red-pen

name	red-pen
description	RedPen — independent review of a proposed root-cause-analysis solution. Spawns an isolated reviewer with no shared memory; returns a structured review doc with verdict, alternatives, and concerns. Reusable from any RCA/bugfix skill (sherlock, fuzzbug-fix, triage) and standalone.
argument-hint	<analysis-source> [solutions-source] [output-path] # sources: *.md | bug:<id> | D<id> | *.patch | <sha> | diff | local | https://...
allowed-tools	["Agent","Read","Write","AskUserQuestion"]

RedPen

Get an independent second opinion on a proposed RCA solution before it goes in front of a human reviewer or the user.

The reviewer runs in an isolated subagent context — it does not see the calling agent's conversation, memory, or prior conclusions. Inputs are passed by file path only. This is the dotfiles equivalent of bringing in an outside engineer: no anchoring on what's already been decided, no rubber stamping.

The reviewer's primary job is to find a more elegant fix if one exists, including fixes that redesign the surrounding codebase when the right design would resolve the root cause and other latent issues at once.

---

Inputs contract

This skill accepts conclusions only by file path. Do not summarize or restate the analysis in the prompt — the reviewer must read it themselves.

Arguments: $0

Tokens are classified by shape. Disambiguation priority — apply per token, in order; first rule that matches wins:

1. Token resolves to an existing file (try as-given, then relative to CWD, then absolute):
   • *.md → markdown role (see role assignment below).
   • *.patch / *.diff → solutions source (distiller required).
   • any other extension or extensionless → AskUserQuestion. Do not guess.
2. bug:<digits> / bz:<digits> / https://bugzilla.mozilla.org/show_bug.cgi?id=<digits> → analysis source (intake required).
3. D<digits> / https://phabricator.services.mozilla.com/D<digits> → solutions source (distiller required).
4. https://github.com/<owner>/<repo>/pull/<n> → solutions source (distiller required).
5. URL ending in .patch or .diff → solutions source (distiller required).
6. Literal diff (and no file by that name in CWD) → solutions source: uncommitted working tree.
7. Literal local or HEAD (and no file by that name in CWD) → solutions source: branch tip vs git merge-base.
8. Token resolves to a git commit (git rev-parse --verify "$tok^{commit}" succeeds) → solutions source: that commit.
9. --desc <text> flag → analysis source: user free-text. The skill writes the text to a scratch file before invoking intake.
10. None of the above → AskUserQuestion. Never silently fall back.

Role assignment for markdown files: a token whose basename ends with -review.md is always the explicit output path, whatever its position — check this first, before assigning any other role. Of the remaining *.md tokens: first (in argument order) → analysis; second → solutions; at most one of each. A third non--review.md markdown token is rejected.

This is why a caller that wants a review written somewhere other than the default (e.g. two different reviews of the same analysis doc within one run) passes an explicit …-review.md path rather than relying on the -N suffix.

Conflict rule: at most one analysis source and one solutions source per invocation. Two analysis-side or two solutions-side tokens → AskUserQuestion. Never silently pick a winner.

Output path resolution (priority order):

1. Explicit token ending -review.md.
2. If any user-supplied *.md was given: <dirname(that md)>/<bug-id-stripped-basename>-review.md. Bug-id-strip rule: if basename matches ^bug-(\d+)-analysis$, strip -analysis first — so sherlock's bug-12345-analysis.md produces bug-12345-review.md.
3. Else if a bug id is derivable (from bug:<id>, from front-matter of a scratch analysis doc, or from a Phab revision's commit message): $PWD/bug-<id>-review.md.
4. Else $PWD/red-pen-review-<run-id>.md.

Print the resolved output path before invoking the critic so the user can abort.

If after parsing there is no analysis source, ask the user via AskUserQuestion. Do not guess.

---

Adapter step (only when non-md sources present)

If every supplied source is already an existing *.md file, skip this section entirely and go to Pre-flight. (Sherlock's Decide.5 always passes two *.md paths, so it never triggers an adapter spawn.)

Otherwise, normalize non-md inputs into markdown docs in a scratch directory at ~/.claude/red-pen-scratch/<run-id>/, where <run-id> is <bug-id-or-arg-hash>-<utc-timestamp>-<4-char-suffix>. The scratch dir persists after the run for debugging; it is never auto-deleted.

Order is fixed and sequential. Each step waits for the previous to write its output file before the next is invoked:

1. Intake — invoked only if no analysis md was supplied. Single Agent call:

   Agent(
     subagent_type: "red-pen-intake",
     description: "Intake for <source-descriptor>",
     prompt: <descriptor + output-path + template-path; no conclusions>,
   )
   

   Confirm the output file exists and is non-empty before continuing. If intake reports an error, abort the skill — do not invoke the critic on partial inputs.

2. Distiller — invoked only if no solutions md was supplied or the solutions source is non-md (Phab revision, patch file, commit, working tree, GitHub PR, raw URL). Single Agent call, same discipline as intake.

3. Critic — same invocation as in Spawn the reviewer below. The resolved analysis-doc path and solutions-doc path (whether user-supplied or scratch) are passed to the critic exactly as today.

The intake and distiller subagents each return only short summaries to this skill (paths and metadata). Never quote the body of an intake/distiller doc into the critic's prompt. The critic reads files by path; the skill is just a path-handler.

