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/fschrhunt/zenagent/agents-mdgit clone --depth 1 https://github.com/fschrhunt/zenAgentWhat 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 | $0.01276 | $0.01276 |
| Opus 5 | $0.00638 | $0.00638 |
| Sonnet 5 | $0.00255 | $0.00255 |
| Haiku 4.5 | $0.00128 | $0.00128 |
Grade A, and why
zenAgent 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 — 113 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AGENTS.md
Working rules for coding agents in this repository. Read .context/todo.md for what to build next and docs/adr/0001-browser-transport.md for why the architecture is what it is.
The product invariants come first
Zen Agent drives a browser the user is actively working in. These are not preferences; a change that breaks one of them is a bug even if every test passes:
- Never focus a Zen window, select a tab, or switch the visible Space as a
side effect.
browsingContext.activateandtabs.update({active: true})are the two calls that violate this most easily. The spike keepsactivatearound only as a positive control. - Look before you open. Discover windows, Spaces, and tabs before deciding to create one.
- Address tabs by stable ID, never by whichever tab happens to be active.
- Keep browser policy in one shared daemon. MCP is the browser automation surface; the CLI is limited to setup, configuration, and diagnostics.
- Fail loudly on ambiguity. Return an explicit ambiguity or unsupported-capability error rather than falling back to something that might disturb the browser.
- Model what you do not know. Use the
Observation<T>three-wayknown/unknown/unsupportedfromsrc/browser/model.tsinstead of inventing a value. Selected and focused state is observable only when the privileged transport reports the corresponding named capability; otherwise it must remain anObservationofunknownorunsupported. - Keep page content out of logs by default — URLs, titles, form values, cookies, and tokens included.
Commands
npm run check # format:check, lint, typecheck, test, build — the CI gate
npm test # vitest, no browser required
npm run dev -- --help # run the CLI from source via tsx
npm run build # tsc to dist/
npm run check is exactly what CI runs. Run it before opening a pull request.
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 · 113 lines · 1,276 tokens per session scan A 0b366a96c5c4
zenAgent AGENTS.md is an instructions file published in the GitHub repository fschrhunt/zenAgent (0 stars, last pushed 23d ago), licensed MIT. It adds 1,276 tokens to every session, about $0.0064 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 2026-08-31.
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).
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.
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
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.
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).
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.