Fix guided generation: include <|endoftext|> as stop token#117
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…xt|> Two fixes for the same bug (defense in depth): 1. When the grammar session terminates (isTerminated), return nil immediately instead of emitting the terminal token's decoded text. This prevents ANY special token from leaking into structured output, regardless of whether it's in the stop sequences list. 2. Add 'endoftext' to turnEndPatterns so <|endoftext|> (token 151643) is picked up from added_tokens_decoder as an additional stop token. Qwen3 declares eos_token as <|im_end|> (151645) but xgrammar can also produce <|endoftext|> as a valid grammar terminal.
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Qwen3 models declare
eos_tokenas<|im_end|>(151645) but the grammar (xgrammar) can also produce<|endoftext|>(151643) as a valid terminal. Since 151643 wasn't in the stop sequences, it passed through to the output as literal text, corrupting structured generation results.Add 'endoftext' to the turnEndPatterns so it's picked up from
added_tokens_decoderalongsideim_end,end_of_turn, andeot_id.