fix(core): handle non-compliant mcpbridge responses from Xcode 26.3#18376
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Summary of ChangesHello @peterfriese, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request addresses a compatibility issue with Xcode 26.3's Highlights
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Code Review
This pull request introduces a fix for non-compliant responses from Xcode's mcpbridge by wrapping the transport and parsing the content to populate the missing structuredContent field. The approach is well-isolated and includes good unit test coverage. My review includes a suggestion to improve encapsulation and type safety by avoiding the use of an any cast to access a private property, which will make the code more maintainable.
| extends EventEmitter | ||
| implements Transport | ||
| { | ||
| constructor(private readonly transport: Transport) { |
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To improve encapsulation and type safety, consider making the transport property public. The mcp-client.ts file needs to access this property to attach a debug listener to the underlying transport's stderr. Making it public allows for direct, type-safe access from the consuming module and avoids the use of any casting, which makes the code more robust and maintainable.
| constructor(private readonly transport: Transport) { | |
| constructor(public readonly transport: Transport) { |
| const underlyingTransport = | ||
| transport instanceof XcodeMcpBridgeFixTransport | ||
| ? // eslint-disable-next-line @typescript-eslint/no-explicit-any | ||
| (transport as any).transport | ||
| : transport; |
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Following the change to make XcodeMcpBridgeFixTransport.transport public, this logic can be simplified to access the property directly. This removes the need for an any cast and the associated eslint-disable comment, leading to more maintainable and type-safe code.
const underlyingTransport =
transport instanceof XcodeMcpBridgeFixTransport
? transport.transport
: transport;
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Summary
Provides a fix for #18371
Details
Xcode 26.3's
xcrun mcpbridgereturns tool results as an unparsed JSON string within thecontentfield, failing to provide the expectedstructuredContent. This behavior breaks strict MCP clients likegemini-cli.This PR introduces XcodeMcpBridgeFixTransport, a transport wrapper that intercepts JSON-RPC messages from the Xcode bridge. It detects responses with missing
structuredContentand attempts to parse thecontentstring as JSON to backfill the missing field.Key Changes:
xcrunand arguments includemcpbridge.Related Issues
Fixes #18371
How to Validate
Unit Tests:
Run the new test suite to verify the fix logic:
npm test packages/core/src/tools/xcode-mcp-fix-transport.test.tsLive Verification (MacOS with Xcode 26.3+):
HelloWorld).Pre-Merge Checklist
(Note: this is only relevant on macOS, since it's not possible to run Xcode on any other platform).