---

Pre-flight

1. Confirm the analysis doc exists and is readable (Read tool). For adapter-produced scratch docs, this also confirms the adapter wrote non-empty output.
2. If a solutions doc was passed (or produced by the distiller), confirm it exists.
3. Resolve the output path per the rules in Inputs contract. If the resolved path already exists, append -N until unique (so re-running the skill produces a new review, never overwrites).
4. Identify the bug ID if present in the analysis doc (look for Bug <id> in the title, summary, or front-matter). Used only for naming.

---

Spawn the reviewer

Single Agent invocation. Do not chain multiple reviewer calls — one isolated review per skill run.

Agent(
  subagent_type: "red-pen-critic",
  description: "Independent review of bug-<id> solutions",
  prompt: <see template below>,
)

Prompt template

The prompt MUST contain only file paths and instructions — never the content of those files, never a summary of prior findings.

You are reviewing a proposed root-cause-analysis solution. You have NO prior
context — read every input fresh.

Inputs (read these directly with the Read tool):
- Analysis doc: <absolute path to analysis doc>
- Solutions doc: <absolute path to solutions doc, OR the same as analysis
  doc with a note: "this document is the analysis; review whatever solution
  or proposal sections it contains, and say so if it contains none">
- Repo root: <absolute path>
- Output path for your review: <absolute path>

Your task:
1. Read the analysis doc and the solutions.
2. Verify cited file:line references against the actual source. Do not
   trust any claim until you have re-read the cited code.
3. Search for a more elegant fix — including codebase redesigns when a
   better design would also resolve other latent issues. See your system
   prompt for what counts as a redesign worth proposing.
4. Write your review to the output path using the structure in
   <skill-dir>/references/review-template.md.
5. Return a 4-line summary in the format your system prompt specifies.

Hard rules:
- No prior context. Trust nothing until verified against source.
- No editing of code or patches.
- No phantom citations. Open the file or admit you couldn't.

Replace <skill-dir> with the absolute path to this skill's directory so the reviewer can locate the template.

---

Result handling

When the reviewer returns:

1. Read the review doc at the output path (Read tool, single call).

2. Extract the verdict, headline finding, and iteration recommendation from the review-doc front matter or first section.

3. Surface to the caller (whether human or another skill) with this exact shape, no additional commentary:

   **Independent review** ([review doc](<relative-path-to-review-doc>))
   - Verdict: <verdict>
   - Headline: <one-sentence headline finding>
   - Iteration: <iteration recommendation>
   

4. Do not re-summarize the reviewer's reasoning. The review doc on disk is the canonical artifact; both human and caller can read it directly. Re- summarizing both wastes context and risks distorting the review.

---

When called from another skill

The calling skill should:

• Pass absolute paths only.
• Pass the analysis doc as it stands — do not pre-edit it to "look better" for the reviewer.
• Wait for the review result before continuing its own workflow.
• Handle each verdict per its own rules. Common pattern (see sherlock Decide.6 for the canonical version):
  • approve → proceed.
  • approve-with-concerns / revise → apply changes, re-invoke if changes are non-trivial.
  • redesign → escalate to user; do not silently expand scope.
  • reject / needs-more-info → loop back to the relevant analysis step.

---

Standalone use

A user can invoke this skill directly without a calling skill. Beyond the classic "two markdown docs" form, any of the wider input shapes documented in Inputs contract work standalone too:

• red-pen bug:1234567 D45678 — review the Phabricator revision against the Bugzilla bug.
• red-pen <abs>/analysis.md foo.patch — review a colleague's patch file against an existing analysis doc.
• red-pen <abs>/analysis.md diff — review uncommitted working-tree changes.
• red-pen <abs>/analysis.md <commit-sha> — review a specific commit.
• red-pen --desc "frob crashes on second call" diff — quick review against a free-text problem description.

Useful for vetting a proposed fix from a colleague's RCA write-up, a Phabricator revision out for review, or your own in-progress changes before posting.

---

Hard rules for this skill

• Never include conclusions in the reviewer prompt — only paths. The same applies to the intake and distiller subagent prompts: pass descriptors and output paths, never embed prior analysis or summaries.
• Never invoke red-pen-critic more than once per skill run. The adapter subagents (red-pen-intake, red-pen-distiller) are each invoked at most once, and only before the critic. Order is fixed: intake → distiller → critic, sequential. None run in parallel. If the caller wants iteration, it invokes the skill again with revised inputs.
• Never modify the analysis doc or solutions doc, nor any user-supplied source artifact (Bugzilla bug, patch file, git commit, working tree, remote repo). The skill writes the review doc and any number of scratch transport docs in ~/.claude/red-pen-scratch/<run-id>/; everything else is read-only.
• The distiller doc is mechanical-only (provenance + raw diff). Do not let the distiller editorialize. The critic reads the diff itself; it does not need a human-readable summary.

---

Future work

• red-pen-loop (deferred). An iteration-driver skill that reads the verdict and either re-invokes the critic on revised inputs (approve-with-concerns, revise) or surfaces to the user (redesign, reject, needs-more-info). Two open design questions block this: (1) the revise verdict needs an "applier" subagent that mutates a copy of the solutions doc without violating the no-mutation rule above; (2) sherlock already encodes the verdict-ladder loop in its Decide.6, so a generic loop skill is only worth building once a non-sherlock caller appears. Build separately; do not embed iteration logic in this skill.