refactor(to-plan,to-issues): prune no-ops in vertical-slice framing

Fold the redundant 'thin vertical slice cuts through all layers, NOT
horizontal' intro sentence into vertical-slice-rules bullet 1 (it was
duplicating the bullet), and cut to-plan's 'no parallelism / top-to-bottom'
restatement — 'sequential' is already anchored as the leading word. Keeps
the shared core identical across the two sibling skills.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.changeset/tdd-reference-only-seams.md

@@ -0,0 +1,7 @@
+---
+"mattpocock-skills": patch
+---
+
+Reshape the `tdd` skill into reference-only. The red → green → refactor loop is anchored by leading words the model already holds, so the step-by-step Workflow was largely restating the loop and duplicating the horizontal-slicing anti-pattern. Dropped the Workflow and per-cycle checklist; folded their one durable idea — vertical slices / tracer bullets — into the Anti-patterns section and a short Rules-of-the-loop list. Introduced **seam** as the leading word for where tests go, collapsing the old Philosophy "public interfaces" prose and the Planning "confirm interface / behaviors" handshake into one rule: test only at pre-agreed seams, confirmed with the user before any test is written.
+
+Also dropped the refactor stage — TDD is now red → green, not red → green → refactor. Refactoring belongs to the review stage, not the implementation loop, so the refactor rule and `refactoring.md` were removed (its home is the `review` skill).

.changeset/to-plan-skill.md

@@ -0,0 +1,5 @@
+---
+"mattpocock-skills": minor
+---
+
+Add a new user-invoked **`to-plan`** skill to the `engineering/` bucket — the sequential, HITL sibling of **`to-issues`**. Both slice work into tracer-bullet vertical slices, but where `to-issues` produces independently-grabbable issues for parallel agents, `to-plan` produces one ordered sequence you drive by hand, one phase per fresh context. It publishes to the tracker `/setup-matt-pocock-skills` configured, shaped to it: a single sequential `plan.md` for a local tracker, or a parent issue with ordered sub-issues (native sub-issues where the platform supports them) for a real one. The `to-*` fork in `ask-matt`'s main flow now offers both, and there's a human-facing docs page at `docs/engineering/to-plan.md`.

.claude-plugin/plugin.json

@@ -9,7 +9,9 @@
     "./skills/engineering/setup-matt-pocock-skills",
     "./skills/engineering/tdd",
     "./skills/engineering/to-issues",
+    "./skills/engineering/to-plan",
     "./skills/engineering/to-prd",
+    "./skills/engineering/implement",
     "./skills/engineering/prototype",
     "./skills/engineering/domain-modeling",
     "./skills/engineering/codebase-design",

README.md

@@ -155,6 +155,7 @@ Skills I use daily for code work.
 - **[improve-codebase-architecture](./skills/engineering/improve-codebase-architecture/SKILL.md)** — Scan a codebase for deepening opportunities, present them as a visual HTML report, then grill through whichever one you pick.
 - **[setup-matt-pocock-skills](./skills/engineering/setup-matt-pocock-skills/SKILL.md)** — Configure this repo for the engineering skills (issue tracker, triage labels, domain doc layout). Run once per repo before using the other engineering skills.
 - **[to-issues](./skills/engineering/to-issues/SKILL.md)** — Break any plan, spec, or PRD into independently-grabbable issues using vertical slices.
+- **[to-plan](./skills/engineering/to-plan/SKILL.md)** — Turn any plan, spec, or PRD into a sequential set of tracer-bullet phases worked one at a time — a single ordered file for a local tracker, or parent-and-sub-issues for a real one.
 - **[to-prd](./skills/engineering/to-prd/SKILL.md)** — Turn the current conversation into a PRD and publish it to the issue tracker. No interview — just synthesizes what you've already discussed.
 
