Extension System
First-class extensions, not guests
Every editor in Nimbalyst uses the same EditorHost contract, whether it ships built-in or comes from a third-party extension. Register a file type, ship a real editor inside the workspace, and let agents talk to it through the same hooks the markdown editor uses.
Capabilities
What the extension system gives you
Same contract as built-in editors
Every editor uses the EditorHost contract. The markdown editor, the diagram editor, and a third-party extension all sit on the same foundation. There is no second-class tier for extensions.
Real editors, not side panels
Register a file type and ship a full editor inside the workspace, not a side panel or an embedded iframe. Your custom format gets the same treatment markdown does.
Shared agent hooks
Agents talk to your extension through the same structured hooks the built-in editors use. An agent that can edit markdown can edit your custom format too, with no special integration.
MCP tool integration
Expose MCP tools from your extension so agents can read and write your data. Tools register alongside the host's tools and show up in the agent's tool list automatically.
Heterogeneous agents
Claude Code and Codex are first-class agents. Other agents are pluggable at the host level. Your extension does not pick a vendor for the user.
Built for the long tail
Existing extensions cover an Astro website editor, a visual git log, a mindmap, a slides editor, and a 3D object editor. The model is built for the editors that do not exist yet.
How It Works
How a Nimbalyst extension works
Register a file type
Declare which file extensions your editor handles in the extension manifest. Nimbalyst routes matching files to your editor automatically.
Implement EditorHost
Your editor receives content from the host, marks itself dirty when the user edits, and saves through the host. The same contract applies to the markdown editor and the diagram editor.
Expose MCP tools
Define the tools agents can call to read and write your editor's data. Tools register alongside Nimbalyst's built-in tools.
Ship to the marketplace or sideload
Submit to the marketplace for distribution, or install a local build with the Extension Dev Kit and iterate with hot reload.