[BUG] Windows desktop: Microsoft 365 connector reports connected but its Outlook draft/write tools vanish across sessions for days; only disable/re-enable restores them

Environment

• Claude desktop app for Windows 2.9939.2.0 (Code tab), Windows 11 Pro build 26200
• claude.ai connector: Microsoft 365
• Claude Code 2.1.283 (WSL) on the same machine, for reference

What happens

• session_connectors_status reports the Microsoft 365 connector as connected with tool_count: 19.
• All 19 are search, read, calendar and Teams tools. The mail write tools (outlook_create_draft, outlook_update_draft and the reply-draft tools) are absent. ToolSearch with select:mcp__<connector-uuid>__outlook_create_draft returns "No matching deferred tools found", the same result as for a tool that never existed.
• Permissions are not the cause. In the same session, the connector's own get_granted_scopes returns Mail.ReadWrite and Mail.Send.
• It persists across brand-new sessions, both interactive and scheduled-task, for days, not minutes. The draft tool last worked 2026-09-07 and 2026-09-13; first seen missing 2026-09-14; missing again today, 2026-09-26.
• reconnect_session_connector cannot help: it only re-dials connectors whose status is failed, and this one reports connected.
• The only fix that works is disabling and re-enabling the connector (Settings → Connectors) and then starting a new session. It keeps recurring.

Impact

Scheduled tasks that stage Outlook drafts lose the tool without any signal, and the model cannot tell a dropped tool from a nonexistent one. We now run a daily canary just to detect it.

Expected

• A connector that reports connected exposes its full tool list, or reports a degraded state (e.g. expected vs exposed tool count).
• Reconnect (reconnect_session_connector / /mcp) re-queries tools/list for a server that reports connected, not only for one marked failed.

Related

• #38043: tools removed after a transient disconnect. Closed as a duplicate of #33779.
• #33779: reconnect should re-query tools/list. Closed as stale.
• #89469 (open): connector tools missing from the deferred index for minutes to hours after session start. This report differs: only a subset of one connector's tools is missing, it lasts for days across sessions, and it clears only after disable/re-enable.