fix(app): settle padded and stalled chat history

Measure the native history edge using the same content area as viewport filling, and bound child history requests so retry can start after a stalled fetch.

docs/timeline-sync.md

@@ -69,8 +69,8 @@ Source coverage still includes interleaved tool updates.
 
 Canonical IDs define runs. With missing IDs, human prompts, heartbeats and typed received
 agent messages each start a fallback turn. This deterministic fallback is shared by paging
-and presentation; it cannot recover historical batching or steering. Older history remains
-user-driven by scrolling upward.
+and presentation; it cannot recover historical batching or steering. An underfilled viewport
+loads older history until it fills or history is exhausted. Further history is user-driven.
 
 A failed catch-up or subscription reconcile retries on its own, doubling from 1s to a 30s ceiling.
 A fixed 1s retry turned a persistent daemon-side refusal — a Codex thread that already has an active

packages/app/e2e/browser/turn-collapse.spec.ts

@@ -407,34 +407,86 @@ async function seedWholeTurnHistory() {
   return agent;
 }
 
-test("loads complete long turns and preserves expansion while revealing older history", async ({
-  page,
-}) => {
+async function expectInitialFillIsConcealed(page: Page) {
+  await expect(page.getByTestId("agent-initial-fill")).toBeVisible();
+  await expect(page.getByTestId("agent-chat-scroll")).toHaveCSS("opacity", "0");
+}
+
+async function expectFilledChatAtBottom(page: Page) {
+  await expect(page.getByTestId("agent-initial-fill")).toBeHidden();
+  const chat = page.getByTestId("agent-chat-scroll");
+  await expect(chat).toHaveCSS("opacity", "1");
+  await expect
+    .poll(() =>
+      chat.evaluate((element) => ({
+        hasOverflow: element.scrollHeight > element.clientHeight,
+        atBottom: Math.abs(element.scrollHeight - element.clientHeight - element.scrollTop) <= 2,
+      })),
+    )
+    .toEqual({ hasOverflow: true, atBottom: true });
+}
+
+test("fills collapsed history before revealing a fresh chat", async ({ page }) => {
   test.setTimeout(120_000);
+  await page.setViewportSize({ width: 1280, height: 1000 });
   await useChatDisplay(page, "collapseTurns");
   const agent = await seedWholeTurnHistory();
   try {
     const history = await holdOlderHistoryPages(page, agent);
     await openAgentRoute(page, agent);
+    await history.expectRequestedPages(1);
+    await expectInitialFillIsConcealed(page);
+    history.releasePage(1);
+    await history.expectRequestedPages(2);
+    await expectInitialFillIsConcealed(page);
+    history.releasePage(2);
+    await expectFilledChatAtBottom(page);
+    await page.setViewportSize({ width: 1280, height: 8000 });
+    await history.expectRequestedPages(3);
+    await expect(page.getByTestId("agent-chat-scroll")).toHaveCSS("opacity", "1");
+    await expect(page.getByTestId("agent-initial-fill")).toBeHidden();
+    history.releasePage(3);
+    await history.expectSettledWithRequestedPages(3);
+    history.expectNoRepeatedEntries();
+  } finally {
+    await agent.cleanup();
+  }
+});
+
+test("loads complete long turns and preserves expansion while revealing older history", async ({
+  page,
+}) => {
+  test.setTimeout(120_000);
+  await page.setViewportSize({ width: 1280, height: 1000 });
+  await useChatDisplay(page, "collapseTurns");
+  const agent = await seedWholeTurnHistory();
+  try {
+    const history = await holdOlderHistoryPages(page, agent);
+    await openAgentRoute(page, agent);
+    await history.expectRequestedPages(1);
+    history.releasePage(1);
+    await history.expectRequestedPages(2);
+    history.releasePage(2);
+    await expectFilledChatAtBottom(page);
     await expectComposerVisible(page);
     const latest = page
       .getByTestId("turn-summary")
       .getByRole("button", { name: "Ran 120 commands", exact: true });
     await expect(latest).toBeVisible();
-    await expect.poll(() => rowsBetweenLatestSummaryAndReply(page)).toBe(0);
-    await latest.click();
-    await expect.poll(() => rowsBetweenLatestSummaryAndReply(page)).toBe(120);
-    await userScrollsTimelineToHistoryStart(page);
-    await history.expectRequestedPages(1);
-    history.releasePage(1);
     await expect(
       page
         .getByTestId("turn-summary")
         .getByRole("button", { name: "Ran 60 commands", exact: true }),
     ).toBeVisible();
+    await expect.poll(() => rowsBetweenLatestSummaryAndReply(page)).toBe(0);
+    await latest.click();
+    await expect.poll(() => rowsBetweenLatestSummaryAndReply(page)).toBe(120);
+    await userScrollsTimelineToHistoryStart(page);
+    await history.expectRequestedPages(3);
+    history.releasePage(3);
+    await page.getByTestId("scroll-to-bottom-button").click();
     await expect.poll(() => rowsBetweenLatestSummaryAndReply(page)).toBe(120);
     history.expectNoRepeatedEntries();
-    await latest.scrollIntoViewIfNeeded();
     await latest.click();
     await expect.poll(() => rowsBetweenLatestSummaryAndReply(page)).toBe(0);
   } finally {

