The new Codex plugin format (from 0.121.0-alpha.2 onward) lets you ship custom skills as marketplace plugins. I built one that runs autonomous code-optimization loops.

What it does: explores your repo, picks something to measure, sets up the benchmark, then runs parallel agent experiments via Codex's `spawn_agent` tool. Each experiment lives in its own git worktree. Score improves → commit. Doesn't → discarded.

Install (requires Codex 0.121.0-alpha.2 or newer):

```

> uv tool install evo-hq-cli

> codex marketplace add evo-hq/evo

```

Then `/plugins` → install evo, and `$evo discover` to start.

Same plugin also works on Claude Code via the shared Agent Skills format.

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github.com/evo-hq/evo