Struct ConstraintDecoder 

pub struct ConstraintDecoder { /* private fields */ }

The Constraint Decoder - makes forbidden tokens PHYSICALLY IMPOSSIBLE

This is not a filter. This is not a guard. This modifies the REALITY of what the model can produce.

Implementations

impl ConstraintDecoder

pub fn new(rules: &[String], vocab_size: usize) -> Self

Create a new constraint decoder from sealed rules

The forbidden space is computed ONCE at initialization. This is the “hard-wiring” - baked into the system.

pub fn apply_constraints(&self, logits: &mut [f32])

Apply constraints to logits - THE CORE OF DIAMOND

This is where the magic happens:

• Forbidden tokens get logit = -∞
• After softmax: P(forbidden) = 0.0
• The model CANNOT generate these tokens

Before:  [0.2, 0.3, 0.5, ...]  ← Any token possible
After:   [0.2, -∞, 0.5, ...]   ← Token 1 IMPOSSIBLE
Softmax: [0.28, 0.0, 0.72, ...] ← P(token1) = 0.0

pub fn apply_constraints_with_context( &self, logits: &mut [f32], context: &[u32], )

Apply constraints with context (for sequence-based constraints)

pub fn check_sequence(&self, tokens: &[u32]) -> Option<String>

Check if a token sequence violates constraints

Returns None if valid, Some(violation) if invalid. But in Diamond, this should NEVER return Some - violations are impossible by construction.

pub fn space_hash(&self) -> [u8; 32]

Get the forbidden space hash (for attestation)

pub fn stats(&self) -> ForbiddenSpaceStats

Get statistics about the forbidden space