diff --git a/frontend/src/components/assistant-editor/debug-preview.tsx b/frontend/src/components/assistant-editor/debug-preview.tsx
index 7f6bbc4..dd02552 100644
--- a/frontend/src/components/assistant-editor/debug-preview.tsx
+++ b/frontend/src/components/assistant-editor/debug-preview.tsx
@@ -49,6 +49,7 @@ import { WaveformTimelinePanel } from "@/components/ui/waveform-timeline";
 import { useCameraPreview, type CameraPreview } from "@/hooks/use-camera-preview";
 import { usePhotoCaptureTool } from "@/hooks/use-photo-capture-tool";
 import {
+  createUserInputId,
   useVoicePreview,
   type ChatMessage,
   type ClientToolDefinition,
@@ -799,6 +800,7 @@ function DebugVoicePanel({
     sendText,
     sendUserInput,
     appendUserImage,
+    removeUserImage,
     connect,
     disconnect,
     audioRef,
@@ -866,6 +868,7 @@ function DebugVoicePanel({
     setSendingInput(true);
     setInputError("");
     let assetToken = "";
+    let inputId = "";
     try {
       const imageUrl = await fileToDataUrl(pendingImage.file);
       const asset = await inputAssetsApi.uploadImage(pendingImage.file);
@@ -878,11 +881,13 @@ function DebugVoicePanel({
       });
 
       const timestamp = new Date().toISOString();
-      const result = await sendUserInput(parts);
-      appendUserImage(result.inputId, imageUrl, timestamp, text);
+      inputId = createUserInputId();
+      appendUserImage(inputId, imageUrl, timestamp, text);
+      await sendUserInput(parts, { inputId });
       setTextDraft("");
       setPendingImage(null);
     } catch (sendError) {
+      if (inputId) removeUserImage(inputId);
       if (assetToken) {
         void inputAssetsApi.remove(assetToken).catch(() => {});
       }
diff --git a/frontend/src/hooks/use-photo-capture-tool.ts b/frontend/src/hooks/use-photo-capture-tool.ts
index c4f9476..955ffc8 100644
--- a/frontend/src/hooks/use-photo-capture-tool.ts
+++ b/frontend/src/hooks/use-photo-capture-tool.ts
@@ -2,7 +2,10 @@
 
 import { useCallback, useEffect, useState } from "react";
 
-import type { VoicePreview } from "@/hooks/use-voice-preview";
+import {
+  createUserInputId,
+  type VoicePreview,
+} from "@/hooks/use-voice-preview";
 
 const PHOTO_BUTTON_TOOL = "set_photo_button_visible";
 const PHOTO_BUTTON_DEFINITION = {
@@ -72,6 +75,7 @@ async function capturePreviewImage(stream: MediaStream | null): Promise<string>
 export function usePhotoCaptureTool(preview: VoicePreview, enabled = true) {
   const {
     appendUserImage,
+    removeUserImage,
     registerClientTool,
     sendUserInput,
     status,
@@ -107,27 +111,37 @@ export function usePhotoCaptureTool(preview: VoicePreview, enabled = true) {
     if (capturing || status !== "connected") return;
     setCapturing(true);
     setError(null);
+    let inputId = "";
     try {
       const timestamp = new Date().toISOString();
       const imageUrl = await capturePreviewImage(videoStream);
-      const result = await sendUserInput(
+      inputId = createUserInputId();
+      appendUserImage(inputId, imageUrl, timestamp);
+      await sendUserInput(
         [
           {
             type: "input_image",
             source: { type: "camera_frame", frame: "current" },
           },
         ],
-        { runImmediately: true, interrupt: true },
+        { runImmediately: true, interrupt: true, inputId },
       );
-      appendUserImage(result.inputId, imageUrl, timestamp);
     } catch (captureError) {
+      if (inputId) removeUserImage(inputId);
       setError(
         captureError instanceof Error ? captureError.message : "拍照提交失败",
       );
     } finally {
       setCapturing(false);
     }
-  }, [appendUserImage, capturing, sendUserInput, status, videoStream]);
+  }, [
+    appendUserImage,
+    capturing,
+    removeUserImage,
+    sendUserInput,
+    status,
+    videoStream,
+  ]);
 
   return {
     visible,
diff --git a/frontend/src/hooks/use-voice-preview.ts b/frontend/src/hooks/use-voice-preview.ts
index 20852e2..88db2d3 100644
--- a/frontend/src/hooks/use-voice-preview.ts
+++ b/frontend/src/hooks/use-voice-preview.ts
@@ -174,15 +174,11 @@ function errorMessage(error: unknown, fallback: string): string {
   return fallback;
 }
 
-function messageOrder(message: ChatMessage): number {
-  const timestamp = Date.parse(message.timestamp);
-  return Number.isNaN(timestamp) ? Number.MAX_SAFE_INTEGER : timestamp;
-}
-
 function sortMessages(messages: ChatMessage[]): ChatMessage[] {
-  return messages.sort(
-    (a, b) => messageOrder(a) - messageOrder(b) || a.sequence - b.sequence,
-  );
+  // Timestamps come from both the browser and the backend server. Remote
+  // deployments can have clock skew, so causal UI order must use the single
+  // client-owned sequence instead of comparing clocks from different hosts.
+  return messages.sort((a, b) => a.sequence - b.sequence);
 }
 
 function encodeHeaderJson(value: unknown): string {
@@ -194,7 +190,7 @@ function encodeHeaderJson(value: unknown): string {
   return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
 }
 
-function newInputId(): string {
+export function createUserInputId(): string {
   if (typeof crypto !== "undefined" && "randomUUID" in crypto) {
     return `input_${crypto.randomUUID()}`;
   }
@@ -831,7 +827,7 @@ export function useVoicePreview(
     const trimmed = text.trim();
     const transport = transportRef.current;
     if (!trimmed || !transport || transport.state !== "connected") return false;
-    const inputId = newInputId();
+    const inputId = createUserInputId();
     transport.sendAppMessage({
       type: "user-input",
       schema_version: 1,
@@ -845,13 +841,17 @@ export function useVoicePreview(
   const sendUserInput = useCallback(
     (
       parts: UserInputPart[],
-      options: { runImmediately?: boolean; interrupt?: boolean } = {},
+      options: {
+        runImmediately?: boolean;
+        interrupt?: boolean;
+        inputId?: string;
+      } = {},
     ): Promise<UserInputResult> => {
       const transport = transportRef.current;
       if (!transport || transport.state !== "connected") {
         return Promise.reject(new Error("当前未连接语音服务"));
       }
-      const inputId = newInputId();
+      const inputId = options.inputId ?? createUserInputId();
       return new Promise<UserInputResult>((resolve, reject) => {
         const timeout = window.setTimeout(() => {
           pendingUserInputsRef.current.delete(inputId);
@@ -914,6 +914,12 @@ export function useVoicePreview(
     [],
   );
 
+  const removeUserImage = useCallback((inputId: string) => {
+    setMessages((previous) =>
+      previous.filter((message) => message.id !== `user-image-${inputId}`),
+    );
+  }, []);
+
   const updateSession = useCallback(
     ({
       dynamicVariables,
@@ -1006,6 +1012,7 @@ export function useVoicePreview(
     sendText,
     sendUserInput,
     appendUserImage,
+    removeUserImage,
     updateSession,
     registerClientTool,
     connect,