From 6408e4aa8aa60d7705f89ee1f7f8badcc2cfcd4f Mon Sep 17 00:00:00 2001
From: Suhrid Marwah <suhridmarwah07@gmail.com>
Date: Thu, 9 Apr 2026 10:27:15 +0530
Subject: [PATCH 1/3] fix(scaffolder): handle after=0 in task events polling
 endpoint

Signed-off-by: Suhrid Marwah <suhridmarwah07@gmail.com>
---
 plugins/scaffolder-backend/src/service/router.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/plugins/scaffolder-backend/src/service/router.ts b/plugins/scaffolder-backend/src/service/router.ts
index 9e84b38e39..f7c5913e61 100644
--- a/plugins/scaffolder-backend/src/service/router.ts
+++ b/plugins/scaffolder-backend/src/service/router.ts
@@ -951,7 +951,8 @@ export async function createRouter(
           isTaskAuthorized,
         });
 
-        const after = Number(req.query.after) || undefined;
+        const after =
+          req.query.after !== undefined ? Number(req.query.after) : undefined;
 
         // cancel the request after 30 seconds. this aligns with the recommendations of RFC 6202.
         const timeout = setTimeout(() => {

From 8a42f77daae98c1dc374d42ae30a1831b6ae2df2 Mon Sep 17 00:00:00 2001
From: Suhrid Marwah <suhridmarwah07@gmail.com>
Date: Thu, 9 Apr 2026 10:46:26 +0530
Subject: [PATCH 2/3] chore(changeset): add changeset for after=0 fix

Signed-off-by: Suhrid Marwah <suhridmarwah07@gmail.com>
---
 .changeset/fix-scaffolder-task-events-after-zero.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/fix-scaffolder-task-events-after-zero.md

diff --git a/.changeset/fix-scaffolder-task-events-after-zero.md b/.changeset/fix-scaffolder-task-events-after-zero.md
new file mode 100644
index 0000000000..5ff9bc2de6
--- /dev/null
+++ b/.changeset/fix-scaffolder-task-events-after-zero.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-scaffolder-backend': patch
+---
+
+Fix handling of `after=0` in task events endpoint

From 1d95cd302d1fb70c210c9a2d20c918dff7c3e7b1 Mon Sep 17 00:00:00 2001
From: Suhrid Marwah <suhridmarwah07@gmail.com>
Date: Thu, 9 Apr 2026 10:54:11 +0530
Subject: [PATCH 3/3] test(scaffolder): add test for after=0 query param
 handling

Signed-off-by: Suhrid Marwah <suhridmarwah07@gmail.com>
---
 .../src/service/router.test.ts                | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/plugins/scaffolder-backend/src/service/router.test.ts b/plugins/scaffolder-backend/src/service/router.test.ts
index 223909f2c9..5b463ee75b 100644
--- a/plugins/scaffolder-backend/src/service/router.test.ts
+++ b/plugins/scaffolder-backend/src/service/router.test.ts
@@ -1572,6 +1572,46 @@ data: {"id":1,"taskId":"a-random-id","type":"completion","createdAt":"","body":{
       });
       expect(subscriber!.closed).toBe(true);
     });
+
+    it('should handle after=0 query param correctly', async () => {
+      const { router, taskBroker } = await createTestRouter();
+      (taskBroker.get as jest.Mocked<TaskBroker>['get']).mockResolvedValue({
+        id: 'a-random-id',
+        spec: {} as any,
+        status: 'completed',
+        createdAt: '',
+        secrets: {
+          __initiatorCredentials: JSON.stringify(credentials),
+        },
+        createdBy: '',
+      });
+      let subscriber: ZenObservable.SubscriptionObserver<{
+        events: SerializedTaskEvent[];
+      }>;
+      (
+        taskBroker.event$ as jest.Mocked<TaskBroker>['event$']
+      ).mockImplementation(() => {
+        return new ObservableImpl(observer => {
+          subscriber = observer;
+          observer.next({ events: [] });
+        });
+      });
+
+      const response = await request(router)
+        .get('/v2/tasks/a-random-id/events')
+        .query({ after: 0 });
+
+      expect(response.status).toEqual(200);
+      expect(response.body).toEqual([]);
+
+      expect(taskBroker.event$).toHaveBeenCalledTimes(1);
+      expect(taskBroker.event$).toHaveBeenCalledWith({
+        taskId: 'a-random-id',
+        after: 0,
+      });
+      expect(subscriber!.closed).toBe(true);
+    });
+
     it('disallows users from seeing events for tasks they do not own', async () => {
       const { permissions, router, taskBroker } = await createTestRouter();