transformers-config-tokenizers-expert

Preflight reference for HuggingFace snapshots — what vLLM, sglang, and transformers.generate see at runtime. Covers config-file precedence (tokenizer.json, tokenizer_config.json, generation_config.json, chat_template.jinja), transformers v5 tokenizer-class taxonomy (TokenizersBackend, PythonBackend, MistralCommonBackend, TikTokenTokenizer), special-token discovery (all_special_ids, added_tokens_decoder, extra_special_tokens, backend_tokenizer.get_added_tokens_decoder), chat-template Jinja contract (ImmutableSandboxedEnvironment, loopcontrols, raise_exception, strftime_now, tojson, add_generation_prompt), and engine knobs (skip_special_tokens, trust_request_chat_template, chat_template_kwargs allowlist, adjust_request, incremental detokenizer, EOS merge). Ships verified 2026 hall-of-shame for Kimi-K2.6, GLM-5.1, Gemma-4, Qwen3, DeepSeek-V3, plus drop-in Python for resolving markers to IDs, detecting turn-primer-as-EOS leaks, and cross-referencing tokenizer.json vs tokenizer_config.json.