Status: prototype (PR #7625). Shareable design asset for review.
SentencePieceTokenizer.CreateFromTokenizerJson loads Hugging Face JSON-only Unigram tokenizers. HF tokenizer.json declares how special tokens wrap an encoded sequence in a post_processor block. The library has no post-processing abstraction today; SentencePiece only supports a single BOS + single EOS via the addBeginningOfSentence / addEndOfSentence switches. That cannot represent common real-world templates.