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 agentmods add instructions/facebook/lexical/agents-mdgit clone --depth 1 https://github.com/facebook/lexicalWhat 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 | $0.04615 | $0.04615 |
| Opus 5 | $0.02308 | $0.02308 |
| Sonnet 5 | $0.00923 | $0.00923 |
| Haiku 4.5 | $0.00462 | $0.00462 |
Grade A, and why
lexical 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 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.
How it starts
The opening of the file, as written. The whole thing — 365 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Lexical Agent Guide
This file provides detailed guidance for AI agents and automated tools working with the Lexical codebase.
Build, Test, and Development Commands
Building
pnpm run build- Build all packages in development modepnpm run build-prod- Clean and build all packages in production modepnpm run build-release- Build production release with error codespnpm run build-types- Build TypeScript type definitions and validate them
Testing
pnpm run test-unit- Run all unit tests (Vitest, jsdom)pnpm run test-unit-watch- Run unit tests in watch modepnpm run test-browser- Run browser-mode unit tests (Vitest + Playwright, real browser)pnpm run test-browser-watch- Run browser-mode tests in watch modepnpm run test-e2e-chromium- Run E2E tests in Chromium (requires dev server running)pnpm run test-e2e-firefox- Run E2E tests in Firefoxpnpm run test-e2e-webkit- Run E2E tests in WebKitpnpm run debug-test-e2e-chromium- Run E2E tests in debug mode (headed)pnpm run debug-test-unit- Debug unit tests with inspector
For E2E testing workflow:
- Start the dev server:
pnpm run start(orpnpm run devif you don't need collab) - In another terminal:
pnpm run test-e2e-chromium
Development Servers
pnpm run start- Start playground dev server + collab server (http://localhost:3000)pnpm run dev- Start only the playground dev server (no collab)pnpm run start:website- Start Docusaurus website (http://localhost:3001)pnpm run collab- Start collab server on localhost:1234
Code Quality
pnpm run lint- Run ESLint on all filespnpm run lint:fix- Auto-fix lint issuespnpm run prettier- Check code formattingpnpm run prettier:fix- Auto-fix formatting issuespnpm run flow- Run Flow type checkerpnpm run tsc- Run TypeScript compilerpnpm run ci-check- Run all checks (TypeScript, Flow, Prettier, ESLint)
Never commit changes to scripts/error-codes/codes.json.
That edit is not yours to make — revert it to the state of
main before staging, and never git add the file.
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.
- 2d ago First seen · 365 lines · 4,615 tokens per session scan A ee9826bd5cf3
lexical AGENTS.md is an instructions file published in the GitHub repository facebook/lexical (23,823 stars, last pushed today), licensed MIT. It adds 4,615 tokens to every session, about $0.0231 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.
Other instructions, from other repositories
codex AGENTS.md
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next.js 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, applying the notice (cutover) and fallback chain (never fail the build).
spec-kit AGENTS.md
AGENTS.md instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
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.