From "What about data and privacy?" in FAQ it sounds like they don't host models themselves. e.g. it says:

  DeepSeek: ZDR agreement is renewed monthly. The current agreement is valid through October 31, 2026.
  https://opencode.ai/go

They also follow official DeepSeek API peak/off peak hour pricing and link to their docs:

  DeepSeek V4.1 Flash / V4 Pro: Peak hours are 01:00-04:00 and 06:00-10:00 UTC, Monday through Friday; all other hours, including weekends, are Off-Peak. Learn more.
  https://opencode.ai/v2/docs/console/go/#usage-limits

edit: they used to explicitly name the providers, at least in the past DeepSeek V4 was served with official API https://github.com/anomalyco/opencode/issues/24649#issuecomm...

Everyone wonders that.