feat(executor): enhance Qwen system message handling with strict injection and merging rules

Closes: #2537

internal/runtime/executor/qwen_executor.go

@@ -172,32 +172,101 @@ func timeUntilNextDay() time.Duration {
 	return tomorrow.Sub(now)
 }
 
-// ensureQwenSystemMessage prepends a default system message if none exists in "messages".
+// ensureQwenSystemMessage ensures the request has a single system message at the beginning.
+// It always injects the default system prompt and merges any user-provided system messages
+// into the injected system message content to satisfy Qwen's strict message ordering rules.
 func ensureQwenSystemMessage(payload []byte) ([]byte, error) {
-	messages := gjson.GetBytes(payload, "messages")
+	isInjectedSystemPart := func(part gjson.Result) bool {
-	if messages.Exists() && messages.IsArray() {
+		if !part.Exists() || !part.IsObject() {
-		var buf bytes.Buffer
+			return false
-		buf.WriteByte('[')
-		buf.Write(qwenDefaultSystemMessage)
-		for _, msg := range messages.Array() {
-			buf.WriteByte(',')
-			buf.WriteString(msg.Raw)
 		}
-		buf.WriteByte(']')
+		if !strings.EqualFold(part.Get("type").String(), "text") {
-		updated, errSet := sjson.SetRawBytes(payload, "messages", buf.Bytes())
+			return false
-		if errSet != nil {
-			return nil, fmt.Errorf("qwen executor: set default system message failed: %w", errSet)
 		}
-		return updated, nil
+		if !strings.EqualFold(part.Get("cache_control.type").String(), "ephemeral") {
+			return false
+		}
+		text := part.Get("text").String()
+		return text == "" || text == "You are Qwen Code."
 	}
 
-	var buf bytes.Buffer
+	defaultParts := gjson.ParseBytes(qwenDefaultSystemMessage).Get("content")
-	buf.WriteByte('[')
+	var systemParts []any
-	buf.Write(qwenDefaultSystemMessage)
+	if defaultParts.Exists() && defaultParts.IsArray() {
-	buf.WriteByte(']')
+		for _, part := range defaultParts.Array() {
-	updated, errSet := sjson.SetRawBytes(payload, "messages", buf.Bytes())
+			systemParts = append(systemParts, part.Value())
+		}
+	}
+	if len(systemParts) == 0 {
+		systemParts = append(systemParts, map[string]any{
+			"type": "text",
+			"text": "You are Qwen Code.",
+			"cache_control": map[string]any{
+				"type": "ephemeral",
+			},
+		})
+	}
+
+	appendSystemContent := func(content gjson.Result) {
+		makeTextPart := func(text string) map[string]any {
+			return map[string]any{
+				"type": "text",
+				"text": text,
+			}
+		}
+
+		if !content.Exists() || content.Type == gjson.Null {
+			return
+		}
+		if content.IsArray() {
+			for _, part := range content.Array() {
+				if part.Type == gjson.String {
+					systemParts = append(systemParts, makeTextPart(part.String()))
+					continue
+				}
+				if isInjectedSystemPart(part) {
+					continue
+				}
+				systemParts = append(systemParts, part.Value())
+			}
+			return
+		}
+		if content.Type == gjson.String {
+			systemParts = append(systemParts, makeTextPart(content.String()))
+			return
+		}
+		if content.IsObject() {
+			if isInjectedSystemPart(content) {
+				return
+			}
+			systemParts = append(systemParts, content.Value())
+			return
+		}
+		systemParts = append(systemParts, makeTextPart(content.String()))
+	}
+
+	messages := gjson.GetBytes(payload, "messages")
+	var nonSystemMessages []any
+	if messages.Exists() && messages.IsArray() {
+		for _, msg := range messages.Array() {
+			if strings.EqualFold(msg.Get("role").String(), "system") {
+				appendSystemContent(msg.Get("content"))
+				continue
+			}
+			nonSystemMessages = append(nonSystemMessages, msg.Value())
+		}
+	}
+
+	newMessages := make([]any, 0, 1+len(nonSystemMessages))
+	newMessages = append(newMessages, map[string]any{
+		"role":    "system",
+		"content": systemParts,
+	})
+	newMessages = append(newMessages, nonSystemMessages...)
+
+	updated, errSet := sjson.SetBytes(payload, "messages", newMessages)
 	if errSet != nil {
-		return nil, fmt.Errorf("qwen executor: set default system message failed: %w", errSet)
+		return nil, fmt.Errorf("qwen executor: set system message failed: %w", errSet)
 	}
 	return updated, nil
 }

internal/runtime/executor/qwen_executor_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/thinking"
+	"github.com/tidwall/gjson"
 )
 
