diff --git a/backend/app/services/chat_history.py b/backend/app/services/chat_history.py
index c98a385..76ceedc 100644
--- a/backend/app/services/chat_history.py
+++ b/backend/app/services/chat_history.py
@@ -147,6 +147,10 @@ def _append_message_in_transaction(
         "SELECT 1 FROM chat_conversations WHERE conversation_id=?", (conversation_id,)
     ).fetchone()
     if conversation is None:
+        # A stream may finish after deletion. Check under BEGIN IMMEDIATE so
+        # deletion and assistant persistence cannot recreate an orphaned chat.
+        if role == "assistant":
+            return
         conn.execute(
             "INSERT INTO chat_conversations(conversation_id,title,created_at,updated_at) VALUES(?,?,?,?)",
             (conversation_id, title, now, now),
diff --git a/backend/tests/test_chat_history.py b/backend/tests/test_chat_history.py
index a4ed03f..f4dec3b 100644
--- a/backend/tests/test_chat_history.py
+++ b/backend/tests/test_chat_history.py
@@ -1,9 +1,11 @@
+import asyncio
 from datetime import datetime, timezone
 from types import SimpleNamespace
 
 from fastapi.testclient import TestClient
+import pytest
 
-from app.contracts import ModelEvent, ModelEventType
+from app.contracts import ChatRequest, ModelEvent, ModelEventType
 from app.main import app
 from app.services import chat_history
 
@@ -80,3 +82,40 @@ def test_chat_conversation_crud_api() -> None:
         missing = client.get("/api/chat/conversations/crud/messages")
         assert missing.status_code == 404
         assert missing.json()["error"]["code"] == "CONVERSATION_NOT_FOUND"
+
+
+@pytest.mark.parametrize("close_early", [True, False])
+@pytest.mark.parametrize("deleted", [True, False])
+def test_stream_finalization_respects_conversation_deletion(monkeypatch, close_early, deleted) -> None:
+    from app import routes
+
+    class Adapter:
+        async def stream(self, _request):
+            now = datetime.now(timezone.utc)
+            yield ModelEvent(event=ModelEventType.text_delta, data={"text": "partial answer"}, timestamp=now)
+            yield ModelEvent(event=ModelEventType.done, timestamp=now)
+
+    monkeypatch.setattr(routes, "provider_or_404", lambda _: SimpleNamespace(adapter=Adapter()))
+
+    async def scenario():
+        response = await routes.chat(ChatRequest(
+            provider_id="configured", model="model", conversation_id="stream",
+            use_rag=False, messages=[{"role": "user", "content": "question"}],
+        ))
+        await anext(response.body_iterator)
+        if deleted:
+            assert chat_history.delete("stream")
+        if close_early:
+            await response.body_iterator.aclose()
+        else:
+            async for _ in response.body_iterator:
+                pass
+        if deleted:
+            assert chat_history.get("stream") is None
+            assert chat_history.list_conversations(50, 0)[1] == 0
+        else:
+            messages, total = chat_history.list_messages("stream", 50, 0)
+            assert total == 2
+            assert [message.content for message in messages] == ["question", "partial answer"]
+
+    asyncio.run(scenario())
diff --git a/frontend/src/features/chat/ChatView.vue b/frontend/src/features/chat/ChatView.vue
index 23e8bd8..b991ad5 100644
--- a/frontend/src/features/chat/ChatView.vue
+++ b/frontend/src/features/chat/ChatView.vue
@@ -94,8 +94,8 @@ async function openCitation(citation: Citation) {
       <textarea v-model="chatStore.inputText" class="textarea" :placeholder="t('输入问题，Ctrl + Enter 发送', 'Enter a question; press Ctrl + Enter to send')"
         @keydown.ctrl.enter.prevent="send" />
       <div class="composer-actions"><span class="subtle">{{ t('回答可能包含错误，请核对 Citation。', 'Answers may contain errors. Verify the citations.') }}</span>
-        <button v-if="chatStore.isStreaming" class="button-danger" @click="chatStore.stopGeneration">{{ t('停止', 'Stop') }}</button>
-        <button v-else class="button-primary" :disabled="!chatStore.inputText.trim() || !chatStore.selectedProviderId || !chatStore.selectedModel.trim()" @click="send">{{ t('发送', 'Send') }}</button>
+        <button v-if="chatStore.isStreaming || chatStore.isPreparing" class="button-danger" @click="chatStore.stopGeneration">{{ t('停止', 'Stop') }}</button>
+        <button v-else class="button-primary" :disabled="!chatStore.canSend || !chatStore.inputText.trim() || !chatStore.selectedProviderId || !chatStore.selectedModel.trim()" @click="send">{{ t('发送', 'Send') }}</button>
       </div>
     </footer>
   </section>
diff --git a/frontend/src/stores/chat.spec.ts b/frontend/src/stores/chat.spec.ts
index f213f44..1b5e30a 100644
--- a/frontend/src/stores/chat.spec.ts
+++ b/frontend/src/stores/chat.spec.ts
@@ -21,6 +21,12 @@ vi.mock('@/services/chatService', () => ({
 
