Fixed: #2281

refactor(claude): centralize usage token calculation logic and add tests for cached token handling

internal/translator/claude/openai/chat-completions/claude_openai_response.go

@@ -36,6 +36,18 @@ type ToolCallAccumulator struct {
 	Arguments strings.Builder
 }
 
+func calculateClaudeUsageTokens(usage gjson.Result) (promptTokens, completionTokens, totalTokens, cachedTokens int64) {
+	inputTokens := usage.Get("input_tokens").Int()
+	completionTokens = usage.Get("output_tokens").Int()
+	cachedTokens = usage.Get("cache_read_input_tokens").Int()
+	cacheCreationInputTokens := usage.Get("cache_creation_input_tokens").Int()
+
+	promptTokens = inputTokens + cacheCreationInputTokens + cachedTokens
+	totalTokens = promptTokens + completionTokens
+
+	return promptTokens, completionTokens, totalTokens, cachedTokens
+}
+
 // ConvertClaudeResponseToOpenAI converts Claude Code streaming response format to OpenAI Chat Completions format.
 // This function processes various Claude Code event types and transforms them into OpenAI-compatible JSON responses.
 // It handles text content, tool calls, reasoning content, and usage metadata, outputting responses that match
@@ -203,14 +215,11 @@ func ConvertClaudeResponseToOpenAI(_ context.Context, modelName string, original
 
 		// Handle usage information for token counts
 		if usage := root.Get("usage"); usage.Exists() {
-			inputTokens := usage.Get("input_tokens").Int()
+			promptTokens, completionTokens, totalTokens, cachedTokens := calculateClaudeUsageTokens(usage)
-			outputTokens := usage.Get("output_tokens").Int()
+			template, _ = sjson.SetBytes(template, "usage.prompt_tokens", promptTokens)
-			cacheReadInputTokens := usage.Get("cache_read_input_tokens").Int()
+			template, _ = sjson.SetBytes(template, "usage.completion_tokens", completionTokens)
-			cacheCreationInputTokens := usage.Get("cache_creation_input_tokens").Int()
+			template, _ = sjson.SetBytes(template, "usage.total_tokens", totalTokens)
-			template, _ = sjson.SetBytes(template, "usage.prompt_tokens", inputTokens+cacheCreationInputTokens)
+			template, _ = sjson.SetBytes(template, "usage.prompt_tokens_details.cached_tokens", cachedTokens)
-			template, _ = sjson.SetBytes(template, "usage.completion_tokens", outputTokens)
-			template, _ = sjson.SetBytes(template, "usage.total_tokens", inputTokens+outputTokens)
-			template, _ = sjson.SetBytes(template, "usage.prompt_tokens_details.cached_tokens", cacheReadInputTokens)
 		}
 		return [][]byte{template}
 
@@ -362,14 +371,11 @@ func ConvertClaudeResponseToOpenAINonStream(_ context.Context, _ string, origina
 				}
 			}
 			if usage := root.Get("usage"); usage.Exists() {
-				inputTokens := usage.Get("input_tokens").Int()
+				promptTokens, completionTokens, totalTokens, cachedTokens := calculateClaudeUsageTokens(usage)
-				outputTokens := usage.Get("output_tokens").Int()
+				out, _ = sjson.SetBytes(out, "usage.prompt_tokens", promptTokens)
-				cacheReadInputTokens := usage.Get("cache_read_input_tokens").Int()
+				out, _ = sjson.SetBytes(out, "usage.completion_tokens", completionTokens)
-				cacheCreationInputTokens := usage.Get("cache_creation_input_tokens").Int()
+				out, _ = sjson.SetBytes(out, "usage.total_tokens", totalTokens)
-				out, _ = sjson.SetBytes(out, "usage.prompt_tokens", inputTokens+cacheCreationInputTokens)
+				out, _ = sjson.SetBytes(out, "usage.prompt_tokens_details.cached_tokens", cachedTokens)
-				out, _ = sjson.SetBytes(out, "usage.completion_tokens", outputTokens)
-				out, _ = sjson.SetBytes(out, "usage.total_tokens", inputTokens+outputTokens)
-				out, _ = sjson.SetBytes(out, "usage.prompt_tokens_details.cached_tokens", cacheReadInputTokens)
 			}
 		}
 	}

internal/translator/claude/openai/chat-completions/claude_openai_response_test.go