packages/app/src/agent-stream/history-start-pagination.test.ts

@@ -1,197 +1,238 @@
-import { describe, expect, it } from "vitest";
+import { nativeHistoryStartGeometry } from "./native-history-start-geometry";
+import { describe, expect, it, vi } from "vitest";
 import {
-  abandonHistoryStartPaginationRequest,
-  createHistoryStartPaginationState,
-  evaluateHistoryStartPagination,
-  isHistoryStartLoadingOperation,
-  rearmHistoryStartPagination,
-  settleHistoryStartPagination,
+  createHistoryStartPagination,
   type HistoryStartPaginationInput,
 } from "./history-start-pagination";
 
-function createArmedHistoryStartPaginationState() {
-  return rearmHistoryStartPagination(createHistoryStartPaginationState());
-}
-
-const visibleHistoryStart: HistoryStartPaginationInput = {
+const initial: HistoryStartPaginationInput = {
   distanceFromHistoryStart: 0,
+  isUnderfilled: true,
   hasOlderHistory: true,
   isLoadingOlderHistory: false,
   isReady: true,
-  progressKey: "epoch-1:20",
+  progressKey: "20",
 };
 
+function harness(initiallyVisible = false) {
+  let geometry = { ...initial };
+  const requests: Array<(value: boolean) => void> = [];
+  let settles = 0;
+  const pagination = createHistoryStartPagination({
+    initiallyVisible,
+    read: () => geometry,
+    load: () => new Promise<boolean>((resolve) => requests.push(resolve)),
+    changed: () => {},
+    scheduleSettle: () => {
+      settles++;
+    },
+  });
+  return {
+    pagination,
+    requests,
+    get settles() {
+      return settles;
+    },
+    set(patch: Partial<HistoryStartPaginationInput>) {
+      geometry = { ...geometry, ...patch };
+      pagination.update();
+    },
+  };
+}
+
 describe("history start pagination", () => {
-  it("treats locally revealed history as progress before remote pagination", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const localReveal = evaluateHistoryStartPagination(first.state, {
-      ...visibleHistoryStart,
-      progressKey: "epoch-1:20:local-60",
-    });
-
-    expect(first.shouldLoad).toBe(true);
-    expect(localReveal.state).toEqual({
-      status: "settling",
-      loadedProgressKey: "epoch-1:20:local-60",
-    });
+  it("waits for a delayed request and its committed page before settling", async () => {
+    const h = harness();
+    h.pagination.update();
+    h.set({ progressKey: "10" });
+    expect(h.settles).toBe(0);
+    h.requests[0](true);
+    await Promise.resolve();
+    expect(h.settles).toBe(1);
+    expect(h.pagination.state.visible).toBe(false);
+    h.set({ isUnderfilled: false });
+    h.pagination.settle();
+    expect(h.pagination.state).toEqual({ status: "dormant", visible: true });
+    h.pagination.dispose();
   });
-  it("waits for user scroll intent before loading", () => {
-    const dormant = createHistoryStartPaginationState();
-    const evaluated = evaluateHistoryStartPagination(dormant, visibleHistoryStart);
-
-    expect(evaluated).toEqual({ state: { status: "dormant" }, shouldLoad: false });
+  it("waits for the committed page after a request completes", async () => {
+    const h = harness();
+    h.pagination.update();
+    h.requests[0](true);
+    await Promise.resolve();
+    expect(h.settles).toBe(0);
+    h.set({ progressKey: "10" });
+    expect(h.settles).toBe(1);
+    h.pagination.dispose();
   });
-
-  it("waits for anchored page geometry before authorizing another page", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const inFlight = evaluateHistoryStartPagination(first.state, {
-      ...visibleHistoryStart,
-      isLoadingOlderHistory: true,
-    });
-    const pageApplied = evaluateHistoryStartPagination(inFlight.state, {
-      ...visibleHistoryStart,
-      isLoadingOlderHistory: true,
-      progressKey: "epoch-1:10",
-    });
-
-    expect([first.shouldLoad, inFlight.shouldLoad, pageApplied.shouldLoad]).toEqual([
-      true,
-      false,
-      false,
-    ]);
-    expect(pageApplied.state).toEqual({ status: "settling", loadedProgressKey: "epoch-1:10" });
+  it("continues short pages and reveals on exhaustion", async () => {
+    const h = harness();
+    h.pagination.update();
+    h.set({ progressKey: "10" });
+    h.requests[0](true);
+    await Promise.resolve();
+    h.pagination.settle();
+    expect(h.requests).toHaveLength(2);
+    h.set({ hasOlderHistory: false });
+    h.requests[1](true);
+    await Promise.resolve();
+    expect(h.pagination.state).toEqual({ status: "dormant", visible: true });
+    h.pagination.dispose();
   });
-
-  it("loads one page each time anchored geometry leaves and returns to history start", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const pageApplied = evaluateHistoryStartPagination(first.state, {
