In rowboat OAuth mode the OAuth2Client is built without a refresh_token
because refreshes go through the api. google-auth-library's default
5-minute eagerRefreshThresholdMillis caused it to attempt a refresh
whenever a Gmail call landed within 5 minutes of token expiry, throwing
"No refresh token is set." before our proactive 60s-margin refresh
could run. Disabling the eager window lets our getClient() refresh path
own all refreshes as the comment intends.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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