diff --git a/src/cli/runtime/runtime-open-timeout-reason.test.ts b/src/cli/runtime/runtime-open-timeout-reason.test.ts
new file mode 100644
index 00000000000..c31d485f414
--- /dev/null
+++ b/src/cli/runtime/runtime-open-timeout-reason.test.ts
@@ -0,0 +1,102 @@
+import { describe, expect, it } from 'vitest'
+import { describeOpenTimeout } from './runtime-open-timeout-reason'
+import type { CliRuntimeUnreachableReason, CliStatusResult } from '../../shared/runtime-types'
+
+// Why: the poll loop can only feed this the states today's local producer happens to emit, so
+// driving it through the client leaves whole arms unpinned. Each arm is a promise about what
+// the message may claim, so each one is asserted against the status it describes (STA-3969).
+function status(overrides: {
+  appRunning: boolean
+  reachable: boolean
+  state: CliStatusResult['runtime']['state']
+  unreachableReason?: CliRuntimeUnreachableReason
+}): CliStatusResult {
+  return {
+    app: { running: overrides.appRunning, pid: overrides.appRunning ? 4242 : null },
+    runtime: {
+      state: overrides.state,
+      reachable: overrides.reachable,
+      runtimeId: overrides.reachable ? 'runtime-1' : null,
+      ...(overrides.unreachableReason ? { unreachableReason: overrides.unreachableReason } : {})
+    },
+    graph: { state: overrides.reachable ? 'ready' : 'unreachable' }
+  }
+}
+
+const history: CliRuntimeUnreachableReason = {
+  code: 'endpoint_missing',
+  message: 'Orca published the socket /tmp/never-listened.sock, but it does not exist.',
+  endpoint: '/tmp/never-listened.sock',
+  endpointKind: 'unix'
+}
+
+describe('describeOpenTimeout', () => {
+  it('reports the current reason as the live diagnosis', () => {
+    const text = describeOpenTimeout(
+      status({
+        appRunning: true,
+        reachable: false,
+        state: 'unreachable',
+        unreachableReason: history
+      }),
+      undefined
+    )
+    expect(text).toContain('the Orca app process is running but its runtime is unreachable')
+    expect(text).toContain(history.message)
+  })
+
+  it('calls a rejected request an answer, never unreachable', () => {
+    const text = describeOpenTimeout(
+      status({
+        appRunning: true,
+        reachable: false,
+        state: 'unreachable',
+        unreachableReason: { ...history, code: 'request_rejected', message: 'refused: bad token' }
+      }),
+      undefined
+    )
+    expect(text).toContain('answered but refused the status request')
+    expect(text).not.toContain('unreachable')
+  })
+
+  it('says the runtime answered when the newest poll was reachable', () => {
+    const text = describeOpenTimeout(
+      status({ appRunning: true, reachable: true, state: 'graph_not_ready' }),
+      history
+    )
+    expect(text).toContain('is responding and still running headlessly')
+    // A poll that answered resolves the earlier failure, so it is not even history any more.
+    expect(text).not.toContain(history.message)
+  })
+
+  // Why: this is the arm the client's own producer cannot currently reach, and dropping it makes
+  // the message claim no process is running while the pid is alive — the exact false report
+  // STA-3969 exists to stop.
+  it('never claims the process is gone while the newest status says it is running', () => {
+    const text = describeOpenTimeout(
+      status({ appRunning: true, reachable: false, state: 'graph_not_ready' }),
+      undefined
+    )
+    expect(text).toBe('. The runtime may still be running headlessly.')
+    expect(text).not.toContain('no longer running')
+    expect(text).not.toContain('No Orca runtime is running')
+  })
+
+  it('reports a dead app process without inheriting the old live verdict', () => {
+    const text = describeOpenTimeout(
+      status({ appRunning: false, reachable: false, state: 'stale_bootstrap' }),
+      history
+    )
+    expect(text).toContain('The Orca app process is no longer running.')
+    expect(text).toContain('The last failure it reported was:')
+    expect(text).not.toContain('but its runtime is unreachable')
+  })
+
+  it('says no runtime is running when none was ever published, with no history to add', () => {
+    const text = describeOpenTimeout(
+      status({ appRunning: false, reachable: false, state: 'not_running' }),
+      undefined
+    )
+    expect(text).toBe('. No Orca runtime is running.')
+  })
+})