diff --git a/src/sdk/builders/tasks/__tests__/factory.test.ts b/src/sdk/builders/tasks/__tests__/factory.test.ts
index fffbb6b4..3c02c34a 100644
--- a/src/sdk/builders/tasks/__tests__/factory.test.ts
+++ b/src/sdk/builders/tasks/__tests__/factory.test.ts
@@ -134,11 +134,23 @@ describe("forkTask", () => {
       name: "forkTaskJoin_join",
       taskReferenceName: "forkTaskJoin_join_ref",
       inputParameters: {},
-      joinOn: [],
+      joinOn: ["forkTaskJoin"],
       optional: true,
       type: "JOIN",
     });
   });
+  it("Should join on the last task of each fork branch", () => {
+    const [, joinTask] = forkTaskJoin("multiStep", [
+      eventTask("first", "prefix", "suffix"),
+      eventTask("second", "prefix", "suffix"),
+      eventTask("last", "prefix", "suffix"),
+    ]);
+    expect(joinTask.joinOn).toEqual(["last"]);
+  });
+  it("Should produce an empty joinOn when there are no fork tasks", () => {
+    const [, joinTask] = forkTaskJoin("emptyFork", []);
+    expect(joinTask.joinOn).toEqual([]);
+  });
 });
 
 describe("httpTask", () => {
diff --git a/src/sdk/builders/tasks/forkJoin.ts b/src/sdk/builders/tasks/forkJoin.ts
index b150ea4f..41a174a3 100644
--- a/src/sdk/builders/tasks/forkJoin.ts
+++ b/src/sdk/builders/tasks/forkJoin.ts
@@ -20,7 +20,16 @@ export const forkTaskJoin = (
   taskReferenceName: string,
   forkTasks: TaskDefTypes[],
   optional?: boolean
-): [ForkJoinTaskDef, JoinTaskDef] => [
-  forkTask(taskReferenceName, forkTasks),
-  generateJoinTask({ name: `${taskReferenceName}_join`, optional }),
-];
+): [ForkJoinTaskDef, JoinTaskDef] => {
+  const fork = forkTask(taskReferenceName, forkTasks);
+  // The server checks joinOn with allMatch(), which short-circuits to true on an
+  // empty list — a JOIN with no joinOn completes without waiting for any branch.
+  // Join on the last task of every branch so the JOIN blocks until each finishes.
+  const joinOn = fork.forkTasks
+    .map((branch) => branch[branch.length - 1]?.taskReferenceName)
+    .filter((ref): ref is string => ref !== undefined);
+  return [
+    fork,
+    generateJoinTask({ name: `${taskReferenceName}_join`, joinOn, optional }),
+  ];
+};