feat(ai-proxy): add mergeConsecutiveMessages option to merge consecutive same-role messages (#3598)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/wasm-plugin-unit-test.yml

@@ -199,12 +199,12 @@ jobs:
     - name: Checkout code
       uses: actions/checkout@v4
       
-    - name: Set up Go 1.24
+    - name: Set up Go 1.25
       uses: actions/setup-go@v4
       with:
-        go-version: 1.24
+        go-version: 1.25
         cache: true
-        
+
     - name: Install required tools
       run: |
         go install github.com/wadey/gocovmerge@latest

plugins/wasm-go/extensions/ai-proxy/provider/provider.go

@@ -462,6 +462,9 @@ type ProviderConfig struct {
 	// @Title zh-CN 智谱AI Code Plan 模式
 	// @Description zh-CN 仅适用于智谱AI服务。启用后将使用 /api/coding/paas/v4/chat/completions 接口
 	zhipuCodePlanMode bool `required:"false" yaml:"zhipuCodePlanMode" json:"zhipuCodePlanMode"`
+	// @Title zh-CN 合并连续同角色消息
+	// @Description zh-CN 开启后，若请求的 messages 中存在连续的同角色消息（如连续两条 user 消息），将其内容合并为一条，以满足要求严格轮流交替（user→assistant→user→...）的模型服务商的要求。
+	mergeConsecutiveMessages bool `required:"false" yaml:"mergeConsecutiveMessages" json:"mergeConsecutiveMessages"`
 }
 
 func (c *ProviderConfig) GetId() string {
@@ -681,6 +684,7 @@ func (c *ProviderConfig) FromJson(json gjson.Result) {
 			c.contextCleanupCommands = append(c.contextCleanupCommands, cmd.String())
 		}
 	}
+	c.mergeConsecutiveMessages = json.Get("mergeConsecutiveMessages").Bool()
 }
 
 func (c *ProviderConfig) Validate() error {
@@ -1120,6 +1124,17 @@ func (c *ProviderConfig) handleRequestBody(
 		}
 	}
 
+	// merge consecutive same-role messages for providers that require strict role alternation
+	if apiName == ApiNameChatCompletion && c.mergeConsecutiveMessages {
+		body, err = mergeConsecutiveMessages(body)
+		if err != nil {
+			log.Warnf("[mergeConsecutiveMessages] failed to merge messages: %v", err)
+			err = nil
+		} else {
+			log.Debugf("[mergeConsecutiveMessages] merged consecutive messages for provider: %s", c.typ)
+		}
+	}
+
 	// convert developer role to system role for providers that don't support it
 	if apiName == ApiNameChatCompletion && !isDeveloperRoleSupported(c.typ) {
 		body, err = convertDeveloperRoleToSystem(body)

plugins/wasm-go/extensions/ai-proxy/provider/request_helper.go

@@ -154,6 +154,54 @@ func cleanupContextMessages(body []byte, cleanupCommands []string) ([]byte, erro
 	return json.Marshal(request)
 }
 
+// mergeConsecutiveMessages merges consecutive messages of the same role (user or assistant).
+// Many LLM providers require strict user↔assistant alternation and reject requests where
+// two messages of the same role appear consecutively. When enabled, consecutive same-role
+// messages have their content concatenated into a single message.
+func mergeConsecutiveMessages(body []byte) ([]byte, error) {
+	request := &chatCompletionRequest{}
+	if err := json.Unmarshal(body, request); err != nil {
+		return body, fmt.Errorf("unable to unmarshal request for message merging: %v", err)
+	}
+	if len(request.Messages) <= 1 {
+		return body, nil
+	}
+
+	merged := false
+	result := make([]chatMessage, 0, len(request.Messages))
+	for _, msg := range request.Messages {
+		if len(result) > 0 &&
+			result[len(result)-1].Role == msg.Role &&
+			(msg.Role == roleUser || msg.Role == roleAssistant) {
+			last := &result[len(result)-1]
+			last.Content = mergeMessageContent(last.Content, msg.Content)
+			merged = true
+			continue
+		}
+		result = append(result, msg)
+	}
+
+	if !merged {
+		return body, nil
+	}
+	request.Messages = result
+	return json.Marshal(request)
+}
+
+// mergeMessageContent concatenates two message content values.
+// If both are plain strings they are joined with a blank line.
+// Otherwise both are converted to content-block arrays and concatenated.
+func mergeMessageContent(prev, curr any) any {
+	prevStr, prevIsStr := prev.(string)
+	currStr, currIsStr := curr.(string)
+	if prevIsStr && currIsStr {
+		return prevStr + "\n\n" + currStr
+	}
+	prevParts := (&chatMessage{Content: prev}).ParseContent()
+	currParts := (&chatMessage{Content: curr}).ParseContent()
+	return append(prevParts, currParts...)
+}
+
 func ReplaceResponseBody(body []byte) error {
 	log.Debugf("response body: %s", string(body))
 	err := proxywasm.ReplaceHttpResponseBody(body)

