DEEPSEEK TELLS EVERY DEVELOPER USING ITS API: MIGRATE BY JULY 24 OR YOUR APPLICATION STOPS WORKING DeepSeek has set a hard deadline: July 24, 2026 at 15:59 UTC, the legacy API model names deepseek-chat and deepseek-reasoner will stop responding. No extension has been announced. For any developer running a production application on DeepSeek’s API without updating their code, that is the moment their product breaks. The migration path is technically straightforward. The base URL does not change. The API key does not change. Developers need to update one parameter, swapping the old model alias for the new name. deepseek-chat routes to deepseek-v4-pro and deepseek-reasoner routes to deepseek-v4-flash. Same setup, new string. The catch is in that second mapping. deepseek-reasoner was the heavy reasoning model. Its replacement alias deepseek-v4-flash is a lower-cost, lower-power tier. Any team that was using deepseek-reasoner for complex analysis work and assumes the migration is a like-for-like swap will end up on flash-tier reasoning at flash prices, which may not match what their application actually requires. Those teams should evaluate deepseek-v4-pro instead. With 15 days remaining and no grace period announced, the window for developers who have not already migrated is closing fast. This is not a suggestion. Keywords: DeepSeek API migration, deepseek-chat deprecated, DeepSeek V4 deadline July 24, deepseek developer update