diff --git a/packages/website/src/pages/docs/advanced/custom-ui/page.tsx b/packages/website/src/pages/docs/advanced/custom-ui/page.tsx
index 95fb832..3ebc83c 100644
--- a/packages/website/src/pages/docs/advanced/custom-ui/page.tsx
+++ b/packages/website/src/pages/docs/advanced/custom-ui/page.tsx
@@ -257,7 +257,8 @@ const root = createRoot(document.getElementById('my-ui')!)
 root.render(<MyAgentUI agent={agent} />)
 
 // 4. Handle user input (optional)
-agent.onAskUser = async (question) => window.prompt(question) || ''
+//    options.signal aborts when the task is stopped or disposed
+agent.onAskUser = async (question, options) => window.prompt(question) || ''
 
 // 5. Execute task
 await agent.execute('Fill the form with test data')
diff --git a/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx b/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx
index 9eb6ccb..4a08017 100644
--- a/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx
+++ b/packages/website/src/pages/docs/advanced/page-agent-core/page.tsx
@@ -354,10 +354,10 @@ const result = await agent.execute('Fill in the form with test data')`}
 						},
 						{
 							name: 'onAskUser',
-							type: '(question: string) => Promise<string>',
+							type: '(question: string, options?: { signal: AbortSignal }) => Promise<string>',
 							description: isZh
-								? '当 agent 需要向用户提问时调用。未设置则禁用 `ask_user` 工具。'
-								: 'Called when the agent needs to ask the user questions. If unset, the `ask_user` tool will be disabled.',
+								? '当 agent 需要向用户提问时调用。未设置则禁用 `ask_user` 工具。实现应在 options.signal 触发 abort 时 reject promise。'
+								: 'Called when the agent needs to ask the user questions. If unset, the `ask_user` tool will be disabled. Implementations should reject the promise when options.signal aborts.',
 						},
 					]}
 				/>
@@ -373,8 +373,8 @@ const result = await agent.execute('Fill in the form with test data')`}
 							name: 'execute(task)',
 							type: 'Promise<ExecutionResult>',
 							description: isZh
-								? '执行任务并返回结果。包含 success、data 和 history 字段。'
-								: 'Execute a task and return result. Contains success, data, and history fields.',
+								? '执行任务并返回结果（包含 success、data 和 history 字段）。若已有任务在运行则抛出错误——不支持并发执行。'
+								: 'Execute a task and return result (contains success, data, and history fields). Throws if a task is already running — concurrent execution is not supported.',
 						},
 						{
 							name: 'stop()',
diff --git a/packages/website/src/pages/docs/features/custom-tools/page.tsx b/packages/website/src/pages/docs/features/custom-tools/page.tsx
index 10c5b3b..8f96431 100644
--- a/packages/website/src/pages/docs/features/custom-tools/page.tsx
+++ b/packages/website/src/pages/docs/features/custom-tools/page.tsx
@@ -38,8 +38,8 @@ import { z } from 'zod/v4'`}
 					</Heading>
 					<p className="text-gray-600 dark:text-gray-300 mb-4">
 						{isZh
-							? '使用 tool() 辅助函数定义自定义工具，每个工具包含 description、inputSchema 和 execute 三个属性。'
-							: 'Use the tool() helper to define custom tools with description, inputSchema, and execute.'}
+							? '使用 tool() 辅助函数定义自定义工具，每个工具包含 description、inputSchema 和 execute 三个属性。异步工具必须 honor ctx.signal。'
+							: 'Use the tool() helper to define custom tools with description, inputSchema, and execute. Async tools must honor ctx.signal.'}
 					</p>
 
 					<CodeEditor
@@ -56,10 +56,11 @@ const pageAgent = new PageAgent({
         productId: z.string(),
         quantity: z.number().min(1).default(1),
       }),
-      execute: async function (input) {
+      execute: async function (input, { signal }) {
         await fetch('/api/cart', {
           method: 'POST',
           body: JSON.stringify(input),
+          signal, // honor cancellation
         })
         return \`Added \${input.quantity}x \${input.productId} to cart.\`
       },
@@ -72,9 +73,10 @@ const pageAgent = new PageAgent({
         query: z.string(),
         limit: z.number().max(10).default(3),
       }),
-      execute: async function (input) {
+      execute: async function (input, { signal }) {
         const res = await fetch(
-          \`/api/kb?q=\${encodeURIComponent(input.query)}&limit=\${input.limit}\`
+          \`/api/kb?q=\${encodeURIComponent(input.query)}&limit=\${input.limit}\`,
+          { signal }
         )
         const articles = await res.json()
         return JSON.stringify(articles)