How do you keep Google Workspace MCP tools (Gmail, Sheets, Drive, Calendar) reliably available across sessions?

I'm running Claude Code on Windows with 6 Google Workspace MCP server instances (different Gmail accounts).

Ideal outcome: Google MCP tools that just work every session without re-auth, and don't disappear mid-conversation.

Two recurring problems:

OAuth token expiry — After a few days, tools start returning auth errors and I need to restart the session and re-grant OAuth. Is there a way to use a Google Service Account instead of OAuth for MCP servers, so tokens never expire? I already have a service account working for Sheets API via scripts, but the MCP servers seem to require OAuth.
MCP tools disappear after context compaction — Mid-session, after the context window compresses, some or all MCP tools vanish and calls fail with "No such tool available". The only fix is restarting the session entirely. Is this a known issue? Any workarounds?

Thanks

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