@@ -0,0 +1,58 @@
+package chat_completions
+
+import (
+	"context"
+	"testing"
+
+	"github.com/tidwall/gjson"
+)
+
+func TestConvertClaudeResponseToOpenAI_StreamUsageIncludesCachedTokens(t *testing.T) {
+	ctx := context.Background()
+	var param any
+
+	out := ConvertClaudeResponseToOpenAI(
+		ctx,
+		"claude-opus-4-6",
+		nil,
+		nil,
+		[]byte(`data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"input_tokens":13,"output_tokens":4,"cache_read_input_tokens":22000,"cache_creation_input_tokens":31}}`),
+		&param,
+	)
+	if len(out) != 1 {
+		t.Fatalf("expected 1 chunk, got %d", len(out))
+	}
+
+	if gotPromptTokens := gjson.GetBytes(out[0], "usage.prompt_tokens").Int(); gotPromptTokens != 22044 {
+		t.Fatalf("expected prompt_tokens %d, got %d", 22044, gotPromptTokens)
+	}
+	if gotCompletionTokens := gjson.GetBytes(out[0], "usage.completion_tokens").Int(); gotCompletionTokens != 4 {
+		t.Fatalf("expected completion_tokens %d, got %d", 4, gotCompletionTokens)
+	}
+	if gotTotalTokens := gjson.GetBytes(out[0], "usage.total_tokens").Int(); gotTotalTokens != 22048 {
+		t.Fatalf("expected total_tokens %d, got %d", 22048, gotTotalTokens)
+	}
+	if gotCachedTokens := gjson.GetBytes(out[0], "usage.prompt_tokens_details.cached_tokens").Int(); gotCachedTokens != 22000 {
+		t.Fatalf("expected cached_tokens %d, got %d", 22000, gotCachedTokens)
+	}
+}
+
+func TestConvertClaudeResponseToOpenAINonStream_UsageIncludesCachedTokens(t *testing.T) {
+	rawJSON := []byte("data: {\"type\":\"message_start\",\"message\":{\"id\":\"msg_123\",\"model\":\"claude-opus-4-6\"}}\n" +
+		"data: {\"type\":\"message_delta\",\"delta\":{\"stop_reason\":\"end_turn\"},\"usage\":{\"input_tokens\":13,\"output_tokens\":4,\"cache_read_input_tokens\":22000,\"cache_creation_input_tokens\":31}}\n")
+
+	out := ConvertClaudeResponseToOpenAINonStream(context.Background(), "", nil, nil, rawJSON, nil)
+
+	if gotPromptTokens := gjson.GetBytes(out, "usage.prompt_tokens").Int(); gotPromptTokens != 22044 {
+		t.Fatalf("expected prompt_tokens %d, got %d", 22044, gotPromptTokens)
+	}
+	if gotCompletionTokens := gjson.GetBytes(out, "usage.completion_tokens").Int(); gotCompletionTokens != 4 {
+		t.Fatalf("expected completion_tokens %d, got %d", 4, gotCompletionTokens)
+	}
+	if gotTotalTokens := gjson.GetBytes(out, "usage.total_tokens").Int(); gotTotalTokens != 22048 {
+		t.Fatalf("expected total_tokens %d, got %d", 22048, gotTotalTokens)
+	}
+	if gotCachedTokens := gjson.GetBytes(out, "usage.prompt_tokens_details.cached_tokens").Int(); gotCachedTokens != 22000 {
+		t.Fatalf("expected cached_tokens %d, got %d", 22000, gotCachedTokens)
+	}
+}