diff --git a/mateclaw-ui/src/components/chat/ChatInput.vue b/mateclaw-ui/src/components/chat/ChatInput.vue
index 6ae1059c..56b35f31 100644
--- a/mateclaw-ui/src/components/chat/ChatInput.vue
+++ b/mateclaw-ui/src/components/chat/ChatInput.vue
@@ -136,14 +136,16 @@
           <el-icon><Paperclip /></el-icon>
         </button>
 
-        <!-- 深度思考开关 -->
+        <!-- 深度思考开关 (RFC-049 PR-1-UI: 不支持 reasoning_effort 的模型灰态) -->
         <button
           type="button"
           class="action-btn thinking-btn"
-          :class="{ active: thinkingEnabled }"
-          :disabled="disabled"
-          @click="emit('toggle-thinking')"
-          :title="thinkingEnabled ? t('chat.thinkingOn') : t('chat.thinkingOff')"
+          :class="{ active: thinkingEnabled && thinkingSupported, unsupported: !thinkingSupported }"
+          :disabled="disabled || !thinkingSupported"
+          @click="thinkingSupported && emit('toggle-thinking')"
+          :title="!thinkingSupported
+            ? t('chat.thinkingUnsupported')
+            : (thinkingEnabled ? t('chat.thinkingOn') : t('chat.thinkingOff'))"
         >
           <el-icon><MagicStick /></el-icon>
         </button>
@@ -239,6 +241,11 @@ interface Props {
   enableTalkMode?: boolean
   /** 深度思考开关状态 */
   thinkingEnabled?: boolean
+  /**
+   * RFC-049 PR-1-UI: 当前 runtime 模型是否支持 reasoning_effort。false 时按钮灰掉，
+   * 不响应点击，tooltip 提示当前模型不支持深度思考。默认 true 以保持向后兼容。
+   */
+  thinkingSupported?: boolean
 }
 
 const props = withDefaults(defineProps<Props>(), {
@@ -257,6 +264,7 @@ const props = withDefaults(defineProps<Props>(), {
   queueSize: 0,
   enableTalkMode: false,
   thinkingEnabled: false,
+  thinkingSupported: true,
 })
 
 const emit = defineEmits<{
@@ -598,6 +606,11 @@ defineExpose({
   border-radius: 50%;
   background: var(--el-color-primary, #409eff);
 }
+/* RFC-049 PR-1-UI: model doesn't support reasoning_effort — stronger grayed state */
+.thinking-btn.unsupported {
+  opacity: 0.35;
+  cursor: not-allowed;
+}
 .thinking-btn:hover:not(:disabled) {
   color: var(--el-color-primary, #409eff);
   background: var(--el-color-primary-light-9, rgba(64, 158, 255, 0.08));
diff --git a/mateclaw-ui/src/i18n/locales/en-US.ts b/mateclaw-ui/src/i18n/locales/en-US.ts
index a11e20ee..6e4af92b 100644
--- a/mateclaw-ui/src/i18n/locales/en-US.ts
+++ b/mateclaw-ui/src/i18n/locales/en-US.ts
@@ -165,6 +165,7 @@ export default {
     messagePlaceholder: 'Type a message... (Enter to send, Shift+Enter for new line)',
     thinkingOn: 'Deep thinking enabled',
     thinkingOff: 'Click to enable deep thinking',
+    thinkingUnsupported: 'Current model does not support deep thinking',
     subtitle: 'Your intelligent AI assistant powered by Spring AI Alibaba',
     // Queue related
     queuedSending: 'Sending queued message...',
diff --git a/mateclaw-ui/src/i18n/locales/zh-CN.ts b/mateclaw-ui/src/i18n/locales/zh-CN.ts
index e014e338..063db738 100644
--- a/mateclaw-ui/src/i18n/locales/zh-CN.ts
+++ b/mateclaw-ui/src/i18n/locales/zh-CN.ts
@@ -165,6 +165,7 @@ export default {
     messagePlaceholder: '输入消息... (Enter 发送, Shift+Enter 换行)',
     thinkingOn: '深度思考已开启',
     thinkingOff: '点击开启深度思考',
+    thinkingUnsupported: '当前模型不支持深度思考',
     subtitle: '基于 Spring AI Alibaba 的智能 AI 助手',
     // 排队相关
     queuedSending: '正在发送排队消息...',
diff --git a/mateclaw-ui/src/types/index.ts b/mateclaw-ui/src/types/index.ts
index 94c48aea..6b1e0607 100644
--- a/mateclaw-ui/src/types/index.ts
+++ b/mateclaw-ui/src/types/index.ts
@@ -586,6 +586,14 @@ export interface ProviderModelInfo {
   probeOk?: boolean
   /** Short error message when probeOk=false */
   probeError?: string
+  /**
+   * RFC-049 PR-1-UI: whether the model's `ModelFamily` accepts the
+   * `reasoning_effort` parameter. Derived server-side from the model name;
+   * true only for the OpenAI reasoning family (gpt-5, o1, o3, o4 variants).
+   * Used by the thinking-depth selector to gray itself out on non-reasoning
+   * models.
+   */
+  supportsReasoningEffort?: boolean
 }
 
 export interface ProviderInfo {
diff --git a/mateclaw-ui/src/views/ChatConsole.vue b/mateclaw-ui/src/views/ChatConsole.vue
index 676f192d..548b7494 100644
--- a/mateclaw-ui/src/views/ChatConsole.vue
+++ b/mateclaw-ui/src/views/ChatConsole.vue
@@ -252,6 +252,7 @@
         @deny="handleDeny"
         :enable-talk-mode="!!selectedAgentId"
         :thinking-enabled="thinkingEnabled"
+        :thinking-supported="currentModelSupportsReasoningEffort"
         @toggle-thinking="thinkingEnabled = !thinkingEnabled"
         @talk="showTalkMode = true"
       />
@@ -635,6 +636,26 @@ const currentRuntimeModel = computed(() => {
   return currentAgent.value?.modelName || 'default'
 })
 
+/**
+ * RFC-049 PR-1-UI: whether the active runtime model supports `reasoning_effort`.
+ * Drives the enable/disable state of the thinking-depth toggle in ChatInput:
+ * chat-type models that don't support thinking must not honor the "deep thinking"
+ * selection (product contract — UI reflects the backend gate).
+ *
+ * Source of truth: ProviderModelInfo.supportsReasoningEffort (set by backend via
+ * ModelFamily.detect(modelName) in ModelInfoDTO).
+ */
+const currentModelSupportsReasoningEffort = computed<boolean>(() => {
+  const providerId = activeModels.value?.activeLlm?.providerId
+  const modelName = activeModels.value?.activeLlm?.model
+  if (!providerId || !modelName) return false
+  const provider = providers.value.find((p) => p.id === providerId)
+  if (!provider) return false
+  const all = [...(provider.models || []), ...(provider.extraModels || [])]
+  const hit = all.find((m) => m.id === modelName || m.name === modelName)
+  return Boolean(hit?.supportsReasoningEffort)
+})
+
 const userInitial = computed(() => (localStorage.getItem('username') || 'U').charAt(0).toUpperCase())
 
 const activeModelValue = computed(() => {