diff --git a/packages/loopover-engine/src/scoring/pending-pr-scenarios.ts b/packages/loopover-engine/src/scoring/pending-pr-scenarios.ts
index c5f8e3f039..d2c7e70fae 100644
--- a/packages/loopover-engine/src/scoring/pending-pr-scenarios.ts
+++ b/packages/loopover-engine/src/scoring/pending-pr-scenarios.ts
@@ -139,6 +139,8 @@ export function classifyOpenPullRequest(args: {
   checks: CheckSummaryRecord[];
   duplicateProne?: boolean | undefined;
   missingTests?: boolean | undefined;
+  // #8872: injected wall-clock for a deterministic staleness boundary; defaults to Date.now() in daysSince.
+  nowMs?: number | undefined;
 }): ClassifiedOpenPullRequest {
   const reasons: string[] = [];
   if (args.roleContext.maintainerLane) {
@@ -159,7 +161,7 @@ export function classifyOpenPullRequest(args: {
   const checkFailureCount = args.checks.filter(
     (check) => check.conclusion === "failure" || check.conclusion === "timed_out" || check.conclusion === "cancelled",
   ).length;
-  const ageDays = daysSince(args.pr.updatedAt ?? args.pr.createdAt);
+  const ageDays = daysSince(args.pr.updatedAt ?? args.pr.createdAt, args.nowMs);
 
   if (args.duplicateProne) reasons.push("Overlapping open work detected in the same repo (possible duplicate or WIP collision).");
   if (args.missingTests) reasons.push("Cached file list shows code changes without matching test files.");
@@ -210,11 +212,14 @@ function sameLogin(value: string | null | undefined, login: string): boolean {
   return Boolean(value && value.toLowerCase() === login.toLowerCase());
 }
 
-function daysSince(value: string | null | undefined): number {
+// #8872: nowMs is injectable (defaulting only here, at the call boundary) so classifyOpenPullRequest's
+// staleness split is deterministic and testable at exact day boundaries, matching this module's own
+// "pure classification/detection logic" contract and the nowMs injection its opportunity-freshness sibling uses.
+function daysSince(value: string | null | undefined, nowMs = Date.now()): number {
   if (!value) return Number.POSITIVE_INFINITY;
   const parsed = Date.parse(value);
   if (!Number.isFinite(parsed)) return Number.POSITIVE_INFINITY;
-  return Math.max(0, (Date.now() - parsed) / 86_400_000);
+  return Math.max(0, (nowMs - parsed) / 86_400_000);
 }
 
 function nonNegative(value: number | undefined): number {
diff --git a/test/unit/pending-pr-scenarios.test.ts b/test/unit/pending-pr-scenarios.test.ts
index 6127d4fbab..788219d971 100644
--- a/test/unit/pending-pr-scenarios.test.ts
+++ b/test/unit/pending-pr-scenarios.test.ts
@@ -99,6 +99,22 @@ describe("pending PR scenario detection", () => {
     expect(classified.reasons.join(" ")).toMatch(/failing or cancelled check/i);
   });
 
+  // #8872: with an injected nowMs the staleness split is deterministic and testable at the exact 14-day
+  // boundary — an approved, passing-checks PR flips from merge_ready to stale_likely_close at ageDays >= 14.
+  it("splits merge_ready vs stale_likely_close at the exact 14-day boundary with an injected nowMs (#8872)", () => {
+    const nowMs = Date.parse("2026-07-01T00:00:00.000Z");
+    const staleMs = 14 * 86_400_000;
+    const base = { roleContext: outsideContributorRole, reviews: [approvedReview(1)], checks: [], nowMs };
+    // exactly 14 days old → ageDays >= STALE_DAYS → stale_likely_close.
+    expect(
+      classifyOpenPullRequest({ ...base, pr: pr({ number: 1, updatedAt: new Date(nowMs - staleMs).toISOString() }) }).classification,
+    ).toBe("stale_likely_close");
+    // one millisecond short of 14 days → still merge_ready.
+    expect(
+      classifyOpenPullRequest({ ...base, pr: pr({ number: 1, updatedAt: new Date(nowMs - staleMs + 1).toISOString() }) }).classification,
+    ).toBe("merge_ready");
+  });
+
   it("counts stale approved PRs as pending closes and projects the post-cleanup open count", () => {
     const staleDate = new Date(Date.now() - 30 * 86_400_000).toISOString();
     const detection = detectPendingPrScenario({