PR: Update git:20260813.f1ed50fA

Immutable. This exact content is served forever at /api/v1/blob/641d72c7ac3c5e29.

---
name: "PR: Update"
description: "{{ ƔƔƔ }} Update a PR description to account for commits made since it was last written"
when_to_use: "When commits have been pushed to a branch after its PR was opened or last described — offer this whenever new work lands on a branch with an open PR, rather than leaving the description stale."
model: sonnet
effort: medium
disable-model-invocation: false # invocable by Claude so it can offer a refresh when new commits leave the description stale; its approval step still gates the write
allowed-tools: ["Bash(git:*)", "Bash(gh:*)", "Bash(~/.claude/library/scripts/pr-facts.sh:*)", "Read", "Glob", "Grep"]
arguments: ["pr"]
argument-hint: "[PR number]"
---

# Update an Existing PR

Update the description of PR #$ARGUMENTS.

## Steps

### 1. Gather the facts in one call

```bash
"$HOME"/.claude/library/scripts/pr-facts.sh $ARGUMENTS
```

It prints the PR metadata, the current body, the watermark (`<!-- pr-update-watermark: <sha> -->`, or "none" when the whole branch is new), every commit since it with per-commit stats, and the SHA to use as the next watermark. Analyse that dump rather than running exploratory `gh`/`git` calls. Exit **3** means no new commits — tell me the description is already up to date and stop. Exit **2**: report the script's message.

### 2. Analyse the new commits

From the dump, understand what changed and why. Group related commits into coherent change categories. Run `git show <sha>` on a specific commit only where the stat alone can't tell you what a change is.

### 3. Produce the updated PR body

Take the existing body (in the dump) and update it:

- **Do not rewrite from scratch.** Preserve existing content unless it is now inaccurate.
- The body structure follows `~/.claude/library/templates/pr-description.md` (the same template `pr-create` fills) — keep updates within that structure rather than adding new top-level sections.
- Update the `## Changes` section to incorporate the new commits. If collapsible `<details>` blocks already exist, add new entries or update existing ones as appropriate.
- If the description references behaviour that has changed, correct it.
- Insert or replace the watermark comment at the very end of the body, using the `next watermark sha` from the dump:

```text
<!-- pr-update-watermark: <latest-sha> -->
```

### 4. Show me the diff

Display the updated body in full and a brief summary of what changed vs the previous description. **Wait for my approval.**

### 5. Apply the update

Once approved: `gh pr edit $ARGUMENTS --body "<updated body>"`. Confirm success.