collect usage

llm/claude/v2/chat.go

@@ -111,6 +111,9 @@ func (c *Claude) Chat(ctx context.Context, chatReq llm.ChatRequest) (*llm.ChatRe
 		return nil, err
 	}
 
+	if c.tokenUsage.Model == "" && resp.Model != "" {
+		c.tokenUsage.Model = string(resp.Model)
+	}
 	c.tokenUsage.PromptTokens += resp.Usage.InputTokens
 	c.tokenUsage.CompletionTokens += resp.Usage.OutputTokens
 	c.tokenUsage.TotalTokens += resp.Usage.InputTokens + resp.Usage.OutputTokens