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.
Borrowing it
Nothing to install: this file belongs to vercel-labs/emulate. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/vercel-labs/emulate/main/AGENTS.mdgit 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/instructions/vercel-labs/emulate/agents-md)<a href="https://agentmods.dev/instructions/vercel-labs/emulate/agents-md"><img src="https://agentmods.dev/badge/instructions/vercel-labs/emulate/agents-md/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/instructions/vercel-labs/emulate/agents-md"><img src="https://agentmods.dev/badge/instructions/vercel-labs/emulate/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.01091 | $0.01091 |
| Opus 5.5 | $0.00436 | $0.00436 |
| Sonnet 5.5 | $0.00218 | $0.00218 |
| Haiku 4.5 | $0.00109 | $0.00109 |
Grade A, and why
emulate AGENTS.md 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 87 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Agents
Package Manager
Use pnpm for all package management commands (not npm or yarn).
Exception: End-user install instructions should use npm (e.g. npx emulate, npm install emulate) since npm is universal.
CLI Invocation
emulate is a zsh built-in command (it sets shell emulation mode). Running bare emulate in zsh invokes the shell built-in, not the npm binary. Always use npx emulate in user-facing CLI examples, docs, skills, help output, and post-command messages. The only exception is when emulate appears as a subprocess argument to another tool (e.g. portless github.emulate emulate start), where the binary is resolved by the parent process rather than the shell.
Dependencies
Always check for the latest npm version when adding dependencies. Use pnpm add <package> (without version) to get the latest, or verify with npm view <package> version first.
No Emojis
Do not use emojis anywhere in this repository (code, comments, output, docs).
Dashes
Never use -- as a dash in prose, comments, or user-facing output. Use an em dash (\u2014) when a dash is needed, but prefer rephrasing to avoid dashes entirely. The only exception is CLI flags (e.g. --port).
Emulator UI Design System
All emulator UIs (inspector pages, OAuth flows, checkout pages, inboxes, etc.) must use the shared design system in packages/@emulators/core/src/ui.ts. Never write inline HTML with custom <style> tags or standalone <!DOCTYPE html> templates in individual emulator packages.
Use the appropriate shared render function for each page type:
renderCardPagefor centered card layouts (OAuth sign-in, email detail, checkout)renderErrorPagefor error statesrenderSettingsPagefor sidebar + main content layouts (OAuth app settings, Slack inspector)renderInspectorPagefor tabbed data dashboards (AWS inspector)renderFormPostPagefor OAuthform_postauto-submit redirectsrenderUserButtonfor user selection buttons in OAuth flows
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.
- 1mo ago First seen · 87 lines · 1,091 tokens per session scan A b7f7b1e50d63
emulate AGENTS.md is an instructions file published in the GitHub repository vercel-labs/emulate (1,952 stars, last pushed today), licensed Apache-2.0. It adds 1,091 tokens to every session, about $0.0044 per session on Opus 5.5. 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
deepseek-harness AGENTS.md
AGENTS.md instructions for deepseek-ai/deepseek-harness, covering agents.md, pre-stable apis and released session data, repository layout, commands and host sandbox failures.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).