diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 7dbbcdd21..d37aedff9 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -6036,7 +6036,10 @@ model AccountGrant {
   revokedBy AccountGrantRevoker? @map("revoked_by")
 
   /// Optional lapse date. Checked live on every resolution, so an expired
-  /// grant stops conferring access without anything having to sweep it.
+  /// grant stops conferring access without anything having to sweep it. A
+  /// managed-profile invitation may carry an expiry while awaiting consent;
+  /// accepting its MANAGE grant clears this field because an active Guardian
+  /// ends only through an explicit lifecycle transition.
   expiresAt  DateTime? @map("expires_at")
   /// Refreshed fire-and-forget when the grant is exercised, the same posture
   /// as `ApiToken.lastUsedAt`. The owner's panel reads it to answer "is this
diff --git a/src/lib/sharing/grants.ts b/src/lib/sharing/grants.ts
index 908294b4e..41b3e067f 100644
--- a/src/lib/sharing/grants.ts
+++ b/src/lib/sharing/grants.ts
@@ -432,6 +432,28 @@ export async function acceptGrant(
     throw await refusalFor(input.grantId, { granteeId: input.granteeId }, db);
   }
 
+  const accepted = await db.accountGrant.findUniqueOrThrow({
+    where: { id: input.grantId },
+    include: { grantor: { select: { managedProfileAt: true } } },
+  });
+
+  // The expiry belongs to the invitation, not to a Guardian relationship. A
+  // managed profile still lets its creator set an expiry while the invitation
+  // waits for the other adult's consent, but once accepted the MANAGE grant is
+  // standing until a Guardian explicitly ends it. Ordinary adult-record grants
+  // retain their requested expiry unchanged.
+  if (accepted.access === "MANAGE" && accepted.grantor.managedProfileAt) {
+    await db.accountGrant.updateMany({
+      where: {
+        id: accepted.id,
+        granteeId: input.granteeId,
+        acceptedAt: { not: null },
+        revokedAt: null,
+      },
+      data: { expiresAt: null },
+    });
+  }
+
   return db.accountGrant.findUniqueOrThrow({ where: { id: input.grantId } });
 }