 const page = { total: 0, limit: 100, offset: 0 }
 
+function deferred<T>() {
+  let resolve!: (value: T) => void
+  const promise = new Promise<T>(done => { resolve = done })
+  return { promise, resolve }
+}
+
 beforeEach(() => {
   setActivePinia(createPinia())
   vi.mocked(streamChat).mockReset().mockReturnValue({ cancel: vi.fn() } as unknown as SseClient)
@@ -96,3 +102,125 @@ it('keeps a conversation visible when backend deletion fails', async () => {
   expect(store.conversations.some(item => item.conversation_id === id)).toBe(true)
   expect(store.historyError).toBe('offline')
 })
+
+it('blocks sends until history is loaded, then includes that history', async () => {
+  const store = useChatStore()
+  store.selectedProviderId = 'real'
+  store.selectedModel = 'model'
+  await store.createNewConversation()
+  const id = store.activeConversationId!
+  const history = deferred<Awaited<ReturnType<typeof listConversationMessages>>>()
+  vi.mocked(listConversationMessages).mockReturnValueOnce(history.promise)
+  const loading = store.setActiveConversation(id)
+  store.inputText = 'followup'
+  expect(store.canSend).toBe(false)
+  await store.sendMessage(store.inputText)
+  expect(streamChat).not.toHaveBeenCalled()
+  expect(store.inputText).toBe('followup')
+  history.resolve({ items: [{ message_id: 'old', conversation_id: id, role: 'user', content: 'previous context', created_at: '' }], page: { ...page, total: 1 } })
+  await loading
+  expect(store.canSend).toBe(true)
+  await store.sendMessage(store.inputText)
+  expect(vi.mocked(streamChat).mock.calls[0]![0].messages).toEqual([
+    { role: 'user', content: 'previous context' }, { role: 'user', content: 'followup' },
+  ])
+  expect(store.messages.map(m => m.content)).toEqual(['previous context', 'followup', ''])
+})
+
+it('keeps sending blocked after history failure until a successful retry', async () => {
+  const store = useChatStore()
+  store.selectedProviderId = 'real'
+  store.selectedModel = 'model'
+  await store.createNewConversation()
+  const id = store.activeConversationId!
+  vi.mocked(listConversationMessages).mockRejectedValueOnce(new Error('offline'))
+  await store.setActiveConversation(id)
+  await store.sendMessage('followup')
+  expect(streamChat).not.toHaveBeenCalled()
+  expect(store.historyError).toBe('offline')
+  expect(store.canSend).toBe(false)
+  await store.setActiveConversation(id)
+  expect(store.canSend).toBe(true)
+})
+
+it.each(['switch', 'stop', 'delete'] as const)('cancels a pending send on %s without touching another send', async action => {
+  const store = useChatStore()
+  store.selectedProviderId = 'real'
+  store.selectedModel = 'model'
+  await store.createNewConversation()
+  const b = store.activeConversationId!
+  const creation = deferred<Conversation>()
+  vi.mocked(createConversation).mockReturnValueOnce(creation.promise)
+  const creating = store.createNewConversation()
+  const a = store.activeConversationId!
+  const saved = { ...store.activeConversation! }
+  const sending = store.sendMessage('belongs to a')
+  expect(store.isPreparing).toBe(true)
+  const deleting = action === 'delete' ? store.deleteConversation(a) : undefined
+  if (action === 'stop') store.stopGeneration()
+  await store.setActiveConversation(b)
+  await store.sendMessage('belongs to b')
+  creation.resolve(saved)
+  await Promise.all([creating, sending, deleting])
+  expect(store.activeConversationId).toBe(b)
+  expect(store.messages.every(m => m.conversation_id === b)).toBe(true)
+  expect(store.messages[0]?.content).toBe('belongs to b')
+  expect(streamChat).toHaveBeenCalledTimes(1)
+  expect(store.isStreaming).toBe(true)
+})
+
+it('locks the initial send while creating its conversation and allows retry after failure', async () => {
+  const store = useChatStore()
+  store.selectedProviderId = 'real'
+  store.selectedModel = 'model'
+  const creation = deferred<Conversation>()
+  vi.mocked(createConversation).mockReturnValueOnce(creation.promise)
+  const sending = store.sendMessage('first')
+  await store.sendMessage('duplicate')
+  expect(createConversation).toHaveBeenCalledTimes(1)
+  expect(streamChat).not.toHaveBeenCalled()
+  creation.resolve({ ...store.activeConversation! })
