Implementation:Predibase Lorax Merged Adapters Validators

Knowledge Sources	LoRAX
Domains	API_Design, Validation
Last Updated	2026-02-08 02:00 GMT

Overview

Concrete tool for validating adapter merge configurations provided by Pydantic validators on the MergedAdapters and Parameters models.

Description

Validation is implemented through Pydantic field_validator and model_validator decorators on the MergedAdapters and Parameters classes. The Parameters.valid_adapter_id model validator enforces mutual exclusivity between adapter_id and merged_adapters. Field validators on MergedAdapters check IDs, weights, strategy, density, and majority sign method.

Usage

Validation runs automatically during Pydantic model construction. Invalid inputs raise ValidationError with descriptive messages.

Code Reference

Source Location

• Repository: LoRAX
• File: clients/python/lorax/types.py
• Lines: 25-58 (MergedAdapters validators), 123-131 (Parameters mutual exclusion)

Signature

class MergedAdapters(BaseModel):
    @field_validator("ids")
    def validate_ids(cls, v): ...

    @field_validator("weights")
    def validate_weights(cls, v, values): ...

    @field_validator("merge_strategy")
    def validate_merge_strategy(cls, v): ...

    @field_validator("density")
    def validate_density(cls, v): ...

    @field_validator("majority_sign_method")
    def validate_majority_sign_method(cls, v): ...

class Parameters(BaseModel):
    @model_validator(mode="after")
    def valid_adapter_id(self):
        """Enforces mutual exclusivity: adapter_id XOR merged_adapters."""
        if self.adapter_id is not None and self.merged_adapters is not None:
            raise ValidationError(
                "you must specify at most one of `adapter_id` or `merged_adapters`"
            )
        return self

Import

from lorax.types import MergedAdapters, Parameters

I/O Contract

Inputs

Name	Type	Required	Description
MergedAdapters fields	Various	Yes	ids, weights, merge_strategy, density, majority_sign_method
Parameters fields	Various	Yes	adapter_id, merged_adapters (mutual exclusion)

Outputs

Name	Type	Description
Validated model	MergedAdapters/Parameters	Valid Pydantic model instance
ValidationError	Exception	Raised if any constraint is violated

Usage Examples

Valid Configuration

from lorax.types import MergedAdapters, Parameters

# Valid merge configuration
merged = MergedAdapters(
    ids=["adapter-A", "adapter-B"],
    weights=[0.6, 0.4],
    merge_strategy="ties",
    density=0.8,
    majority_sign_method="total",
)

params = Parameters(merged_adapters=merged, max_new_tokens=100)
# OK: no adapter_id, so no mutual exclusion violation

Invalid: Mutual Exclusion

# This raises ValidationError
params = Parameters(
    adapter_id="some-adapter",
    merged_adapters=MergedAdapters(ids=["a"], weights=[1.0], density=1.0),
)
# Error: "you must specify at most one of `adapter_id` or `merged_adapters`"

Related Pages

Implements Principle

• Principle:Predibase_Lorax_Merge_Weight_Validation