agentsync

An MCP server that lets two (or more) AI agents collaborate on the same git repository without stepping on each other. Each agent declares what it's building before it builds, sees what its partner has claimed, and detects conflicts when work lands — all coordinated through the repo itself, with no lock server and no requirement that both agents be online at once.

How it works (one paragraph)

Coordination state is a single claims.json living on a dedicated agentsync branch (kept out of main, so it never pollutes your code history and isn't blocked by main's branch protection). Each agent's claim declares the work, the files it will touch, what it requires, its branch, and a status. Overlap is plain set intersection. Writes use a read-modify-write loop with git push as a compare-and-swap: if the push is rejected, the server re-fetches the latest claims and re-evaluates, so a colliding peer claim is observed before this agent's claim is committed. All git work happens in a private worktree under .git/, so your agent's actual code branch is never disturbed.

See DESIGN.md for the architecture rationale and AGENTS.md for the playbook your agent follows to drive the tools.

Related MCP server: Shift MCP Server

Install

pip install -r requirements.txt      # just `mcp`

For repo provisioning you also need the GitHub CLI, authenticated with repo scope:

gh auth login        # one-time; check with `gh auth status`

Configure

Both collaborators add the server to their MCP client, each with their own agent id and their own local clone. See mcp.config.example.json:

{
  "mcpServers": {
    "agentsync": {
      "command": "python3",
      "args": ["/abs/path/to/agentsync_server.py"],
      "env": {
        "AGENTSYNC_REPO": "/abs/path/to/your/clone",
        "AGENTSYNC_AGENT_ID": "jonny"
      }
    }
  }
}

The agentsync branch is created automatically on the first survey() or claim() call — no manual setup.

Starting from nothing (no repo yet)

If the shared repo doesn't exist on GitHub yet, one person runs provision() once. Point AGENTSYNC_REPO at the folder you want the project in (it can be empty or not yet created) and call:

provision(repo="you/our-project", partner_github="their-username")

This creates the GitHub repo (private by default), makes the first commit, seeds the agentsync coordination branch, and invites your partner as a push collaborator. It's idempotent — safe to re-run. Then send your partner the clone_url it returns; once they accept the invite and clone, both of you point the MCP server at your own clones and the normal protocol below takes over.

Tools

provision(repo="", partner_github="", private=True, description="") — one-time bootstrap when the shared repo doesn't exist yet. Creates the GitHub repo via gh, makes the first commit, seeds the agentsync branch, and invites the partner as a push collaborator. Idempotent. Returns the clone_url to hand your partner. (Needs the gh CLI authenticated with repo scope.)

add_collaborator(github_username, permission="push") — invite someone to the existing shared repo so they can push (pull|triage|push|maintain |admin). Use this when the repo already exists and you just want to grant a partner access. They must accept the GitHub invite, then clone. Returns the clone URL to hand them. (Needs gh with admin on the repo.)

survey() — pull the latest state and report what every other agent has claimed: task, files, dependencies, branch, status, timestamp. Run it before planning and again after finishing.

claim(task, touches, requires=None, branch="", force=False) — stake a unit of work. Refuses with status: "blocked" if your touches hits a partner's active files (you'd get in their way) or your requires hits their in-progress files (you'd build on unstable ground), returning exactly what overlaps and with whom. The overlap is checked against freshly-fetched state immediately before the push. Pass force=True to claim anyway (e.g. same large file, disjoint regions).

check_conflicts(against_branch="") — after building, diff your branch against your partners' branches at two levels:

• claim_overlap — declared-file intersection (intent).

• merge_conflict — a real git merge-tree dry-run merge (textual). Catches collisions the claims didn't predict.

Defaults to every branch named in an active peer claim; pass against_branch to check one specific branch.

update_status(status, note="") — set your own claim's status (planning | in-progress | done) and optionally leave a note for your partner. Pushes immediately.

The workflow (what your agent does)

1. provision(...) — once, only if the repo doesn't exist yet (then both clone)

2. survey() — what's my partner working on, if anything?

3. plan a slice that doesn't overlap their active work

4. claim(...) — if blocked, narrow the slice or wait

5. build on your branch

6. survey() again — where are they now?

7. check_conflicts() — does their landed work collide with mine?

8. reconcile (rebase/merge or flag) → update_status("done", note=...)

The full prompt your agent should run is in AGENTS.md.

Test

python3 test_agentsync.py     # spins up real git repos and drives every path

The suite (19 cases, isolated per test) covers the protocol (claim/block on shared files and dependency-on-WIP, force override, done-claims-don't-block, status validation), conflict detection (textual conflict and clean-merge), the compare-and-swap guarantee (a peer claim landing mid-flight both survives our retry and is observed in time to block a collision), error paths, provisioning (create + seed + invite, partner-from-env, existing-remote skip, invite-failure reporting), and add_collaborator (invite + bad-permission + no-remote) with the gh CLI stubbed so no real GitHub repo is touched. CI runs it on every push via GitHub Actions.

Limitations

• Textual, not semantic. check_conflicts catches files that won't merge; it does not catch "their API signature change breaks my caller." That reasoning is the agent's job (read both diffs) — the server gives it the signal, not the judgment.

• Both sides must opt in. This only works fully if your partner's agent runs the same server and honors the same claim protocol. Without that, yours degrades to branch inspection: it sees what has landed, not what's planned.

• Advisory locks. Claims prevent collisions by convention, not enforcement; force=True exists precisely because some overlaps are fine.

License

PolyForm Noncommercial License 1.0.0 — free to use, modify, and share for any noncommercial purpose. Commercial use requires a separate license.