2.1.0

Released 2026-11-09.

Readers, coding agents, and the AI assistant can now save a component with their own args, and every reader sees it next to the built previews. Components and patterns above 4.5 MB now publish.

New

Custom previews

• A signed-in registry member can save a custom preview: a component rendered with their own args. It appears in the preview picker next to the built previews. See Custom previews.
• Create on a component page opens an editor with the args of the selected preview. The editor has a live preview, a Form view with one control per property (object, array, and union properties included), and a JSON view that checks the args as you type.
• A republished component does not break a custom preview. Each read reports unknown properties, missing required properties, and type mismatches. At render time, a missing required property gets its default value.
• Only the author or an administrator can change or delete a custom preview.
• The registry renders custom previews in a sandboxed frame, from a render shell that the build emits.

MCP and the assistant

• Five registry-only MCP tools: handoff_list_custom_previews, handoff_get_custom_preview, handoff_create_custom_preview, handoff_update_custom_preview, handoff_delete_custom_preview.
• In a registry, handoff_get_component also returns argsSchema and customPreviews.
• The AI assistant can create and change custom previews for the signed-in reader. In the editor, it changes the open preview, and the editor offers to load the change.

Access tokens

• New previews:write scope: read, plus save custom previews, without publish rights. Any member can create such a token. See Accounts and access.

Publishing

• publish sends components and patterns above 4.5 MB by uploading the largest artifacts as blobs first. Against an older registry, publish still stops at 4.5 MB.
• The registry deletes blobs and artifact rows that nothing uses.

Documentation app

• Redesigned preview card: the component code sits behind View Code, with GitHub code colors and dark mode.
• A preview shows a loading spinner while its frame loads.
• Previews of element components (the default type) are centered on a transparent background. A toolbar button shows the page background, and the app remembers the choice. block components keep the full-width layout.
• The type field suggests element and block in your editor, and still accepts any value.
• CSF stories keep the options of select and radio controls. A component imported from another file gets its property types from that file.

Breaking changes

None.

Upgrade

1. Install handoff-app@2.1.0.
2. Run db:migrate against the registry database. It adds the component_custom_previews table.
3. Rebuild and redeploy the registry.
4. Republish your components. A component published before 2.1.0 has no render shell, so Create stays disabled for it.