dev-browser lets coding agents control a Chrome browser with JavaScript while keeping pages and tabs available between calls. Agents use it to navigate websites, inspect accessible page structures, perform actions, and verify results.
Borrowing it
Nothing to install: this file belongs to SawyerHood/dev-browser. 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/SawyerHood/dev-browser/main/AGENTS.mdgit clone --depth 1 https://github.com/SawyerHood/dev-browserWrote 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/sawyerhood/dev-browser/agents-md)<a href="https://agentmods.dev/instructions/sawyerhood/dev-browser/agents-md"><img src="https://agentmods.dev/badge/instructions/sawyerhood/dev-browser/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/sawyerhood/dev-browser/agents-md"><img src="https://agentmods.dev/badge/instructions/sawyerhood/dev-browser/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 | $0.00209 | $0.00209 |
| Opus 5.5 | $0.00084 | $0.00084 |
| Sonnet 5.5 | $0.00042 | $0.00042 |
| Haiku 4.5 | $0.00021 | $0.00021 |
Grade A, and why
dev-browser 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.
What it actually says
Repository guide
This repository ships dev-browser, a Bun-compiled browser automation CLI and warm daemon built on Puppeteer.
Tooling
- Use Bun for dependency installation, builds, tests, and TypeScript tooling. Do not use pnpm.
- The npm package contains a small Node-compatible shim and download scripts; test those under Node as well as Bun.
docs/help.mdis embedded into the binary and is the source of truth fordev-browser --help.
Validation
Run before finishing runtime changes:
bun install --frozen-lockfile
bun x tsc --noEmit
bun run build
bun run test
For packaging or release changes, also run:
npm pack --dry-run
dist/dev-browser --version
dist/dev-browser --help | head -n 1
Tests that launch Chrome should set DEV_BROWSER_HOME to a temporary directory. Never point tests at a user's real
~/.dev-browser/v1 state.
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 Changed · +3 lines · -38 tokens per session 9deb4c9c6b0d
- 1mo ago First seen · 29 lines · 247 tokens per session scan A 87b2b779bf0f
dev-browser AGENTS.md is an instructions file published in the GitHub repository SawyerHood/dev-browser (6,701 stars, last pushed 8d ago), licensed MIT. It adds 209 tokens to every session, about $0.0008 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.
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