fix(core): complete MCP discovery when configured servers are skipped

[LyalinDotCom]

Summary

Fixes an MCP readiness edge case that could block normal prompt execution indefinitely.

When configured MCP servers are all skipped during startup (for example, user-disabled or blocked), discovery could remain in IN_PROGRESS forever. The UI then kept queueing prompts behind "Waiting for MCP servers to initialize...".

Details

• Update startConfiguredMcpServers() in packages/core/src/tools/mcp-client-manager.ts:
  • after startup attempts complete, if no discovery promise exists, mark discovery as COMPLETED and emit mcp-client-update.
• Add regression coverage in packages/core/src/tools/mcp-client-manager.test.ts:
  • should mark discovery completed when all configured servers are user-disabled
  • should mark discovery completed when all configured servers are blocked

Behavioral flow:

before: configured servers -> IN_PROGRESS -> all skipped -> no discovery promise -> stuck IN_PROGRESS
after:  configured servers -> IN_PROGRESS -> all skipped -> no discovery promise -> COMPLETE + update event

Related Issues

Fixes #18585

How to Validate

1. Run focused MCP manager tests:
   • npm run test --workspace @google/gemini-cli-core -- src/tools/mcp-client-manager.test.ts
2. Run MCP-related core tests:
   • npm run test --workspace @google/gemini-cli-core -- src/tools/mcp-client.test.ts src/tools/mcp-tool.test.ts src/prompts/mcp-prompts.test.ts src/tools/xcode-mcp-fix-transport.test.ts src/code_assist/admin/mcpUtils.test.ts
3. Run CLI MCP readiness queue tests:
   • npm run test --workspace @google/gemini-cli -- src/ui/hooks/useMcpStatus.test.tsx src/ui/hooks/useMessageQueue.test.tsx
4. Run full core suite:
   • npm run test --workspace @google/gemini-cli-core

Expected result: all listed suites pass; when all configured MCP servers are skipped, discovery transitions to COMPLETED and prompts are not permanently queued.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello @LyalinDotCom, 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 resolves a critical bug that prevented the MCP discovery process from finalizing when all configured servers were intentionally bypassed. By ensuring that the system correctly transitions to a completed state under these conditions, it prevents the user interface from indefinitely waiting for initialization and unblocks prompt execution.

Highlights

• Fixes MCP discovery deadlock: Addresses an edge case where MCP discovery could remain 'IN_PROGRESS' indefinitely if all configured servers are skipped (e.g., user-disabled or blocked), leading to blocked prompt execution.
• Ensures discovery completion: Modifies 'startConfiguredMcpServers()' to explicitly set the discovery state to 'COMPLETED' and emit an 'mcp-client-update' event when no discovery promise is created, indicating all servers were skipped.
• Adds regression tests: Introduces new test cases in 'mcp-client-manager.test.ts' to verify correct discovery completion when all configured servers are user-disabled or blocked.

Changelog

• packages/core/src/tools/mcp-client-manager.test.ts
  • Added a test case to ensure discovery completes when all configured servers are user-disabled.
  • Added a test case to ensure discovery completes when all configured servers are blocked.
• packages/core/src/tools/mcp-client-manager.ts
  • Implemented logic within 'startConfiguredMcpServers' to check if 'discoveryPromise' was created. If not, it explicitly sets 'discoveryState' to 'COMPLETED' and emits an 'mcp-client-update' event.

Activity

• Fixes issue Prompts queue indefinitely when all configured MCP servers are skipped #18585.
• Added new regression tests to cover scenarios where all configured servers are user-disabled or blocked.
• Provided detailed validation steps for testing the fix, including running specific test suites.
• Validated the changes on MacOS using 'npm run'.

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[gemini-code-assist]

Code Review

This pull request correctly identifies and fixes an important edge case where MCP discovery could remain in an IN_PROGRESS state indefinitely if all configured servers are skipped on startup. The addition of regression tests is also a valuable contribution. The provided critical review comment with a suggested code change makes the logic more robust by checking the discovery state directly, which correctly handles all scenarios. With this change, the fix will be solid.

[github-actions]

Size Change: +210 B (0%)

Total Size: 24.3 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	24.3 MB	+210 B (0%)
./bundle/sandbox-macos-permissive-closed.sb	1.03 kB	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-closed.sb	3.29 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B

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