Forced decoding is the decoding mode where specific tokens or token spans are mandated at defined positions in the output - it enforces strict structural or lexical constraints during generation.

What Is Forced decoding?

• Definition: Generation process with hard constraints on required token emission.
• Constraint Scope: Can force prefixes, delimiters, labels, or full schema scaffolds.
• Implementation: Runtime masks candidate sets to ensure required tokens are selected.
• Use Cases: Template filling, form completion, and controlled protocol responses.

Why Forced decoding Matters

• Format Compliance: Guarantees mandatory tokens appear in required locations.
• Integration Reliability: Prevents malformed output for downstream deterministic parsers.
• Policy Enforcement: Ensures critical disclaimers or headers are always present.
• Operational Predictability: Reduces variance in generated structure across requests.
• Automation Enablement: Makes model output safer for direct machine consumption.

How It Is Used in Practice

• Constraint Authoring: Define forced token positions relative to prompt and output schema.
• Conflict Testing: Check for collisions between forced tokens and other penalties or stop rules.
• Fallback Handling: Provide graceful error path when constraints become unsatisfiable.

Forced decoding is a strict control mechanism for schema-critical generation - forced decoding trades flexibility for deterministic compliance and integration safety.