qa: paginate Slack channel observations

extensions/qa-lab/src/live-transports/slack/slack-live.contracts.ts

@@ -328,6 +328,11 @@ export type SlackMessage = Omit<z.infer<typeof slackHistoryMessageSchema>, "ts">
 export const slackHistorySchema = z.object({
   ok: z.boolean().optional(),
   messages: z.array(slackHistoryMessageSchema).optional(),
+  response_metadata: z
+    .object({
+      next_cursor: z.string().optional(),
+    })
+    .optional(),
 });
 
 export const slackRepliesSchema = z.object({

extensions/qa-lab/src/live-transports/slack/slack-live.observations.ts

@@ -26,9 +26,10 @@ import {
 } from "./slack-live.contracts.js";
 import { buildSlackInvalidBlocksTableProbe } from "./slack-live.invalid-blocks.js";
 
-// Isolated Slack flows share one live QA channel. Presentation sends precede
-// their final markers, so retain enough history to survive concurrent traffic.
-const SLACK_QA_CHANNEL_HISTORY_LIMIT = 200;
+// Isolated flows share one channel, so presentation sends can move across pages
+// before their final markers arrive. Cap traversal to bound each polling pass.
+const SLACK_QA_CHANNEL_HISTORY_PAGE_LIMIT = 200;
+const SLACK_QA_CHANNEL_HISTORY_MAX_PAGES = 5;
 
 export async function getSlackIdentity(token: string): Promise<SlackAuthIdentity> {
   const client = createSlackWebClient(token, { timeout: SLACK_QA_WEB_API_TIMEOUT_MS });
@@ -70,15 +71,25 @@ export async function listSlackMessages(params: {
   client: WebClient;
   oldestTs: string;
 }) {
-  const history = slackHistorySchema.parse(
-    await params.client.conversations.history({
-      channel: params.channelId,
-      inclusive: true,
-      limit: SLACK_QA_CHANNEL_HISTORY_LIMIT,
-      oldest: params.oldestTs,
-    }),
-  );
-  return history.messages ?? [];
+  const messages: SlackMessage[] = [];
+  let cursor: string | undefined;
+  for (let page = 0; page < SLACK_QA_CHANNEL_HISTORY_MAX_PAGES; page += 1) {
+    const history = slackHistorySchema.parse(
+      await params.client.conversations.history({
+        ...(cursor ? { cursor } : {}),
+        channel: params.channelId,
+        inclusive: true,
+        limit: SLACK_QA_CHANNEL_HISTORY_PAGE_LIMIT,
+        oldest: params.oldestTs,
+      }),
+    );
+    messages.push(...(history.messages ?? []));
+    cursor = history.response_metadata?.next_cursor?.trim() || undefined;
+    if (!cursor) {
+      break;
+    }
+  }
+  return messages;
 }
 
 export async function listSlackThreadMessages(params: {

extensions/qa-lab/src/live-transports/slack/slack-live.runtime.test.ts

@@ -993,12 +993,10 @@ describe("Slack live QA runtime helpers", () => {
       throw new Error("missing Slack chart scenario verifier");
     }
     const accessibleText = renderExpectedSlackChartAccessibleText(summaryText);
-    const history = vi.fn(async (request: { limit: number }) => ({
-      // Shared-channel concurrency can push the earlier chart beyond the old
-      // 50-message observation window before the final marker arrives.
-      messages:
-        request.limit >= 200
-          ? [
+    const history = vi.fn(async (request: { cursor?: string }) =>
+      request.cursor === "page-2"
+        ? {
+            messages: [
               {
                 blocks: [
                   {
@@ -1028,9 +1026,13 @@ describe("Slack live QA runtime helpers", () => {
                 ts: "2.000000",
                 user: "U999999999",
               },
-            ]
-          : [],
-    }));
+            ],
+          }
+        : {
+            messages: [],
+            response_metadata: { next_cursor: "page-2" },
+          },
+    );
 
     await expect(
       afterReply(
@@ -1043,12 +1045,19 @@ describe("Slack live QA runtime helpers", () => {
         } as never,
       ),
     ).resolves.toBe("verified native data_visualization block and deterministic accessible text");
-    expect(history).toHaveBeenCalledWith({
+    expect(history).toHaveBeenNthCalledWith(1, {
       channel: "C123456789",
       inclusive: true,
       limit: 200,
       oldest: "1.000000",
     });
+    expect(history).toHaveBeenNthCalledWith(2, {
+      channel: "C123456789",
+      cursor: "page-2",
+      inclusive: true,
+      limit: 200,
+      oldest: "1.000000",
+    });
   });
 
   it("rejects fallback-only Slack chart delivery", async () => {