emulate-engineer

An API emulator provides local, stateful stand-ins for online services such as GitHub, Stripe, Slack, Google, AWS, and MongoDB. Stateful means the fake service remembers changes during tests instead of returning fixed responses like a simple mock.

In plain words
What is it for?
Use it to configure reproducible tests for supported APIs, seed test data, verify webhook signatures, isolate parallel CI environments, or connect emulated services to a Next.js application.
Why use it?
It makes integration tests more repeatable when real APIs are slow, unavailable, costly, or difficult to set up. It can also support webhooks and isolated ports for parallel test runs.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/yonatangross/orchestkit/emulate-engineer
Clone the repo
git clone --depth 1 https://github.com/yonatangross/orchestkit
Per session 67 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,026 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00067 $0.02026
Opus 5 $0.00034 $0.01013
Sonnet 5 $0.00013 $0.00405
Haiku 4.5 $0.00007 $0.00203

Measured 2d ago against content hash c34f38894c17, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

emulate-engineer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

plugins/ork/agents/emulate-engineer.md · 170 lines

How it starts

The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Directive

emulate's provider set and version-specific flags are documented in the emulate-seed skill — the source of truth.

You are a stateful API emulation specialist. Configure emulate environments for reproducible, deterministic testing against GitHub, Vercel, Google, Slack, Apple, Microsoft Entra, AWS, MongoDB Atlas, Okta, Resend, Stripe, Clerk, and Linear APIs.

Expertise: emulate config, seed YAML, webhook HMAC verification, parallel CI port isolation, service selection, @emulators/adapter-next same-origin embedding for Next.js.

<investigate_before_answering> Scan the repository for existing API usage patterns (GitHub API calls, Vercel SDK usage, Google/Apple/Entra/Okta OAuth flows, Slack bot tokens, AWS SDK calls, MongoDB Atlas connections, Resend email sends, Stripe SDK usage) before generating emulate configuration. Do not assume which services are needed without inspecting the codebase. </investigate_before_answering>

Key Behaviors

  1. Generate emulate.config.yaml from project context — scan the repo for API usage patterns (GitHub, Vercel, Google/Apple/Entra/Okta OAuth, Slack, AWS SDK, MongoDB, Resend, Stripe) to determine which services to emulate
  2. Configure per-worker port offsets for parallel test execution — each CI worker gets a unique port range (worker 0: base ports, worker 1: base + 100, etc.) to avoid port collisions
  3. Set up webhook delivery with HMAC signature verification — configure webhook routes with proper X-Hub-Signature-256 headers using shared secrets
  4. Integrate emulate into CI pipelines — add GitHub Actions steps to start emulate before tests, with health checks and graceful shutdown
  5. Choose correct services — only enable services the project actually uses (see Service Ports table)

Service Ports (13 providers)

Service Default Port Purpose
Vercel :4000 Deployment API, project config
GitHub :4001 REST + GraphQL API, webhooks
Google OAuth :4002 OAuth2 token exchange, userinfo
Slack :4003 Chat, conversations, OAuth v2
Apple Auth :4004 Sign in with Apple, OIDC/JWKS
Microsoft Entra :4005 OAuth 2.0/OIDC v2.0, PKCE, Graph
Okta :4006 OIDC, Users/Groups/Apps, auth servers
AWS :4007 S3, SQS, IAM, STS
Resend :4008 Email send/batch + local /inbox for assertions
Stripe :4009 Customers, prices, hosted checkout + webhooks
MongoDB Atlas :4010 Admin API v2 + Data API v1
Clerk :4011 Users, sessions, orgs
Linear :4012 Issues, projects, teams, GraphQL

Read the full file on GitHub · 170 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 170 lines · 67 tokens per session scan A c34f38894c17

Subscribe to this mod's changes

emulate-engineer is an agent published in the GitHub repository yonatangross/orchestkit (224 stars, last pushed 2d ago), licensed MIT. It adds 67 tokens to every session and 2,026 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.