diff --git a/src/renderer/utils/memberLaunchDiagnostics.ts b/src/renderer/utils/memberLaunchDiagnostics.ts
index 2ea06e17..208082cf 100644
--- a/src/renderer/utils/memberLaunchDiagnostics.ts
+++ b/src/renderer/utils/memberLaunchDiagnostics.ts
@@ -381,11 +381,6 @@ function buildDiagnosticHints(input: {
       'Bootstrap submit was rejected because local prompt/bash command queue was not empty.'
     );
   }
-  if (textIncludesAny(text, ['no stdin data received in 3s'])) {
-    hints.push(
-      'CLI read empty stdin before bootstrap submit; verify headless teammate runtime flag/env and startup input handling.'
-    );
-  }
   if (
     textIncludesAny(text, ['bootstrap_submit_rejected', 'submit rejected by local prompt handler'])
   ) {
@@ -401,6 +396,11 @@ function buildDiagnosticHints(input: {
   ) {
     hints.push('Parent process timed out waiting for durable bootstrap_submitted evidence.');
   }
+  if (textIncludesAny(text, ['no stdin data received in 3s'])) {
+    hints.push(
+      'CLI read empty stdin before bootstrap submit; verify headless teammate runtime flag/env and startup input handling.'
+    );
+  }
   if (
     input.livenessKind === 'stale_metadata' ||
     textIncludesAny(text, ['persisted runtime pid is not alive'])
diff --git a/test/renderer/utils/memberLaunchDiagnostics.test.ts b/test/renderer/utils/memberLaunchDiagnostics.test.ts
index 32e57b57..ea7fb2e0 100644
--- a/test/renderer/utils/memberLaunchDiagnostics.test.ts
+++ b/test/renderer/utils/memberLaunchDiagnostics.test.ts
@@ -1,12 +1,11 @@
-import { describe, expect, it } from 'vitest';
-
 import {
   buildMemberLaunchDiagnosticsPayload,
   formatMemberLaunchDiagnosticsPayload,
+  getMemberLaunchDiagnosticsErrorMessage,
   hasMemberLaunchDiagnosticsDetails,
   hasMemberLaunchDiagnosticsError,
-  getMemberLaunchDiagnosticsErrorMessage,
 } from '@renderer/utils/memberLaunchDiagnostics';
+import { describe, expect, it } from 'vitest';
 
 describe('member launch diagnostics', () => {
   it('builds a bounded copy payload from spawn and runtime evidence', () => {
@@ -1180,4 +1179,59 @@ describe('member launch diagnostics', () => {
       'Anthropic API error. resolved_behavior_changed:old->new'
     );
   });
+
+  it('prioritizes durable bootstrap timeout over no-stdin stderr noise', () => {
+    const payload = buildMemberLaunchDiagnosticsPayload({
+      teamName: 'signal-ops',
+      runId: 'run-mailbox-written-no-submit',
+      memberName: 'atlas',
+      spawnEntry: {
+        status: 'error',
+        launchState: 'failed_to_start',
+        hardFailure: true,
+        error:
+          'Teammate process atlas@signal-ops did not submit bootstrap prompt: timed out waiting for bootstrap_submitted; last transport stage: mailbox_bootstrap_written: messageId=bootstrap-atlas-1 Last stderr: Warning: no stdin data received in 3s, proceeding without it.',
+        livenessKind: 'stale_metadata',
+        runtimeDiagnostic: 'persisted runtime pid is not alive',
+        runtimeDiagnosticSeverity: 'warning',
+        updatedAt: '2026-05-19T13:53:36.668Z',
+      },
+    });
+
+    expect(payload.probableCause).toBe(
+      'Parent process timed out waiting for durable bootstrap_submitted evidence.'
+    );
+    expect(payload.diagnosticHints?.[0]).toBe(
+      'Parent process timed out waiting for durable bootstrap_submitted evidence.'
+    );
+    expect(payload.diagnosticHints).toContain(
+      'CLI read empty stdin before bootstrap submit; verify headless teammate runtime flag/env and startup input handling.'
+    );
+  });
+
+  it('prioritizes bootstrap submit rejection over no-stdin stderr noise', () => {
+    const payload = buildMemberLaunchDiagnosticsPayload({
+      teamName: 'signal-ops',
+      runId: 'run-submit-rejected-no-stdin',
+      memberName: 'bob',
+      spawnEntry: {
+        status: 'error',
+        launchState: 'failed_to_start',
+        hardFailure: true,
+        error:
+          'Teammate process bob@signal-ops did not submit bootstrap prompt: timed out waiting for bootstrap_submitted; last transport stage: bootstrap_submit_rejected: submit rejected by local prompt handler retryable=true Last stderr: Warning: no stdin data received in 3s, proceeding without it.',
+        updatedAt: '2026-05-19T13:53:36.668Z',
+      },
+    });
+
+    expect(payload.probableCause).toBe(
+      'The teammate process observed bootstrap mail, but local prompt submission did not accept the bootstrap turn.'
+    );
+    expect(payload.diagnosticHints?.[0]).toBe(
+      'The teammate process observed bootstrap mail, but local prompt submission did not accept the bootstrap turn.'
+    );
+    expect(payload.diagnosticHints).toContain(
+      'CLI read empty stdin before bootstrap submit; verify headless teammate runtime flag/env and startup input handling.'
+    );
+  });
 });