+  await sending
+  expect(streamChat).toHaveBeenCalledTimes(1)
+  store.stopGeneration()
+  store.activeConversationId = null
+  vi.mocked(createConversation).mockRejectedValueOnce(new Error('offline'))
+  await store.sendMessage('retry')
+  expect(store.isPreparing).toBe(false)
+  expect(store.canSend).toBe(true)
+  await store.sendMessage('retry')
+  expect(streamChat).toHaveBeenCalledTimes(2)
+})
+
+it('stops the first send before creation completes without switching conversations', async () => {
+  const store = useChatStore()
+  store.selectedProviderId = 'real'
+  store.selectedModel = 'model'
+  const creation = deferred<Conversation>()
+  vi.mocked(createConversation).mockReturnValueOnce(creation.promise)
+  const sending = store.sendMessage('cancelled')
+  const saved = { ...store.activeConversation! }
+  store.stopGeneration()
+  creation.resolve(saved)
+  await sending
+  expect(streamChat).not.toHaveBeenCalled()
+  expect(store.messages).toEqual([])
+  expect(store.canSend).toBe(true)
+})
+
+it('ignores old history after switching to a new conversation and sending', async () => {
+  const store = useChatStore()
+  store.selectedProviderId = 'real'
+  store.selectedModel = 'model'
+  await store.createNewConversation()
+  const id = store.activeConversationId!
+  const history = deferred<Awaited<ReturnType<typeof listConversationMessages>>>()
+  vi.mocked(listConversationMessages).mockReturnValueOnce(history.promise)
+  const loading = store.setActiveConversation(id)
+  await store.createNewConversation()
+  await store.sendMessage('new question')
+  history.resolve({ items: [], page })
+  await loading
+  expect(store.messages.map(m => m.content)).toEqual(['new question', ''])
+  expect(store.isStreaming).toBe(true)
+})
diff --git a/frontend/src/stores/chat.ts b/frontend/src/stores/chat.ts
index 429b0fe..68ad589 100644
--- a/frontend/src/stores/chat.ts
+++ b/frontend/src/stores/chat.ts
@@ -16,6 +16,9 @@ export const useChatStore = defineStore('chat', () => {
   const activeConversationId = ref<string | null>(null)
   const messages = ref<ChatMessage[]>([])
   const isStreaming = ref(false)
+  const isPreparing = ref(false)
+  const messagesReady = ref(true)
+  const canSend = computed(() => messagesReady.value && !isPreparing.value && !isStreaming.value)
   const inputText = ref('')
   const useRag = ref(true)
   const selectedSkillId = ref<string | null>(null)
@@ -70,6 +73,7 @@ export const useChatStore = defineStore('chat', () => {
     if (loading) return loading
     if (initialized && !force) return
     const version = ++loadVersion
+    messagesReady.value = false
     loading = (async () => {
       historyError.value = ''
       try {
@@ -81,7 +85,7 @@ export const useChatStore = defineStore('chat', () => {
           ? activeConversationId.value
           : items[0]?.conversation_id || null
         if (selected) await setActiveConversation(selected)
-        else { activeConversationId.value = null; messages.value = [] }
+        else { activeConversationId.value = null; messages.value = []; messagesReady.value = true }
       } catch (error) {
         if (version === loadVersion) historyError.value = error instanceof Error ? error.message : t('聊天记录加载失败', 'Failed to load chat history')
       } finally {
@@ -95,12 +99,14 @@ export const useChatStore = defineStore('chat', () => {
     stopGeneration()
     const version = ++loadVersion
     activeConversationId.value = id
+    messagesReady.value = false
     messages.value = []
     historyError.value = ''
     try {
       const loadedMessages = await fetchAllMessages(id)
       if (version === loadVersion && activeConversationId.value === id) {
         messages.value = loadedMessages.map(normalizeMessage)
+        messagesReady.value = true
       }
     } catch (error) {
       if (version === loadVersion) historyError.value = error instanceof Error ? error.message : t('消息加载失败', 'Failed to load messages')
@@ -116,6 +122,7 @@ export const useChatStore = defineStore('chat', () => {
     conversations.value.unshift(conversation)
     activeConversationId.value = conversation.conversation_id
     messages.value = []
+    messagesReady.value = true
     return conversation
   }
 
