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DeepSeek V4 Flash 0731 uses a pre-tokenizer regex shared by DeepSeek V3, Hunyuan Dense, and JoyAI presets. No custom path means falling through to std::regex. Long letter runs send libstdc++ into recursive backtracking. Large tool output can pile up tens of thousands of frames and blow a server thread's stack before inference gets a shot. Route this exact regex through a non-recursive scanner. Keep Unicode property handling and number groups from earlier passes intact. Check short inputs against std::regex, then hammer custom path with 128 KiB letter runs. DeepSeek V4 Flash 0731 produces identical 8,624 token IDs for a 17,368-byte corpus before and after this change. Patched 51,294-, 51,295-, and 131,072-byte runs finish without a crash. Signed-off-by: Lance Yang <lance.yang@linux.dev>
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Issue: #26965 |
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August 13, 2026 02:32
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Overview
DeepSeek V4 Flash 0731 shares a pre-tokenizer regex with the DeepSeek V3, Hunyuan Dense, and JoyAI presets. Without a custom implementation, it falls back to
std::regex.Long letter runs can trigger recursive backtracking in libstdc++, accumulating tens of thousands of stack frames and crashing a server thread before inference starts.
This change routes the exact regex through a non-recursive scanner while preserving Unicode property handling and number grouping from earlier passes.
Additional information
Validation performed:
std::regex.Requirements