From 94708f8305ac5ce514f439b106aa7f3773f19544 Mon Sep 17 00:00:00 2001
From: euvre <93761161+euvre@users.noreply.github.com>
Date: Mon, 20 Jul 2026 14:30:15 +0800
Subject: [PATCH] Fix: regenerate chat message does not truncate history
 (#17087)

---
 web/src/hooks/logic-hooks.ts                        | 13 +++++++------
 .../pages/next-chats/hooks/use-send-chat-message.ts | 10 ++++++----
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/web/src/hooks/logic-hooks.ts b/web/src/hooks/logic-hooks.ts
index a8b926e771..da0b9272a1 100644
--- a/web/src/hooks/logic-hooks.ts
+++ b/web/src/hooks/logic-hooks.ts
@@ -26,7 +26,6 @@ import {
   useRef,
   useState,
 } from 'react';
-import { v4 as uuid } from 'uuid';
 import { useTranslate } from './common-hooks';
 import { useSetPaginationParams } from './route-hook';
 import { useSaveSetting } from './use-user-setting-request';
@@ -714,12 +713,14 @@ export const useRegenerateMessage = ({
       if (message.id) {
         removeMessagesAfterCurrentMessage(message.id);
         const index = messages.findIndex((x) => x.id === message.id);
-        let nextMessages;
-        if (index !== -1) {
-          nextMessages = messages.slice(0, index);
-        }
+        // Always pass the truncated history explicitly, even when it is
+        // empty (regenerating the first question), so the backend can
+        // overwrite the session with it via pass_all_history_messages.
+        const nextMessages = index !== -1 ? messages.slice(0, index) : [];
         sendMessage({
-          message: { ...message, id: uuid() },
+          // Keep the original id so the question/answer pair id stays
+          // consistent between local state and the persisted session.
+          message: { ...message },
           messages: nextMessages,
         });
       }
diff --git a/web/src/pages/next-chats/hooks/use-send-chat-message.ts b/web/src/pages/next-chats/hooks/use-send-chat-message.ts
index f72e9e0ada..49895d4530 100644
--- a/web/src/pages/next-chats/hooks/use-send-chat-message.ts
+++ b/web/src/pages/next-chats/hooks/use-send-chat-message.ts
@@ -102,10 +102,10 @@ export const useSendMessage = (controller: AbortController) => {
         {
           chat_id: chatId,
           session_id: sessionId,
+          // An explicitly provided list is authoritative, even when empty
+          // (e.g. regenerating the first question must truncate history).
           messages: [
-            ...(Array.isArray(messages) && messages?.length > 0
-              ? messages
-              : (derivedMessages ?? [])),
+            ...(Array.isArray(messages) ? messages : (derivedMessages ?? [])),
             message,
           ],
           pass_all_history_messages: true,
@@ -171,7 +171,9 @@ export const useSendMessage = (controller: AbortController) => {
         setValue('');
         sendMessage({
           currentConversationId: targetConversationId,
-          messages: currentMessages,
+          // For an existing conversation currentMessages is empty; fall back
+          // to derivedMessages instead of sending an empty history.
+          messages: currentMessages.length > 0 ? currentMessages : undefined,
           message: {
             id,
             content: value.trim(),