---
name: plan-rollout
preamble-tier: 3
interactive: true
version: 0.1.0
description: |
  Decomposition-as-artifact. Reads a working diff (and `SYSTEM.md` if
  present), writes `decomposition.md` with per-slice file lists,
  reader-time estimates, dependency edges, and reconciliation flags.
  Runs after a diff exists. Use when asked to "decompose the diff",
  "write a decomposition.md", or "plan-rollout". (gstack)
voice-triggers:
  - "decompose the diff"
  - "write a decomposition"
  - "plan-rollout"
allowed-tools:
  - Read
  - Write
  - Grep
  - Glob
  - AskUserQuestion
  - Bash
triggers:
  - decompose the diff
  - write decomposition.md
  - plan rollout
---

{{PREAMBLE}}

# /plan-rollout

Write `decomposition.md` describing how a real diff should ship as a
PR stack. Never code, never split branches, never run `/ship`.

**Don't run** on diffs that are ≤1 component + ≤30 min reader time +
no hard edges — output one line ("This is one PR. No decomposition
needed.") and stop. False slicing is worse than no slicing.

**Don't run** before code exists. Tell the user to write a real diff
first.

Out of v1: `rollout.md`, spill-check, `/ship`/`/review` integration,
SYSTEM.md scaffolder.

## Step 0 — Detect

1. Repo root: `git rev-parse --show-toplevel`.
2. Base: `gh pr view --json baseRefName -q .baseRefName`, then
   `origin/main`, then `origin/master`. AskUserQuestion if unresolved.
3. Head: `git rev-parse --abbrev-ref HEAD`.
4. Plan source: arg path → `~/.gstack/projects/<slug>/...-design-*.md`
   → AskUserQuestion (paste / path / diff-only).

Echo each value in one line. Facts only.

## Step 1 — Read SYSTEM.md if present

```bash
test -f SYSTEM.md && cat SYSTEM.md || echo "(no SYSTEM.md — using path heuristics)"
```

If present: parse YAML, build path→component map (longest-path-wins),
build contract graph (`rollout-edge: hard` edges drive coordinated-
deploy warnings later).

If absent: one component = one top-level directory of change.

## Step 2 — Enumerate the diff

```bash
git diff --name-status "<base>"     # tracked: committed + staged + unstaged
git diff --numstat "<base>"
git ls-files --others --exclude-standard   # untracked, treat as fully added
```

Use `git diff <base>` (no triple-dot) so working-tree changes count.
Union, dedupe by path. Empty → "Nothing to decompose" + stop.
>200 files → warn + ask before proceeding.

Bucket each file: with SYSTEM.md, via the path map (unmatched →
`(unmapped)`, flagged). Without, by top-level directory.

## Step 3 — Light import discovery

```bash
grep -E "^import .* from |^const .* = require\(" <file>   # TS/JS
grep -E "^(from |import )" <file>                          # Python
grep -E "^import " <file>                                  # Go
```

Resolve each import to a component. Record directed edges. External
or ambiguous imports: log + skip.

## Step 4 — Propose the stack

Priority order:

1. `rollout-edge: hard` (SYSTEM.md): both-sides-changed → one slice
   tagged "coordinated deploy required — \<breaks-if reason\>".
2. Topological by import edges. Cycles flagged + merged.
3. `rollout-order` (lower first) breaks ties.
4. `leaf-util` / `types-only` float to slice 0.
5. Alphabetical for remaining ties.

Per slice: files, lines +/-, dependencies, reader-time
(`ceil(lines/80) + ceil(files/5)` min; cap 30 min — split or flag),
reader guide (2-4 sentences, tired-reviewer voice).

**One-PR escape:** ≤1 component + ≤30 min + no hard edges → one-line
decomposition.md + exit.

## Step 5 — Reconciliation flags (informational, never blocking)

With SYSTEM.md present, print:
- `import-without-contract`: A imports B but no contract declared.
- `contract-without-imports`: contract declared, no supporting import
  edge, no `note: runtime-only`.
- `rollout-order-inversion`: declared order ≠ discovered order.

## Step 6 — Artifact location

AskUserQuestion:
- In-repo: `.gstack/plan-rollout/<branch-slug>-decomposition.md`
- User scope: `~/.gstack/projects/<repo-slug>/<branch-slug>-decomposition.md`

Recommend in-repo when other `.gstack/` planning artifacts already
exist on the branch; user scope otherwise.

## Step 7 — Write decomposition.md

```markdown
# Decomposition: <branch>

**Base:** <base>  **Head:** <head>  **Diff:** <N files, +A / -D>
**SYSTEM.md:** <present | absent — heuristics used>
**Generated:** <ISO>  **By:** /plan-rollout vX.Y.Z

## Verdict

<One paragraph. "This is one PR — no decomposition needed." | "Ship
as N PRs in this order. Total reviewer time: ~M min." | "Stop.
<issue>. Do <X> first.">

## Slices

### Slice 1: <name>
**Files (<n>):** <list>
**Diff:** +A / -D  **Reader time:** ~M min  **Depends on:** none | Slice K
**Coordinated deploy:** <only if hard-edge applies>
**Reader guide.** <2-4 sentences>

## Reconciliation flags (informational)
- ...
(Emit only if SYSTEM.md present and ≥1 flag fired.)

## What's NOT in this decomposition
<Excluded files. "All changed files allocated." if none.>
```

Write the file, print its path, stop.

## Self-check before exit

1. Every file → exactly one slice (or `(unmapped)` flagged).
2. No slice depends on a later slice.
3. Verdict matches the math. 4 min on 2 files = one PR, not a stack.
4. With SYSTEM.md, every slice maps to a real component name.

If a check fails and you can't fix it, write the file with the
failure flagged in the verdict.

## Limits

- Produces a doc — never enforces, never splits branches.
- Does not validate `breaks-if` claims (human judgment).
- Reader-time is heuristic; v1 has no calibration data.
- Mostly-one-component diffs with stray files: one PR with a "stray
  files" flag, not a forced 2-slice stack.