fix(reasoning): force-open poolside_v1 on bare </think> - #49728
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Poolside Laguna emits chain-of-thought then a literal </think> with no opening <think> (force-opened block). The poolside_v1 parser previously subclassed DeepSeekV3ReasoningParser, which only installs the DeepSeek R1 force-open path when chat_template_kwargs.thinking/enable_thinking is True and otherwise falls back to IdentityReasoningParser. That Identity fallback leaked CoT and the bare close tag into content with an empty reasoning channel. Subclass DeepSeekR1ReasoningParser directly so force-open is always on, and keep the assistant-turn-scoped is_reasoning_end walk so a stray </think> in prior conversation history does not short-circuit streaming. Adds unit tests covering force-open non-stream/stream without thinking kwargs and the scoped is_reasoning_end behavior.
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Summary
Poolside Laguna force-opens the thinking block: the model emits chain-of-thought then a literal
</think>with no opening<think>. The stockpoolside_v1reasoning parser previously subclassedDeepSeekV3ReasoningParser, which only installs the DeepSeek R1 force-open path whenchat_template_kwargs.thinking/enable_thinkingis True and otherwise falls back toIdentityReasoningParser(passthrough). With that Identity fallback, CoT and a bare</think>land incontentand the reasoning channel stays empty.This change subclasses
DeepSeekR1ReasoningParserdirectly so force-open is always on (same semantics as--reasoning-format deepseekon the llama.cpp side), and keeps the assistant-turn-scopedis_reasoning_endwalk so a stray</think>in prior conversation history does not short-circuit the streaming path.Related discussion class: #49379 (force-open / asymmetric
</think>handling for poolside).Changes
vllm/reasoning/poolside_v1_reasoning_parser.py: inherit fromDeepSeekR1ReasoningParser; drop the DeepSeekV3 / Identity delegation path; keep<assistant>-scopedis_reasoning_end.tests/reasoning/test_poolside_v1_reasoning_parser.py: force-open non-stream + streaming without thinking kwargs; scopedis_reasoning_end; fail-loud on missing<assistant>token.Test plan
thinkingkwargsis_reasoning_endignores a prior-turn</think>reason...</think>answer-> reasoning=reason..., content=answer