> For the complete documentation index, see [llms.txt](https://docs.nimbalyst.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.nimbalyst.com/extensions/extension-system-and-marketplace.md).

# Extension System & Marketplace

Install Nimbalyst extensions from the marketplace registry to add editors, AI tools, and panels, or publish an extension you built yourself.

This page explains what Nimbalyst extensions are, how to install and manage them from the built-in Marketplace, and where to start if you want to build your own. It is written for anyone using Nimbalyst; no development experience is needed until the final section.

The full list of published extensions, with screenshots, is at [nimbalyst.com/extensions](https://nimbalyst.com/extensions/).

## What Are Extensions?

Extensions are add-ons that give Nimbalyst new capabilities. Each extension can add custom editors for new file types, AI tools that let your agent interact with your content, sidebar panels, settings pages, themes, keyboard shortcuts, and more.

Extensions work seamlessly alongside Nimbalyst's built-in editors. When you open a file, Nimbalyst checks whether any extension handles that file type and loads the right editor automatically. Extensions have full access to Nimbalyst's theming system, so they always match your current look and feel.

## Browsing the Marketplace

Go to **Settings > Extensions > Marketplace** to browse and install extensions.

<figure><img src="https://562749618-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FiVUeHZHlFlZrZt02syRC%2Fuploads%2Fgit-blob-55af2eb57e5f333f3dc88d926c63d7118a759b19%2Fdocs-marketplace-discover.png?alt=media" alt="Extension Marketplace showing featured extensions and category filters"><figcaption><p>The Extension Marketplace in Settings, with a search box, category filters, and featured extension cards such as CSV Spreadsheet, DatamodelLM, Excalidraw, and MockupLM.</p></figcaption></figure>

Click any extension card to see its full details, screenshots, permissions, and install button.

<figure><img src="https://562749618-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FiVUeHZHlFlZrZt02syRC%2Fuploads%2Fgit-blob-21600c4395a3c15ec84ef257a44653e05b93087c%2Fdocs-marketplace-detail.png?alt=media" alt="Extension detail modal showing description, screenshots, and install button"><figcaption><p>The detail view for the CSV Spreadsheet extension, showing its description, feature highlights, a screenshot, and the version number.</p></figcaption></figure>

### What's in the catalog

The catalog is updated as extensions are released, so use the Marketplace for the current list, versions, screenshots, and permissions. Recent additions include:

* **Electronics Studio**: work with tscircuit and Circuit JSON in schematic, PCB, assembly, and 3D views, run simulations, and export manufacturing and review artifacts.
* **Replicad CAD**: build parametric 3D models in TypeScript with a live B-rep preview, STEP import and export, geometry inspection, and printability tools.
* **Media Viewer**: open and play `.mp4` files in a tab, including scrubbing through long recordings.

Marketplace cards show whether an extension is installed and whether an update is available.

### Managing Installed Extensions

View all installed extensions under **Settings > Extensions > Installed**. This is the single panel for everything you have installed. Marketplace, GitHub, local dev, and built-in extensions all show up here, each with a source pill so you can tell them apart at a glance.

<figure><img src="https://562749618-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FiVUeHZHlFlZrZt02syRC%2Fuploads%2Fgit-blob-ed6c417884faeec78d98c2c2f1b9cf2c2578a108%2Fdocs-extensions-installed.png?alt=media" alt="Installed Extensions panel showing all active extensions with details"><figcaption><p>The Installed Extensions panel, with the extension list and enable toggles on the left and the selected extension's plugin, contributed AI tools, and permissions on the right.</p></figcaption></figure>

Each row has an enable toggle and an indicator if an update is available. Click an extension to open the detail pane, which includes its AI tools, permissions, file path, and **Update**, **Repository**, **Reveal**, and **Uninstall** actions.

The Marketplace page itself only shows the Discover catalog. An **Installed** button at the top of the page shows your install count and any pending updates, and takes you to the Installed panel.

### Themes from Extensions

Extensions can ship themes. Any theme contributed by an installed extension shows up under **Settings > Application > Themes** in an **Extension Themes** group, and in the gutter theme popup, alongside the built-in themes. Pick one and Nimbalyst applies it just like a first-party theme.

If you later disable or uninstall the extension that provided the active theme, Nimbalyst falls back gracefully so your workspace stays usable.

### Installing from GitHub

At the bottom of the Marketplace discover page, you can paste a GitHub repository URL to install any extension directly from source. The repository must contain a valid `manifest.json` file.

## Build Your Own Extensions

Extensions are self-contained packages that declare their file types, editors, and UI contributions via a manifest. You can build extensions that do everything the built-in ones do.

**What you can build:**

* **Custom editors** for any file type (spreadsheets, diagrams, visual tools)
* **AI tools** that Claude can use to read and modify your editor's content
* **Panels** for sidebar views, fullscreen modes, or floating windows
* **Application or Project settings pages** with project-aware context
* **Project filesystem access** for editors that manage related files
* **Typed tracker item pickers and live references**
* **Themes, slash commands, file icons, and new file templates**

**How development works:**

* The **Extension Dev Kit** (bundled with Nimbalyst) scaffolds a new extension project with a starter template, hot reload, and MCP tools for build, install, and reload from inside Nimbalyst.
* Editors integrate through the **EditorHost contract** (load/save, dirty state, theme, external change handling) so custom editors behave exactly like first-party ones.
* The full **Extension SDK** provides clipboard access, screenshot export, AI and network permissions, and the same MCP tooling that first-party extensions use.

For full technical documentation on building extensions, see [Building Your Own Extensions](/extensions/building-extensions.md).


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