DevSnoopDevSnoop

Installation

DevSnoop requires the Chrome extension, a local native host, and one skill file for your coding agent.

Install takes about 30 seconds on macOS or Linux. After that, Codex, Claude Code, Cursor, and other HTTP-capable agents can inspect pages, click UI, read console logs and network failures, and verify what changed in your real Chrome tab.

See the checkout debugging demo first
1

Install the Chrome Extension

Get the extension from the Chrome Web Store. It is the Chrome-side bridge; it still needs the native host in step 2 before your agent can call it.

Add to Chrome
2

Install the Native Host

The native host runs on your machine at 127.0.0.1:9400 and bridges your agent's HTTP requests to Chrome via Native Messaging. It's a self-contained binary — no Node, npm, or runtime needed.

bash
curl -fsSL https://devsnoop.com/install.sh | bash

What this does:

  1. 1. Detects your OS and architecture
  2. 2. Downloads the native host binary to ~/.devsnoop/devsnoop-host
  3. 3. Writes the native messaging manifest so Chrome can find the host
  4. 4. Downloads SKILL.md to ~/.devsnoop/
3

Configure Your Coding Agent

The install script downloads SKILL.md to ~/.devsnoop/. Copy or symlink it to your agent's skill/command location so it knows how to use DevSnoop.

Claude Code

Copy to your commands directory or add as a project skill:

cp ~/.devsnoop/SKILL.md ~/.claude/commands/devsnoop.md

Codex

Append to your project's AGENTS.md or pass as instructions:

cat ~/.devsnoop/SKILL.md >> AGENTS.md

Cursor

Add the file contents to your project's .cursorrules or reference it as context.

Other agents

Any agent that can make HTTP requests works — paste the contents of ~/.devsnoop/SKILL.md into your agent's system prompt or custom instructions.

Need project instructions too?

DevSnoop's SKILL.md teaches browser commands. Your repo still needs its own AGENTS.md so the agent follows your stack, naming, tests, and deploy rules. Generate a starting AGENTS.md with Stacknaut.

4

Verify It Works

Run ping from your terminal. Then start the preview in the extension popup and try one real browser command.

bash
curl -s -X POST http://127.0.0.1:9400/ \
  -H 'Content-Type: application/json' \
  -d '{"command":"ping","params":{}}'
response
{"ok":true,"result":{"pong":true,"timestamp":1718...,"version":"1.0.0"}}
bash
curl -s -X POST http://127.0.0.1:9400/ \
  -H 'Content-Type: application/json' \
  -d '{"command":"page_summary","params":{"depth":2}}'

If you see "pong": true, the extension and native host are connected. Start the 24h preview in the popup, then page_summary works before you buy.

5

Run One Useful Browser Check

The fastest proof is not another setup command. Ask your agent to click something that matters and explain what Chrome saw.

prompt
Use DevSnoop on the active Chrome tab.
Click the main checkout or signup button, then report:
- selector clicked
- console errors
- failed network requests
- whether the page changed visually

A good first report includes:

  • - the selector the agent acted on
  • - console errors and failed network requests
  • - a screenshot path or short visual-state note
  • - the next implementation step
See example report
6

Get a License

Purchase a license to activate DevSnoop. After checkout, you'll receive a license key to paste into the extension popup.

Purchase

What Gets Installed

Component Location Purpose
devsnoop-host~/.devsnoop/HTTP server + native messaging bridge
com.devsnoop.agent.jsonChrome NativeMessagingHosts/Tells Chrome where to find the host binary
SKILL.md~/.devsnoop/ Teaches coding agents all available commands (copy to your agent's config)

Platform Support

macOSApple Silicon (arm64), Intel (x64)
supported
Linuxx64, arm64
supported
Windows—
planned

Troubleshooting

"Connection failed" — ping returns nothing

  • - Make sure the Chrome extension is installed and enabled
  • - Open a page in Chrome (the extension needs at least one tab)
  • - Check that the native host binary exists at ~/.devsnoop/devsnoop-host
  • - Verify the manifest file is in the right location for your OS

"Permission needed" error

Click the DevSnoop extension icon in Chrome and grant access for the site you're inspecting. This is a one-time action per origin.

Extension installed but agent doesn't know commands

Make sure you've copied ~/.devsnoop/SKILL.md to your agent's config location (see step 3 above). Restart your coding agent after configuring.