MCP enabled but no registry servers or tools discovered (no registry UI)

从 Settings → Tools → MCP 开始，检查本地 mcp.json 配置和 MCP 刷新路径。使用文档中说明的、采用 registry-only 模式的 GitHub.com Copilot Business 设置，然后对比显示 0 个服务器和 0 个工具的刷新日志。配置的注册表中允许的服务器和工具能够在 MCP UI 中被发现，且没有 MCP 刷新错误，即表示完成。

Title
Copilot for Xcode: MCP enabled but always discovers 0 servers / 0 tools on GitHub.com (no registry UI)

Describe the bug
GitHub Copilot for Xcode shows MCP as enabled and triggers MCP refresh, but it never discovers any MCP servers or tools (Servers: 0, Total tools: 0). Our org has a private MCP registry configured in allow “registry-only” mode, with GitHub's MCP server in the allowlist. The same registry works on github.com browser Copilot chats and in other IDEs (VS Code, IntelliJ), but not in Copilot for Xcode.

In Settings → Tools → MCP:

• MCP is enabled
• “Available MCP Tools” is empty
• UI consistently reports “Servers: 0, Total tools: 0”

The only editable MCP configuration is a local mcp.json file (via “Edit Config”) containing a servers object. There is no UI to view/configure an MCP registry base URL for GitHub.com (non-GHES) accounts. Logs show refresh succeeds but results are always 0 servers / 0 tools, with no MCP errors.

Versions

• Copilot for Xcode: 0.46.0
• Xcode: 26.1.1 (17B100)
• macOS: 26.2 (Tahoe)

Steps to reproduce

1. Install Copilot for Xcode 0.46.0
2. Sign in with a GitHub.com Copilot Business account (non-GHES)
3. Open Copilot for Xcode Settings → Tools → MCP
4. Confirm MCP is enabled and “Available MCP Tools” is empty
5. Click “Edit Config”; observe default mcp.json contains "servers": {}
6. Enable Verbose Logging
7. Trigger an MCP refresh (activation or settings change)
8. Observe logs: refresh succeeds but servers/tools remain 0

Screenshots

• Tools → MCP showing MCP enabled and “Available MCP Tools” empty (“Servers: 0, Total tools: 0”)

• mcp.json opened via “Edit Config” showing "servers": {}

• Tools → Built-In showing built-in tools present (tools UI otherwise works)

Logs

Copilot policy updated: customAgent=true, mcp=true, subagent=true
Refreshing MCP server tools…
Refreshed MCP tools - Servers: 0, Total tools: 0, Server names: []

Additional context

• Occurs on GitHub.com Copilot Business (not GHES)
• No MCP-related errors/warnings during refresh; result is consistently 0 servers / 0 tools
• Logs also show an Apple Events permission error on activation: ‘Not authorized to send Apple events to System Events.’ (NSAppleScriptErrorNumber=-1743). seems unrelated