diff --git a/app/api/ready/route.ts b/app/api/ready/route.ts
index 0c37117..4eeaedd 100644
--- a/app/api/ready/route.ts
+++ b/app/api/ready/route.ts
@@ -10,9 +10,11 @@ import { checkAllDependencies, isReady } from "@/lib/health-checks";
 // readiness probe at this route, not /api/health, to stop routing traffic to
 // an instance whose database is down without restarting it.
 //
-// Today the only load-bearing dependency is the database (see
+// Load-bearing by absence: only the database (see
 // `lib/health-checks.ts#isReady`) -- engine/stripe/queue are optional
-// integrations 0pt is designed to run without.
+// integrations 0pt is designed to run without. Load-bearing by FAILURE: all
+// of them. A dependency somebody configured and that then fails a live round
+// trip makes this instance not-ready, whichever one it is.
 export async function GET() {
   const deps = await checkAllDependencies();
   const ready = isReady(deps);
diff --git a/lib/health-checks.ts b/lib/health-checks.ts
index 2e737e0..084906d 100644
--- a/lib/health-checks.ts
+++ b/lib/health-checks.ts
@@ -165,10 +165,31 @@ export function hasDegradedDependency(deps: DependencyResults): boolean {
 
 /**
  * Readiness (unlike liveness) treats "not configured" for the deps this app
- * cannot serve real traffic without as not-ready too. Only `db` is load-bearing
- * today -- engine/stripe/queue are optional integrations the app is designed
- * to run without (see .env.example).
+ * cannot serve real traffic without as not-ready too. `db` is the only
+ * dependency that is load-bearing merely by being absent -- engine/stripe/
+ * queue are optional integrations the app is designed to run WITHOUT (see
+ * .env.example), so "not_configured" for those stays ready.
+ *
+ * But "optional to run without" is not the same as "optional to run BROKEN".
+ * A dependency in the "error" state was deliberately configured by an
+ * operator AND then failed a live round trip -- somebody asked for it and it
+ * is not answering. Readiness fails closed on that too.
+ *
+ * Measured 2026-09-25 on the production deployment (0pt.app / api.0pt.app),
+ * which is exactly the hole this closes:
+ *
+ *   GET /api/health -> HTTP 200  {"ok":false, ..., "engine":"error",
+ *                                 "detail":{"engine":"This operation was aborted"}}
+ *   GET /api/ready  -> HTTP 200  {"ready":true, "db":"ok", "engine":"error"}
+ *
+ * ENGINE_URL pointed at `http://0pt-engine:8000`, a hostname with no DNS
+ * record anywhere on the fleet (`getent hosts 0pt-engine` -> nothing; no such
+ * container on server5-11). The data engine -- 0pt's whole product -- had
+ * been absent for the container's entire 17.9 h uptime, and every signal
+ * above it was green. `ok:false` in a 200 body is not a signal; nothing reads
+ * bodies.
  */
 export function isReady(deps: DependencyResults): boolean {
-  return deps.db.status === "ok";
+  if (deps.db.status !== "ok") return false;
+  return !Object.values(deps).some((d) => d.status === "error");
 }
diff --git a/tests/lib/health-checks.test.ts b/tests/lib/health-checks.test.ts
index 406b339..50ed15f 100644
--- a/tests/lib/health-checks.test.ts
+++ b/tests/lib/health-checks.test.ts
@@ -179,7 +179,31 @@ describe("hasDegradedDependency / isReady", () => {
     expect(isReady(deps({ db: { status: "error" } }))).toBe(false);
   });
 
-  it("isReady is true once db is ok, regardless of optional integrations", () => {
+  it("isReady is true once db is ok and no configured integration is failing", () => {
     expect(isReady(deps({ db: { status: "ok" } }))).toBe(true);
   });
+
+  it("isReady stays true for integrations that are merely absent (0pt boots without them)", () => {
+    expect(
+      isReady(
+        deps({
+          db: { status: "ok" },
+          engine: { status: "not_configured" },
+          stripe: { status: "not_configured" },
+          queue: { status: "not_integrated" },
+        }),
+      ),
+    ).toBe(true);
+  });
+
+  it("REGRESSION: isReady is false when a CONFIGURED integration is failing its live round trip", () => {
+    // Mätt i prod 2026-09-25: ENGINE_URL pekade på 0pt-engine:8000, en värd
+    // utan DNS-post någonstans i flottan, och /api/ready svarade ändå
+    // {"ready":true,...,"engine":"error"}. En konfigurerad-men-död motor är
+    // inte "valfri" -- någon har bett om den och den svarar inte.
+    expect(isReady(deps({ db: { status: "ok" }, engine: { status: "error", detail: "fetch failed" } }))).toBe(
+      false,
+    );
+    expect(isReady(deps({ db: { status: "ok" }, stripe: { status: "error", detail: "bad key" } }))).toBe(false);
+  });
 });