diff --git a/desktop/test/agents/cli/cli-acp-tolerance.test.cjs b/desktop/test/agents/cli/cli-acp-tolerance.test.cjs
index 8f8e48b..adc25b4 100644
--- a/desktop/test/agents/cli/cli-acp-tolerance.test.cjs
+++ b/desktop/test/agents/cli/cli-acp-tolerance.test.cjs
@@ -5,11 +5,7 @@ const os = require('node:os')
 const path = require('node:path')
 
 const adapters = require('../../../src/agents/cli/cli-adapters.cjs')
-const {
-  executable,
-  readJsonWhenReady,
-  within,
-} = require('../../support/cli-adapters-test-helpers.cjs')
+const { executable, within } = require('../../support/cli-adapters-test-helpers.cjs')
 
 function noisyHermes(directory) {
   return executable(directory, 'hermes-noisy-acp.cjs', `
@@ -26,8 +22,8 @@ input.on('line', (line) => {
   let message
   try { message = JSON.parse(line) } catch { return }
   const sessionId = message.params?.sessionId || 'noisy-session'
-  if (message.id === 9001 && !message.method) {
-    fs.writeFileSync(process.env.MELDWORK_TEST_UNKNOWN_RESPONSE, JSON.stringify(message))
+  if (message.id >= 9001 && message.id <= 9004 && !message.method) {
+    fs.appendFileSync(process.env.MELDWORK_TEST_UNKNOWN_RESPONSE, JSON.stringify(message) + '\\n')
     return
   }
   if (message.method === 'initialize') {
@@ -41,6 +37,11 @@ input.on('line', (line) => {
     send({ jsonrpc: '2.0', method: '_vendor/progress', params: { done: 1 } })
     send({ jsonrpc: '2.0', method: 'session/update', params: { sessionId, update: { sessionUpdate: 'brand_new_update_kind', payload: 1 } } })
     send({ jsonrpc: '2.0', id: 9001, method: 'vendor/unknown_request', params: { sessionId } })
+    // Methods the client never advertised: a conforming Agent does not call
+    // them, a non-conforming one must get an error, never a made-up success.
+    send({ jsonrpc: '2.0', id: 9002, method: 'fs/read_text_file', params: { sessionId, path: '/etc/hosts' } })
+    send({ jsonrpc: '2.0', id: 9003, method: 'fs/write_text_file', params: { sessionId, path: '/tmp/x', content: 'x' } })
+    send({ jsonrpc: '2.0', id: 9004, method: 'terminal/create', params: { sessionId, command: 'id' } })
     send({ jsonrpc: '2.0', method: 'session/update', params: { sessionId, update: {
       sessionUpdate: 'agent_message_chunk', content: { type: 'text', text: 'acp answer despite the noise' },
     } } })
@@ -56,7 +57,7 @@ test('ACP turns survive banners, unknown notifications, new update kinds and unk
     await adapters.shutdownAcpSessionRuntime?.()
     fs.rmSync(directory, { recursive: true, force: true })
   })
-  const unknownResponse = path.join(directory, 'unknown-response.json')
+  const unknownResponse = path.join(directory, 'unknown-responses.jsonl')
   const agent = { kind: 'hermes', executable: noisyHermes(directory), name: 'Hermes' }
 
   const result = await within(adapters.runAgent(agent, 'say something', directory, {
@@ -65,8 +66,21 @@ test('ACP turns survive banners, unknown notifications, new update kinds and unk
   }), 10000)
 
   assert.equal(result.text, 'acp answer despite the noise')
-  // The Agent is told the method is unknown instead of being left waiting.
-  const response = await readJsonWhenReady(unknownResponse)
-  assert.equal(response.id, 9001)
-  assert.equal(response.error?.code, -32601)
+  // Every request the client does not support is answered with an error, so
+  // the Agent is never left waiting and never receives a made-up success.
+  const deadline = Date.now() + 5000
+  let responses = []
+  while (Date.now() < deadline) {
+    try {
+      responses = fs.readFileSync(unknownResponse, 'utf8').trim().split('\n').filter(Boolean).map(line => JSON.parse(line))
+    } catch { /* not written yet */ }
+    if (responses.length >= 4) break
+    await new Promise(resolve => setTimeout(resolve, 20))
+  }
+  assert.deepEqual(responses.map(response => response.id).sort(), [9001, 9002, 9003, 9004])
+  for (const response of responses) {
+    assert.equal('result' in response, false, `request ${response.id} must not succeed`)
+    assert.equal(typeof response.error?.code, 'number')
+  }
+  assert.equal(responses.find(response => response.id === 9001).error.code, -32601)
 })