diff --git a/backend/internal/service/channel_monitor_const.go b/backend/internal/service/channel_monitor_const.go
index 2e1614f7..d1dffac5 100644
--- a/backend/internal/service/channel_monitor_const.go
+++ b/backend/internal/service/channel_monitor_const.go
@@ -47,6 +47,8 @@ const (
 
 	// providerOpenAIPath OpenAI Chat Completions 路径。
 	providerOpenAIPath = "/v1/chat/completions"
+	// providerOpenAIResponsesPath OpenAI Responses API 路径。
+	providerOpenAIResponsesPath = "/v1/responses"
 	// providerAnthropicPath Anthropic Messages 路径。
 	providerAnthropicPath = "/v1/messages"
 	// providerGeminiPathTemplate Gemini generateContent 路径模板（含 model 占位）。
@@ -112,6 +114,12 @@ var (
 	ErrChannelMonitorInvalidProvider = infraerrors.BadRequest(
 		"CHANNEL_MONITOR_INVALID_PROVIDER", "provider must be one of openai/anthropic/gemini",
 	)
+	ErrChannelMonitorInvalidAPIMode = infraerrors.BadRequest(
+		"CHANNEL_MONITOR_INVALID_API_MODE", "api_mode must be chat_completions or responses; responses is only supported for openai",
+	)
+	ErrChannelMonitorInvalidRequestBody = infraerrors.BadRequest(
+		"CHANNEL_MONITOR_INVALID_REQUEST_BODY", "openai replace-mode body_override must include non-empty messages for chat_completions or non-empty instructions and input for responses",
+	)
 	ErrChannelMonitorInvalidInterval = infraerrors.BadRequest(
 		"CHANNEL_MONITOR_INVALID_INTERVAL", "interval_seconds must be in [15, 3600]",
 	)
diff --git a/backend/internal/service/channel_monitor_template_types.go b/backend/internal/service/channel_monitor_template_types.go
index e5bf7568..03cd518d 100644
--- a/backend/internal/service/channel_monitor_template_types.go
+++ b/backend/internal/service/channel_monitor_template_types.go
@@ -12,6 +12,7 @@ type ChannelMonitorRequestTemplate struct {
 	ID               int64
 	Name             string
 	Provider         string
+	APIMode          string
 	Description      string
 	ExtraHeaders     map[string]string
 	BodyOverrideMode string
@@ -23,12 +24,14 @@ type ChannelMonitorRequestTemplate struct {
 // ChannelMonitorRequestTemplateListParams 列表过滤。
 type ChannelMonitorRequestTemplateListParams struct {
 	Provider string // 空 = 全部；非空则按 provider 过滤
+	APIMode  string // 空 = 全部；非空则按 api_mode 过滤
 }
 
 // ChannelMonitorRequestTemplateCreateParams 创建参数。
 type ChannelMonitorRequestTemplateCreateParams struct {
 	Name             string
 	Provider         string
+	APIMode          string
 	Description      string
 	ExtraHeaders     map[string]string
 	BodyOverrideMode string
@@ -39,6 +42,7 @@ type ChannelMonitorRequestTemplateCreateParams struct {
 // 注意 Provider 不可修改：改 provider 会让已关联监控的 body 黑名单语义错乱。
 type ChannelMonitorRequestTemplateUpdateParams struct {
 	Name             *string
+	APIMode          *string
 	Description      *string
 	ExtraHeaders     *map[string]string
 	BodyOverrideMode *string
@@ -53,6 +57,9 @@ var (
 	ErrChannelMonitorTemplateInvalidProvider = infraerrors.BadRequest(
 		"CHANNEL_MONITOR_TEMPLATE_INVALID_PROVIDER", "template provider must be one of openai/anthropic/gemini",
 	)
+	ErrChannelMonitorTemplateInvalidAPIMode = infraerrors.BadRequest(
+		"CHANNEL_MONITOR_TEMPLATE_INVALID_API_MODE", "template api_mode must be chat_completions or responses; responses is only supported for openai",
+	)
 	ErrChannelMonitorTemplateMissingName = infraerrors.BadRequest(
 		"CHANNEL_MONITOR_TEMPLATE_MISSING_NAME", "template name is required",
 	)
@@ -71,6 +78,9 @@ var (
 	ErrChannelMonitorTemplateProviderMismatch = infraerrors.BadRequest(
 		"CHANNEL_MONITOR_TEMPLATE_PROVIDER_MISMATCH", "monitor provider does not match template provider",
 	)
+	ErrChannelMonitorTemplateAPIModeMismatch = infraerrors.BadRequest(
+		"CHANNEL_MONITOR_TEMPLATE_API_MODE_MISMATCH", "monitor api_mode does not match template api_mode",
+	)
 	ErrChannelMonitorTemplateApplyEmpty = infraerrors.BadRequest(
 		"CHANNEL_MONITOR_TEMPLATE_APPLY_EMPTY", "monitor_ids must be a non-empty array",
 	)
diff --git a/backend/internal/service/channel_monitor_types.go b/backend/internal/service/channel_monitor_types.go
index b797a89b..ef86eeb8 100644
--- a/backend/internal/service/channel_monitor_types.go
+++ b/backend/internal/service/channel_monitor_types.go
@@ -15,11 +15,23 @@ const (
 	MonitorBodyOverrideModeReplace = "replace"
 )
 
+// MonitorAPIMode 描述 OpenAI provider 的请求协议。
+//
+//   - chat_completions  OpenAI-compatible Chat Completions: /v1/chat/completions + messages
+//   - responses         OpenAI Responses API: /v1/responses + instructions/input
+//
+// 非 OpenAI provider 固定使用 chat_completions 作为占位默认值，避免为每个 provider 单独扩表。
+const (
+	MonitorAPIModeChatCompletions = "chat_completions"
+	MonitorAPIModeResponses       = "responses"
+)
+
 // ChannelMonitor 渠道监控配置（service 层模型，不直接暴露 ent 类型）。
 type ChannelMonitor struct {
 	ID              int64
 	Name            string
 	Provider        string
+	APIMode         string
 	Endpoint        string
 	APIKey          string // 解密后的明文 API Key（仅在 service 内部使用，handler 层不应直接序列化返回）
 	PrimaryModel    string
@@ -56,6 +68,7 @@ type ChannelMonitorListParams struct {
 type ChannelMonitorCreateParams struct {
 	Name             string
 	Provider         string
+	APIMode          string
 	Endpoint         string
 	APIKey           string
 	PrimaryModel     string
@@ -74,6 +87,7 @@ type ChannelMonitorCreateParams struct {
 type ChannelMonitorUpdateParams struct {
 	Name            *string
 	Provider        *string
+	APIMode         *string
 	Endpoint        *string
 	APIKey          *string // 空字符串表示不修改；非空字符串覆盖
 	PrimaryModel    *string