DeepSeek: Insufficient Balance (API 402)

DeepSeek's API platform is pay-as-you-go. When an API key's linked account runs out of credit, every subsequent API call returns HTTP 402 with this error. Unlike most API errors, a 402 should never be retried — the issue is purely account-side and retrying only confirms the depleted balance. This is a developer or API error only; users of the free chat.deepseek.com interface are not affected.