diff --git a/DECISIONS.md b/DECISIONS.md
index db78733..f98ff76 100644
--- a/DECISIONS.md
+++ b/DECISIONS.md
@@ -1782,3 +1782,7 @@ Implementation decisions not spelled out in `memory-bank/implementation-plan.md`
 ## CR-023 recorded (Shop Time Counts as Rest)
 
 - **Numbering:** received as "CR-021 — Shop Time Counts as Rest" for "Phase 21"; stored as **CR-023**, built as **Phase 23** (its 21.n = 23.n), since CR-021 (Independent Pilots) and CR-022 (Welcome Screens) exist. Its decision CR-021.D1 is **0.5.135**. Its references: CR-006 → CR-009, CR-011 → CR-014, CR-019 → CR-021; CR-004 is unchanged.
+
+## Step 23.1
+
+- **The content test compares in game hours**, as the CR asks: shop time is set in real minutes and rest in game hours, so the shop time is multiplied by the time compression first.
diff --git a/memory-bank/progress.md b/memory-bank/progress.md
index 723f09d..d04c113 100644
--- a/memory-bank/progress.md
+++ b/memory-bank/progress.md
@@ -510,7 +510,7 @@ Spec: `memory-bank/change-requests/CR-022-welcome-screens.md` (received as "CR-0
 
 Spec: `memory-bank/change-requests/CR-023-shop-time-rest.md` (received as "CR-021 … Phase 21"). New decision recorded as plan §0.5.135.
 
-- [ ] Step 23.1 — Content test
+- [x] **Step 23.1 — Content test.** Every upgrade level's shop time, in game hours (real minutes × time compression), is at least `restGameHours`: today 10, 20 and 30 game hours against a 10-hour rest. Test: `packages/content/test/upgrades.test.ts`.
 - [ ] Step 23.2 — Sim and engine: duty reset on upgrade completion
 - [ ] Step 23.3 — Client: status line
 - [ ] Step 23.4 — Regression
diff --git a/packages/content/test/upgrades.test.ts b/packages/content/test/upgrades.test.ts
index 264e7cd..07f1dad 100644
--- a/packages/content/test/upgrades.test.ts
+++ b/packages/content/test/upgrades.test.ts
@@ -81,3 +81,14 @@ describe("ship upgrades content (CR-009)", () => {
     );
   });
 });
+
+describe("shop time counts as rest (Step 23.1, decision 0.5.135)", () => {
+  it("keeps every upgrade level in the shop for at least a full rest, in game hours", () => {
+    const { upgradeLevels, timeCompression, restGameHours } = gameConfig;
+    for (const level of upgradeLevels) {
+      // Real minutes × compression = game minutes.
+      const shopGameHours = (level.shopRealMinutes * timeCompression) / 60;
+      expect(shopGameHours).toBeGreaterThanOrEqual(restGameHours);
+    }
+  });
+});