SkillsMay 12, 2026·2 min read

AIMock — Mock LLM, MCP, A2A, Vector APIs

AIMock is a mock server for AI app testing: it simulates LLM providers, MCP tools, A2A agents, and vector/search APIs so tests avoid real paid endpoints.

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This asset can be installed after the agent chooses its runtime, checks the plan, and runs the matching command.

Native · 98/100Policy: allow
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Any MCP/CLI agent
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Install
Single
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Trust: Established
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Asset
Direct install command
npx -y tokrepo@latest install 84631ebc-4610-44f0-a551-734d42f5d904 --target codex

Run after dry-run confirms the install plan.

Intro

AIMock is a mock server for AI app testing: it simulates LLM providers, MCP tools, A2A agents, and vector/search APIs so tests avoid real paid endpoints.

  • Best for: teams writing agent tests who need deterministic fixtures, record/replay, and one-port mocks
  • Works with: Node.js projects, test runners (Jest/Vitest), OpenAI-compatible SDKs via OPENAI_BASE_URL
  • Setup time: 10 minutes

Practical Notes

  • Mocks many surfaces from one port (LLM APIs, MCP, A2A, vector/search/rerank, etc.)
  • Supports 12 LLM providers (per project docs) and streaming behaviors for realistic tests
  • GitHub stars/forks (verified): see Source & Thanks

AIMock pays for itself the first time you avoid a flaky test or a surprise token bill.

Use it in three steps:

  1. Start llmock (fixtures-first) or the full suite via --config.
  2. Point your SDK to the mock by setting OPENAI_BASE_URL (and a dummy key if the SDK requires it).
  3. Record real traces once (optional), then replay deterministically in CI forever.

Two good guardrails:

  • Keep fixtures in version control and review them like code.
  • Add a CI check that fails if your tests accidentally talk to real endpoints (base URL not patched).

FAQ

Q: What does it mock? A: LLM APIs plus agent protocols like MCP/A2A and common infra like vector DBs, search, and rerank.

Q: Can it record real responses? A: Yes — it supports record & replay so you can capture and replay fixtures deterministically.

Q: How do I adopt it safely? A: Patch base URLs via env vars in tests and add a CI guard to prevent real endpoint calls.

🙏

Source & Thanks

Source: https://github.com/CopilotKit/aimock > License: MIT > GitHub stars: 581 · forks: 37

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