fix: persist OAuth states to disk to survive server restarts #336
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OAuth authentication was failing with 'Invalid or expired OAuth state parameter' when the MCP server restarted during an OAuth flow. This happened because OAuth states were stored only in memory and lost on restart. Changes: - Add file-based persistence for OAuth states to ~/.google_workspace_mcp/oauth_states.json - Load persisted states on OAuth21SessionStore initialization - Clean up expired states on load - States now survive server restarts Fixes the common issue where users complete OAuth in browser but get an error because the server process was restarted (common in stdio MCP mode).
- OAuth callback server now starts on-demand, not at MCP startup - Uses random port from range 9876-9899 to avoid conflicts - Server auto-shuts down 2 seconds after successful auth - Eliminates port conflicts when running multiple opencode sessions
Follow XDG Base Directory Specification by storing credentials in ~/.config/google-workspace-mcp/ instead of ~/.google_workspace_mcp/. Also set default OAuth port to 9876 for consistency.
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Summary
OAuth authentication was failing with "Invalid or expired OAuth state parameter" when the MCP server restarted during an OAuth flow. This happened because OAuth states were stored only in memory (
self._oauth_statesdict) and lost on restart.This is a common issue in stdio MCP mode where the server process may restart between when the user clicks the auth link and when they complete the OAuth flow in the browser.
Changes
~/.google_workspace_mcp/oauth_states.jsonOAuth21SessionStoreinitializationTesting
Added 8 test cases in
tests/test_oauth_state_persistence.py:test_get_oauth_states_file_path_with_env_vartest_store_oauth_state_persists_to_disktest_load_oauth_states_from_disktest_expired_states_cleaned_on_loadtest_validate_and_consume_persists_deletiontest_state_survives_store_recreation(key test - simulates server restart)test_handles_missing_file_gracefullytest_handles_corrupted_file_gracefullyAll tests pass:
Backward Compatibility