fix: allow null values for prompt_tokens_details and completion_tokens_details

[devin-ai-integration]

Fix null validation for prompt_tokens_details and completion_tokens_details

Fixes #73

Problem

The OpenRouter API can return null for prompt_tokens_details and completion_tokens_details fields (e.g., with models like deepseek/deepseek-chat-v3-0324:free), but the current Zod schema validation only allows these fields to be objects or undefined with .optional(). This causes type validation errors:

Expected object, received null
path: ["usage", "prompt_tokens_details"]

Solution

Changed both prompt_tokens_details and completion_tokens_details in OpenRouterChatCompletionBaseResponseSchema from .optional() to .nullish() to allow null, undefined, or the object values.

Changes

• Updated schema in src/openrouter-chat-language-model.ts lines 732-742
• Both fields now use .nullish() instead of .optional()

Testing

• Existing tests continue to pass with object values
• Schema now accepts null values from OpenRouter API responses
• No breaking changes to existing functionality

Link to Devin run

https://app.devin.ai/sessions/2bcf790816c649e1ae7b047c64262726

Requested by: Louis ([email protected])

[devin-ai-integration]

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