attrs 26.1: Aliases Resolved Before Transformer

Overview

attrs 26.1, released on March 19, 2026, resolves field aliases before the transformer.

Main Features

Aliases resolved before transformer

Field aliases are now resolved before the transformer is applied, allowing transformers to work with final names.

import attrs

@attrs.define
class Config:
    full_name: str = attrs.field(alias='fullName')
    age: int = attrs.field(default=0)

c = Config(fullName='Alice', age=30)
print(c.full_name)  # Alice

Improved compatibility

This change improves compatibility with serialization tools that use transformers to modify fields.

Sources

• attrs Changelog