Module json_mode 

JSON mode logits processor.

Constrains generation to produce valid JSON by tracking a state machine and masking tokens that would produce invalid syntax at each step.

Approach

Rather than full grammar-guided generation (which requires tokenizer-level mapping), this processor uses a lightweight state machine that tracks whether we’re inside a string, after a key, expecting a value, etc. It biases logits to favor JSON-structural tokens without fully preventing all invalid outputs.

For a production-quality implementation, this would need:

• Tokenizer integration to map token IDs to byte sequences
• Full JSON grammar with recursive descent validation
• Efficient bitset masking over the vocabulary

This MVP provides the infrastructure and demonstrates the pattern.

Structs

JsonModeProcessor

JSON mode logits processor.

Enums

JsonState

Tracks the current position in JSON structure.