Mergetrain: A Local Merge Queue for Parallel Claude Code Sessions That Prevents Trampled Pushes

If you're running multiple Claude Code sessions in parallel, you've probably hit the trampling problem: branch A passes tests, branch B passes tests, but A-then-B breaks. Worktrees isolate editing, but not landing. And CLAUDE.md rules like "never push to main" hold until one session breaks them at the worst moment. Rules aren't enforcement.

Mergetrain is a local merge queue that solves this. It runs entirely on your machine — no server, no GitHub App, no CI service, no runtime dependencies. MIT licensed.

How It Works

• Each Claude Code session works in its own worktree and enqueues instead of pushing (mergetrain enqueue).
• A repo-owned pre-push hook blocks direct pushes to main.
• One runner assembles the queued branches into a "train" on top of origin/main, runs gates (tests + a full Unity build) once over the whole train, then pushes atomically.
• mergetrain hub serves a read-only dashboard for every repo on the machine: who's running gates, what's ready to ship, what needs attention. Agents read the same info as JSON (hub status --json).
• If your laptop dies mid-push, mergetrain recover asks the remote what actually landed and reconciles — nothing ships twice, nothing mislabeled.
• Repos that must never see unattended deploys can be registered with --no-daemon: visible on the board, never swept.

Getting Started

Install with pip: pip install mergetrain
Then run mergetrain init to scaffold the config plus a CLAUDE.md contract that your agents pick up automatically.

Dogfooding Results

Three weeks on a commercial game: 70+ trains landed, zero trampled pushes since.

Who Is This For?

Developers running parallel AI coding agents (Claude Code, etc.) who need a lightweight, local integration solution without relying on hosted PR pipelines or file locking.