diff --git a/src/renderer/stores/chatStore.ts b/src/renderer/stores/chatStore.ts
index 2695d5c..45f6bbb 100644
--- a/src/renderer/stores/chatStore.ts
+++ b/src/renderer/stores/chatStore.ts
@@ -165,6 +165,15 @@ const abortControllers = new Map<string, AbortController>();
 /** Per-conversation ask-user resolvers */
 const askUserResolvers = new Map<string, (answer: string) => void>();
 
+function cancelConversationRun(convId: string): void {
+  const resolver = askUserResolvers.get(convId);
+  if (resolver) {
+    resolver('__ABORT__');
+    askUserResolvers.delete(convId);
+  }
+  abortControllers.get(convId)?.abort();
+}
+
 async function runAgentWithModel(
   convId: string,
   assistantMsgId: string,
@@ -505,16 +514,26 @@ export const useChatStore = create<ChatState>((set, get) => ({
   },
 
   deleteConversation: (id) => {
+    cancelConversationRun(id);
     set((s) => {
       const conversations = s.conversations.filter((c) => c.id !== id);
       const activeConversationId =
         s.activeConversationId === id
           ? (conversations[0]?.id ?? null)
           : s.activeConversationId;
-      if (activeConversationId) {
-        dbAPI.setConfig('activeConversationId', activeConversationId).catch(console.error);
-      }
-      return { conversations, activeConversationId };
+      const streamingConversationIds = s.streamingConversationIds.filter((convId) => convId !== id);
+      const isStreaming = activeConversationId
+        ? streamingConversationIds.includes(activeConversationId)
+        : false;
+      dbAPI.setConfig('activeConversationId', activeConversationId ?? '').catch(console.error);
+      return {
+        conversations,
+        activeConversationId,
+        isStreaming,
+        streamingConversationIds,
+        pendingQuestion: s.pendingQuestion?.convId === id ? null : s.pendingQuestion,
+        agentTurnInfo: s.agentTurnInfo?.convId === id ? null : s.agentTurnInfo,
+      };
     });
     dbAPI.deleteConversation(id).catch(console.error);
   },
@@ -594,7 +613,8 @@ export const useChatStore = create<ChatState>((set, get) => ({
     }
 
     const updatedConv = get().conversations.find((c) => c.id === convId);
-    const messagesForAgent = updatedConv ? updatedConv.messages.slice(0, -1) : [userMsg];
+    if (!updatedConv) return;
+    const messagesForAgent = updatedConv.messages.slice(0, -1);
 
     await runAgentWithModel(convId!, assistantMsg.id, messagesForAgent, set, get);
   },
@@ -690,17 +710,12 @@ export const useChatStore = create<ChatState>((set, get) => ({
 