 **Model-invoked**

docs/engineering/to-plan.md

@@ -0,0 +1,53 @@
+Quickstart:
+
+```bash
+npx skills add mattpocock/skills --skill=to-plan
+```
+
+```bash
+npx skills update to-plan
+```
+
+[Source](https://github.com/mattpocock/skills/tree/main/skills/engineering/to-plan)
+
+## What it does
+
+`to-plan` turns a PRD, spec, or the current conversation into a **sequential** plan — an ordered list of phases you work through one at a time, in a fresh context per phase.
+
+Every phase is a **tracer bullet** — a thin *vertical* slice that cuts through all integration layers end-to-end (schema, API, UI, tests), never a horizontal slice of one layer. A completed slice is demoable or verifiable on its own, and is sized to fit a single fresh context window.
+
+## When to reach for it
+
+You invoke this by typing `/to-plan` — the agent won't reach for it on its own.
+
+Reach for it once you have an agreed plan or a written spec and you want it turned into a sequence of phases you'll build **by hand, one at a time**. Point it at the conversation, or pass a PRD or issue reference and it reads that first. If the change hasn't been written up as a spec yet, produce one first — for that, use [to-prd](https://aihero.dev/skills-to-prd).
+
+## Sequential, not parallel
+
+`to-plan` is the sequential, HITL sibling of [to-issues](https://aihero.dev/skills-to-issues). Both slice work into tracer bullets, but they're for different workflows:
+
+- **`to-issues`** produces *independently-grabbable* issues, so parallel agents can pick them up at once (it applies the ready-for-agent label).
+- **`to-plan`** produces one *ordered sequence* you drive yourself, phase by phase, staying in the loop — no ready-for-agent label.
+
+## Publishes to your configured tracker
+
+Like the other skills, `to-plan` publishes through the tracker [setup-matt-pocock-skills](https://aihero.dev/skills-setup-matt-pocock-skills) configured, and it adapts the shape to that tracker:
+
+- **Local files** → a single sequential `plan.md` in the repo root, all phases in order.
+- **A real issue tracker (GitHub, Linear)** → a parent issue for the whole plan, with one sub-issue per phase, in order — using the platform's native sub-issue relationship where it has one, otherwise sequential issues each blocked by the previous.
+
+## Vertical slices, not horizontal ones
+
+The whole skill turns on one distinction. A **horizontal** slice ships one layer of the change — all the schema, or all the API — and nothing works until every layer lands. A **vertical** slice, the tracer bullet, ships one narrow path through *every* layer at once, so it can be demoed the moment it's done.
+
+Before slicing, `to-plan` looks for prefactoring — "make the change easy, then make the easy change" — and orders that work first. It then quizzes you on the breakdown (granularity, ordering, what to merge or split) before publishing anything.
+
+## Where it fits
+
+`to-plan` is the sequential branch of the main build chain:
+
+```txt
+grill-with-docs → to-prd → to-plan → implement → code-review
+```
+
+It sits between [to-prd](https://aihero.dev/skills-to-prd), which hands it a settled spec to slice against, and [implement](https://aihero.dev/skills-implement), which builds each phase, driving [tdd](https://aihero.dev/skills-tdd) internally to write the tests test-first, before its [code-review](https://aihero.dev/skills-code-review) pass. Work one phase per fresh context, clearing between them. When you're unsure which skill or flow fits, [ask-matt](https://aihero.dev/skills-ask-matt) routes you.

skills/engineering/README.md

@@ -12,6 +12,7 @@ Reachable only when you type them (`disable-model-invocation: true`).
 - **[improve-codebase-architecture](./improve-codebase-architecture/SKILL.md)** — Scan a codebase for deepening opportunities, present them as a visual HTML report, then grill through whichever one you pick.
 - **[setup-matt-pocock-skills](./setup-matt-pocock-skills/SKILL.md)** — Configure this repo for the engineering skills (issue tracker, triage labels, domain doc layout). Run once per repo.
 - **[to-issues](./to-issues/SKILL.md)** — Break any plan, spec, or PRD into independently-grabbable issues using vertical slices.
+- **[to-plan](./to-plan/SKILL.md)** — Turn any plan, spec, or PRD into a sequential set of tracer-bullet phases worked one at a time — a single ordered file for a local tracker, or parent-and-sub-issues for a real one.
 - **[to-prd](./to-prd/SKILL.md)** — Turn the current conversation into a PRD and publish it to the issue tracker.
 
 ## Model-invoked

skills/engineering/ask-matt/SKILL.md

@@ -20,7 +20,9 @@ The route most work travels. You have an idea and want it built.
    - **`/prototype`** to answer the question with throwaway code,
    - **`/handoff`** back what you learned, and reference it from the original idea thread.
 3. **Branch — is this a multi-session build?**
-   - **Yes** → **`/to-prd`** (turn the thread into a PRD) → **`/to-issues`** (split the PRD into independently-grabbable issues). Because the issues are independent, **clear context between each one**: start a fresh session per issue and kick off **`/implement`** by passing it the PRD and the single issue to work on.
+   - **Yes** → **`/to-prd`** (turn the thread into a PRD), then split it into tracer-bullet slices one of two ways:
+     - **`/to-issues`** — independently-grabbable issues on your tracker, for **parallel/AFK** agents. Because the issues are independent, **clear context between each one** and kick off **`/implement`** per issue.
+     - **`/to-plan`** — a **sequential** plan you drive **by hand**, staying in the loop. Publishes to the same tracker, shaped to it: a single ordered `plan.md` for a local tracker, or a parent issue with ordered sub-issues for a real one. Work one phase per fresh context, clearing between them, with **`/implement`**.
    - **No** → **`/implement`** right here, in the same context window.
 
