amicus

Give your coding agent a second opinion from a different model.

amicus is one MCP server that fronts Codex, Kimi and Claude. The backend is a parameter, not a separate installation — so instead of running three servers and learning three tool surfaces, you ask for a consult, a review, or a delegated task and say which model should answer.

• Consult — a read-only second opinion on an approach, a bug, or a design.
• Review — a structured review of changes gathered from git, with findings tied to evidence.
• Delegate — a task implemented in a throwaway git worktree, returned as a diff you review. It is never applied to your working tree.
• Adversarial review — a fixed critic aimed at a plan, claim, or decision.

Long-running calls can be started in the background and polled, so a broad review does not block your session.

Install

Claude Code

/plugin marketplace add briandconnelly/amicus
/plugin install amicus@amicus

Codex

codex plugin marketplace add briandconnelly/amicus
codex plugin add amicus@amicus

Start a new session afterwards so the host loads the bundled skill and tools.

Any other MCP client

The plugins launch the server from a published release tag, pinned in .mcp.json. Point your client at the same command:

{
  "mcpServers": {
    "amicus": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/briandconnelly/amicus.git@v0.1.0", "amicus-mcp"]
    }
  }
}

Requirements

• Python 3.11 or newer, and uv.
• The CLI for each backend you enable, installed and authenticated: codex, kimi, claude. amicus drives those CLIs; it does not talk to the providers itself, and it stores no credentials.

Using it

Choose which backends are available with AMICUS_BACKENDS — a comma-separated list of codex, kimi and claude. Only the backends you name are enabled.

Then just ask, in your own words:

• "Get a second opinion on this approach from another model."
• "Have another model review my current changes."
• "Delegate this task to another model and show me the proposed diff."

In Claude Code there are also slash commands:

Start with /amicus:status — it tells you which backends are actually usable before you spend anything.

The tools

Eighteen tools, in five groups. Everything paid has a free way to inspect it first.

Not every backend does everything:

A no is amicus's routing decision, not a claim about the model. delegate is absent on Claude by a deliberate review-only policy. adversarial_review is scoped to Claude for v1, but the verb is amicus's own: the prompt it builds and the result shape it returns are amicus's for any backend, and what Claude contributes is a critic stance layered on top. So nothing about Codex or Kimi stops either from reviewing adversarially — ask them through consult or review_changes and supply the adversarial stance yourself. What the verb adds is that stance fixed, plus its target and evidence carriers.

Asking a backend for something it does not support returns a feature_unsupported error naming the backend and the feature, rather than failing obscurely.

Safety

• A delegated diff is never applied. It runs in a throwaway git worktree and comes back for you to read and apply yourself.
• Every verb call spends the selected backend's quota. The dry runs and the discovery and job tools do not.
• Enabling a backend that can write makes the tool surface carry that backend's approval annotations — see docs/MIGRATION.md.
• Your prompts go to whichever provider you selected, through that provider's own CLI. Each backend discloses how it carries your text — visible on amicus_backends.

Configuration

AMICUS_BACKENDS is the one most people set. Beyond it, each backend takes an optional model, reasoning effort, and binary path (AMICUS_CODEX_MODEL, AMICUS_KIMI_REASONING_EFFORT, AMICUS_CLAUDE_BIN, and so on), and there are limits for timeouts, job retention and payload sizes. The full list is the env_vars array in .mcp.json.

Coming from codex-in-claude, moonbridge, or claude-in-codex

amicus replaces all three. docs/MIGRATION.md maps the old tool names onto the new ones.

Status and known limits

0.2.0 is the current release, and it is a breaking one: the discovery surface moved from amicus/0.1/schema-7 to amicus/0.1/schema-13 and stored job results from RESULT_FORMAT 2 to 4. CHANGELOG.md says what moved and what a cached client should re-read. The server's wire contract is exercised by the test suite and by host captures against Claude Code and Codex, but:

• Two router-skill evaluation scenarios are unresolved — S6 (diff-safety wording) and S7 (approval friction) — recorded in docs/adr/0012-m6-packaging-decisions.md. Neither is a defect in the server's wire contract.
• A third-party backend distribution loads through the amicus.backends entry-point group, but cannot yet be enabled or called: AMICUS_BACKENDS and the backend parameter accept only the in-tree ids.

Development

uv sync
uv run prek install --prepare-hooks   # one-time local hooks

The gate is defined once, in AGENTS.md (Rules, item 2); CI runs it on every supported Python version.

License

MIT. See LICENSE.