Derived from Qwen/Qwen3-4B (hybrid thinking model). The chat template no longer strips <think> from prior assistant turns and the nonthinking branch is removed, so the generation prompt always opens <think> (like Qwen3-4B-Thinking-2507).

Thinking is always preserved across multi-turn history (append-only). Every assistant turn keeps its <think>...</think> reasoning, not just the latest one, and the generation prompt always opens <think> (passing enable_thinking=False has no effect). This makes multi-turn agent training match evaluation — the model always sees its own prior reasoning. Model weights are identical to Qwen/Qwen3-4B; only the chat template differs.