diff --git a/src-tauri/src/commands/ai/agentic/context_lifecycle.rs b/src-tauri/src/commands/ai/agentic/context_lifecycle.rs
index c0649ba..8335cf9 100644
--- a/src-tauri/src/commands/ai/agentic/context_lifecycle.rs
+++ b/src-tauri/src/commands/ai/agentic/context_lifecycle.rs
@@ -270,7 +270,7 @@ pub(super) async fn maybe_auto_compress(
                         );
                         // 复位 is_compressing 收口进 keyword_fallback_commit 单锁(909①-补:
                         // 原先此处单独取锁复位,与提交之间留并发二次压缩窗口)。
-                        keyword_fallback_commit(
+                        let degraded = keyword_fallback_commit(
                             &session_arc,
                             &conv_id,
                             protect_start,
@@ -281,6 +281,16 @@ pub(super) async fn maybe_auto_compress(
                             recall_on.then_some(data_dir.as_path()),
                         )
                         .await;
+                        // E2:降级不再静默(实证 76730ce8 seq166 用户被迫原句重发)
+                        if degraded {
+                            emit_ai_chat_event(
+                                &app_handle,
+                                AiChatEvent::AiContextDegraded {
+                                    conversation_id: Some(conv_id.to_string()),
+                                    reason: "压缩 provider 重建失败,已降级为关键词摘要".into(),
+                                },
+                            );
+                        }
                         return;
                     }
                 };
@@ -384,7 +394,7 @@ pub(super) async fn maybe_auto_compress(
                             "[ai] 自动压缩失败(后台),降级走关键词摘要兜底(KEYWORD_FALLBACK_ENABLED={})",
                             KEYWORD_FALLBACK_ENABLED,
                         );
-                        keyword_fallback_commit(
+                        let degraded = keyword_fallback_commit(
                             &session_arc,
                             &conv_id,
                             protect_start,
@@ -395,6 +405,17 @@ pub(super) async fn maybe_auto_compress(
                             recall_on.then_some(data_dir.as_path()),
                         )
                         .await;
+                        // E2:降级不再静默——AiError 语义是生成结束,此处 loop 仍在跑,
+                        // 用专用事件让前端透出降级状态条/提示(不打断流)
+                        if degraded {
+                            emit_ai_chat_event(
+                                &app_handle,
+                                AiChatEvent::AiContextDegraded {
+                                    conversation_id: Some(conv_id.to_string()),
+                                    reason: "LLM 压缩失败,已降级为关键词摘要".into(),
+                                },
+                            );
+                        }
                     }
                 }
                 }) // 闭 catch_unwind 内 async move
@@ -444,11 +465,11 @@ async fn keyword_fallback_commit(
     log_head: &str,
     head_id: &Option<String>,
     recall: Option<&Path>,
-) {
+) -> bool {
     let inserted = {
         let mut session = session_arc.lock().await;
         if !session.per_conv.contains_key(conv_id) {
-            return;
+            return false;
         }
         let conv = session.conv(conv_id);
         // 939⑪ 内容版本守卫:上下文已被整体替换 → 丢弃兜底提交(标志亦不复位)。
@@ -458,7 +479,7 @@ async fn keyword_fallback_commit(
                 "[ai] {}兜底提交前上下文版本已变(疑似 clear 重建),丢弃",
                 log_head
             );
-            return;
+            return false;
         }
         // 复位与提交同锁原子(909①-补):消「锁外复位→再取锁提交」之间的并发二次压缩窗口。
         conv.messages.set_compressing(false);
@@ -495,6 +516,7 @@ async fn keyword_fallback_commit(
             log_head
         );
     }
+    inserted
 }
 
