fix: 修正 conversion 代理路径和错误边界

backend/internal/conversion/stream.go

@@ -1,6 +1,11 @@
 package conversion
 
-import "nex/backend/internal/conversion/canonical"
+import (
+	"bytes"
+	"strings"
+
+	"nex/backend/internal/conversion/canonical"
+)
 
 // StreamDecoder 流式解码器接口
 type StreamDecoder interface {
@@ -39,11 +44,12 @@ func (c *PassthroughStreamConverter) Flush() [][]byte {
 }
 
 // SmartPassthroughStreamConverter 同协议 Smart Passthrough 流式转换器
-// 逐 chunk 改写 model 字段
+// 按 SSE frame 改写 data JSON 中的 model 字段
 type SmartPassthroughStreamConverter struct {
 	adapter       ProtocolAdapter
 	modelOverride string
 	interfaceType InterfaceType
+	buffer        []byte
 }
 
 // NewSmartPassthroughStreamConverter 创建 Smart Passthrough 流式转换器
@@ -55,24 +61,45 @@ func NewSmartPassthroughStreamConverter(adapter ProtocolAdapter, modelOverride s
 	}
 }
 
-// ProcessChunk 改写 chunk 中的 model 字段
+// ProcessChunk 按 SSE frame 改写 data JSON 中的 model 字段
 func (c *SmartPassthroughStreamConverter) ProcessChunk(rawChunk []byte) [][]byte {
 	if len(rawChunk) == 0 {
 		return nil
 	}
 
-	rewrittenChunk, err := c.adapter.RewriteResponseModelName(rawChunk, c.modelOverride, c.interfaceType)
-	if err != nil {
-		// 改写失败，返回原始 chunk
-		return [][]byte{rawChunk}
-	}
+	c.buffer = append(c.buffer, rawChunk...)
+	frames, rest := splitSSEFrames(c.buffer)
+	c.buffer = rest
 
-	return [][]byte{rewrittenChunk}
+	result := make([][]byte, 0, len(frames))
+	for _, frame := range frames {
+		result = append(result, c.rewriteFrame(frame))
+	}
+	return result
 }
 
-// Flush 无缓冲数据
+func (c *SmartPassthroughStreamConverter) rewriteFrame(frame []byte) []byte {
+	payload, ok := sseFrameDataPayload(frame)
+	if !ok || strings.TrimSpace(payload) == "[DONE]" {
+		return frame
+	}
+
+	rewrittenPayload, err := c.adapter.RewriteResponseModelName([]byte(payload), c.modelOverride, c.interfaceType)
+	if err != nil {
+		return frame
+	}
+
+	return rebuildSSEFrameWithData(frame, string(rewrittenPayload))
+}
+
+// Flush 输出未形成完整 frame 的剩余数据
 func (c *SmartPassthroughStreamConverter) Flush() [][]byte {
-	return nil
+	if len(c.buffer) == 0 {
+		return nil
+	}
+	frame := append([]byte(nil), c.buffer...)
+	c.buffer = nil
+	return [][]byte{c.rewriteFrame(frame)}
 }
 
 // CanonicalStreamConverter 跨协议规范流式转换器
@@ -153,3 +180,86 @@ func (c *CanonicalStreamConverter) applyModelOverride(event *canonical.Canonical
 		event.Message.Model = c.modelOverride
 	}
 }
+
+func splitSSEFrames(data []byte) ([][]byte, []byte) {
+	var frames [][]byte
+	for len(data) > 0 {
+		idx, sepLen := findSSEFrameSeparator(data)
+		if idx < 0 {
+			break
+		}
+		end := idx + sepLen
+		frames = append(frames, append([]byte(nil), data[:end]...))
+		data = data[end:]
+	}
+	return frames, data
+}
+
+func findSSEFrameSeparator(data []byte) (int, int) {
+	lf := bytes.Index(data, []byte("\n\n"))
+	crlf := bytes.Index(data, []byte("\r\n\r\n"))
+	switch {
+	case lf < 0 && crlf < 0:
+		return -1, 0
+	case lf < 0:
+		return crlf, 4
+	case crlf < 0:
+		return lf, 2
+	case crlf <= lf:
+		return crlf, 4
+	default:
+		return lf, 2
+	}
+}
+
+func sseFrameDataPayload(frame []byte) (string, bool) {
+	text := strings.TrimRight(string(frame), "\r\n")
+	lines := strings.Split(text, "\n")
+	var dataLines []string
+	for _, line := range lines {
+		line = strings.TrimRight(line, "\r")
+		if strings.HasPrefix(line, "data:") {
+			value := strings.TrimPrefix(line, "data:")
+			if strings.HasPrefix(value, " ") {
+				value = value[1:]
+			}
+			dataLines = append(dataLines, value)
+		}
+	}
+	if len(dataLines) == 0 {
+		return "", false
+	}
+	return strings.Join(dataLines, "\n"), true
+}
+
+func rebuildSSEFrameWithData(frame []byte, data string) []byte {
+	lineEnding, separator := sseLineEnding(frame)
+	text := strings.TrimRight(string(frame), "\r\n")
+	lines := strings.Split(text, "\n")
+	out := make([]string, 0, len(lines)+1)
+	dataWritten := false
+	for _, line := range lines {
+		line = strings.TrimRight(line, "\r")
+		if strings.HasPrefix(line, "data:") {
+			if !dataWritten {
+				for _, dataLine := range strings.Split(data, "\n") {
+					out = append(out, "data: "+dataLine)
+				}
+				dataWritten = true
+			}
+			continue
+		}
+		out = append(out, line)
+	}
+	if !dataWritten {
+		out = append(out, "data: "+data)
+	}
+	return []byte(strings.Join(out, lineEnding) + separator)
+}
+
+func sseLineEnding(frame []byte) (string, string) {
+	if bytes.Contains(frame, []byte("\r\n")) {
+		return "\r\n", "\r\n\r\n"
+	}
+	return "\n", "\n\n"
+}