fix(sdk): cap createStartSessionAction tags at 5 to match schema

SessionTriggerConfig.tags allows at most 5 entries; align
createChatStartSessionAction with chat.headStart and the Zod schema.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: saasjesus

packages/trigger-sdk/src/v3/ai.ts

@@ -9710,8 +9710,8 @@ function createChatStartSessionAction<TChat extends AnyTask = AnyTask>(
     // run-list filter by chat works without the customer having to wire it
     // up. Mirrors the browser-mediated `TriggerChatTransport.doStart` path.
     const userTags = params.triggerConfig?.tags ?? options?.triggerConfig?.tags ?? [];
-    // Platform cap is 10 tags per run; the auto chat tag takes one slot.
-    const tags = [`chat:${params.chatId}`, ...userTags].slice(0, 10);
+    // SessionTriggerConfig.tags allows at most 5; the auto chat tag takes one slot.
+    const tags = [`chat:${params.chatId}`, ...userTags].slice(0, 5);
 
     const clientDataMetadata =
       params.clientData !== undefined ? { metadata: params.clientData } : {};

packages/trigger-sdk/src/v3/createStartSessionAction.test.ts

@@ -96,6 +96,25 @@ describe("chat.createStartSessionAction — runtime", () => {
     expect(lastStartBody?.triggerConfig.basePayload).not.toHaveProperty("metadata");
   });
 
+  it("prepends chat:{chatId} to triggerConfig.tags and caps at 5", async () => {
+    installStartFixture();
+
+    const start = chat.createStartSessionAction("fake-chat", {
+      triggerConfig: {
+        tags: ["org:acme", "a", "b", "c", "d", "e"],
+      },
+    });
+    await start({ chatId: "chat-tags" });
+
+    expect(lastStartBody?.triggerConfig.tags).toEqual([
+      "chat:chat-tags",
+      "org:acme",
+      "a",
+      "b",
+      "c",
+    ]);
+  });
+
   it("keeps session-level metadata distinct from per-turn clientData", async () => {
     installStartFixture();