Delta

A small browser extension that adds power-user tools to the Claude web UI:

1. Copy any Claude response as Plain, Markdown, or Rich (HTML).
2. Branch from here — open a transcript of every turn up to and including a chosen Claude response, copy or download it, and paste it into a new chat to continue from that point.

The extension is content-script-only. No background pages, no remote services, no bundler.

Install — Chrome / Chromium

1. Download delta-chrome.zip from the latest release.
2. Unzip it somewhere permanent (the extension loads from this folder — don't delete it).
3. Visit chrome://extensions.
4. Toggle Developer mode (top right).
5. Click Load unpacked and pick the unzipped folder.
6. Open https://claude.ai/chat/... and reload the tab.

To update: download the new release, unzip over the existing folder, and click the refresh icon on the extension card.

Install — Firefox / Zen

Coming soon. Firefox requires Mozilla-signed .xpi files for stable distribution; once signed, the install path becomes a one-click .xpi download.

In the meantime, see Develop below for the temporary-add-on flow.

Permissions

The extension only runs on https://claude.ai/chat/*. It makes no outbound fetch calls to any host other than claude.ai (locked in by a test in tests/conversationClient.test.js).

Develop

npm install
npm test                    # vitest run
npm run build               # rebuilds dist/chrome/ and dist/firefox/
npm run package:chrome      # builds + zips dist/chrome/ into dist/delta-chrome.zip

There is no watcher — re-run npm run build after editing src/.

Project layout

src/            Runtime modules (ES modules, loaded via loader.js)
vendor/         Vendored Turndown + GFM tables (no npm install needed at runtime)
tests/          Vitest suites + captured API fixtures
scripts/        build.js — copies src + vendor + the right manifest into dist/<target>/
dist/chrome/    Loadable unpacked extension for Chrome
dist/firefox/   Loadable temporary add-on for Firefox / Zen

Load unpacked from source

For Chrome, follow the install steps above but pick dist/chrome/ after npm run build instead of an unzipped release.

For Firefox / Zen (temporary add-on, unloaded on browser quit):

1. npm run build
2. Visit about:debugging → This Firefox → Load Temporary Add-on…
3. Pick any file inside dist/firefox/ (Firefox loads the whole containing folder).
4. Open https://claude.ai/chat/... and reload the tab.

After editing source: rebuild, return to about:debugging, and click Reload on the extension's card.