@@ -145,15 +152,24 @@ export const useChatStore = defineStore('chat', () => {
 
   async function sendMessage(text: string) {
     const content = text.trim()
-    if (!content || isStreaming.value || !selectedProviderId.value || !selectedModel.value) return
+    if (!content || !canSend.value || !selectedProviderId.value || !selectedModel.value) return
+    const version = ++streamVersion
+    isPreparing.value = true
     historyError.value = ''
     let conversation = activeConversation.value
-    if (!conversation) {
-      conversation = addLocalConversation(content.slice(0, 30))
-      try { await persistConversation(conversation) } catch { return }
-    } else if (pendingCreates.has(conversation.conversation_id)) {
-      try { await pendingCreates.get(conversation.conversation_id) } catch { return }
+    try {
+      if (!conversation) {
+        conversation = addLocalConversation(content.slice(0, 30))
+        await persistConversation(conversation)
+      } else if (pendingCreates.has(conversation.conversation_id)) {
+        await pendingCreates.get(conversation.conversation_id)
+      }
+    } catch { return }
+    finally {
+      if (version === streamVersion) isPreparing.value = false
     }
+    // Switching, stopping or deleting cancels sends still waiting for creation.
+    if (version !== streamVersion || activeConversationId.value !== conversation.conversation_id) return
 
     const conversationId = conversation.conversation_id
     if (conversation.message_count === 0) conversation.title = content.slice(0, 30)
@@ -171,7 +187,6 @@ export const useChatStore = defineStore('chat', () => {
     conversation.updated_at = new Date().toISOString()
     conversation.message_count = messages.value.length
 
-    const version = ++streamVersion
     const argumentBuffers = new Map<string, string>()
     sseClient = streamChat({
       provider_id: selectedProviderId.value,
@@ -241,6 +256,7 @@ export const useChatStore = defineStore('chat', () => {
 
   function stopGeneration() {
     streamVersion++
+    isPreparing.value = false
     if (sseClient) { sseClient.cancel(); sseClient = null }
     isStreaming.value = false
   }
@@ -255,7 +271,7 @@ export const useChatStore = defineStore('chat', () => {
       if (activeConversationId.value === id) {
         const next = sortedConversations.value[0]
         if (next) await setActiveConversation(next.conversation_id)
-        else { activeConversationId.value = null; messages.value = [] }
+        else { loadVersion++; activeConversationId.value = null; messages.value = []; messagesReady.value = true }
       }
     } catch (error) {
       historyError.value = error instanceof Error ? error.message : t('会话删除失败', 'Failed to delete conversation')
@@ -264,7 +280,7 @@ export const useChatStore = defineStore('chat', () => {
 
   return {
     conversations, activeConversationId, activeConversation, sortedConversations, messages,
-    isStreaming, inputText, useRag, selectedSkillId, selectedProviderId, selectedModel, historyError,
+    isStreaming, isPreparing, canSend, inputText, useRag, selectedSkillId, selectedProviderId, selectedModel, historyError,
     loadConversations, setActiveConversation, sendMessage, stopGeneration, createNewConversation, deleteConversation,
   }
 })