DeepSeek official API via OpenAI-compatible mode: old conversation shows “Sorry, no response was returned.”, retry/continue often reproduces, new chat works Environment

**Environment**
Visual Studio Code Version: 1.137.0

API mode: OpenAI-compatible (OAI)

Provider: DeepSeek official API

Model: [deepseek-chat / deepseek-reasoner]

Streaming: [true/false]

OS / version / network: [fill]

Repro rate: ~80–100% on retry/continue in the affected chat; new chat works normally

**Steps to reproduce**
Start a new chat and have a multi-turn conversation.

After some response, the client shows: Sorry, no response was returned.

Without starting a new chat, click retry or send the next message.

The same error appears with high probability.

Start a new chat with the same key, model, and network; it works normally.