 #[cfg(test)]
diff --git a/src-tauri/src/commands/ai/mod.rs b/src-tauri/src/commands/ai/mod.rs
index 37fb1af..17f5a19 100644
--- a/src-tauri/src/commands/ai/mod.rs
+++ b/src-tauri/src/commands/ai/mod.rs
@@ -317,6 +317,11 @@ pub enum AiChatEvent {
     /// 摘要 system 消息已由后端 insert_at,后续 stream 自然带出,无需整会话刷新。
     /// miniapp 仍插摘要气泡(对端发生压缩告知用户)。
     AiAutoCompressed { conversation_id: Option<String>, summary: String },
+    /// E2 压缩失败降级透出(2026-10-18):LLM 压缩失败走关键词摘要兜底时,loop 仍在继续
+    /// (不发 AiError——其 case 无条件 setStreaming(false) 会误判生成结束),但用户须知晓
+    /// 上下文已降级(实证 76730ce8 seq166:静默降级→AI 失忆→用户被迫原句重发)。
+    /// 前端弹一次性状态提示,不中断流。
+    AiContextDegraded { conversation_id: Option<String>, reason: String },
     /// L1 求助协议(aichat 体验与 agent 能力系统化重构 §2.3,2026-06-21):
     ///
     /// agent 断路器(§2.2)熔断 / 自省(识别"我反复失败")时发,区别于 prompt 教 AI
diff --git a/src/api/types.ts b/src/api/types.ts
index 7331941..b511b03 100644
--- a/src/api/types.ts
+++ b/src/api/types.ts
@@ -539,6 +539,9 @@ export type AiChatEvent = ({
 } | {
   // 上下文已清空:前端刷新消息列表 + toast 提示
   type: 'AiContextCleared'
+} | {
+  // E2 压缩失败降级(关键词摘要兜底,loop 仍在跑):前端 toast 提示不中断流
+  type: 'AiContextDegraded'; reason: string
 }) & {
   conversation_id?: ConvId
 }
diff --git a/src/components/AiChat.vue b/src/components/AiChat.vue
index 70064cb..4d03d10 100644
--- a/src/components/AiChat.vue
+++ b/src/components/AiChat.vue
@@ -698,6 +698,10 @@ async function initContextEventListeners(): Promise<void> {
     onError: (_convId, message) => {
       showToast(t('aiChat.compressError', { msg: message }), 'error')
     },
+    // E2 压缩失败降级:仅提示不刷新不打断流(loop 仍在跑,实证静默降级致用户原句重发)
+    onContextDegraded: (_convId, reason) => {
+      showToast(t('aiChat.contextDegraded', { reason }), 'warning')
+    },
   })
 }
 </script>
diff --git a/src/composables/ai/useAiContext.ts b/src/composables/ai/useAiContext.ts
index 124bc7c..6d38436 100644
--- a/src/composables/ai/useAiContext.ts
+++ b/src/composables/ai/useAiContext.ts
@@ -46,6 +46,7 @@ async function initContextListener(callbacks: {
   onCleared?: (conversationId: string) => void
   onCompressed?: (conversationId: string, summary: string) => void
   onError?: (conversationId: string, message: string) => void
+  onContextDegraded?: (conversationId: string, reason: string) => void
 }): Promise<void> {
   setContextCallbacks({
     onCompressing: () => { isCompressing.value = true },
@@ -62,6 +63,11 @@ async function initContextListener(callbacks: {
       autoCompressedFlashTimer = setTimeout(() => { autoCompressedFlash.value = false }, 4000)
     },
     onCleared: (convId) => callbacks.onCleared?.(convId),
+    onContextDegraded: (convId, reason) => {
+      // E2:压缩失败降级为关键词摘要兜底——复位 loading + 上抛 toast(不中断 LLM 流)
+      isCompressing.value = false
+      callbacks.onContextDegraded?.(convId, reason)
+    },
     onError: (convId, message) => {
       // AiError 也用于流式生成失败(useAiEvents 已处理);此处仅在压缩中时复位 + toast,
       // 避免双重处理流式错误。
diff --git a/src/composables/ai/useAiLifecycleEvents.ts b/src/composables/ai/useAiLifecycleEvents.ts
index aa0f42a..f23892d 100644
--- a/src/composables/ai/useAiLifecycleEvents.ts
+++ b/src/composables/ai/useAiLifecycleEvents.ts
@@ -30,6 +30,8 @@ export interface ContextCallbacks {
   onCleared?: (conversationId: string) => void
   /** 错误(AiError,含压缩失败):仅在 loading 时置 false + toast */
   onError?: (conversationId: string, message: string) => void
+  /** E2 压缩失败降级(AiContextDegraded):loop 仍在跑,仅提示上下文已降级不中断流 */
+  onContextDegraded?: (conversationId: string, reason: string) => void
 }
 let _contextCallbacks: ContextCallbacks = {}
 
@@ -344,6 +346,11 @@ export async function handleLifecycleEvent(event: AiChatEvent): Promise<boolean>
       _contextCallbacks.onCleared?.(event.conversation_id || '')
       return true
 
+    case 'AiContextDegraded':
+      // E2:压缩失败已走关键词摘要兜底,loop 继续——透出降级提示而非静默失忆
+      _contextCallbacks.onContextDegraded?.(event.conversation_id || '', event.reason || '')
+      return true
+
     default:
       return false
   }
diff --git a/src/i18n/en/aiChat.ts b/src/i18n/en/aiChat.ts
index ce350a6..a0f60a5 100644
--- a/src/i18n/en/aiChat.ts
+++ b/src/i18n/en/aiChat.ts
@@ -275,6 +275,7 @@ export default {
     // B4: one-shot auto-compress notice (loop auto-compress no longer fully silent)
     autoCompressed: 'Context auto-compressed (earlier messages folded into summary)',
     compressError: 'Compression failed: {msg}',
+    contextDegraded: 'Context degraded: {reason} — the AI may be missing some earlier details',
     clearError: 'Clear failed: {msg}',
     initError: 'AI panel init failed: {msg} (reopen panel to retry)',
     initDegraded: 'List load failed, continuing in degraded mode: {msg}',
diff --git a/src/i18n/zh-CN/aiChat.ts b/src/i18n/zh-CN/aiChat.ts
index 9d6e9d1..35042c4 100644
--- a/src/i18n/zh-CN/aiChat.ts
+++ b/src/i18n/zh-CN/aiChat.ts
@@ -276,6 +276,8 @@ export default {
     // B4: 自动压缩完成一次性提示(loop 自动压缩不再全程静默)
     autoCompressed: '上下文已自动压缩(较早消息已折叠为摘要)',
     compressError: '压缩失败:{msg}',
+    // E2:压缩失败走关键词摘要兜底,loop 继续——提示降级而非静默失忆
+    contextDegraded: '上下文已降级:{reason},AI 可能缺失部分早前细节',
     clearError: '清空失败:{msg}',
     initError: 'AI 面板初始化失败:{msg}(重开面板可重试)',
     initDegraded: '列表加载失败,面板降级继续:{msg}',
diff --git a/vite.config.ts b/vite.config.ts
index 5b9d305..0d3cbc6 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -23,7 +23,9 @@ export default defineConfig(async () => ({
         }
       : undefined,
     watch: {
-      ignored: ["**/src-tauri/**"],
+      // target/ 同理须忽略:cargo 编译写 .o/.rlib 时 watcher 触发 EBUSY(文件被写锁),
+      // chokidar 直接抛异常杀掉 dev 进程(2026-10-18 实证:watch sqlite3.o 崩溃)
+      ignored: ["**/src-tauri/**", "**/target/**"],
     },
   },
 }));