diff --git a/src/components/medications/sections/inventory-section.tsx b/src/components/medications/sections/inventory-section.tsx
index 6473f207f..c31979542 100644
--- a/src/components/medications/sections/inventory-section.tsx
+++ b/src/components/medications/sections/inventory-section.tsx
@@ -75,6 +75,7 @@ import {
   apiPost,
   apiPut,
 } from "@/lib/api/api-fetch";
+import { startsInUseClock } from "@/lib/medications/inventory/clock-container-types";
 import type { SupplySummary } from "@/lib/medications/inventory/summary";
 
 /**
@@ -169,15 +170,6 @@ const STATE_BADGE: Record<
   USED_UP: "outline",
 };
 
-/**
- * Container kinds whose first opening starts a 30-day degradation clock.
- * Mirrors `IN_USE_CLOCK_CONTAINER_TYPES` in
- * `src/lib/medications/inventory/state-machine.ts` — the server owns the
- * transition; the client only needs to know which helper text to show
- * beside the opening date.
- */
-const CLOCK_CONTAINER_TYPES: readonly ContainerType[] = ["PEN", "AMPOULE"];
-
 /** Default container kind for the register flow, from the delivery form. */
 function defaultContainerType(deliveryForm: string | undefined): ContainerType {
   if (deliveryForm === "INJECTION") return "PEN";
@@ -971,7 +963,7 @@ export function AdjustInventoryDialog({
             id="inventory-edit-opened-helper"
             className="text-muted-foreground text-xs"
           >
-            {CLOCK_CONTAINER_TYPES.includes(item.containerType)
+            {startsInUseClock(item.containerType)
               ? t("medications.detail.bestand.editOpenedHelperClock")
               : t("medications.detail.bestand.editOpenedHelper")}
           </p>
diff --git a/src/lib/medications/inventory/clock-container-types.ts b/src/lib/medications/inventory/clock-container-types.ts
new file mode 100644
index 000000000..ed37c367f
--- /dev/null
+++ b/src/lib/medications/inventory/clock-container-types.ts
@@ -0,0 +1,33 @@
+/**
+ * The one owner of "which container kinds start a degradation clock when
+ * they are first opened".
+ *
+ * The state machine decides the transition and the settings client decides
+ * which helper text to put beside the opening date. Both need the same
+ * list, but the state machine types itself against the generated Prisma
+ * client, which a browser bundle cannot carry — so the client kept its own
+ * copy of the two literals with a comment promising they matched. Nothing
+ * held the promise, and a release spent fixing a fact that drifted is a bad
+ * place to keep a second one.
+ *
+ * So the list lives here: string literals and a pure predicate, no imports,
+ * safe on either side of the boundary. `state-machine.ts` re-exports it
+ * under the Prisma enum (`satisfies`), which turns a renamed or dropped
+ * container kind into a compile error rather than a member that silently
+ * stops matching. The per-kind reasoning stays in the state machine's
+ * docblock, where the transition it drives is.
+ */
+
+export const IN_USE_CLOCK_CONTAINER_TYPES = ["PEN", "AMPOULE"] as const;
+
+/**
+ * Does opening this container start the in-use window? Takes a loose
+ * `string` so the client can ask about a container kind it read off the
+ * wire without narrowing first; an unrecognised kind answers `false`,
+ * which is the honest side (no deadline nobody entered).
+ */
+export function startsInUseClock(containerType: string): boolean {
+  return (IN_USE_CLOCK_CONTAINER_TYPES as readonly string[]).includes(
+    containerType,
+  );
+}
diff --git a/src/lib/medications/inventory/state-machine.ts b/src/lib/medications/inventory/state-machine.ts
index 10b49884c..e3c5ca27f 100644
--- a/src/lib/medications/inventory/state-machine.ts
+++ b/src/lib/medications/inventory/state-machine.ts
@@ -79,6 +79,10 @@ import type {
   MedicationContainerType,
   MedicationInventoryState,
 } from "@/generated/prisma/client";
+import {
+  IN_USE_CLOCK_CONTAINER_TYPES as CLOCK_CONTAINER_TYPES,
+  startsInUseClock,
+} from "./clock-container-types";
 
 /** Default in-use window per EMA EPAR §6.3 for the strictest GLP-1
  *  agonists (Mounjaro, Saxenda). 30 days. */
@@ -90,17 +94,18 @@ export const DEFAULT_IN_USE_WINDOW_DAYS = 30;
  * Every other kind holds individually sealed units (or an unknown
  * arrangement) and expires only on its printed date. See the module
  * docblock for the per-member reasoning.
+ *
+ * The list itself lives in `./clock-container-types`, which the settings
+ * client can import; `satisfies` here is the drift guard, so a container
+ * kind renamed or dropped from the column stops compiling instead of
+ * quietly never matching.
  */
-export const IN_USE_CLOCK_CONTAINER_TYPES = [
-  "PEN",
-  "AMPOULE",
-] as const satisfies readonly MedicationContainerType[];
+export const IN_USE_CLOCK_CONTAINER_TYPES =
+  CLOCK_CONTAINER_TYPES satisfies readonly MedicationContainerType[];
 
 /** Does opening this container start the in-use window? */
 export function hasInUseClock(containerType: MedicationContainerType): boolean {
-  return (IN_USE_CLOCK_CONTAINER_TYPES as readonly string[]).includes(
-    containerType,
-  );
+  return startsInUseClock(containerType);
 }
 
 const MS_PER_DAY = 24 * 60 * 60 * 1000;