diff --git a/test/gstack-capy-install.test.ts b/test/gstack-capy-install.test.ts
index 491b1ae20..85082d723 100644
--- a/test/gstack-capy-install.test.ts
+++ b/test/gstack-capy-install.test.ts
@@ -156,6 +156,17 @@ describe('gstack-capy-install', () => {
     expect(run(f, ['--revision']).status).toBe(2);
   });
 
+  // Value: protects=--project names the project the verdict and launch file are keyed to;
+  //   fails_when=a repo slug (owner/name) that is no directory silently keys the verdict to no project, so a later check reads a stale one;
+  //   why_new=GST-743, HARN-12 lost three pregate runs to it; seam=bin/gstack-capy-install --project; no_claim=resolving slugs
+  test('--project that is not a directory (a repo slug) is a usage error: exit 2, no setup, no verdict', () => {
+    const f = fixture();
+    const r = run(f, ['--for', 'ship', '--project', 'garrytan/harness-evals']);
+    expect([r.status, r.stderr.trim()]).toEqual([2, "gstack-capy-install: --project takes a directory path; 'garrytan/harness-evals' is not a directory (pass the project checkout's path, not a repo slug)"]);
+    expect(f.calls().filter(l => l.startsWith('setup') || l.startsWith('doctor '))).toEqual([]);
+    expect(fs.existsSync(path.join(f.home, '.gstack-state/install-verdicts'))).toBe(false);
+  });
+
   test('preflight: a missing tool stops with exit 3 and INSTALL_PREFLIGHT_FAILED before ./setup runs', () => {
     const f = fixture({ jq: false });
     const r = run(f);