diff --git a/nodejs/routes/group.js b/nodejs/routes/group.js
index 9523c50..9e51bd3 100644
--- a/nodejs/routes/group.js
+++ b/nodejs/routes/group.js
@@ -82,8 +82,13 @@ router.put('/:group/:uid', async function(req, res, next){
 
 		var group = await Group.get(req.params.group);
 		var user = await User.get(req.params.uid);
+		const results = await group.addMember(user);
+		// Group membership feeds directly into cached-User-derived state
+		// (isServiceAccount, isAdmin, group-gated nav/UI) -- without this,
+		// a membership change here is invisible for up to the cache's TTL.
+		User.clearCache();
 		return res.json({
-			results: await group.addMember(user),
+			results,
 			message: `Added user ${req.params.uid} to ${req.params.group} group.`
 		});
 	}catch(error){
@@ -98,8 +103,10 @@ router.delete('/:group/:uid', async function(req, res, next){
 
 		var group = await Group.get(req.params.group);
 		var user = await User.get(req.params.uid);
+		const results = await group.removeMember(user);
+		User.clearCache();
 		return res.json({
-			results: await group.removeMember(user),
+			results,
 			message: `Removed user ${req.params.uid} from ${req.params.group} group.`
 		});
 	}catch(error){
diff --git a/nodejs/tests/group.test.js b/nodejs/tests/group.test.js
index 9c2009f..8a20a0d 100644
--- a/nodejs/tests/group.test.js
+++ b/nodejs/tests/group.test.js
@@ -151,6 +151,32 @@ describe('Groups — member management', () => {
 		const members = Array.isArray(group.member) ? group.member : [group.member];
 		expect(members.some(dn => dn && dn.includes(MEMBER_UID))).toBe(false);
 	});
+
+	// Regression: adding/removing a member here didn't clear User's LRU
+	// cache (ttl 5 minutes), so isServiceAccount -- derived from
+	// app_sso_service_account membership at GET /api/user/:uid time -- could
+	// stay wrong for up to 5 minutes after the group change. In production
+	// this hid a real person's account from the Users page's "People" tab
+	// (it filters out anything with isServiceAccount) for however long the
+	// stale cache entry lived, which looked exactly like the account had
+	// vanished.
+	test('PUT app_sso_service_account/:uid immediately flips isServiceAccount (no stale cache)', async () => {
+		const added = await request(app)
+			.put(`/api/group/app_sso_service_account/${MEMBER_UID}`)
+			.set('auth-token', token);
+		expect(added.status).toBe(200);
+
+		const afterAdd = await request(app).get(`/api/user/${MEMBER_UID}`).set('auth-token', token);
+		expect(afterAdd.body.results.isServiceAccount).toBeTruthy();
+
+		const removed = await request(app)
+			.delete(`/api/group/app_sso_service_account/${MEMBER_UID}`)
+			.set('auth-token', token);
+		expect(removed.status).toBe(200);
+
+		const afterRemove = await request(app).get(`/api/user/${MEMBER_UID}`).set('auth-token', token);
+		expect(afterRemove.body.results.isServiceAccount).toBeFalsy();
+	});
 });
 
 describe('Groups — owner management', () => {