diff --git a/src/tools/manual-kpi.test.ts b/src/tools/manual-kpi.test.ts
new file mode 100644
index 0000000..af0348c
--- /dev/null
+++ b/src/tools/manual-kpi.test.ts
@@ -0,0 +1,57 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { spawn } from 'node:child_process'
+import { fileURLToPath } from 'node:url'
+
+const toolUrl = new URL('./manual-kpi.tool.ts', import.meta.url).href
+const root = fileURLToPath(new URL('../..', import.meta.url))
+
+const SCRIPT = `
+  const { manualKpiTool } = await import(${JSON.stringify(toolUrl)})
+  process.stdout.write('RESULT:' + (await manualKpiTool.invoke({})))
+`
+
+// readline writes the prompt to stdout, which would corrupt the test runner's own
+// channel — so the tool runs in a child, the way a workflow step runs it.
+function collect(typed: string | null): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const child = spawn(process.execPath, ['--import', 'tsx', '--input-type=module', '--eval', SCRIPT], {
+      cwd: root,
+      env: { ...process.env, MANUAL_ACTIVITIES: '' },
+      stdio: [typed === null ? 'ignore' : 'pipe', 'pipe', 'pipe'],
+    })
+
+    let out = ''
+
+    child.stdout?.on('data', (chunk) => (out += chunk))
+    child.stdin?.end(typed ?? '')
+
+    const timer = setTimeout(() => {
+      child.kill('SIGKILL')
+      reject(new Error('collect_manual_kpi_input never settled'))
+    }, 60_000)
+
+    child.on('error', reject)
+    child.on('exit', () => {
+      clearTimeout(timer)
+      resolve(out.slice(out.indexOf('RESULT:') + 'RESULT:'.length))
+    })
+  })
+}
+
+const activitiesFrom = (out: string) => JSON.parse(out).activities
+
+test('returns no activities when stdin is closed rather than waiting for input that can never arrive', async () => {
+  const out = await collect(null)
+
+  assert.ok(out.startsWith('{'), 'the tool must settle on a closed stdin, not leave the job hanging')
+  assert.deepEqual(activitiesFrom(out), [])
+})
+
+test('still records an activity that arrived before stdin ended', async () => {
+  assert.deepEqual(activitiesFrom(await collect('Reviewed 3 PRs\n')), ['Reviewed 3 PRs'])
+})
+
+test('still treats a blank line as the end of input', async () => {
+  assert.deepEqual(activitiesFrom(await collect('Paired on the auth bug\n\n')), ['Paired on the auth bug'])
+})
diff --git a/src/tools/manual-kpi.tool.ts b/src/tools/manual-kpi.tool.ts
index ab0871b..a392945 100644
--- a/src/tools/manual-kpi.tool.ts
+++ b/src/tools/manual-kpi.tool.ts
@@ -7,10 +7,12 @@ function promptUser(question: string): Promise<string> {
   const rl = readline.createInterface({ input: process.stdin, output: process.stdout })
 
   return new Promise((resolve) => {
-    rl.question(question, (answer) => {
-      rl.close()
+    rl.on('close', () => resolve(''))
 
+    rl.question(question, (answer) => {
       resolve(answer.trim())
+
+      rl.close()
     })
   })
 }