How to sync AGENTS.md and CLAUDE.md across all your repos

Sync one file: AGENTS.md

Codex, Cursor and Copilot read AGENTS.md. Claude Code reads it when the repo has no CLAUDE.md, and otherwise through a line that says @AGENTS.md at the top of the CLAUDE.md (Does Claude Code read AGENTS.md?). So the shared rules belong in AGENTS.md, and CLAUDE.md keeps the import plus anything only Claude needs. Which file each tool reads is in AGENTS.md vs CLAUDE.md.

Push: a GitHub Action that opens a pull request in every repo

repo-file-sync-action runs in the rules repo on every push and copies the files you list into the repos you list. By default it opens a pull request in each one, so every team still decides what merges:

# .github/sync.yml in your rules repo
group:
  - files:
      - source: AGENTS.md
        dest: AGENTS.md
    repos: |
      acme/payments
      acme/web
      acme/api

• It needs its own token. The default GITHUB_TOKEN cannot write to other repos. Its README asks for a personal access token with full repo scope, or a GitHub App installation token.
• It copies the whole file. A repo's own root rules are overwritten on the next sync, so this suits repos whose root rules are all shared. To mix in each repo's own, use rulesync, below.
• Check it is still maintained. Its last release, v1.21.1, is from May 2024. A short workflow of your own with gh pr create does the same job.

Pull: rulesync and a shared rules repo

rulesync is a command-line tool that writes the rules file for each agent (Claude Code, Codex, Cursor, Copilot and dozens more) from one source in a .rulesync/ folder. It can also pull rules from another GitHub repo and pin them in a lockfile:

# in each repo, once
npx rulesync add acme/ai-standards --rules team-rules
npx rulesync install && npx rulesync generate

# in CI: fail when this repo is behind the shared rules
npx rulesync install --outdated

Each repo keeps its own rules next to the shared ones, and rulesync combines them into one AGENTS.md, so nothing is overwritten. The pull runs when someone runs it, so add the --outdated check to CI to see which repos are behind.

Without touching the repos: each vendor's admin setting

An admin setting reaches every repo on a machine or in an organization, one tool at a time:

That is three admin consoles, each on its own plan, and nothing for Codex, which is why most teams end up syncing a file anyway.

What a sync does not do

• Edits in one repo do not travel back. Someone fixes a rule in acme/web, and the next sync either overwrites it or conflicts with it. Only edits made in the rules repo reach everyone.
• Nobody writes the new rule down. A correction typed in an agent session, or a review comment on a pull request, stays where it was said unless a person copies it into the rules repo.
• A file grows until it stops working. One shared file for every repo gets long, and agents follow a long file less well (why a growing CLAUDE.md stops working).

With Harbor: one source the agents read, no copies

Harbor keeps the team's rules in one place and hands them to Claude Code, Codex, Cursor and Copilot at the start of each session, through hooks that npx harborloop init installs, so there is no file in each repo to keep in step. Each session gets the rules that apply to its repo and task, not the whole set. New rules come from where the team already decides (agent sessions, pull request reviews, Slack threads and docs), and you set the gate on which go live without a person. The AGENTS.md and CLAUDE.md files you already have are imported when you set it up, and each of their rules waits for a person to review it (rules files). The steps are in the quickstart, and the wider picture in sharing memory across Claude Code, Codex and Cursor.