diff --git a/changelog.d/maintenance/11866-config-expiry-time-bomb-test.md b/changelog.d/maintenance/11866-config-expiry-time-bomb-test.md
new file mode 100644
index 0000000000..9e58941cfc
--- /dev/null
+++ b/changelog.d/maintenance/11866-config-expiry-time-bomb-test.md
@@ -0,0 +1,4 @@
+- Added a unit test that fails seven days before any dated pack under `config/`
+  (`validUntil` and sibling keys) lapses, naming the file and key. The Alibaba
+  free-tier pack expired on 2026-08-27 and turned every PR red the next morning
+  with no commit involved; renewal now happens on someone's terms, not the clock's.
diff --git a/scripts/check/lib/configExpiry.mjs b/scripts/check/lib/configExpiry.mjs
new file mode 100644
index 0000000000..110a998c66
--- /dev/null
+++ b/scripts/check/lib/configExpiry.mjs
@@ -0,0 +1,90 @@
+/**
+ * scripts/check/lib/configExpiry.mjs
+ *
+ * Finds dated validity fields in JSON config packs so a test can fail BEFORE
+ * they lapse. Origin: config/alibaba-free-tier-allowlist.json carried
+ * `"validUntil": "2026-08-27"`; on 2026-08-28 the loader started (correctly)
+ * rejecting the pack and a test that asserted "the shipped pack loads" turned
+ * every PR and main red with no commit involved (#11866). A time bomb, not a
+ * regression — and the only kind of defect a diff review can never catch.
+ *
+ * Pure helpers; the repo-wide assertion lives in
+ * tests/unit/config-expiry-time-bomb.test.ts.
+ */
+import fs from "node:fs";
+import path from "node:path";
+
+export const EXPIRY_KEY =
+  /^(validUntil|valid_until|validTo|valid_to|expiresAt|expires_at|expiry|expires)$/;
+const DAY_MS = 86_400_000;
+
+/**
+ * Walks a parsed JSON value and returns every string-valued expiry field.
+ * @returns {{ file: string, keyPath: string, raw: string, expiresAt: number|null }[]}
+ */
+export function collectExpiryFields(value, file, keyPath = []) {
+  const out = [];
+  if (Array.isArray(value)) {
+    value.forEach((v, i) => out.push(...collectExpiryFields(v, file, [...keyPath, String(i)])));
+    return out;
+  }
+  if (!value || typeof value !== "object") return out;
+  for (const [key, v] of Object.entries(value)) {
+    const kp = [...keyPath, key];
+    if (EXPIRY_KEY.test(key) && typeof v === "string") {
+      const ms = Date.parse(v);
+      out.push({ file, keyPath: kp.join("."), raw: v, expiresAt: Number.isFinite(ms) ? ms : null });
+    } else if (v && typeof v === "object") {
+      out.push(...collectExpiryFields(v, file, kp));
+    }
+  }
+  return out;
+}
+
+/** @returns {"expired"|"expiring"|"ok"|"unparseable"} */
+export function classifyExpiry(field, nowMs, warnDays = 7) {
+  if (field.expiresAt === null) return "unparseable";
+  if (field.expiresAt < nowMs) return "expired";
+  if (field.expiresAt < nowMs + warnDays * DAY_MS) return "expiring";
+  return "ok";
+}
+
+/** All *.json under dir, recursively, skipping node_modules. Sorted for stable output. */
+export function walkJsonFiles(dir) {
+  const out = [];
+  const stack = [dir];
+  while (stack.length > 0) {
+    const current = stack.pop();
+    let entries;
+    try {
+      entries = fs.readdirSync(current, { withFileTypes: true });
+    } catch {
+      continue;
+    }
+    for (const e of entries) {
+      const full = path.join(current, e.name);
+      if (e.isDirectory()) {
+        if (e.name !== "node_modules") stack.push(full);
+      } else if (e.isFile() && e.name.endsWith(".json")) {
+        out.push(full);
+      }
+    }
+  }
+  return out.sort();
+}
+
+/**
+ * Scans every JSON file under `dir`; `file` in the result is relative to `dir`
+ * with forward slashes, so allowlists can key on it portably.
+ */
+export function scanConfigExpiry(dir) {
+  return walkJsonFiles(dir).flatMap((f) => {
+    let parsed;
+    try {
+      parsed = JSON.parse(fs.readFileSync(f, "utf8"));
+    } catch {
+      return []; // not this scanner's job to validate JSON
+    }
+    return collectExpiryFields(parsed, path.relative(dir, f).split(path.sep).join("/"));
+  });
+}
diff --git a/tests/unit/config-expiry-time-bomb.test.ts b/tests/unit/config-expiry-time-bomb.test.ts
new file mode 100644
index 0000000000..7740e09e5c
--- /dev/null
+++ b/tests/unit/config-expiry-time-bomb.test.ts
@@ -0,0 +1,135 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+
+import {
+  classifyExpiry,
+  collectExpiryFields,
+  scanConfigExpiry,
+} from "../../scripts/check/lib/configExpiry.mjs";
+
+/**
+ * Time bombs: config packs with a `validUntil` (or sibling key) that lapse with
+ * no commit involved. The Alibaba free-tier pack expired on 2026-08-27 and from
+ * the 28th every PR and main carried a red Unit Tests shard (#11866). Nothing a
+ * diff review could have caught.
+ *
+ * This suite fails SEVEN DAYS BEFORE any pack under config/ lapses, naming the
+ * file and key, so renewal happens on someone's terms instead of the clock's.
