diff --git a/packages/cli/src/acp-integration/acpAgent.test.ts b/packages/cli/src/acp-integration/acpAgent.test.ts
index 3a9c2bfffc1..d953efeca01 100644
--- a/packages/cli/src/acp-integration/acpAgent.test.ts
+++ b/packages/cli/src/acp-integration/acpAgent.test.ts
@@ -2849,6 +2849,43 @@ describe('QwenAgent MCP SSE/HTTP support', () => {
     await agentPromise;
   });
 
+  it('qwen/settings/setMcpServer rejects malformed timeout strings', async () => {
+    const settings = makeCoreSettings();
+    const { agent, agentPromise } = await bootCoreSettingsAgent(settings);
+
+    await expect(
+      agent.extMethod('qwen/settings/setMcpServer', {
+        scope: 'user',
+        name: 'bad-timeout',
+        server: { transport: 'stdio', command: 'node', timeout: '10ms' },
+      }),
+    ).rejects.toThrowError(/Expected a positive integer/);
+
+    await expect(
+      agent.extMethod('qwen/settings/setMcpServer', {
+        scope: 'user',
+        name: 'fractional-timeout',
+        server: { transport: 'stdio', command: 'node', timeout: '1.5' },
+      }),
+    ).rejects.toThrowError(/Expected a positive integer/);
+
+    await agent.extMethod('qwen/settings/setMcpServer', {
+      scope: 'user',
+      name: 'valid-timeout',
+      server: { transport: 'stdio', command: 'node', timeout: '1500' },
+    });
+
+    const persisted = vi
+      .mocked(settings.setValue)
+      .mock.calls.find((call) => call[1] === 'mcpServers')?.[2] as {
+      'valid-timeout': { timeout: number };
+    };
+    expect(persisted['valid-timeout'].timeout).toBe(1500);
+
+    mockConnectionState.resolve();
+    await agentPromise;
+  });
+
   it('qwen/settings/removeMcpServer drops the named server and rejects a missing name', async () => {
     const settings = makeCoreSettings();
     (settings.user.settings as Record<string, unknown>)['mcpServers'] = {
@@ -2947,6 +2984,24 @@ describe('QwenAgent MCP SSE/HTTP support', () => {
     await agentPromise;
   });
 
+  it('qwen/settings/setHook rejects malformed timeout strings', async () => {
+    const settings = makeCoreSettings();
+    const { agent, agentPromise } = await bootCoreSettingsAgent(settings);
+
+    await expect(
+      agent.extMethod('qwen/settings/setHook', {
+        scope: 'user',
+        event: 'PreToolUse',
+        hook: {
+          hooks: [{ type: 'command', command: 'echo hi', timeout: '10ms' }],
+        },
+      }),
+    ).rejects.toThrowError(/Expected a positive integer/);
+
+    mockConnectionState.resolve();
+    await agentPromise;
+  });
+
   it('qwen/settings/setHook replaces in place at a valid index and appends for out-of-range', async () => {
     const settings = makeCoreSettings();
     (settings.user.settings as Record<string, unknown>)['hooks'] = {
diff --git a/packages/cli/src/acp-integration/acpAgent.ts b/packages/cli/src/acp-integration/acpAgent.ts
index 641ed35430f..2381f4efae0 100644
--- a/packages/cli/src/acp-integration/acpAgent.ts
+++ b/packages/cli/src/acp-integration/acpAgent.ts
@@ -1757,10 +1757,17 @@ function normalizeStringRecord(
 
 function normalizeOptionalNumber(value: unknown): number | undefined {
   if (value === undefined || value === null || value === '') return undefined;
-  const numberValue =
-    typeof value === 'number' ? value : Number.parseInt(String(value), 10);
-  if (!Number.isFinite(numberValue) || numberValue <= 0) {
-    throw RequestError.invalidParams(undefined, 'Expected a positive number');
+  let numberValue: number;
+  if (typeof value === 'number') {
+    numberValue = value;
+  } else if (typeof value === 'string') {
+    const trimmed = value.trim();
+    numberValue = /^\d+$/.test(trimmed) ? Number(trimmed) : Number.NaN;
+  } else {
+    numberValue = Number.NaN;
+  }
+  if (!Number.isInteger(numberValue) || numberValue <= 0) {
+    throw RequestError.invalidParams(undefined, 'Expected a positive integer');
   }
   return numberValue;
 }