-      ...visibleHistoryStart,
-      progressKey: "epoch-1:10",
-    });
-    const settledAway = settleHistoryStartPagination(pageApplied.state, {
-      ...visibleHistoryStart,
-      distanceFromHistoryStart: 300,
-      progressKey: "epoch-1:10",
-    });
-    const returned = evaluateHistoryStartPagination(settledAway.state, {
-      ...visibleHistoryStart,
-      progressKey: "epoch-1:10",
-    });
-
-    expect([
-      first.shouldLoad,
-      pageApplied.shouldLoad,
-      settledAway.shouldLoad,
-      returned.shouldLoad,
-    ]).toEqual([true, false, false, true]);
+  it("releases a failed or stalled request and allows retry", async () => {
+    vi.useFakeTimers();
+    const h = harness();
+    h.pagination.update();
+    vi.advanceTimersByTime(15_000);
+    expect(h.pagination.state).toEqual({ status: "failed", visible: true });
+    h.pagination.rearm();
+    expect(h.requests).toHaveLength(2);
+    h.requests[1](false);
+    await Promise.resolve();
+    expect(h.pagination.state.status).toBe("failed");
+    h.pagination.dispose();
+    vi.useRealTimers();
   });
-
-  it("continues the same loading operation when anchored geometry remains at history start", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const pageApplied = evaluateHistoryStartPagination(first.state, {
-      ...visibleHistoryStart,
-      progressKey: "epoch-1:10",
-    });
-    const continued = settleHistoryStartPagination(pageApplied.state, {
-      ...visibleHistoryStart,
-      progressKey: "epoch-1:10",
-    });
-
-    expect(continued.shouldLoad).toBe(true);
-    expect(isHistoryStartLoadingOperation(first.state)).toBe(true);
-    expect(isHistoryStartLoadingOperation(pageApplied.state)).toBe(true);
-    expect(isHistoryStartLoadingOperation(continued.state)).toBe(true);
+  it("keeps visible history visible while filling", () => {
+    const h = harness(true);
+    h.pagination.update();
+    expect(h.pagination.state.visible).toBe(true);
+    h.pagination.dispose();
   });
-
-  it("latches a request that finishes without cursor progress", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const inFlight = evaluateHistoryStartPagination(first.state, {
-      ...visibleHistoryStart,
-      isLoadingOlderHistory: true,
-    });
-    const finished = evaluateHistoryStartPagination(inFlight.state, visibleHistoryStart);
-    const duplicate = evaluateHistoryStartPagination(finished.state, visibleHistoryStart);
-    const away = evaluateHistoryStartPagination(duplicate.state, {
-      ...visibleHistoryStart,
-      distanceFromHistoryStart: 300,
-    });
-
-    expect(finished.state).toEqual({ status: "latched" });
-    expect([finished.shouldLoad, duplicate.shouldLoad, away.shouldLoad]).toEqual([
-      false,
-      false,
-      false,
-    ]);
-    expect(away.state).toEqual({ status: "ready" });
+  it("does not load a full viewport until user intent and respects inactive views", () => {
+    const h = harness();
+    h.set({ isUnderfilled: false });
+    expect(h.requests).toHaveLength(0);
+    h.set({ isReady: false });
+    h.pagination.rearm();
+    expect(h.requests).toHaveLength(0);
+    h.set({ isReady: true });
+    expect(h.requests).toHaveLength(1);
+    h.pagination.dispose();
   });
-
-  it("allows another user attempt after a request finishes without progress", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const inFlight = evaluateHistoryStartPagination(first.state, {
-      ...visibleHistoryStart,
-      isLoadingOlderHistory: true,
-    });
-    const failed = evaluateHistoryStartPagination(inFlight.state, visibleHistoryStart);
-    const retried = evaluateHistoryStartPagination(
-      rearmHistoryStartPagination(failed.state),
-      visibleHistoryStart,
-    );
-
-    expect(failed.state).toEqual({ status: "latched" });
-    expect(retried.shouldLoad).toBe(true);
-  });
-
-  it("latches an attempt that becomes invalid before entering flight", () => {
-    const requested = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-
-    expect(abandonHistoryStartPaginationRequest(requested.state, "epoch-1:20")).toEqual({
-      status: "latched",
-    });
-  });
-
-  it("does not mistake repeated edge observations for a finished request", () => {
-    const first = evaluateHistoryStartPagination(
-      createArmedHistoryStartPaginationState(),
-      visibleHistoryStart,
-    );
-    const repeated = evaluateHistoryStartPagination(first.state, visibleHistoryStart);
-
-    expect(repeated.state).toBe(first.state);
-    expect(repeated.shouldLoad).toBe(false);
-  });
-