   stopStreaming: () => {
     const { activeConversationId, pendingQuestion } = get();
-    // If there's a pending AG2U question, resolve it with __ABORT__ so the agent loop unblocks
-    if (activeConversationId && pendingQuestion?.convId === activeConversationId) {
-      const resolver = askUserResolvers.get(activeConversationId);
-      if (resolver) {
-        resolver('__ABORT__');
-        askUserResolvers.delete(activeConversationId);
-      }
-      set({ pendingQuestion: null });
-    }
     if (activeConversationId) {
-      abortControllers.get(activeConversationId)?.abort();
+      cancelConversationRun(activeConversationId);
+    }
+    // Clear the active conversation's pending AG2UI question after unblocking its agent.
+    if (pendingQuestion?.convId === activeConversationId) {
+      set({ pendingQuestion: null });
     }
     // isStreaming/streamingConversationIds will be cleaned up in runAgentWithModel's finally block
   },
diff --git a/tests/chat-store-delete-cancellation.test.cjs b/tests/chat-store-delete-cancellation.test.cjs
new file mode 100644
index 0000000..4c093fa
--- /dev/null
+++ b/tests/chat-store-delete-cancellation.test.cjs
@@ -0,0 +1,288 @@
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const Module = require('node:module');
+const path = require('node:path');
+const test = require('node:test');
+const ts = require('typescript');
+
+const chatStorePath = path.join(__dirname, '..', 'src', 'renderer', 'stores', 'chatStore.ts');
+const sleep = (ms) => new Promise((resolve) => setTimeout(resolve, ms));
+
+async function waitFor(predicate, message) {
+  const deadline = Date.now() + 1000;
+  while (Date.now() < deadline) {
+    if (predicate()) return;
+    await sleep(5);
+  }
+  assert.fail(message);
+}
+
+async function settlesWithin(promise, timeoutMs) {
+  let timer;
+  const timeout = new Promise((resolve) => {
+    timer = setTimeout(() => resolve(false), timeoutMs);
+  });
+  try {
+    return await Promise.race([promise.then(() => true), timeout]);
+  } finally {
+    clearTimeout(timer);
+  }
+}
+
+async function withChatStore({ ids, runReactAgent, upsertMessage = async () => {} }, run) {
+  const originalTsLoader = require.extensions['.ts'];
+  const originalLoad = Module._load;
+  const originalLocalStorage = global.localStorage;
+  const deletedConversationIds = [];
+  const configWrites = [];
+  let memoryCalls = 0;
+
+  global.localStorage = {
+    getItem: () => null,
+    setItem: () => {},
+    removeItem: () => {},
+  };
+
+  require.extensions['.ts'] = (mod, filename) => {
+    const source = fs.readFileSync(filename, 'utf8');
+    const output = ts.transpileModule(source, {
+      compilerOptions: {
+        module: ts.ModuleKind.CommonJS,
+        target: ts.ScriptTarget.ES2022,
+        esModuleInterop: true,
+      },
+    }).outputText;
+    mod._compile(output, filename);
+  };
+
+  const model = {
+    id: 'local-model',
+    name: 'Local model',
+    provider: 'ollama',
+    modelId: 'test-model',
+    apiKey: '',
+    baseUrl: 'http://localhost',
+  };
+  const configState = {
+    models: [model],
+    activeModelId: model.id,
+    language: 'zh-CN',
+    memoryShortTermRounds: 5,
+    setActiveModel: () => {},
+  };
+
+  const dbAPI = {
+    getConversations: async () => [],
+    getMessages: async () => [],
+    getConfig: async () => null,
+    setConfig: async (key, value) => {
+      configWrites.push([key, value]);
+    },
+    upsertConversation: async () => {},
+    upsertMessage,
+    updateConversationTitle: async () => {},
+    deleteConversation: async (id) => {
+      deletedConversationIds.push(id);
+    },
+    deleteMessage: async () => {},
+  };
+
+  const mocks = {
+    uuid: { v4: () => ids.shift() },
+    './configStore': { useConfigStore: { getState: () => configState } },
+    './subagentStore': { useSubagentStore: { getState: () => ({ clearTodos: () => {} }) } },
+    '../services/reactAgent': { runReactAgent },
+    '../services/memoryService': {
+      consolidateSessionMemory: async () => {
+        memoryCalls += 1;
+      },
+    },
+    '../services/dbAPI': { dbAPI, isElectron: () => true },
+    './suggestionsStore': {
+      useSuggestionsStore: { getState: () => ({ setSuggestions: () => {} }) },
+      parseSuggestionsFromMessage: () => [],
+    },
+    '../i18n': { getLocale: () => ({ sidebar: { newConversationTitle: 'New conversation' } }) },
+  };
+
+  Module._load = function loadWithMocks(request, parent, isMain) {
+    if (parent?.filename === chatStorePath && Object.hasOwn(mocks, request)) {
+      return mocks[request];
+    }
+    return originalLoad.call(this, request, parent, isMain);
+  };
+
+  try {
+    delete require.cache[chatStorePath];
+    const { useChatStore } = require(chatStorePath);
+    await run({
+      useChatStore,
+      configWrites,
+      deletedConversationIds,
+      getMemoryCalls: () => memoryCalls,
+    });
+  } finally {
+    delete require.cache[chatStorePath];
+    Module._load = originalLoad;
+    if (originalTsLoader) require.extensions['.ts'] = originalTsLoader;
+    else delete require.extensions['.ts'];
+    global.localStorage = originalLocalStorage;
+  }
+}
+
+test('deleting a background run cancels only that conversation', async () => {
+  const signals = new Map();
+  const settledRuns = [];
+
+  async function* runReactAgent(messages, _model, signal) {
+    const label = messages.at(-1)?.content;
+    signals.set(label, signal);
+    if (!signal.aborted) {