 func TestQwenExecutorParseSuffix(t *testing.T) {
@@ -28,3 +29,123 @@ func TestQwenExecutorParseSuffix(t *testing.T) {
 		})
 	}
 }
+
+func TestEnsureQwenSystemMessage_MergeStringSystem(t *testing.T) {
+	payload := []byte(`{
+		"model": "qwen3.6-plus",
+		"stream": true,
+		"messages": [
+			{ "role": "system", "content": "ABCDEFG" },
+			{ "role": "user", "content": [ { "type": "text", "text": "你好" } ] }
+		]
+	}`)
+
+	out, err := ensureQwenSystemMessage(payload)
+	if err != nil {
+		t.Fatalf("ensureQwenSystemMessage() error = %v", err)
+	}
+
+	msgs := gjson.GetBytes(out, "messages").Array()
+	if len(msgs) != 2 {
+		t.Fatalf("messages length = %d, want 2", len(msgs))
+	}
+	if msgs[0].Get("role").String() != "system" {
+		t.Fatalf("messages[0].role = %q, want %q", msgs[0].Get("role").String(), "system")
+	}
+	parts := msgs[0].Get("content").Array()
+	if len(parts) != 2 {
+		t.Fatalf("messages[0].content length = %d, want 2", len(parts))
+	}
+	if parts[0].Get("text").String() != "You are Qwen Code." || parts[0].Get("cache_control.type").String() != "ephemeral" {
+		t.Fatalf("messages[0].content[0] = %s, want injected system part", parts[0].Raw)
+	}
+	if parts[1].Get("type").String() != "text" || parts[1].Get("text").String() != "ABCDEFG" {
+		t.Fatalf("messages[0].content[1] = %s, want text part with ABCDEFG", parts[1].Raw)
+	}
+	if msgs[1].Get("role").String() != "user" {
+		t.Fatalf("messages[1].role = %q, want %q", msgs[1].Get("role").String(), "user")
+	}
+}
+
+func TestEnsureQwenSystemMessage_MergeObjectSystem(t *testing.T) {
+	payload := []byte(`{
+		"messages": [
+			{ "role": "system", "content": { "type": "text", "text": "ABCDEFG" } },
+			{ "role": "user", "content": [ { "type": "text", "text": "你好" } ] }
+		]
+	}`)
+
+	out, err := ensureQwenSystemMessage(payload)
+	if err != nil {
+		t.Fatalf("ensureQwenSystemMessage() error = %v", err)
+	}
+
+	msgs := gjson.GetBytes(out, "messages").Array()
+	if len(msgs) != 2 {
+		t.Fatalf("messages length = %d, want 2", len(msgs))
+	}
+	parts := msgs[0].Get("content").Array()
+	if len(parts) != 2 {
+		t.Fatalf("messages[0].content length = %d, want 2", len(parts))
+	}
+	if parts[1].Get("text").String() != "ABCDEFG" {
+		t.Fatalf("messages[0].content[1].text = %q, want %q", parts[1].Get("text").String(), "ABCDEFG")
+	}
+}
+
+func TestEnsureQwenSystemMessage_PrependsWhenMissing(t *testing.T) {
+	payload := []byte(`{
+		"messages": [
+			{ "role": "user", "content": [ { "type": "text", "text": "你好" } ] }
+		]
+	}`)
+
+	out, err := ensureQwenSystemMessage(payload)
+	if err != nil {
+		t.Fatalf("ensureQwenSystemMessage() error = %v", err)
+	}
+
+	msgs := gjson.GetBytes(out, "messages").Array()
+	if len(msgs) != 2 {
+		t.Fatalf("messages length = %d, want 2", len(msgs))
+	}
+	if msgs[0].Get("role").String() != "system" {
+		t.Fatalf("messages[0].role = %q, want %q", msgs[0].Get("role").String(), "system")
+	}
+	if !msgs[0].Get("content").IsArray() || len(msgs[0].Get("content").Array()) == 0 {
+		t.Fatalf("messages[0].content = %s, want non-empty array", msgs[0].Get("content").Raw)
+	}
+	if msgs[1].Get("role").String() != "user" {
+		t.Fatalf("messages[1].role = %q, want %q", msgs[1].Get("role").String(), "user")
+	}
+}
+
+func TestEnsureQwenSystemMessage_MergesMultipleSystemMessages(t *testing.T) {
+	payload := []byte(`{
+		"messages": [
+			{ "role": "system", "content": "A" },
+			{ "role": "user", "content": [ { "type": "text", "text": "hi" } ] },
+			{ "role": "system", "content": "B" }
+		]
+	}`)
+
+	out, err := ensureQwenSystemMessage(payload)
+	if err != nil {
+		t.Fatalf("ensureQwenSystemMessage() error = %v", err)
+	}
+
+	msgs := gjson.GetBytes(out, "messages").Array()
+	if len(msgs) != 2 {
+		t.Fatalf("messages length = %d, want 2", len(msgs))
+	}
+	parts := msgs[0].Get("content").Array()
+	if len(parts) != 3 {
+		t.Fatalf("messages[0].content length = %d, want 3", len(parts))
+	}
+	if parts[1].Get("text").String() != "A" {
+		t.Fatalf("messages[0].content[1].text = %q, want %q", parts[1].Get("text").String(), "A")
+	}
+	if parts[2].Get("text").String() != "B" {
+		t.Fatalf("messages[0].content[2].text = %q, want %q", parts[2].Get("text").String(), "B")
+	}
+}