-  it("waits while history loading is unavailable or already active", () => {
-    const state = createArmedHistoryStartPaginationState();
-
-    expect([
-      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, isReady: false }).shouldLoad,
-      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, hasOlderHistory: false })
-        .shouldLoad,
-      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, isLoadingOlderHistory: true })
-        .shouldLoad,
-      evaluateHistoryStartPagination(state, { ...visibleHistoryStart, progressKey: null })
-        .shouldLoad,
-    ]).toEqual([false, false, false, false]);
+  it("preserves the reading position after an anchored page moves away from the start", async () => {
+    const h = harness(true);
+    h.set({ isUnderfilled: false });
+    h.pagination.rearm();
+    h.set({ progressKey: "10", distanceFromHistoryStart: 300 });
+    h.requests[0](true);
+    await Promise.resolve();
+    h.pagination.settle();
+    expect(h.requests).toHaveLength(1);
+    h.set({ distanceFromHistoryStart: 0 });
+    expect(h.requests).toHaveLength(2);
+    h.pagination.dispose();
   });
 });
+
+it("ignores a timed-out response after the reader retries", async () => {
+  vi.useFakeTimers();
+  const h = harness();
+  h.pagination.update();
+  vi.advanceTimersByTime(15_000);
+  h.pagination.rearm();
+  h.requests[0](true);
+  await Promise.resolve();
+  expect(h.pagination.state.status).toBe("loading");
+  expect(h.settles).toBe(0);
+  h.requests[1](false);
+  await Promise.resolve();
+  expect(h.pagination.state.status).toBe("failed");
+  h.pagination.dispose();
+  vi.useRealTimers();
+});
+
+it("does not repeat a successful page that made no progress", async () => {
+  vi.useFakeTimers();
+  const h = harness();
+  h.pagination.update();
+  h.requests[0](true);
+  await Promise.resolve();
+  h.pagination.update();
+  expect(h.requests).toHaveLength(1);
+  vi.advanceTimersByTime(15_000);
+  expect(h.pagination.state).toEqual({ status: "failed", visible: true });
+  h.pagination.dispose();
+  vi.useRealTimers();
+});
+
+it("waits until the cursor and active history are available", () => {
+  const h = harness();
+  h.set({ isReady: false, progressKey: null });
+  h.set({ isReady: true, isLoadingOlderHistory: true });
+  h.set({ isLoadingOlderHistory: false });
+  expect(h.requests).toHaveLength(0);
+  h.set({ progressKey: "20" });
+  expect(h.requests).toHaveLength(1);
+  h.pagination.dispose();
+});
+
+it("reveals immediately on exhausted history without offering retry", () => {
+  const h = harness();
+  h.set({ hasOlderHistory: false });
+  expect(h.requests).toHaveLength(0);
+  expect(h.pagination.state).toEqual({ status: "dormant", visible: true });
+  h.pagination.dispose();
+});
+
+it("keeps a settled page pending while its view is inactive", async () => {
+  const h = harness();
+  h.pagination.update();
+  h.set({ progressKey: "10" });
+  h.requests[0](true);
+  await Promise.resolve();
+  h.set({ isReady: false });
+  h.pagination.settle();
+  expect(h.pagination.state.status).toBe("settling");
+  expect(h.requests).toHaveLength(1);
+  h.set({ isReady: true, isUnderfilled: false });
+  h.pagination.settle();
+  expect(h.pagination.state).toEqual({ status: "dormant", visible: true });
+  h.pagination.dispose();
+});
+
+it("keeps cached history visible after synchronization and subsequent pagination", async () => {
+  const h = harness();
+  h.pagination.reveal();
+  h.pagination.update();
+  h.set({ progressKey: "10" });
+  h.requests[0](true);
+  await Promise.resolve();
+  h.pagination.settle();
+  expect(h.pagination.state.visible).toBe(true);
+  expect(h.requests).toHaveLength(2);
+  h.pagination.dispose();
+});
+
+it.each([
+  [true, 123, 0],
+  [false, 123, 0],
+  [true, 0, 123],
+  [false, 0, 123],
+])(
+  "handles native padding when short history has older=%s",
+  (hasOlderHistory, topOverlayInset, bottomPadding) => {
+    const geometry = nativeHistoryStartGeometry({
+      contentHeight: 825,
+      viewportHeight: 700,
+      offsetY: 0,
+      topOverlayInset,
+      bottomPadding,
+    });
+    let requests = 0;
+    const pagination = createHistoryStartPagination({
+      initiallyVisible: false,
+      read: () => ({ ...initial, ...geometry, hasOlderHistory }),
+      load: () => {
+        requests++;
+        return new Promise<boolean>(() => {});
+      },
+      changed: () => {},
+      scheduleSettle: () => {},
+    });
+    pagination.update();
+    expect(requests).toBe(hasOlderHistory ? 1 : 0);
+    expect(pagination.state.visible).toBe(!hasOlderHistory);
+    pagination.dispose();
+  },
+);