+ */
+const ROOT = join(import.meta.dirname, "../..");
+const CONFIG_DIR = join(ROOT, "config");
+const DAY = 86_400_000;
+const WARN_DAYS = 7;
+
+/**
+ * Packs known to be expired/expiring, each pinned to the issue that owns the
+ * renewal decision. An entry whose pack is no longer expiring FAILS below as a
+ * stale allowlist entry — remove it when the pack is renewed.
+ */
+const ALLOWLIST: Record<string, string> = {
+  "alibaba-free-tier-allowlist.json":
+    "#11866 — validUntil 2026-08-27 has passed; the loader already falls back to the embedded list, and renewing the curated free-tier pack is an operator data decision, not a test fix",
+};
+
+const NOW = Date.UTC(2026, 7, 28); // 2026-08-28, fixed: this suite must not itself depend on the clock
+const day = (offset: number) => new Date(NOW + offset * DAY).toISOString().slice(0, 10);
+
+test("collectExpiryFields: finds nested and array-nested expiry keys, ignores non-string values", () => {
+  const fields = collectExpiryFields(
+    {
+      validUntil: day(3),
+      nested: { expiresAt: day(30), other: "x" },
+      list: [{ expiry: day(-1) }, { expires: 12345 }],
+      expires_at: "not a date",
+    },
+    "pack.json"
+  );
+  assert.deepEqual(
+    fields.map((f) => [f.keyPath, f.expiresAt === null ? null : "date"]),
+    [
+      ["validUntil", "date"],
+      ["nested.expiresAt", "date"],
+      ["list.0.expiry", "date"],
+      ["expires_at", null],
+    ]
+  );
+});
+
+test("classifyExpiry: expired / expiring inside the warning window / ok / unparseable", () => {
+  const f = (raw: string) => ({
+    file: "p",
+    keyPath: "validUntil",
+    raw,
+    expiresAt: Number.isFinite(Date.parse(raw)) ? Date.parse(raw) : null,
+  });
+  assert.equal(classifyExpiry(f(day(-1)), NOW, WARN_DAYS), "expired");
+  assert.equal(
+    classifyExpiry(f(day(0)), NOW, WARN_DAYS),
+    "expiring",
+    "lapsing today is already too late to be 'ok'"
+  );
+  assert.equal(classifyExpiry(f(day(6)), NOW, WARN_DAYS), "expiring");
+  assert.equal(classifyExpiry(f(day(8)), NOW, WARN_DAYS), "ok");
+  assert.equal(classifyExpiry(f("never"), NOW, WARN_DAYS), "unparseable");
+});
+
+test("scanConfigExpiry: walks a config tree, skips node_modules and invalid JSON, keys files portably", () => {
+  const dir = mkdtempSync(join(tmpdir(), "cfg-expiry-"));
+  try {
+    mkdirSync(join(dir, "sub"), { recursive: true });
+    mkdirSync(join(dir, "node_modules", "dep"), { recursive: true });
+    writeFileSync(join(dir, "a.json"), JSON.stringify({ validUntil: day(3) }));
+    writeFileSync(join(dir, "sub", "b.json"), JSON.stringify({ deep: { expiresAt: day(40) } }));
+    writeFileSync(
+      join(dir, "node_modules", "dep", "c.json"),
+      JSON.stringify({ validUntil: day(-5) })
+    );
+    writeFileSync(join(dir, "broken.json"), "{ not json");
+    writeFileSync(join(dir, "notes.txt"), JSON.stringify({ validUntil: day(-5) }));
+    const found = scanConfigExpiry(dir).map((f) => `${f.file}:${f.keyPath}`);
+    assert.deepEqual(found, ["a.json:validUntil", "sub/b.json:deep.expiresAt"]);
+  } finally {
+    rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+test(`repo: no pack under config/ lapses within ${WARN_DAYS} days unless its renewal is tracked`, (t) => {
+  const fields = scanConfigExpiry(CONFIG_DIR);
+  // Positive anchor: the scanner must be seeing SOMETHING, or a renamed key
+  // would silently turn this whole suite into a no-op.
+  assert.ok(
+    fields.length >= 1,
+    "expected at least one dated pack under config/ (the Alibaba allowlist) — if the key was renamed, extend EXPIRY_KEY"
+  );
+
+  const failures: string[] = [];
+  const seenAllowlisted = new Set<string>();
+  for (const f of fields) {
+    const status = classifyExpiry(f, Date.now(), WARN_DAYS);
+    const tracked = ALLOWLIST[f.file];
+    if (status === "unparseable") {
+      t.diagnostic(`${f.file} ${f.keyPath}="${f.raw}" is not a date — not monitored`);
+      continue;
+    }
+    if (status === "ok") continue;
+    if (tracked) {
+      seenAllowlisted.add(f.file);
+      t.diagnostic(`${f.file} ${f.keyPath}=${f.raw} is ${status} — tracked: ${tracked}`);
+      continue;
+    }
+    failures.push(
+      `${f.file} → ${f.keyPath}=${f.raw} is ${status}: renew the pack (or track it in ALLOWLIST with its issue)`
+    );
+  }
+  for (const file of Object.keys(ALLOWLIST)) {
+    if (!seenAllowlisted.has(file)) {
+      failures.push(
+        `stale ALLOWLIST entry: ${file} is no longer expired/expiring — remove it (${ALLOWLIST[file]})`
+      );
+    }
+  }
+  assert.deepEqual(failures, [], failures.join("\n"));
+});