metamask-extension: Instructions file for Codex

AGENTS.md

metamask-extension AGENTS.md is an instructions file for Codex, OpenCode from MetaMask/metamask-extension. It costs 14,591 tokens per session, scanned C, original, no licence file.

A set of instructions for coding agents working in the MetaMask browser-extension repository. It points agents to the repository’s rules and setup guidance.

In plain words
What is it for?
Use it when asking an agent to inspect, modify, or set up the MetaMask extension codebase.
Why use it?
It gives agents the project-specific rules they need before changing code, reducing mistakes caused by missing repository context.

Instructions file for CodexOpenCode

Written for Codex and OpenCode: the file is AGENTS.md.

This is MetaMask/metamask-extension's own configuration. It tells Codex and OpenCode how to work on metamask-extension itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything metamask-extension configures →

Reuse

Borrowing it

Nothing to install: this file belongs to MetaMask/metamask-extension. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/MetaMask/metamask-extension/main/AGENTS.md
Clone the repo
git clone --depth 1 https://github.com/MetaMask/metamask-extension

Made for: Codex, OpenCode.

Wrote 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.

agentmods badge for metamask-extension AGENTS.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/metamask/metamask-extension/agents-md/github.svg)](https://agentmods.dev/instructions/metamask/metamask-extension/agents-md)
Your own site
<a href="https://agentmods.dev/instructions/metamask/metamask-extension/agents-md"><img src="https://agentmods.dev/badge/instructions/metamask/metamask-extension/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.

agentmods 80×15 button for metamask-extension AGENTS.md

Your own site · 80×15
<a href="https://agentmods.dev/instructions/metamask/metamask-extension/agents-md"><img src="https://agentmods.dev/badge/instructions/metamask/metamask-extension/agents-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 14,591 This file is loaded in full into every session.
When invoked 14,591 The same file — it is already loaded in full.
Security scan C 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown 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 5.1 $0.14591 $0.14591
Opus 5.5 $0.05836 $0.05836
Sonnet 5.5 $0.02918 $0.02918
Haiku 4.5 $0.01459 $0.01459

Measured 1mo ago against content hash 5f77e366feb1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade C, and why

metamask-extension AGENTS.md scanned grade C 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 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.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

rm -rf node_modules/ && yarn
AGENTS.md · 1,743 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

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. 1mo ago Changed · -13 lines · -83 tokens per session 5f77e366feb1
  2. 2mo ago First seen · 1,756 lines · 14,674 tokens per session scan C c4c6f3a2264e

Subscribe to this mod's changes

metamask-extension AGENTS.md is an instructions file published in the GitHub repository MetaMask/metamask-extension (13,247 stars, last pushed today), with no licence file. It adds 14,591 tokens to every session, about $0.0584 per session on Opus 5.5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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