packages/app/src/agent-stream/history-start-pagination.ts

@@ -1,138 +1,135 @@
 export const HISTORY_START_THRESHOLD_PX = 96;
 
-export type HistoryStartPaginationState =
-  | { status: "dormant" }
-  | { status: "ready" }
-  | { status: "loading"; requestedProgressKey: string; requestObserved: boolean }
-  | { status: "settling"; loadedProgressKey: string }
-  | { status: "latched" };
-
 export interface HistoryStartPaginationInput {
   distanceFromHistoryStart: number;
+  isUnderfilled: boolean;
   hasOlderHistory: boolean;
   isLoadingOlderHistory: boolean;
   isReady: boolean;
   progressKey: string | null;
 }
 
-export interface HistoryStartPaginationTransition {
-  state: HistoryStartPaginationState;
-  shouldLoad: boolean;
-}
-
-export function createHistoryStartPaginationState(): HistoryStartPaginationState {
-  return { status: "dormant" };
+export interface HistoryStartPaginationState {
+  status: "dormant" | "ready" | "loading" | "settling" | "failed";
+  visible: boolean;
 }
 
 export function isHistoryStartLoadingOperation(state: HistoryStartPaginationState): boolean {
   return state.status === "loading" || state.status === "settling";
 }
 
-export function rearmHistoryStartPagination(
-  state: HistoryStartPaginationState,
-): HistoryStartPaginationState {
-  return state.status === "dormant" || state.status === "latched" ? { status: "ready" } : state;
-}
+/** Owns one pagination operation, including the initial viewport reveal. */
+export function createHistoryStartPagination(input: {
+  initiallyVisible: boolean;
+  read: () => HistoryStartPaginationInput | null;
+  load: () => Promise<boolean>;
+  changed: (state: HistoryStartPaginationState) => void;
+  scheduleSettle: () => void;
+}) {
+  let state: HistoryStartPaginationState = { status: "dormant", visible: input.initiallyVisible };
+  let requestedKey: string | null = null;
+  let completed = false;
+  let fill = false;
+  let generation = 0;
+  let timeout: ReturnType<typeof setTimeout> | undefined;
 
-export function abandonHistoryStartPaginationRequest(
-  state: HistoryStartPaginationState,
-  requestedProgressKey: string,
-): HistoryStartPaginationState {
-  if (
-    state.status !== "loading" ||
-    state.requestObserved ||
-    state.requestedProgressKey !== requestedProgressKey
-  ) {
-    return state;
-  }
-  return { status: "latched" };
-}
+  const publish = (status: HistoryStartPaginationState["status"], visible = state.visible) => {
+    if (status === state.status && visible === state.visible) return;
+    state = { status, visible };
+    input.changed(state);
+  };
+  const clear = () => {
+    generation++;
+    clearTimeout(timeout);
+    timeout = undefined;
+  };
+  const finish = (status: HistoryStartPaginationState["status"]) => {
+    clear();
+    publish(status, true);
+  };
+  const fail = () => finish("failed");
 
