ext-apps 2.0.0 moves to the split TypeScript SDK 2.0 packages with breaking API changes

The official MCP Apps extension, ext-apps, released v2.0.0 on 2026-09-08. The release notes state that "ext-apps 2.0 moves to the MCP TypeScript SDK 2.0 split packages" and that "The MCP Apps wire protocol is unchanged." A cross-version interop test runs the published 1.7.5 against 2.0.0 in both directions, confirming 2.x Views still run in 1.x hosts and 2.x hosts still render 1.x Views.

The break is in dependencies and the TypeScript API. @modelcontextprotocol/sdk@^1 is replaced by a required @modelcontextprotocol/client@^2.0.0, since App and AppBridge extend its Protocol, an optional @modelcontextprotocol/server@^2.0.0 for the ./server helpers, and zod@^4.2.0 on Node.js 20+. zod 3 is no longer supported: the 1.x fallback for zod 3.25 is gone, though raw zod shapes passed to registerAppTool still work as a deprecated overload. setRequestHandler and setNotificationHandler are now keyed by method name rather than by schema, with the 1.x (Schema, handler) form kept as a deprecated overload slated for removal in 3.0.

Error handling changed too. Remote JSON-RPC errors now arrive as ProtocolError with a numeric code, while local failures are SdkError with a string code. The release notes list the resulting wire deltas: a handler-thrown -32002 now reaches the View as -32602, invalid params on ui/* methods move from -32603 to -32602, and the MCP error N: message prefix is gone.