carbon-pr — Claude Code skill: what it does, how to install

---
name: carbon-pr
description: Post the development footprint of the current branch as a sticky PR comment
---

Run the following bash script from the repository the PR belongs to, and present the output to the user.

```bash
#!/usr/bin/env bash
# Locate the install wired into the status line (honours CLAUDE_CONFIG_DIR),
# then fall back to CLAUDE_PLUGIN_ROOT / CLAUDE_CARBON_DIR / the default path.
# Windows (Git Bash): CLAUDE_* variables and the paths stored in settings.json can
# arrive in the native "C:\Users\..." spelling, which bash cannot open. cygpath
# ships with Git for Windows; everywhere else this is the identity function.
ccp() {
  case "${OSTYPE:-}" in msys*|cygwin*) ;; *) printf '%s' "$1"; return 0 ;; esac
  case "$1" in
    [A-Za-z]:[\\/]*|*\\*) cygpath -u "$1" 2>/dev/null || printf '%s' "$1" ;;
    *) printf '%s' "$1" ;;
  esac
}
CFG="$(ccp "${CLAUDE_CONFIG_DIR:-$HOME/.claude}")"
# A jq the installer fetched into the data folder (a Mac older than macOS 15 has none)
if ! command -v jq >/dev/null 2>&1 && [ -x "$CFG/claude-carbon/bin/jq" ]; then PATH="$CFG/claude-carbon/bin:$PATH"; fi
REPO_DIR=""
if command -v jq >/dev/null 2>&1 && [ -f "$CFG/settings.json" ]; then
  SL_CMD="$(jq -r '.statusLine.command // empty' "$CFG/settings.json" 2>/dev/null)"
  # statusLine.command stores a path, shell-escaped, or in double quotes on Windows:
  # unquote, expand ~ and unescape spaces
  SL_CMD="${SL_CMD#\"}"; SL_CMD="${SL_CMD%\"}"
  SL_CMD="${SL_CMD//\\ / }"; SL_CMD="${SL_CMD/#\~/$HOME}"; SL_CMD="$(ccp "$SL_CMD")"
  [ -n "$SL_CMD" ] && [ -f "$SL_CMD" ] && REPO_DIR="$(cd "$(dirname "$SL_CMD")/.." 2>/dev/null && pwd)"
fi
[ -z "$REPO_DIR" ] && [ -n "${CLAUDE_PLUGIN_ROOT:-}" ] && REPO_DIR="$(ccp "$CLAUDE_PLUGIN_ROOT")"
[ -z "$REPO_DIR" ] && [ -n "${CLAUDE_CARBON_DIR:-}" ] && REPO_DIR="$(ccp "$CLAUDE_CARBON_DIR")"
if [ -z "$REPO_DIR" ]; then
  # Pure marketplace installs reach here: no statusLine.command in settings.json and
  # no CLAUDE_PLUGIN_ROOT in a skill's bash env. Pick the newest cached plugin copy,
  # keeping only candidates that ship the PR report script.
  CACHE_LATEST=""
  for D in "$CFG/plugins/cache"/*/claude-carbon/*/; do
    [ -f "${D}scripts/generate-pr-report.sh" ] || continue
    if [ -z "$CACHE_LATEST" ] || [ "$(printf '%s\n%s\n' "$CACHE_LATEST" "$D" | sort -V | tail -1)" = "$D" ]; then
      CACHE_LATEST="$D"
    fi
  done
  [ -n "$CACHE_LATEST" ] && REPO_DIR="${CACHE_LATEST%/}"
fi
[ -z "$REPO_DIR" ] && REPO_DIR="$HOME/code/claude-carbon"

bash "$REPO_DIR/scripts/generate-pr-report.sh"
```

The script sums the local Claude Code sessions recorded for the current branch of the current project and posts (or updates in place) one sticky comment on the branch's open PR, through the user's own `gh` auth. Report its final line to the user as printed; never recompute or reformat the numbers.

With `--pr <number>` the script reports that PR's own branch (read through `gh`, so even `--dry-run` needs it), wherever it runs; never pass a PR number to report the current branch's sessions on another PR. It refuses a PR opened from a fork: tell the user to run it without `--pr` from the fork's clone, on the PR's branch. It also refuses a branch checked out in no worktree whose name sessions of other folders carry: say that nothing was posted and pass on its suggestion (run it from the branch's worktree, or switch to the branch in the folder its sessions ran in and run it there without `--pr`). If it reports no sessions for the branch, say that nothing was posted, that a session counts for the branch it ended on and so do its agents, except an agent that worked in a worktree of another branch and ended with this version installed (it counts there), that only sessions recorded since the `git_branch` column exists carry a branch, and that `scripts/backfill.sh` repairs older rows while their transcripts are still on disk. If it reports no open PR, suggest pushing the branch and opening one first, or passing `--pr <number>`. If the script itself is missing (an install that predates it), suggest `/carbon-update`.