Code Mode is an AI build agent inside LumaBrowser that turns a plain-English request into a real, installable extension. It plans the files, writes them with live syntax checking, then installs and activates the extension without a restart; so the thing you described is running before you finish reading the build log.
Code Mode is a build agent, not a snippet generator. You describe the outcome; it plans the files, writes them one at a time with validation, fixes its own mistakes, then installs the result live. Here is the full loop.
Open the Extensions panel and click the ✨ Vibe button, or pick the Code chat mode, then describe what you want in plain English.
The agent outlines the files it needs, manifest.js, main.js, and any optional UI or REST routes the feature calls for.
It writes each file while a build panel shows a live validation status dot per file: writing → valid, or flagged when a file has problems.
Generated code is syntax-checked as it is written. The agent fixes any errors it finds before moving on to the next file.
Once the files are clean, the agent installs and activates the extension live. No app restart and no manual file copying.
The extension is registered like any other. Its routes, tools, and panels are available the moment the build finishes.
Code Mode produces real LumaBrowser extensions, so it can target the same capabilities you would reach for by hand, all hot-loaded into the running browser. For the complete extension API and what each surface can do, see the Extensions guide.
Express routes mounted under the extension's prefix, callable from your own scripts, CI, or other tools.
Tools registered with the MCP aggregator so AI agents can call your extension directly.
New modes that show up in the chat mode picker alongside the built-in ones.
HTML panels and settings pages injected into the browser UI for configuration and interaction.
Namespaced handlers bridging the main and renderer processes for panel-driven actions.
Every surface above is wired up at install time and live immediately; the browser never restarts.
Under the hood, the build agent works through a small, focused set of tools against a sandboxed per-build workspace. You do not call these yourself, the agent does, but they explain exactly how a build comes together and gets cleaned up.
| Tool | What it does |
|---|---|
write_extension_file |
Create or overwrite a file in the workspace, validating its syntax as it is written. |
read_extension_file |
Read back a file the agent has already written so it can review or revise it. |
list_extension_files |
List the files currently in the build workspace to track progress against the plan. |
install_extension |
Validate the full set of files, then install and activate the extension live. |
discard_build |
Abandon the build and clean up the workspace, leaving nothing behind. |
Each build runs in its own sandboxed workspace, so a build in progress never touches your installed extensions until install_extension succeeds. If a build goes sideways, discard_build removes the workspace cleanly.
Built extensions are real files, not a black box. What Code Mode installs is a normal user extension on disk, identical in every way to one you wrote by hand. You can open it, edit it, and version it like any other code.
From the Extensions panel you can keep it, disable it, or permanently delete it whenever you like. First-party bundled extensions can only be disabled; but the ones you build with Code Mode are yours, so deleting is always an option.
Code Mode is built into LumaBrowser, free to download and run locally. Describe what you want, let the agent plan, write, validate, and install it live, then keep and edit the result like any other extension you own.