diff --git a/frontend/src/api/admin/channelMonitor.ts b/frontend/src/api/admin/channelMonitor.ts
index 949c4bc8..bdef7d33 100644
--- a/frontend/src/api/admin/channelMonitor.ts
+++ b/frontend/src/api/admin/channelMonitor.ts
@@ -8,11 +8,13 @@ import { apiClient } from '../client'
 export type Provider = 'openai' | 'anthropic' | 'gemini'
 export type MonitorStatus = 'operational' | 'degraded' | 'failed' | 'error'
 export type BodyOverrideMode = 'off' | 'merge' | 'replace'
+export type APIMode = 'chat_completions' | 'responses'
 
 export interface ChannelMonitor {
   id: number
   name: string
   provider: Provider
+  api_mode: APIMode
   endpoint: string
   api_key_masked: string
   /**
@@ -70,6 +72,7 @@ export interface ListResponse {
 export interface CreateParams {
   name: string
   provider: Provider
+  api_mode?: APIMode
   endpoint: string
   api_key: string
   primary_model: string
diff --git a/frontend/src/api/admin/channelMonitorTemplate.ts b/frontend/src/api/admin/channelMonitorTemplate.ts
index 01b3c2d0..7b048104 100644
--- a/frontend/src/api/admin/channelMonitorTemplate.ts
+++ b/frontend/src/api/admin/channelMonitorTemplate.ts
@@ -6,12 +6,13 @@
  */
 
 import { apiClient } from '../client'
-import type { BodyOverrideMode, Provider } from './channelMonitor'
+import type { APIMode, BodyOverrideMode, Provider } from './channelMonitor'
 
 export interface ChannelMonitorTemplate {
   id: number
   name: string
   provider: Provider
+  api_mode: APIMode
   description: string
   extra_headers: Record<string, string>
   body_override_mode: BodyOverrideMode
@@ -24,6 +25,7 @@ export interface ChannelMonitorTemplate {
 
 export interface ListParams {
   provider?: Provider
+  api_mode?: APIMode
 }
 
 export interface ListResponse {
@@ -33,6 +35,7 @@ export interface ListResponse {
 export interface CreateParams {
   name: string
   provider: Provider
+  api_mode?: APIMode
   description?: string
   extra_headers?: Record<string, string>
   body_override_mode?: BodyOverrideMode
@@ -41,6 +44,7 @@ export interface CreateParams {
 
 export interface UpdateParams {
   name?: string
+  api_mode?: APIMode
   description?: string
   extra_headers?: Record<string, string>
   body_override_mode?: BodyOverrideMode
@@ -55,6 +59,7 @@ export interface AssociatedMonitorBrief {
   id: number
   name: string
   provider: Provider
+  api_mode: APIMode
   enabled: boolean
 }
 
diff --git a/frontend/src/constants/channelMonitor.ts b/frontend/src/constants/channelMonitor.ts
index 7523a878..eb99680c 100644
--- a/frontend/src/constants/channelMonitor.ts
+++ b/frontend/src/constants/channelMonitor.ts
@@ -7,18 +7,26 @@
  * `useChannelMonitorFormat`.
  */
 
-import type { Provider, MonitorStatus } from '@/api/admin/channelMonitor'
+import type { APIMode, Provider, MonitorStatus } from '@/api/admin/channelMonitor'
 
 export const PROVIDER_OPENAI: Provider = 'openai'
 export const PROVIDER_ANTHROPIC: Provider = 'anthropic'
 export const PROVIDER_GEMINI: Provider = 'gemini'
 
+export const API_MODE_CHAT_COMPLETIONS: APIMode = 'chat_completions'
+export const API_MODE_RESPONSES: APIMode = 'responses'
+
 export const PROVIDERS: readonly Provider[] = [
   PROVIDER_OPENAI,
   PROVIDER_ANTHROPIC,
   PROVIDER_GEMINI,
 ]
 
+export const API_MODES: readonly APIMode[] = [
+  API_MODE_CHAT_COMPLETIONS,
+  API_MODE_RESPONSES,
+]
+
 export const STATUS_OPERATIONAL: MonitorStatus = 'operational'
 export const STATUS_DEGRADED: MonitorStatus = 'degraded'
 export const STATUS_FAILED: MonitorStatus = 'failed'