    Either way, **`/implement`** builds each issue by driving **`/tdd`** internally — one red-green slice at a time — then closes out by running **`/code-review`**, a two-axis review (Standards + Spec) of the diff, before committing. Reach for **`/tdd`** on its own when you just want to build a concrete behaviour test-first without a full spec, and **`/code-review`** on its own whenever you want to review a branch or PR against a fixed point.

skills/engineering/tdd/SKILL.md

@@ -5,107 +5,32 @@ description: Test-driven development. Use when the user wants to build features
 
 # Test-Driven Development
 
-## Philosophy
+TDD is the red → green loop. This skill is the reference that makes that loop produce tests worth keeping: what a good test is, where tests go, the anti-patterns, and the rules of the loop. Every section applies on every cycle — consult them before and during the loop, not after.
 
-**Core principle**: Tests should verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't.
+When exploring the codebase, read `CONTEXT.md` (if it exists) so test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.
 
-**Good tests** are integration-style: they exercise real code paths through public APIs. They describe _what_ the system does, not _how_ it does it. A good test reads like a specification - "user can checkout with valid cart" tells you exactly what capability exists. These tests survive refactors because they don't care about internal structure.
+## What a good test is
 
-**Bad tests** are coupled to implementation. They mock internal collaborators, test private methods, or verify through external means (like querying a database directly instead of using the interface). The warning sign: your test breaks when you refactor, but behavior hasn't changed. If you rename an internal function and tests fail, those tests were testing implementation, not behavior.
+Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification — "user can checkout with valid cart" tells you exactly what capability exists — and survives refactors because it doesn't care about internal structure.
-
-**Tautological tests** restate the implementation inside the assertion, so they pass by construction and give zero confidence. When the expected value is computed the way the code computes it — `expect(add(a, b)).toBe(a + b)`, snapshotting a figure you derived by hand the same way the code does, asserting a constant equals itself — the test can never disagree with the code: break the code wrong and the assertion breaks wrong with it. The expected value must come from an independent source of truth — a known-good literal, a worked example, the spec.
 
 See [tests.md](tests.md) for examples and [mocking.md](mocking.md) for mocking guidelines.
 
-## Anti-Pattern: Horizontal Slices
+## Seams — where tests go
 
-**DO NOT write all tests first, then all implementation.** This is "horizontal slicing" - treating RED as "write all tests" and GREEN as "write all code."
+A **seam** is the public boundary you test at: the interface where you observe behavior without reaching inside. Tests live at seams, never against internals.
 
-This produces **crap tests**:
+**Test only at pre-agreed seams.** Before writing any test, write down the seams under test and confirm them with the user. No test is written at an unconfirmed seam. You can't test everything — agreeing the seams up front is how testing effort lands on the critical paths and complex logic instead of every edge case.
 
-- Tests written in bulk test _imagined_ behavior, not _actual_ behavior
+Ask: "What's the public interface, and which seams should we test?"
-- You end up testing the _shape_ of things (data structures, function signatures) rather than user-facing behavior
-- Tests become insensitive to real changes - they pass when behavior breaks, fail when behavior is fine
-- You outrun your headlights, committing to test structure before understanding the implementation
 
-**Correct approach**: Vertical slices via tracer bullets. One test → one implementation → repeat. Each test responds to what you learned from the previous cycle. Because you just wrote the code, you know exactly what behavior matters and how to verify it.
+## Anti-patterns
 
