StuntAPI

Local API simulators — test against real public APIs without remote accounts, network, or bills.

stuntapi.com · stunt (the tool) · adapter catalog · docs

stunt is an open-source tool that spins up local simulators for the public APIs your code calls — a stunt double for the real thing. Instead of creating remote accounts, fighting rate limits, and paying for sandboxes, you run a faithful local mock that behaves like the real API (stateful, real-shaped responses, webhooks).

brew install stuntapi/tap/stunt   # or: go install stuntapi.com/stunt/cmd/stunt@latest
stunt demo                         # boots a stateful Stripe-style sim + prints curl commands

You just want to write a feature. The API has other plans — account-gated sandboxes, slow approval, rate limits at 2am, test modes that don't fire webhooks, surprise bills. stunt stands in: a safe, local, deterministic stand-in so your tests run offline and reset clean.

• Stateful, not stubbed — create a charge, list it, capture it, watch the webhook fire. SQLite-backed state survives across requests.
• Sandboxed adapters — adapter logic runs in a Starlark VM: no filesystem, no network, no load(). Safe to install a stranger's mock.
• 91 reference adapters — Stripe, Twilio, GitHub, Slack, AWS, Google Workspace, and 86 more, all embedded in the binary (no cloning).
• All four transports — REST, gRPC (unary + streaming), WebSocket, and GraphQL.
• Synthetic, enforced — stunt adapter lint rejects real-looking data (emails, tokens, cards). Everything is fake by construction.
• Operable by machines — --json on catalog/plan/doctor, an AGENTS.md, and a stunt llm reference so coding agents drive it unaided.

• stunt — the Go tool: the simulator engine, CLI, and 91 embedded adapters.

• ⭐ Star stunt if it unblocks you.
• 🐛 Open an issue for bugs or adapter requests.
• 🛠️ Adapters are just a YAML manifest + sandboxed Starlark — see CONTRIBUTING.md.

_{Made in Europe with care by @polyMatto / @deblasis & contributors}

_{Apache-2.0 · pre-1.0 · the safe stand-in for the real thing}