+      await new Promise((resolve) => signal.addEventListener('abort', resolve, { once: true }));
+    }
+    settledRuns.push(label);
+  }
+
+  await withChatStore(
+    {
+      ids: ['conv-a', 'user-a', 'assistant-a', 'conv-b', 'user-b', 'assistant-b'],
+      runReactAgent,
+    },
+    async ({ useChatStore, deletedConversationIds, getMemoryCalls }) => {
+      const runA = useChatStore.getState().sendMessage('A', []);
+      await waitFor(() => signals.has('A'), 'conversation A did not start');
+
+      assert.equal(useChatStore.getState().createConversation(), 'conv-b');
+      const runB = useChatStore.getState().sendMessage('B', []);
+      await waitFor(() => signals.has('B'), 'conversation B did not start');
+
+      useChatStore.getState().deleteConversation('conv-a');
+      const afterDelete = useChatStore.getState();
+      const deletionSnapshot = {
+        aAborted: signals.get('A').aborted,
+        bAborted: signals.get('B').aborted,
+        conversations: afterDelete.conversations.map((conversation) => conversation.id),
+        activeConversationId: afterDelete.activeConversationId,
+        isStreaming: afterDelete.isStreaming,
+        streamingConversationIds: afterDelete.streamingConversationIds,
+      };
+
+      useChatStore.getState().stopStreaming();
+      useChatStore.getState().setActiveConversation('conv-a');
+      useChatStore.getState().stopStreaming();
+      useChatStore.getState().setActiveConversation('conv-b');
+      await Promise.all([runA, runB]);
+
+      assert.deepEqual(deletionSnapshot, {
+        aAborted: true,
+        bAborted: false,
+        conversations: ['conv-b'],
+        activeConversationId: 'conv-b',
+        isStreaming: true,
+        streamingConversationIds: ['conv-b'],
+      });
+      assert.deepEqual(deletedConversationIds, ['conv-a']);
+      assert.deepEqual(new Set(settledRuns), new Set(['A', 'B']));
+      assert.equal(getMemoryCalls(), 0);
+
+      const finalState = useChatStore.getState();
+      assert.deepEqual(finalState.conversations.map((conversation) => conversation.id), ['conv-b']);
+      assert.deepEqual(finalState.streamingConversationIds, []);
+      assert.equal(finalState.isStreaming, false);
+    },
+  );
+});
+
+test('deleting an ask_user run resolves it with the abort sentinel', async () => {
+  let signalSeen;
+  let answerSeen;
+
+  async function* runReactAgent(_messages, _model, signal, onAskUser) {
+    signalSeen = signal;
+    answerSeen = await onAskUser('ask-1', 'Choose one');
+  }
+
+  await withChatStore(
+    {
+      ids: ['conv-question', 'user-question', 'assistant-question'],
+      runReactAgent,
+    },
+    async ({ useChatStore, getMemoryCalls }) => {
+      const sendPromise = useChatStore.getState().sendMessage('question', []);
+      await waitFor(() => useChatStore.getState().pendingQuestion != null, 'ask_user did not become pending');
+
+      useChatStore.getState().deleteConversation('conv-question');
+      const settledAfterDelete = await settlesWithin(sendPromise, 500);
+      const afterDelete = useChatStore.getState();
+      const deletionSnapshot = {
+        signalAborted: signalSeen.aborted,
+        settledAfterDelete,
+        answerSeen,
+        pendingQuestion: afterDelete.pendingQuestion,
+        isStreaming: afterDelete.isStreaming,
+        streamingConversationIds: afterDelete.streamingConversationIds,
+      };
+
+      if (!settledAfterDelete) {
+        useChatStore.getState().answerQuestion('__TEST_CLEANUP__');
+        useChatStore.getState().setActiveConversation('conv-question');
+        useChatStore.getState().stopStreaming();
+        await sendPromise;
+      }
+
+      assert.deepEqual(deletionSnapshot, {
+        signalAborted: true,
+        settledAfterDelete: true,
+        answerSeen: '__ABORT__',
+        pendingQuestion: null,
+        isStreaming: false,
+        streamingConversationIds: [],
+      });
+      assert.equal(getMemoryCalls(), 0);
+    },
+  );
+});
+
+test('deleting before agent startup prevents a late run', async () => {
+  let releaseUserPersistence;
+  let userPersistenceStarted = false;
+  let agentCalls = 0;
+  const userPersistenceGate = new Promise((resolve) => {
+    releaseUserPersistence = resolve;
+  });
+
+  const runReactAgent = () => {
+    agentCalls += 1;
+    return (async function* emptyAgentRun() {})();
+  };
+
+  await withChatStore(
+    {
+      ids: ['conv-before-start', 'user-before-start', 'assistant-before-start'],
+      runReactAgent,
+      upsertMessage: async (message) => {
+        if (message.id === 'user-before-start') {
+          userPersistenceStarted = true;
+          await userPersistenceGate;
+        }
+      },
+    },
+    async ({ useChatStore, configWrites, deletedConversationIds, getMemoryCalls }) => {
+      const sendPromise = useChatStore.getState().sendMessage('go', []);
+      await waitFor(() => userPersistenceStarted, 'user persistence did not start');
+
+      useChatStore.getState().deleteConversation('conv-before-start');
+      releaseUserPersistence();
+      await sendPromise;
+
+      const state = useChatStore.getState();
+      assert.equal(agentCalls, 0);
+      assert.equal(getMemoryCalls(), 0);
+      assert.deepEqual(deletedConversationIds, ['conv-before-start']);
+      assert.deepEqual(configWrites.at(-1), ['activeConversationId', '']);
+      assert.deepEqual(state.conversations, []);
+      assert.deepEqual(state.streamingConversationIds, []);
+      assert.equal(state.isStreaming, false);
+    },
+  );
+});