Write an agent-runnable upstream sync skill #106

Current scope (maintainer, 2026-10-20)

Shrunk. The Cursor pstack 0.15.29 sync (#234) refreshes the "Incorporate a change" steps in UPSTREAM.md from its own run: the per-commit decision table, how to handle files that need review, the verifier registry's skills list, recipe updates, and --wide. This issue no longer waits on #105.

A repository-local sync skill stays unscheduled until a contributor's sync goes wrong because the written steps were not enough.

Original request

Goal

Turn the "Incorporate a change" section of UPSTREAM.md into a repository-local skill that any agent follows to sync Cursor pstack, in Claude Code or Codex, as a maintainer or a contributor. It sits beside verify-open-pstack.

Why the change from Factory (2026-10-12)

The original body asked for a runbook that a Factory planner and builder follow. No Factory branch has merged here since PR #111 on 2026-10-04, and the 0.15.17 sync came from a contributor's fork (#143, PR #145). Contributor-facing tooling should not depend on Factory.

Acceptance criteria

The skill covers these steps, in order:

1. Open or update the sync issue.
2. Run upstream-audit.py, upstream-merge.py, the merge probe and the port-patch ledger check (Add a checked port-patch ledger for upstream divergences #105).
3. Resolve each review row, and record each upstream commit as applied, adapted or excluded.
4. Update CHANGES.md, NOTICE.md, UPSTREAM.md and README-UPSTREAM.md.
5. Run the CI-equivalent checks locally: Bun tests, strict typecheck, static invariants and plugin validation.
6. Run the live gate in Claude Code and Codex through verify-open-pstack.
7. Merge the reviewed PR, then publish with python3 scripts/release.py publish.

Also:

• It lives at .claude/skills/<name>/ with the Codex path under .agents/skills/, as verify-open-pstack does, and the verifier registry maps it.
• The 0.15.20 sync (Sync Cursor pstack 0.15.20 as Open Pstack 1.7.0 #161) runs by hand with the existing scripts. Its step notes are the first draft.
• The next real Cursor sync after Add a checked port-patch ledger for upstream divergences #105 runs through the skill end to end, and that run is the proof.

Order

After #105.

Source: docs/plans/2026-10-01-triage-and-roadmap.md, section 3, item 5, and triage 2026-10-12.