[BUG] iMessage MCP tools fail with "Cannot access Messages database" despite Full Disk Access being granted

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The read_imessages, get_unread_imessages, and likely other iMessage MCP tools always return an error stating Full Disk Access is needed, even when it has been properly granted and Claude has been restarted.

What Should Happen?

The iMessage tools should read from chat.db successfully when Full Disk Access is granted.

Error Messages/Logs

Error: "Cannot access Messages database"

Evidence that this is a permissions issue with the MCP tool (not a real permission problem):
- Full Disk Access is enabled for Claude in System Settings
- Running `sqlite3 ~/Library/Messages/chat.db "SELECT COUNT(*) FROM message;"` via Bash tool succeeds and returns results (300k+ messages)
- This proves the Claude process has database access
- The MCP tool's internal permission check is incorrectly failing

Steps to Reproduce

1. Grant Full Disk Access to Claude in System Settings > Privacy & Security > Full Disk Access
2. 2. Ensure chat.db database file exists at ~/Library/Messages/chat.db
3. 3. Call read_imessages or get_unread_imessages MCP tool
4. 4. Tool returns "Cannot access Messages database" error

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

latest

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_Likely cause: The MCP server is checking permissions in a way that doesn't reflect the actual access level of the process (e.g., a pre-flight check that's too strict, or running in a subprocess that doesn't inherit FDA).

Environment: macOS Darwin 24.6.0, Claude Code with iMessage MCP server_