ctab

A Bun CLI + Chrome extension that captures the active tab in your everyday Chrome (real logins, real profiles — not headless, not CDP) and writes a PNG to disk. Built for feeding LLM coding agents a snapshot of what you're looking at.

See DECISIONS.md for the architecture rationale and rejected alternatives.

Quick start (no clone, via bunx)

Requires Bun 1.3+ and macOS.

bunx @httpete/ctab setup       # installs the extension files to ~/.ctab/extension/

Then in Chrome:

1. Open chrome://extensions.
2. Toggle Developer mode (top right).
3. Click Load unpacked and select ~/.ctab/extension/.

That's it. Now run:

bunx @httpete/ctab screenshot              # writes /tmp/ctab-<ms>.png, prints path
bunx @httpete/ctab screenshot ./shot.png   # writes to ./shot.png

For a shorter ctab invocation, see "Local install" below.

Local install (CLI on $PATH, plus optional Claude Code skill)

git clone https://github.com/pierregoutheraud/tabli && cd tabli
bun install

1. Build and load the extension

bun run build:ext

In Chrome → chrome://extensions → Developer mode → Load unpacked → select extension/dist/.

2. Get the ctab command on your $PATH

bun run install:cli

This builds a ~60MB self-contained binary and drops it in ~/.bun/bin/ctab (which Bun's installer already adds to your $PATH). No Bun needed at runtime after that. Re-run after code changes. To remove: bun run uninstall:cli.

If you'd rather symlink the source (skip the rebuild step on every change):

chmod +x cli/index.ts
ln -s "$PWD/cli/index.ts" ~/.bun/bin/ctab

3. Install the Claude Code skill (optional)

bun run install:skill

Symlinks skill/ to ~/.claude/skills/ctab/. After restarting Claude Code, prompts like "look at my current tab" or "what am I seeing right now?" will auto-trigger ctab screenshot and read the resulting PNG — no need to mention ctab by name. To remove: bun run uninstall:skill.

4. Install the /ctab slash command (optional)

bun run install:command

Symlinks commands/ctab.md to ~/.claude/commands/ctab.md. After restarting Claude Code, you can type /ctab why is this button misaligned? and Claude will capture the active tab and answer in one turn — handy when you want to explicitly attach your current tab to a prompt. Pairs well with the skill: skill for ambient ("look at my tab"), command for explicit (/ctab does this match the design?). To remove: bun run uninstall:command.

Usage

ctab screenshot                  # writes /tmp/ctab-<ms>.png, prints path
ctab screenshot ./shot.png       # writes to ./shot.png
ctab setup                       # install/refresh the bundled extension files
ctab help                        # show usage

Stdout: absolute path of the written PNG, single line. Errors go to stderr; exit 1 on failure.

Capture-and-open in one shot:

open (ctab screenshot)             # fish

open "$(ctab screenshot)"          # bash/zsh

Options

| | | |---|---| | Positional arg to screenshot | output path (default: /tmp/ctab-<unix-ms>.png) | | CTAB_PORT | override the localhost port (default: 47821) |

Limitations

• macOS only (Bun + MV3 work elsewhere; just untested).
• Cannot capture restricted pages: chrome://, devtools, Chrome Web Store, the PDF viewer, file://. Switch to a normal tab and retry.
• captureVisibleTab returns the viewport only — content below the fold is not captured. (Full-page capture is on the deferred list in DECISIONS.md.)
• If you run multiple Chrome profiles in parallel, install the extension in each. The CLI auto-picks the most recently focused profile.

Troubleshooting

No Chrome extension responded within 5s — Chrome isn't running, or the extension isn't loaded. Run ctab setup and load ~/.ctab/extension/ in chrome://extensions.

Cannot capture restricted page — switch to a normal https:// tab.

Port 47821 is in use — another ctab screenshot is mid-flight, or the port is taken. Wait a moment, or set CTAB_PORT.