-```
+- **Implementation-coupled** — mocks internal collaborators, tests private methods, or verifies through a side channel (querying the database instead of using the interface). The tell: the test breaks when you refactor but behavior hasn't changed.
-WRONG (horizontal):
+- **Tautological** — the assertion recomputes the expected value the way the code does (`expect(add(a, b)).toBe(a + b)`, a snapshot derived by hand the same way, a constant asserted equal to itself), so it passes by construction and can never disagree with the code. Expected values must come from an independent source of truth — a known-good literal, a worked example, the spec.
-  RED:   test1, test2, test3, test4, test5
+- **Horizontal slicing** — writing all tests first, then all implementation. Bulk tests verify _imagined_ behavior: you test the _shape_ of things rather than user-facing behavior, the tests go insensitive to real changes, and you commit to test structure before understanding the implementation. Work in **vertical slices** instead — one test → one implementation → repeat, each test a **tracer bullet** that responds to what the last cycle taught you.
-  GREEN: impl1, impl2, impl3, impl4, impl5
 
-RIGHT (vertical):
+## Rules of the loop
-  RED→GREEN: test1→impl1
-  RED→GREEN: test2→impl2
-  RED→GREEN: test3→impl3
-  ...
-```
 
-## Workflow
+- **Red before green.** Write the failing test first, then only enough code to pass it. Don't anticipate future tests or add speculative features.
-
+- **One slice at a time.** One seam, one test, one minimal implementation per cycle.
-### 1. Planning
+- **Refactoring is not part of the loop.** It belongs to the review stage (see the `review` skill), not the red → green implementation cycle.
-
-When exploring the codebase, read `CONTEXT.md` (if it exists) so that test names and interface vocabulary match the project's domain language, and respect ADRs in the area you're touching.
-
-Before writing any code:
-
-- [ ] Confirm with user what interface changes are needed
-- [ ] Confirm with user which behaviors to test (prioritize)
-- [ ] Identify opportunities for deep modules (small interface, deep implementation) — run the `/codebase-design` skill for the vocabulary and the testability checks
-- [ ] List the behaviors to test (not implementation steps)
-- [ ] Get user approval on the plan
-
-Ask: "What should the public interface look like? Which behaviors are most important to test?"
-
-**You can't test everything.** Confirm with the user exactly which behaviors matter most. Focus testing effort on critical paths and complex logic, not every possible edge case.
-
-### 2. Tracer Bullet
-
-Write ONE test that confirms ONE thing about the system:
-
-```
-RED:   Write test for first behavior → test fails
-GREEN: Write minimal code to pass → test passes
-```
-
-This is your tracer bullet - proves the path works end-to-end.
-
-### 3. Incremental Loop
-
-For each remaining behavior:
-
-```
-RED:   Write next test → fails
-GREEN: Minimal code to pass → passes
-```
-
-Rules:
-
-- One test at a time
-- Only enough code to pass current test
-- Don't anticipate future tests
-- Keep tests focused on observable behavior
-
-### 4. Refactor
-
-After all tests pass, look for [refactor candidates](refactoring.md):
-
-- [ ] Extract duplication
-- [ ] Deepen modules (move complexity behind simple interfaces)
-- [ ] Apply SOLID principles where natural
-- [ ] Consider what new code reveals about existing code
-- [ ] Run tests after each refactor step
-
-**Never refactor while RED.** Get to GREEN first.
-
-## Checklist Per Cycle
-
-```
-[ ] Test describes behavior, not implementation
-[ ] Test uses public interface only
-[ ] Test would survive internal refactor
-[ ] Expected values are independent literals, not recomputed from the code
-[ ] Code is minimal for this test
-[ ] No speculative features added
-```

skills/engineering/tdd/refactoring.md

@@ -1,10 +0,0 @@
-# Refactor Candidates
-
-After TDD cycle, look for:
-
-- **Duplication** → Extract function/class
-- **Long methods** → Break into private helpers (keep tests on public interface)
-- **Shallow modules** → Combine or deepen
-- **Feature envy** → Move logic to where data lives
-- **Primitive obsession** → Introduce value objects
-- **Existing code** the new code reveals as problematic

skills/engineering/to-issues/SKILL.md

@@ -24,11 +24,11 @@ Look for opportunities to prefactor the code to make the implementation easier.
 
 ### 3. Draft vertical slices
 
-Break the plan into **tracer bullet** issues. Each issue is a thin vertical slice that cuts through ALL integration layers end-to-end, NOT a horizontal slice of one layer.
+Break the plan into **tracer bullet** issues.
 
