diff --git a/e2e/account-sharing.spec.ts b/e2e/account-sharing.spec.ts
index b7e0a7984..0046c15d5 100644
--- a/e2e/account-sharing.spec.ts
+++ b/e2e/account-sharing.spec.ts
@@ -203,10 +203,19 @@ test.describe("account sharing", () => {
     // date mapping, and BOTH still pass with the card wired back to `null`.
     // Only reading the posted body proves the value a person typed is the
     // value the server receives, which is the half that was missing.
-    const lapse = ownerPage.locator('[data-slot="grant-invite-expires"]');
+    // The VISIBLE overlay, not the hidden ISO mirror: `data-slot` rides
+    // `{...rest}` onto `DateField`'s hidden input, so the old selector resolved
+    // to an element that can never be visible and typed into nothing.
+    const lapse = ownerPage.getByTestId("grant-invite-expires-input");
     await expect(lapse).toBeVisible();
     const chosenDay = isoDayFromNow(30);
     await lapse.fill(chosenDay);
+    // The overlay commits on blur; without it the ISO text sits in local state
+    // and the hidden mirror still holds the old value when the form submits.
+    await lapse.blur();
+    await expect(
+      ownerPage.locator('input[data-slot="grant-invite-expires"]'),
+    ).toHaveValue(chosenDay);
 
     // The level, through the real control and onto the real wire.
     //
diff --git a/src/components/settings/access/grant-invite-card.tsx b/src/components/settings/access/grant-invite-card.tsx
index eeac08f28..be3a92285 100644
--- a/src/components/settings/access/grant-invite-card.tsx
+++ b/src/components/settings/access/grant-invite-card.tsx
@@ -297,7 +297,15 @@ export function GrantInviteCard() {
           </Label>
           <DateField
             id="grant-invite-expires"
+            // `data-slot` rides `{...rest}` onto `DateField`'s HIDDEN mirror
+            // input — the one that carries the ISO value for a native submit.
+            // A browser test that targeted it found an invisible element and a
+            // `fill()` that typed into nothing. `data-testid` is the
+            // primitive's own affordance for the VISIBLE overlay, which is the
+            // control a person actually types into, so the browser test uses
+            // that and the slot stays where every other caller expects it.
             data-slot="grant-invite-expires"
+            data-testid="grant-invite-expires-input"
             value={expiresOn}
             min={tomorrowIso(ownerTimezone)}
             onChange={setExpiresOn}