I gave Claude Code a crew. Codex and Gemini found a race in the plugin that runs them.

TL;DR crewmate is a Claude Code plugin that lets Claude hand a task to OpenAI Codex or Google Gemini, keep working, and watch every step land in the conversation. It installs with 2 commands and has 0 dependencies. When I asked it to review its own code, both models found the same race condition, one I had decided was too rare to matter. If Codex is the only other model you use, OpenAI's own plugin is the better choice; more on that below.

You know the move. Claude wrote something you're unsure about, so you open another terminal and paste it into Codex or Gemini. You wait, copy the answer back, and paste it into Claude.

The second opinion is often worth it. The copy-paste isn't. I wanted Claude to make that hand-off itself, and I wanted three things from it:

That last one is the command I use most. A reviewer who hasn't seen your reasoning finds the gaps you filled in mentally, and two different models find different gaps.

You don't need a slash command. I asked Claude in plain words: "I want a second opinion from a different model than you: does add.js handle string inputs safely? Get Gemini's view, then tell me where you agree or disagree."

Skill crewmate Bash crewmate ask gemini --detach <<'PROMPT' … PROMPT Bash crewmate watch --brief gemini-mvxp4oxz-o0o6 Bash crewmate result gemini-mvxp4oxz-o0o6 Enter fullscreen mode Exit fullscreen mode It wrote Gemini's brief, watched the job, checked the answer itself, and told me where the two agreed. An agent orchestrating a bigger task can hand work to Codex or Gemini the same way, without waiting for you.

Late in the build, I ran /crewmate:critique on crewmate's own lock: the code that stops two writing jobs from editing your files at once. Codex and Gemini both flagged the same race.

I had decided that race was too rare to matter, and written that down in my plan. Codex quoted the line back at me. It's fixed now. That's the second opinion I built crewmate to get.

If Codex is the only other model you use, install codex-plugin-cc: it's built on Codex's own app server and has extras like a hand-off into a native Codex session. crewmate is for having both Codex and Gemini behind one install.

/plugin marketplace add aashish-g03/crewmate /plugin install crewmate@crewmate /crewmate:setup Enter fullscreen mode Exit fullscreen mode /crewmate:setup checks everything and tells you exactly what's missing. You need Node 20+ and at least one of these, installed and signed in:

npm i -g @openai/codex && codex login # Codex curl -fsSL https://antigravity.google/cli/install.sh | bash && agy # Gemini (Antigravity CLI) Enter fullscreen mode Exit fullscreen mode 2. Use it:

/crewmate:ask gemini Read src/ and list any exported functions nothing uses /crewmate:critique --diff Enter fullscreen mode Exit fullscreen mode Or just ask Claude: "get a second opinion from Codex on this migration."

Next on my list: more models behind the same commands, and falling back to another model when one runs out of quota. If you try it, tell me where the second opinion surprised you.

AI disclosure: I built crewmate with Claude Code as the implementer, working from a design and plan I directed and approved, with Codex, Gemini and fresh Claude reviewers checking the work. This post was drafted with Claude and edited by me. Every terminal frame is real output.