Parallel Codex/agent sessions kept sabotaging each other, so we built an open-source coordination protocol above Git

If you only ever run one coding agent, you might not need this (though I still think its good for compliance audits too). If you run two or more on the same repo (Codex plus Claude Code, multiple sessions, worktrees), you have probably hit the failure it exists for: two agents make incompatible changes with zero textual conflict. Git only compares diffs, so it cannot warn you that one session is replacing a class the other is extending.

We hit this constantly building GPTree, so we built an internal tool to fix it. This week we open-sourced it.

Foremerge is a local-first coordination protocol above Git. Init into any git repo. Each session publishes its intent, a semantic scope, and the operation (symbol:PaymentService=replace) before editing. Deterministic rules compare the declarations and raise a finding with the rule that fired and a suggested resolution, while the work is still a plan. Claims are advisory leases, not locks. Acceptance is gated on a verification run Foremerge executes itself against the exact candidate fingerprint, so "tests pass" is something the tool verified, not something an agent claimed.

It ships an MCP server plus a native skill. foremerge setup codex registers it at user level, and one registration serves every repository: start Codex inside the repo you want coordinated. There is also a prompt in the README you can paste into Codex or any client that sets the whole thing up.

One Rust binary, SQLite inside the repo, Apache-2.0. Pre-1.0 and honest about limits: detection is heuristic and can warn on compatible work, and there are no published benchmarks yet (but we ran it on 96 parrallel agents against our backlog with 0 conflicts in PRs).

Repo: https://github.com/naw103/foremerge

Where would this warn on compatible work in your setup? That is the feedback we need most.