 <vertical-slice-rules>
 
-- Each slice delivers a narrow but COMPLETE path through every layer (schema, API, UI, tests)
+- Each slice cuts a narrow but COMPLETE path through every layer (schema, API, UI, tests) — vertical, NOT a horizontal slice of one layer
 - A completed slice is demoable or verifiable on its own
 - Any prefactoring should be done first
 

skills/engineering/to-plan/SKILL.md

@@ -0,0 +1,112 @@
+---
+name: to-plan
+description: Turn a PRD, spec, or the current conversation into a sequential plan of tracer-bullet vertical slices, published to the configured tracker — one ordered file for local, or parent-and-sub-issues for a real tracker.
+disable-model-invocation: true
+---
+
+# To Plan
+
+Turn a plan, spec, or PRD into a **sequential** plan of vertical slices (tracer bullets) — an ordered list of phases you work through one at a time, in a fresh context per phase.
+
+This is the sequential, HITL sibling of `/to-issues`. Where `to-issues` produces independently-grabbable issues for parallel agents, `to-plan` produces one ordered sequence you drive by hand, top to bottom.
+
+The issue tracker and triage label vocabulary should have been provided to you — run `/setup-matt-pocock-skills` if not.
+
+## Process
+
+### 1. Gather context
+
+Work from whatever is already in the conversation context. If the user passes a reference (a PRD path, an issue number or URL) as an argument, fetch it and read its full body.
+
+### 2. Explore the codebase (optional)
+
+If you have not already explored the codebase, do so to understand the current state of the code. Phase titles and descriptions should use the project's domain glossary vocabulary, and respect ADRs in the area you're touching.
+
+Look for opportunities to prefactor the code to make the implementation easier. "Make the change easy, then make the easy change."
+
+### 3. Draft vertical slices
+
+Break the work into **tracer bullet** phases.
+
+<vertical-slice-rules>
+
+- Each slice cuts a narrow but COMPLETE path through every layer (schema, API, UI, tests) — vertical, NOT a horizontal slice of one layer
+- A completed slice is demoable or verifiable on its own
+- Each slice is sized to fit in a single fresh context window
+- Any prefactoring should be done first
+
+</vertical-slice-rules>
+
+Order the phases in dependency order — each builds on the ones before it.
+
+### 4. Quiz the user
+
+Present the proposed breakdown as a numbered list. For each phase, show:
+
+- **Title**: short descriptive name
+- **What it delivers**: the end-to-end behaviour this phase makes work
+
+Ask the user:
+
+- Does the granularity feel right? (too coarse / too fine)
+- Is the ordering correct — does each phase build on the ones before it?
+- Should any phases be merged or split further?
+
+Iterate until the user approves the breakdown.
+
+### 5. Publish the plan to the configured tracker
+
+Publish the approved phases in order. **How** depends on the tracker `/setup-matt-pocock-skills` configured:
+
+- **Local files** → write one sequential `plan.md` in the repo root, all phases in order, using the file template below.
+- **A real issue tracker (GitHub, Linear, …)** → create **one parent issue** for the whole plan, then **one sub-issue per phase, in order**. Use the platform's native sub-issue / child-issue relationship if it supports one; otherwise create sequential issues and set each phase's "Blocked by" to the previous phase. Use the issue template below for the parent and each phase.
+
+These are worked **sequentially by hand**, not handed to parallel agents, so do NOT apply the ready-for-agent triage label.
+
+<plan-file-template>
+
+# Plan: <short name of the work>
+
+A one-line summary of what this plan builds. Reference the source PRD or spec if there is one.
+
+## Phases
+
+Each phase is one tracer bullet — a vertical slice worked in a fresh context, top to bottom.
+
+### 1. <Phase title>
+
+**Delivers:** the end-to-end behaviour this phase makes work, from the user's perspective — not a layer-by-layer implementation list.
+
+- [ ] Acceptance criterion 1
+- [ ] Acceptance criterion 2
+
+### 2. <Phase title>
+
+...
+
+</plan-file-template>
+
+<issue-template>
+
+**Parent issue** — title: the plan's short name. Body: the one-line summary, a reference to the source PRD/spec, and the ordered list of phase titles.
+
+**Each phase sub-issue:**
+
+## What to build
+
+The end-to-end behaviour this phase makes work, from the user's perspective — not layer-by-layer implementation.
+
+## Acceptance criteria
+
+- [ ] Criterion 1
+- [ ] Criterion 2
+
+## Blocked by
+
+The previous phase (omit for the first phase).
+
+</issue-template>
+
+In either form, avoid specific file paths or code snippets — they go stale fast. Exception: if a prototype produced a snippet that encodes a decision more precisely than prose can (state machine, reducer, schema, type shape), inline it and note briefly that it came from a prototype. Trim to the decision-rich parts — not a working demo, just the important bits.
+
+Work the plan one phase at a time with `/implement`, clearing context between phases.