diff --git a/scripts/guard-push.mjs b/scripts/guard-push.mjs
index 7d0d5681ca..2a42ca1f0e 100755
--- a/scripts/guard-push.mjs
+++ b/scripts/guard-push.mjs
@@ -414,13 +414,18 @@ export function defaultRunsFetch(branch, exec = execFileSync) {
 export function inFlightCiGuard(
   branches,
   _ranges = [],
-  { prViewer = defaultPrView, runFetcher = defaultRunsFetch } = {},
+  // `ghAvailable` is injectable for the same reason `prViewer`/`runFetcher` are:
+  // without it this "unit" test still spawned the real `gh` binary just to ask
+  // whether it exists, so the test's runtime was hostage to an external process.
+  // On a loaded machine `gh --version` was measured at 97 s, blowing vitest's 30 s
+  // limit and failing a test that injects every other dependency.
+  { prViewer = defaultPrView, runFetcher = defaultRunsFetch, ghAvailable = ghIsAvailable } = {},
 ) {
   void _ranges;
   if (process.env.SKIP_IN_FLIGHT_CI_GUARD === "1") {
     return { name: "in-flight-ci", ok: true, skipped: "SKIP_IN_FLIGHT_CI_GUARD=1" };
   }
-  if (!ghIsAvailable()) {
+  if (!ghAvailable()) {
     return { name: "in-flight-ci", ok: true, note: "gh not available — in-flight CI check skipped (fail-open)" };
   }
 
diff --git a/tests/guard-push.test.ts b/tests/guard-push.test.ts
index 27a79f32f4..19f3efe076 100644
--- a/tests/guard-push.test.ts
+++ b/tests/guard-push.test.ts
@@ -464,6 +464,7 @@ describe("in-flight CI push guard (#HSSHRG)", () => {
     const result = inFlightCiGuard(["claude/my-fix"], [], {
       prViewer: () => ({ state: "OPEN", number: 77 }),
       runFetcher: () => runs,
+      ghAvailable: () => true,
     });
     expect(result.ok).toBe(false);
     expect(result.message).toContain("PR #77 on claude/my-fix has required CI run(s) currently IN-FLIGHT");
@@ -472,6 +473,39 @@ describe("in-flight CI push guard (#HSSHRG)", () => {
     expect(result.message).toContain("#HSSHRG");
   });
 
+  it("inFlightCiGuard fails open when gh is unavailable, without consulting the PR", () => {
+    let prViewerCalls = 0;
+    const result = inFlightCiGuard(["claude/my-fix"], [], {
+      prViewer: () => {
+        prViewerCalls += 1;
+        return { state: "OPEN", number: 77 };
+      },
+      runFetcher: () => [{ databaseId: 555, name: "CI", status: "in_progress" }],
+      ghAvailable: () => false,
+    });
+    expect(result.ok).toBe(true);
+    expect(result.note).toContain("gh not available");
+    expect(prViewerCalls).toBe(0);
+  });
+
+  it("inFlightCiGuard never spawns a process when every dependency is injected (#HSSHRG)", () => {
+    // Regression guard: the availability probe used to call the real `gh` binary
+    // even here. `gh --version` was measured at 97 s on a loaded machine, which
+    // timed this suite out at vitest's 30 s limit — a unit test must not be
+    // hostage to an external process it never asked for.
+    let spawned = 0;
+    const result = inFlightCiGuard(["claude/my-fix"], [], {
+      prViewer: () => ({ state: "OPEN", number: 77 }),
+      runFetcher: () => [{ databaseId: 555, name: "CI", status: "in_progress" }],
+      ghAvailable: () => {
+        spawned += 1;
+        return true;
+      },
+    });
+    expect(spawned).toBe(1);
+    expect(result.ok).toBe(false);
+  });
+
   it("inFlightCiGuard skips when SKIP_IN_FLIGHT_CI_GUARD=1 is set", () => {
     const previous = process.env.SKIP_IN_FLIGHT_CI_GUARD;
     process.env.SKIP_IN_FLIGHT_CI_GUARD = "1";
@@ -479,6 +513,7 @@ describe("in-flight CI push guard (#HSSHRG)", () => {
       const result = inFlightCiGuard(["claude/my-fix"], [], {
         prViewer: () => ({ state: "OPEN", number: 77 }),
         runFetcher: () => [{ databaseId: 555, name: "CI", status: "in_progress" }],
+        ghAvailable: () => true,
       });
       expect(result.ok).toBe(true);
       expect(result.skipped).toBe("SKIP_IN_FLIGHT_CI_GUARD=1");