mcp: update draft typings and announce mcp apps support #291654
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Implements https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx#client-host-capabilities Updates MCP typings to the latest draft to be able to specify that field.
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Pull request overview
This PR updates the MCP (Model Context Protocol) typings to the latest draft specification and adds support for announcing MCP apps capability. The primary changes include type refinements for better clarity, the addition of a lastUpdatedAt field to tasks, and the declaration of client support for the MCP UI extension.
Changes:
- Refined JSON-RPC response types by splitting
JSONRPCResponseintoJSONRPCResultResponseandJSONRPCErrorResponse, withJSONRPCResponsebecoming a union type - Added
lastUpdatedAtfield to theTaskinterface to track when tasks are last modified - Added
extensionsfield to client and server capabilities to support MCP protocol extensions, specifically announcing support forio.modelcontextprotocol/uiwithtext/html;profile=mcp-appMIME type - Enhanced type definitions with new interfaces for metadata objects (
MetaObject,RequestMetaObject) and specific error types (ParseError,InvalidRequestError,MethodNotFoundError,InvalidParamsError,InternalError) - Improved documentation throughout with extensive JSDoc comments and example references
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.
Show a summary per file
| File | Description |
|---|---|
| src/vs/workbench/contrib/mcp/common/modelContextProtocol.ts | Updated MCP protocol type definitions including refined JSON-RPC response types, new metadata and error interfaces, lastUpdatedAt field in Task interface, and extensions field in capabilities |
| src/vs/workbench/contrib/mcp/common/mcpServerRequestHandler.ts | Updated handler to use refined response types (JSONRPCResultResponse, JSONRPCErrorResponse), added defensive null checks for response IDs, and declared client support for io.modelcontextprotocol/ui extension |
| src/vs/workbench/contrib/mcp/common/mcpTaskManager.ts | Added lastUpdatedAt field initialization and updates in task creation and status change methods |
| src/vs/workbench/contrib/mcp/test/common/mcpServerRequestHandler.test.ts | Updated test assertions to use new JSONRPCResultResponse type and added lastUpdatedAt field to test task objects |
| src/vs/workbench/contrib/chat/browser/widget/chatContentParts/toolInvocationParts/chatMcpAppModel.ts | Updated error response construction to use new JSONRPCErrorResponse type |
bpasero
approved these changes
Jan 29, 2026
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Implements https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx#client-host-capabilities
Updates MCP typings to the latest draft to be able to specify that field.