Changes from 0.1.x to 0.2.2 · modelcontextprotocol/ext-apps · Discussion #181

ochafik
Dec 18, 2025
Maintainer

Hi all! We've just pushed @modelcontextprotocol/ext-apps versions 0.2.0, 0.2.1 and 0.2.2 in quick succession, so here's what's changed since 0.1.x

Warning

The registerAppTool helper makes sure defining _meta.ui.resourceUri is backward-compatible w/ clients expecting "ui/resourceUri"

Server helpers — New registerAppTool() and registerAppResource() simplify server setup with proper type safety. connect() now defaults to PostMessageTransport(window.parent), enabling simpler initialization with just await app.connect() #165
Github warning:
Tool _meta key change: Restructured _meta format from flat "ui/resourceUri" to nested _meta.ui.resourceUri docs: add tool visibility and restructure _meta.ui #131
Tool visibility control — New visibility array field controls whether tools are visible to the agent, apps, or both. Restructured _meta format from flat "ui/resourceUri" to nested _meta.ui.resourceUri #131
Host-provided theming — Apps receive 36 standardized CSS variables for colors, typography, and spacing via styles.variables, enabling visual consistency with the host #127
Display mode requests — Apps can request display mode changes (e.g., fullscreen) via requestDisplayMode, with hosts able to accept or reject #152
Custom fonts support — Apps can receive custom fonts via styles.css.fonts and apply them using applyHostFonts() or useHostFonts() helpers #159

MCP SDK as peer dependency — Consumers control their SDK version, reducing duplication #168
React as peer dependency — Supports React 17, 18, and 19 #164
Renamed request methods — Removed send prefix: openLink() and teardownResource(). Deprecated aliases maintained #161
Optional Client in AppBridge — Enables custom forwarding scenarios without direct MCP client access #146
Zod v3 and v4 support — Bring your own Zod in #49
Zod schemas now version-agnostic — Generated schemas work with both Zod 3.25+ and v4, using z.object().passthrough() instead of v4-only z.looseObject() #178

Windows compatibility — Bun as optional dependency with automatic setup, cross-env for examples. Just run npm install #145
Widened @oven/bun-* version range — Lowered the minimum from ^1.3.4 to ^1.2.21, helping contributors whose registries may not have the latest packages #176
SSE transport support — All examples now support both stdio and HTTP transports with SSE endpoints for older clients #136
Playwright E2E tests — Screenshot golden testing across all 9 example servers with parallel execution (~28s) #115
hostContext exposure — Access hostContext directly from the App class #139

Responsive UIs — Fixed narrow viewport handling for mobile and sidebar experiences #135
Sandbox notification fix — Fixed sandbox-ready notification name to match implementation #160
Fixed non-UI tool registration — Use server.registerTool for tools without UI and fix missing imports across examples #173

Full Changelog: v0.1.1...v0.2.2