Load the lead's scrollback 50 turns at a time

web/src/state.ts

@@ -1,4 +1,4 @@
-import { get, put, subscribe, type AgentSession, type ByreEvent, type Focus, type InboxItem, type Project, type Snapshot, type Task, type TaskTab, type User } from "./api.js";
+import { get, put, subscribe, type AgentSession, type ByreEvent, type Focus, type InboxItem, type Project, type Schemas, type Snapshot, type Task, type TaskTab, type User } from "./api.js";
 import { notifyInbox, notifyTurn } from "./notifications.js";
 
 export type Topic =
@@ -441,8 +441,39 @@ export function selectTask(taskId: string | undefined): void {
   notify("selection");
 }
 
-export function startLeadStream(): void {
-  subscribe(0, { lead: true }, leadFeed.push, () => undefined, () => leadFeed.load([]));
+const leadPage = 50;
+let leadMore = false;
+
+async function fetchLeadTail(): Promise<Schemas["EventPage"]> {
+  for (;;) {
+    try {
+      return await get("/api/me/lead/events", { query: { turns: leadPage } });
+    } catch (err) {
+      console.error("load lead history", err);
+      await new Promise((resolve) => setTimeout(resolve, 2_000));
+    }
+  }
+}
+
+export async function startLeadStream(): Promise<void> {
+  const page = await fetchLeadTail();
+  leadMore = page.more;
+  subscribe(page.events.at(-1)?.seq ?? 0, { lead: true }, leadFeed.push, () => undefined, () => leadFeed.load(page.events));
+}
+
+export function leadHasOlder(): boolean {
+  return leadFeed.ready && leadMore;
+}
+
+export async function loadOlderLead(): Promise<ByreEvent[]> {
+  const first = leadFeed.events[0];
+  if (!first) {
+    return [];
+  }
+  const page = await get("/api/me/lead/events", { query: { before: first.seq, turns: leadPage } });
+  leadMore = page.more;
+  leadFeed.events.unshift(...page.events);
+  return page.events;
 }
 
 export function handleEvent(ev: ByreEvent): void {