Principle:Predibase Lorax Schema Constrained Request

Knowledge Sources	LoRAX Structured Output
Domains	Structured_Output, Validation
Last Updated	2026-02-08 02:00 GMT

Overview

A request validation pipeline that extracts JSON schema constraints from the request format specification and threads them through to the token generation layer.

Description

Schema Constrained Request bridges the gap between the user-facing response format specification and the internal token-level constraint enforcement. The pipeline:

1. Client includes ResponseFormat with JSON schema in the request
2. Server-side validation (Validation::validate()) extracts the schema string
3. Schema is serialized and passed as NextTokenChooserParameters.schema
4. The schema string reaches the logits processor which compiles the FSM

If no schema is provided but json_object type is specified, a default permissive JSON schema is used.

Usage

Applied automatically when response_format is included in a request. No additional configuration needed beyond providing the schema.

Theoretical Basis

Pseudo-code:

# Schema extraction pipeline
def validate(request):
    if request.response_format:
        if request.response_format.schema:
            schema_str = json.dumps(request.response_format.schema)
        else:
            schema_str = default_json_schema()
        params.schema = schema_str
    return validated_request

Related Pages

Implemented By

• Implementation:Predibase_Lorax_Validation_Schema_Extraction