Missing `cost` and `cost_details` fields in `usage` response

[the-dream-machine]

According to the OpenRouter Usage Accounting documentation, the usage object in API responses should include cost and cost_details fields:

The usage response includes detailed cost information:

• cost: The total amount charged to your account
• cost_details.upstream_inference_cost: The actual cost charged by the upstream AI provider

However, the SDK's ChatGenerationTokenUsage type only includes token-related fields and does not expose the cost information.

Current SDK type definition

// From @openrouter/sdk/esm/models/chatgenerationtokenusage.d.ts
export type ChatGenerationTokenUsage = {
    completionTokens: number;
    promptTokens: number;
    totalTokens: number;
    completionTokensDetails?: CompletionTokensDetails | null | undefined;
    promptTokensDetails?: PromptTokensDetails | null | undefined;
};

Expected type definition

export type ChatGenerationTokenUsage = {
    completionTokens: number;
    promptTokens: number;
    totalTokens: number;
    completionTokensDetails?: CompletionTokensDetails | null | undefined;
    promptTokensDetails?: PromptTokensDetails | null | undefined;
    cost?: number | null | undefined;
    costDetails?: {
        upstreamInferenceCost?: number | null | undefined;
    } | undefined;
};

Steps to reproduce

1. Install @openrouter/sdk@0.5.1
2. Make a chat completion request (streaming or non-streaming)
3. Access response.usage or the final streaming chunk's usage
4. Observe that cost and cost_details are not available on the typed object

Actual API response

The raw API response includes cost data:

{
  "usage": {
    "completion_tokens": 68,
    "prompt_tokens": 515,
    "total_tokens": 583,
    "completion_tokens_details": {
      "reasoning_tokens": 0
    },
    "prompt_tokens_details": {
      "cached_tokens": 159
    },
    "cost": 0.00123,
    "cost_details": {
      "upstream_inference_cost": null
    }
  }
}

Environment

• SDK version: 0.5.1
• Node.js version: 25.6.0

Additional context

The OpenResponsesUsage type in the SDK does include cost and costDetails fields, but ChatGenerationTokenUsage (used for chat completions) does not.

[akicool]

Yes, the same problem with missing required fields.

[akicool]

I created PR to resolve this issue