a feature and need to figure out what it should do, how to build it, and then build it test-first.
 - **[Investigate a bug or failure](#path-b--investigate-a-bug-or-failure).** Something is broken or behaving oddly and you need a root cause.
 - **[Review code or architecture](#path-c--review-code-or-architecture).** You want a second set of eyes on a branch, a PR, or an existing module.
 - **[Set up a project for everything else](#path-d--set-up-a-project-for-everything-else).** You want to document your project, formalize standards, and give every other skill richer context.
@@ -23,8 +23,9 @@ You have a feature idea and want a specification grounded in evidence, then a pl
 2. **[`/plan-a-phased-build`](./skills/plan-a-phased-build.md)** *(optional).* When the feature is large enough to ship in slices rather than all at once, split the spec into a numbered sequence of vertical-slice phases, each independently demoable to a real person.
 3. **[`/plan-implementation`](./skills/plan-implementation.md).** Turn the specification (or a single phase from the phased build) into an implementation plan through a project-manager-led team conversation.
 4. **[`/iterative-plan-review`](./skills/iterative-plan-review.md)** *(optional).* Stress-test either plan through multiple codebase-grounded review passes before committing to it.
+5. **[`/tdd`](./skills/tdd.md)** *(when you build it).* Implement the plan test-first through a BDD-framed red-green-refactor loop. The specification becomes the behavior test list; the skill enforces an observed-failure gate and applies your coding standards and ADRs in green and refactor.
 
-**You are done when:** you have a `feature-specification.md` and a `feature-implementation-plan.md` in the same folder, each with a cross-referenced decision log and review findings. If the feature was large enough to phase, you also have a `build-phase-outline.md` that orders the work into demoable vertical slices.
+**You are done when:** you have a `feature-specification.md` and a `feature-implementation-plan.md` in the same folder, each with a cross-referenced decision log and review findings. If the feature was large enough to phase, you also have a `build-phase-outline.md` that orders the work into demoable vertical slices. When you build it, the code lands behavior by behavior through `/tdd`, with tests leading.
 
 ---
 
@@ -78,12 +79,13 @@ You can reference multiple skills in one prompt and Claude runs them in sequence
 - *"Scan this repo, document the auth system, and create a coding standard for how we handle tokens."* → [`/project-discovery`](./skills/project-discovery.md) → [`/project-documentation`](./skills/project-documentation.md) → [`/coding-standard`](./skills/coding-standard.md).
 - *"Review my branch, then create an ADR for any architectural decisions in the diff."* → [`/code-review`](./skills/code-review.md) → [`/architectural-decision-record`](./skills/architectural-decision-record.md).
 - *"Plan the retry feature, then plan the implementation, then create a test plan for it."* → [`/plan-a-feature`](./skills/plan-a-feature.md) → [`/plan-implementation`](./skills/plan-implementation.md) → [`/test-planning`](./skills/test-planning.md).
+- *"Spec the discount engine, then build it test-first."* → [`/plan-a-feature`](./skills/plan-a-feature.md) → [`/tdd`](./skills/tdd.md) → [`/code-review`](./skills/code-review.md).
 - *"Compare the auth implementation to the auth spec, then plan how to close the gaps."* → [`/gap-analysis`](./skills/gap-analysis.md) → [`/plan-implementation`](./skills/plan-implementation.md).
 - *"Compare the share v1 implementation to the share v2 spec, split the gaps into a phased rollout, then plan implementation for the first phase."* → [`/gap-analysis`](./skills/gap-analysis.md) → [`/plan-a-phased-build`](./skills/plan-a-phased-build.md) → [`/plan-implementation`](./skills/plan-implementation.md).
 
 ## A note on sizing
 
-Five skills (`/code-review`, `/gap-analysis`, `/iterative-plan-review`, `/plan-a-feature`, `/plan-implementation`) classify the work as **small**, **medium**, or **large** before dispatching agents, default to small, and scale the team and iteration depth to the chosen band. Pass the size as the first positional argument to override (`/code-review medium`, `/plan-a-feature large "describe the feature"`). See [Sizing](./sizing.md) for the full model.
+Six skills (`/architectural-analysis`, `/code-review`, `/gap-analysis`, `/iterative-plan-review`, `/plan-a-feature`, `/plan-implementation`) classify the work as **small**, **medium**, or **large** before dispatching agents, default to small, and scale the team and iteration depth to the chosen band. Pass the size as the first positional argument to override (`/code-review medium`, `/plan-a-feature large "describe the feature"`). See [Sizing](./sizing.md) for the full model.
 
 ## A note on YAGNI