How do I mock the Tenderly Simulation API locally?

Install stunt, add a one-service block to stunt.yaml (adapter: embedded:tenderly-style), and run stunt up. You get a local, stateful stand-in for Tenderly Simulation API v1 — 5 routes over rest — with no remote account, no network, and no bills.

Is the Tenderly Simulation API mock data synthetic?

Yes — entirely. The adapter returns generated data only; stunt's adapter lint rejects real-looking secrets and PII at build time. It simulates the shape and behavior of Tenderly Simulation API (routes, status codes, pagination, webhooks), never real records.

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tenderly-style

simulates Tenderly Simulation API v1

restadapter v0.1.05 routes

verification

VMVM tier — no SDK suite yet· surface 5 · not implemented 3 · differs 4

use it

# add to stunt.yaml
services:
  tenderly:
    adapter: embedded:tenderly-style

# then
$ stunt up

The embedded: source extracts this adapter from the binary — no git clone, fully offline.

how to mock the Tenderly Simulation API locally

Install stunt, paste the service block above into stunt.yaml, run stunt up — then point your client at localhost instead of Tenderly Simulation API. It works offline, keeps state across requests and restarts, and every response is synthetic: the route shapes, status codes, pagination, and webhook delivery follow the real Tenderly Simulation API v1 surface — the data is fake, the behavior is real.

backing stores

simulations

api surface (5)

generated from the adapter manifest — exactly what boots, nothing more

5 routes

POST/api/v1/account/{account}/project/{project}/simulate

POST/api/v1/account/{account}/project/{project}/simulate-bundle

GET/api/v1/account/{account}/project/{project}/simulations

GET/api/v1/account/{account}/project/{project}/simulations/{id}

GET/api/v1/networks

VM-verified behaviors (6)

✓the access-key gate rejects missing and unknown bearers with the slug envelope
✓networks answer the bare array and switch to the paged envelope under perPage
✓a plain simulation round-trips the deterministic Tenderly shape
✓a value transfer emits the ERC-20 Transfer log and balance overrides
✓reverting simulations carry the ABI-encoded Error(string) output
✓bundles fan out per simulation and stored results list and retrieve by id

Not implemented (3)

No contracts endpoints (import/verify/update contracts per project)
No alerts or notification-rules API
No transaction lookup/list endpoints (transactions by hash)

Differs from the real API (4)

gas_used is derived from input length, not real EVM execution; status defaults to true
An explicit revert:true body flag forces the revert path; real API has no such switch
Bearer auth where real Tenderly uses the X-Access-Key header
Responses mix camelCase where Tenderly is snake_case and nests simulation.id

full scorecard →

want more of the Tenderly Simulation API surface? adapters are YAML + Starlark — the authoring guide covers adding routes, fixtures, and state machines. Open an issue for anything big first, or just file a PR — merged routes ship in the next release.