Task tools (TaskCreate/TaskUpdate/...) permanently lost mid-session after /login — 'MCP server disconnected'

Summary

Built-in Task tools (TaskCreate/TaskUpdate/TaskList/TaskGet/TaskOutput/TaskStop) permanently disappear mid-session after running /login, with a misleading "MCP server disconnected" notice. They never reconnect for the lifetime of the session. Fresh sessions get them normally.

Environment

• Claude Code v2.1.216, macOS (darwin 25.5.0), Homebrew install
• Max subscription OAuth (interactive claude login)
• Also reproduced on Linux hosts (Ubuntu) across a fleet after credential/OAuth token changes mid-session

Steps to reproduce

1. Start an interactive session; observe TaskCreate/TaskGet/TaskList/TaskOutput/TaskStop/TaskUpdate present in the deferred tools list.
2. Run /login mid-session (re-authenticate).
3. A system notice appears: the Task tools are "no longer available (their MCP server disconnected)"; ToolSearch for them returns no match from then on.

Expected

Task tools survive re-auth, or reconnect after it — like the rest of the built-in toolset does.

Actual

Tools are gone until the session is restarted. Headless probe (claude -p) in a fresh session confirms the tools are available product-side, so this is purely a mid-session re-auth issue.

Impact

Long-lived agent sessions (tmux fleets) that undergo token refresh/re-login lose task tracking permanently; Stop hooks that require TaskCreate/TaskUpdate lock those agents into repeated enforcement blocks. TodoWrite is likewise absent in the affected session, so there is no todo tool at all after the drop.