-export function evaluateHistoryStartPagination(
-  state: HistoryStartPaginationState,
-  input: HistoryStartPaginationInput,
-): HistoryStartPaginationTransition {
-  if (state.status === "dormant") {
-    return { state, shouldLoad: false };
-  }
-  if (state.status === "loading") {
-    if (input.progressKey !== null && input.progressKey !== state.requestedProgressKey) {
-      return {
-        state: { status: "settling", loadedProgressKey: input.progressKey },
-        shouldLoad: false,
-      };
+  const update = () => {
+    const geometry = input.read();
+    if (!geometry) return;
+    if (state.status === "loading") {
+      if (!completed) return;
+      if (geometry.progressKey !== null && geometry.progressKey !== requestedKey) {
+        publish("settling");
+        input.scheduleSettle();
+      } else if (!geometry.hasOlderHistory) {
+        finish("dormant");
+      }
+      return;
     }
-    if (input.isLoadingOlderHistory && !state.requestObserved) {
-      return { state: { ...state, requestObserved: true }, shouldLoad: false };
+    if (state.status === "settling" || state.status === "failed" || !geometry.isReady) return;
+    const atStart = geometry.distanceFromHistoryStart <= HISTORY_START_THRESHOLD_PX;
+    if (state.status === "dormant" && !geometry.isUnderfilled) {
+      publish("dormant", true);
+      return;
     }
-    if (!input.isLoadingOlderHistory && !input.hasOlderHistory) {
-      return { state: { status: "latched" }, shouldLoad: false };
+    if (!atStart || (!geometry.isUnderfilled && state.status !== "ready")) return;
+    if (!geometry.hasOlderHistory) {
+      finish("dormant");
+      return;
     }
-    if (
-      state.requestObserved &&
-      !input.isLoadingOlderHistory &&
-      input.progressKey === state.requestedProgressKey
-    ) {
-      return { state: { status: "latched" }, shouldLoad: false };
-    }
-    return { state, shouldLoad: false };
-  }
-
-  if (state.status === "settling") {
-    return { state, shouldLoad: false };
-  }
-
-  const isAtHistoryStart = input.distanceFromHistoryStart <= HISTORY_START_THRESHOLD_PX;
-  if (!isAtHistoryStart) {
-    return state.status === "ready"
-      ? { state, shouldLoad: false }
-      : { state: { status: "ready" }, shouldLoad: false };
-  }
-  if (
-    state.status === "latched" ||
-    !input.isReady ||
-    !input.hasOlderHistory ||
-    input.isLoadingOlderHistory ||
-    input.progressKey === null
-  ) {
-    return { state, shouldLoad: false };
-  }
+    if (geometry.isLoadingOlderHistory || geometry.progressKey === null) return;
+    fill = geometry.isUnderfilled;
+    requestedKey = geometry.progressKey;
+    completed = false;
+    publish("loading");
+    const request = ++generation;
+    timeout = setTimeout(() => {
+      if (request === generation) fail();
+    }, 15_000);
+    void input.load().then(
+      (applied) => {
+        if (request !== generation) return undefined;
+        if (!applied) {
+          fail();
+          return undefined;
+        }
+        completed = true;
+        update();
+        return undefined;
