How to Call DeepSeek V4.1 Flash Before It Expires

DeepSeek quietly opened an experimental test window for V4.1 Flash on its official API. For about one dollar, you can run through roughly 58 million tokens — and it responds at up to 500+ tokens per second.

The endpoint is scheduled to stay live only until September 10th, so the window to test it is short.

Tutorial

1. Copy your API key from https://platform.deepseek.com/api_keys.
2. Set your base URL to https://api.deepseek.com.
3. Swap the model ID to deepseek-v4.1-flash-expires-on-0910. This test endpoint expires on September 10th.
4. Plug the key, base URL, and model ID into Claude Code, Cursor, or your agent harness.

Wrapping Up

Now you can route real prompts through DeepSeek V4.1 Flash and see what that token price gets you. Run your own benchmarks before September 10th, because the endpoint disappears when the test window closes.