emulate provides local, stateful replacements for APIs and services so software can run in CI or environments without network access. It is used by developers who need production-like integrations with services such as GitHub, Stripe, AWS, Slack, and databases during testing. Its catalogue skills and instruction support agent workflows that use these local emulators.
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.
npx skills add vercel-labs/emulate --skill githubgit clone --depth 1 https://github.com/vercel-labs/emulateWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/vercel-labs/emulate/github)<a href="https://agentmods.dev/skills/vercel-labs/emulate/github"><img src="https://agentmods.dev/badge/skills/vercel-labs/emulate/github/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/vercel-labs/emulate/github"><img src="https://agentmods.dev/badge/skills/vercel-labs/emulate/github.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 8 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Privilege Escalation · line 62 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- high Privilege Escalation · line 454 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- high Privilege Escalation · line 603 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
- medium MCP Rug Pull · line 4 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 15 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium MCP Rug Pull · line 61 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium Data Exfiltration · line 134 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
- medium Data Exfiltration · line 207 Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00116 | $0.05926 |
| Opus 5.5 | $0.00046 | $0.02370 |
| Sonnet 5.5 | $0.00023 | $0.01185 |
| Haiku 4.5 | $0.00012 | $0.00593 |
Grade A, and why
github scanned grade A with 1 finding 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 9d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
allowed-tools: Bash(npx emulate:*), Bash(curl:*) Copies of this mod
1 near-identical copy found in the catalogue:
- github — 91% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 646 lines — stays where its author put it; the contents beside it link to each section on GitHub.
GitHub API Emulator
Fully stateful GitHub REST API emulation. Creates, updates, and deletes persist in memory and affect related entities.
Start
Local listeners bind to 127.0.0.1 by default. For access from containers or other machines, pass --host 0.0.0.0 to the CLI or hostname: '0.0.0.0' to createEmulator. Configure --base-url or baseUrl for advertised URLs reachable by those clients.
# GitHub only
npx emulate --service github
# Default port
# http://localhost:4001
Or programmatically:
import { createEmulator } from 'emulate'
const github = await createEmulator({ service: 'github', port: 4001 })
// github.url === 'http://localhost:4001'
For a programmatic GitHub App, omit private_key and read the generated RSA key from the instance:
const github = await createEmulator({
service: 'github',
port: 4001,
seed: {
github: {
users: [{ login: 'octocat' }],
apps: [{
app_id: 12345,
slug: 'my-github-app',
name: 'My GitHub App',
installations: [{ installation_id: 100, account: 'octocat' }],
}],
},
},
})
const privateKey = github.generatedSecrets.find(
secret => secret.kind === 'github.app_private_key' && secret.id === '12345',
)?.value
The key remains stable across github.reset(). Explicit keys are not included in generatedSecrets.
The Next.js and Nuxt adapters also generate omitted keys. Retain the returned handler and call its server-only generatedSecrets() method. With persistence configured, the identity survives cold starts. Keep snapshots private because they contain the signing key, and require custom persistence backends to implement atomic initialize() semantics.
For the CLI, omit private_key only when requesting a private delivery file:
npx emulate start --service github --seed emulate.config.yaml \
--generated-secrets-file .emulate-secrets.json
The destination must not exist. emulate removes inherited ACLs, verifies effective owner-only access, and publishes complete JSON before any listener or portless alias starts. Handled startup failures remove the invocation-owned artifact. A hard termination can leave a complete artifact that must be removed manually after confirming no invocation is using it. Read generatedSecrets from the artifact, then keep the file out of source control. Linux requires setfacl and getfacl from the acl package. The flag fails closed when access controls cannot be verified and is not supported on Windows. Without --generated-secrets-file, CLI seed files still require private_key.
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.
- 9d ago Changed · +4 lines a403f3d82a97
- 21d ago Changed · +2 lines 1f740e0148d3
- 29d ago Changed · +4 lines 0e23001d830c
- 1mo ago Changed · -2 lines d7af691c0251
- 1mo ago Changed · +11 lines bed122871299
- 1mo ago Changed · +5 lines b9c195c027d0
- 1mo ago First seen · 622 lines · 116 tokens per session scan A f1035689ccb7
github is a skill published in the GitHub repository vercel-labs/emulate (1,947 stars, last pushed 2d ago), licensed Apache-2.0. It adds 116 tokens to every session and 5,926 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
server-side-calls
Call tRPC procedures directly from server code using t.createCallerFactory() and router.createCaller(context) for integration testing, internal server logic, and custom API endpoints. Catch TRPCError and extract HTTP status with getHTTPStatusCodeFromError(). Error handling via onError option.
mem0-test-integration
Verify a Mem0 integration produced by /mem0-integrate. Runs in the same workspace on the same branch (loose coupling) — installs dependencies, runs the repo's native test suite, then exercises a real end-to-end smoke flow against the user's API key. Produces a scorecard. TRIGGER when: user has just run /mem0-integrate…
prowler-test-api
Testing patterns for Prowler API: JSON:API, Celery tasks, RLS isolation, RBAC. Trigger: When writing tests for api/ (JSON:API requests/assertions, cross-tenant isolation, RBAC, Celery tasks, viewsets/serializers).
python-sdk
Implement or modify Python SDK behavior under python/composio, including tools, toolkits, sessions, auth configs, connected accounts, client integration, and shared Python models. Use for Python core runtime/API work; pair with python-testing and cross-sdk-parity when TypeScript must match.
convex-test
Generate convex-test tests for the app's Convex functions.
voiden
Create and edit Voiden .void files for API testing. Covers the .void file format and all enabled extension block types.