PR to enhance the Usage object and related logic, to support more granular token accounting, matching the details available in the OpenAI Responses API . Specifically, it:

• Adds input_tokens_details and output_tokens_details fields to the Usage dataclass, storing detailed token breakdowns (e.g., cached_tokens, reasoning_tokens).
• Flows this change through
• Updates and extends tests to match
• Adds a test for the Usage.add method

Motivation

• Aligns the SDK’s usage with the latest OpenAI responses API Usage object
• Supports downstream use cases that require fine-grained token usage data (e.g., billing, analytics, optimization) requested by startups