plugins/wasm-go/extensions/ai-proxy/provider/request_helper_test.go

@@ -8,6 +8,131 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestMergeConsecutiveMessages(t *testing.T) {
+	t.Run("no_consecutive_messages", func(t *testing.T) {
+		input := chatCompletionRequest{
+			Messages: []chatMessage{
+				{Role: "user", Content: "你好"},
+				{Role: "assistant", Content: "你好！"},
+				{Role: "user", Content: "再见"},
+			},
+		}
+		body, err := json.Marshal(input)
+		require.NoError(t, err)
+
+		result, err := mergeConsecutiveMessages(body)
+		assert.NoError(t, err)
+		// No merging needed, returned body should be identical
+		assert.Equal(t, body, result)
+	})
+
+	t.Run("merges_consecutive_user_messages", func(t *testing.T) {
+		input := chatCompletionRequest{
+			Messages: []chatMessage{
+				{Role: "user", Content: "第一条"},
+				{Role: "user", Content: "第二条"},
+				{Role: "assistant", Content: "回复"},
+			},
+		}
+		body, err := json.Marshal(input)
+		require.NoError(t, err)
+
+		result, err := mergeConsecutiveMessages(body)
+		assert.NoError(t, err)
+
+		var output chatCompletionRequest
+		require.NoError(t, json.Unmarshal(result, &output))
+
+		assert.Len(t, output.Messages, 2)
+		assert.Equal(t, "user", output.Messages[0].Role)
+		assert.Equal(t, "第一条\n\n第二条", output.Messages[0].Content)
+		assert.Equal(t, "assistant", output.Messages[1].Role)
+	})
+
+	t.Run("merges_consecutive_assistant_messages", func(t *testing.T) {
+		input := chatCompletionRequest{
+			Messages: []chatMessage{
+				{Role: "user", Content: "问题"},
+				{Role: "assistant", Content: "第一段"},
+				{Role: "assistant", Content: "第二段"},
+			},
+		}
+		body, err := json.Marshal(input)
+		require.NoError(t, err)
+
+		result, err := mergeConsecutiveMessages(body)
+		assert.NoError(t, err)
+
+		var output chatCompletionRequest
+		require.NoError(t, json.Unmarshal(result, &output))
+
+		assert.Len(t, output.Messages, 2)
+		assert.Equal(t, "user", output.Messages[0].Role)
+		assert.Equal(t, "assistant", output.Messages[1].Role)
+		assert.Equal(t, "第一段\n\n第二段", output.Messages[1].Content)
+	})
+
+	t.Run("merges_multiple_consecutive_same_role", func(t *testing.T) {
+		input := chatCompletionRequest{
+			Messages: []chatMessage{
+				{Role: "user", Content: "A"},
+				{Role: "user", Content: "B"},
+				{Role: "user", Content: "C"},
+				{Role: "assistant", Content: "回复"},
+			},
+		}
+		body, err := json.Marshal(input)
+		require.NoError(t, err)
+
+		result, err := mergeConsecutiveMessages(body)
+		assert.NoError(t, err)
+
+		var output chatCompletionRequest
+		require.NoError(t, json.Unmarshal(result, &output))
+
+		assert.Len(t, output.Messages, 2)
+		assert.Equal(t, "A\n\nB\n\nC", output.Messages[0].Content)
+	})
+
+	t.Run("system_messages_not_merged", func(t *testing.T) {
+		input := chatCompletionRequest{
+			Messages: []chatMessage{
+				{Role: "system", Content: "系统提示1"},
+				{Role: "system", Content: "系统提示2"},
+				{Role: "user", Content: "问题"},
+			},
+		}
+		body, err := json.Marshal(input)
+		require.NoError(t, err)
+
+		result, err := mergeConsecutiveMessages(body)
+		assert.NoError(t, err)
+		// system messages are not merged, body unchanged
+		assert.Equal(t, body, result)
+	})
+
+	t.Run("single_message_unchanged", func(t *testing.T) {
+		input := chatCompletionRequest{
+			Messages: []chatMessage{
+				{Role: "user", Content: "只有一条"},
+			},
+		}
+		body, err := json.Marshal(input)
+		require.NoError(t, err)
+
+		result, err := mergeConsecutiveMessages(body)
+		assert.NoError(t, err)
+		assert.Equal(t, body, result)
+	})
+
+	t.Run("invalid_json_body", func(t *testing.T) {
+		body := []byte(`invalid json`)
+		result, err := mergeConsecutiveMessages(body)
+		assert.Error(t, err)
+		assert.Equal(t, body, result)
+	})
+}
+
 func TestCleanupContextMessages(t *testing.T) {
 	t.Run("empty_cleanup_commands", func(t *testing.T) {
 		body := []byte(`{"messages":[{"role":"user","content":"hello"}]}`)