fix: prevent disabled MCP servers from starting processes and show correct status

[roomote]

This PR fixes the issue where disabled MCP servers were still starting processes and showing incorrect status indicators in the UI. It also ensures that when MCP is globally disabled, all servers are immediately disconnected and prevented from starting.

Problem

• Disabled MCP servers were still attempting to start processes
• UI showed incorrect status indicators for disabled servers
• When "Enable MCP Servers" was unchecked globally, servers continued running until plugin reload
• Error messages and retry buttons were shown for disabled servers

Solution

When "Enable MCP Servers" is unchecked globally:

All MCP servers are now immediately disconnected and prevented from starting.

When individual MCP server toggle is set to off:

The individual MCP server is properly disabled and shows correct status.

Changes Made

Backend Changes

McpHub.ts

• Added isMcpEnabled() helper to centralize MCP enabled state checking
• Created createPlaceholderConnection() helper to eliminate duplicate code
• Modified connectToServer() to check both global MCP state and individual server disabled state
• Updated refreshAllConnections() to respect global MCP setting
• Enhanced toggleServerDisabled() to properly disconnect/reconnect servers
• Fixed type safety by allowing null client/transport in McpConnection type
• Added proper null checks throughout the codebase
• Only setup file watchers for enabled servers

webviewMessageHandler.ts

• Added logic to actively disconnect all running MCP servers when MCP is globally disabled
• Added error handling to server disconnection loop
• Servers automatically reconnect when MCP is re-enabled

Frontend Changes (McpView.tsx)

• Updated getStatusColor() to always show grey (--vscode-descriptionForeground) for disabled servers
• Modified UI to hide error messages and retry buttons for disabled servers
• Prevented expansion of disabled servers in the UI
• Added isExpandable computed property to centralize expansion logic
• Updated cursor and chevron display logic for disabled servers

Test Coverage (McpHub.spec.ts)

• Added comprehensive tests for toggling global MCP enabled state while servers are active
• Added tests for handling refreshAllConnections() when MCP is disabled
• Added tests for skipping connection restart when MCP is disabled
• Added tests to verify servers don't start when MCP is globally disabled
• Added tests for toggling individual server disabled state
• Added edge case tests for various scenarios

Result

• Disabled servers no longer attempt to start processes
• UI shows a clear grey status indicator for disabled servers
• No misleading error messages or retry buttons are shown for disabled servers
• Servers are immediately disconnected when MCP is globally disabled
• The full configuration (including disabled servers) is maintained in the mcp.json file for user management
• Improved code maintainability with helper functions and better type safety

Fixes #6036

Co-authored-by: Hannes Rudolph [email protected]

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Important

Fixes MCP server management to prevent disabled servers from starting and updates UI to reflect correct status.

• Behavior:
  • Disabled MCP servers no longer start processes and show correct status in UI.
  • Global MCP disable immediately disconnects all servers.
  • UI hides error messages and retry buttons for disabled servers.
• Backend Changes:
  • McpHub.ts: Added isMcpEnabled() and createPlaceholderConnection() helpers.
  • Updated connectToServer() and refreshAllConnections() to respect global MCP state.
  • Enhanced toggleServerDisabled() to handle server state changes.
• Frontend Changes:
  • McpView.tsx: Updated getStatusColor() to show grey for disabled servers.
  • Prevented expansion of disabled servers in UI.
  • Added isExpandable property for server expansion logic.
• Test Coverage:
  • Added tests for global MCP state toggling and server state handling in McpHub.spec.ts.

^{This description was created by for 7485066. You can customize this summary. It will automatically update as commits are pushed.}

[ellipsis-dev]

The handleMcpEnabledChange method cleanly disconnects all servers when MCP is globally disabled and then refreshes connections. However, inline fallback strings (using the || operator) in translation calls should be removed to adhere to i18n best practices.

^{This comment was generated because it violated a code review rule: irule_C0ez7Rji6ANcGkkX.}

[daniel-lxs]

LGTM