Database query returns "Message does not exist" on macOS 15.7.4 (Intel) — v1.9.8 and v1.9.9

[PTH1021]

Environment:

• macOS: 15.7.4 Sequoia (Intel Mac, 2018 Mac Mini)
• BlueBubbles Server: 1.9.8 and 1.9.9 (auto-updates to 1.9.9)
• Private API: Not enabled (not needed for my use case)
• Full Disk Access: Granted to BlueBubbles

Problem:
API queries to /api/v1/message/query and /api/v1/chat/query return 404 errors with "Message does not exist" / "Chat does not exist", even though:

• Server info shows iMessage stats (39.4k messages detected)
• Database is accessible via command line (confirmed with sqlite3)
• Messages exist in ~/Library/Messages/chat.db (confirmed with direct SQL queries)
• Server shows "Helper Connected: false"

Error messages:

{"status":404,"message":"The requested resource was not found","error":{"type":"Database Error","message":"Message does not exist!"}}

What I've tried:

• Reset BlueBubbles app
• Complete reinstall (deleted app and all data)
• Downgraded to v1.9.8
• Restarted Mac
• Confirmed Full Disk Access permissions
• Confirmed no port conflicts
• Closed Messages app (IMDPersistenceAgent still holds database lock)

Database verification:

$ sqlite3 ~/Library/Messages/chat.db "SELECT COUNT(*) FROM message;"
515415

Database is readable and has data. BlueBubbles can see stats but cannot query individual messages.

Expected behavior:
API should return message/chat data for queries.

Actual behavior:
API returns 404 "does not exist" errors for all queries.