fix(transformer): add fallback for token usage in streaming responses of claude

Author: zsuroy

internal/proxy/streaming.go

@@ -5,12 +5,14 @@ import (
 	"bytes"
 	"compress/gzip"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"strings"
 
 	"github.com/lich0821/ccNexus/internal/config"
 	"github.com/lich0821/ccNexus/internal/logger"
+	"github.com/lich0821/ccNexus/internal/tokencount"
 	"github.com/lich0821/ccNexus/internal/transformer"
 	"github.com/lich0821/ccNexus/internal/transformer/cc"
 	"github.com/lich0821/ccNexus/internal/transformer/cx/chat"
@@ -85,6 +87,43 @@ func (p *Proxy) handleStreamingResponse(w http.ResponseWriter, resp *http.Respon
 		}
 
 		if strings.Contains(line, "data: [DONE]") {
+			// Fallback: update output_tokens if not provided
+			if outputTokens == 0 && outputText.String() != "" {
+				outputTokens = tokencount.EstimateOutputTokens(outputText.String())
+			}
+
+			if streamCtx != nil {
+				streamCtx.OutputTokens = outputTokens
+				streamCtx.InputTokens = inputTokens
+			}
+
+			// Create message_delta to output
+			deltaEvent := map[string]interface{}{
+				"type": "message_delta",
+				"delta": map[string]interface{}{
+					"stop_reason":   "end_turn",
+					"stop_sequence": nil,
+				},
+				"usage": map[string]interface{}{
+					"output_tokens": outputTokens,
+				},
+			}
+			deltaData, _ := json.Marshal(deltaEvent)
+			deltaSSE := fmt.Sprintf("data: %s\n\n", deltaData)
+
+			// For cc_claude, send directly to avoid transformer modifying it
+			if transformerName == "cc_claude" {
+				w.Write([]byte(deltaSSE))
+				flusher.Flush()
+			} else {
+				// Transform event for other transformers
+				transformedDelta, _ := p.transformStreamEvent([]byte(deltaSSE), trans, transformerName, streamCtx)
+				if len(transformedDelta) > 0 {
+					w.Write(transformedDelta)
+					flusher.Flush()
+				}
+			}
+
 			streamDone = true
 			buffer.WriteString(line + "\n")
 			eventData := buffer.Bytes()
@@ -115,6 +154,47 @@ func (p *Proxy) handleStreamingResponse(w http.ResponseWriter, resp *http.Respon
 				p.extractTokensFromEvent(transformedEvent, &inputTokens, &outputTokens)
 				p.extractTextFromEvent(transformedEvent, &outputText)
 
+				// Check if this is message_stop event - send custom message_delta before it
+				isMessageStop := strings.Contains(string(transformedEvent), `"type":"message_stop"`)
+				if isMessageStop {
+					// Estimate output tokens if not provided
+					if outputTokens == 0 && outputText.String() != "" {
+						outputTokens = tokencount.EstimateOutputTokens(outputText.String())
+					}
+
+					if streamCtx != nil {
+						streamCtx.OutputTokens = outputTokens
+						streamCtx.InputTokens = inputTokens
+					}
+
+					// Create message_delta event with output_tokens
+					deltaEvent := map[string]interface{}{
+						"type": "message_delta",
+						"delta": map[string]interface{}{
+							"stop_reason":   "end_turn",
+							"stop_sequence": nil,
+						},
+						"usage": map[string]interface{}{
+							"output_tokens": outputTokens,
+						},
+					}
+					deltaData, _ := json.Marshal(deltaEvent)
+					deltaSSE := fmt.Sprintf("data: %s\n\n", deltaData)
+
+					// For cc_claude, send directly
+					if transformerName == "cc_claude" {
+						w.Write([]byte(deltaSSE))
+						flusher.Flush()
+					} else {
+						// Transform event for other transformers
+						transformedDelta, _ := p.transformStreamEvent([]byte(deltaSSE), trans, transformerName, streamCtx)
+						if len(transformedDelta) > 0 {
+							w.Write(transformedDelta)
+							flusher.Flush()
+						}
+					}
+				}
+
 				if _, writeErr := w.Write(transformedEvent); writeErr != nil {
 					// Client disconnected (broken pipe) is normal for cancelled requests
 					if strings.Contains(writeErr.Error(), "broken pipe") || strings.Contains(writeErr.Error(), "connection reset") {
@@ -223,6 +303,20 @@ func (p *Proxy) extractTextFromEvent(transformedEvent []byte, outputText *string
 			continue
 		}
 
+		eventType, _ := event["type"].(string)
+
+		// Handle content_block_delta (new format)
+		if eventType == "content_block_delta" {
+			if delta, ok := event["delta"].(map[string]interface{}); ok {
+				if deltaType, _ := delta["type"].(string); deltaType == "text_delta" {
+					if text, ok := delta["text"].(string); ok {
+						outputText.WriteString(text)
+					}
+				}
+			}
+		}
+
+		// Handle content_block (old format)
 		if delta, ok := event["delta"].(map[string]interface{}); ok {
 			if text, ok := delta["text"].(string); ok {
 				outputText.WriteString(text)

internal/transformer/cc/claude.go

@@ -76,11 +76,23 @@ func (t *ClaudeTransformer) TransformResponseWithContext(resp []byte, isStreamin
 				} else if eventType == "message_delta" {
 					// Fallback: fill input_tokens if 0
 					if usage, ok := event["usage"].(map[string]interface{}); ok {
+						modified := false
+
 						if input, ok := usage["input_tokens"].(float64); ok && int(input) == 0 && ctx.InputTokens > 0 {
 							usage["input_tokens"] = ctx.InputTokens
-							modified, _ := json.Marshal(event)
+							modified = true
+						}
+
+						// Fallback: fill output_tokens if 0
+						if output, ok := usage["output_tokens"].(float64); ok && int(output) == 0 && ctx.OutputTokens > 0 {
+							usage["output_tokens"] = ctx.OutputTokens
+							modified = true
+						}
+
+						if modified {
+							modifiedData, _ := json.Marshal(event)
 							result.WriteString("data: ")
-							result.Write(modified)
+							result.Write(modifiedData)
 							result.WriteString("\n")
 							continue
 						}