+      },
+      () => {
+        if (request === generation) fail();
+      },
+    );
+  };
   return {
-    state: {
-      status: "loading",
-      requestedProgressKey: input.progressKey,
-      requestObserved: false,
+    get state() {
+      return state;
     },
-    shouldLoad: true,
-  };
-}
-
-export function settleHistoryStartPagination(
-  state: HistoryStartPaginationState,
-  input: HistoryStartPaginationInput,
-): HistoryStartPaginationTransition {
-  if (state.status !== "settling") {
-    return { state, shouldLoad: false };
-  }
-  const isAtHistoryStart = input.distanceFromHistoryStart <= HISTORY_START_THRESHOLD_PX;
-  if (
-    !isAtHistoryStart ||
-    !input.isReady ||
-    !input.hasOlderHistory ||
-    input.isLoadingOlderHistory ||
-    input.progressKey === null
-  ) {
-    return {
-      state: isAtHistoryStart ? { status: "latched" } : { status: "ready" },
-      shouldLoad: false,
-    };
-  }
-  return {
-    state: {
-      status: "loading",
-      requestedProgressKey: input.progressKey,
-      requestObserved: false,
+    update,
+    settle() {
+      if (state.status !== "settling") return;
+      const geometry = input.read();
+      if (!geometry?.isReady) return;
+      clear();
+      if (fill && !geometry.isUnderfilled) {
+        publish("dormant", true);
+      } else if (geometry.distanceFromHistoryStart > HISTORY_START_THRESHOLD_PX) {
+        publish("ready", true);
+      } else if (!geometry.hasOlderHistory) {
+        publish("dormant", true);
+      } else {
+        publish("ready");
+        update();
+      }
     },
-    shouldLoad: true,
+    rearm() {
+      if (state.status === "dormant" || state.status === "failed") publish("ready", true);
+      update();
+    },
+    reveal() {
+      publish(state.status, true);
+    },
+    reset(visible: boolean) {
+      clear();
+      publish("dormant", visible);
+    },
+    dispose: clear,
   };
 }

packages/app/src/agent-stream/native-history-start-geometry.ts

@@ -0,0 +1,13 @@
+export function nativeHistoryStartGeometry(input: {
+  contentHeight: number;
+  viewportHeight: number;
+  offsetY: number;
+  topOverlayInset: number;
+  bottomPadding: number;
+}) {
+  const contentHeight = input.contentHeight - 32 - input.topOverlayInset - input.bottomPadding;
+  return {
+    distanceFromHistoryStart: contentHeight - input.viewportHeight - input.offsetY,
+    isUnderfilled: contentHeight < input.viewportHeight,
+  };
+}

packages/app/src/agent-stream/strategy-native.tsx

@@ -1,12 +1,4 @@
-import {
-  Fragment,
-  type ReactElement,
-  useCallback,
-  useEffect,
-  useMemo,
-  useRef,
-  useState,
-} from "react";
+import { Fragment, type ReactElement, useCallback, useEffect, useMemo, useRef } from "react";
 import {
   FlatList,
   Platform,
@@ -19,6 +11,9 @@ import {
 } from "react-native";
 import { withUnistyles } from "react-native-unistyles";
 import { LoadingSpinner } from "@/components/ui/loading-spinner";
+import { Button } from "@/components/ui/button";
+import { useRetainedPanelActive } from "@/components/retained-panel";
+import { useTranslation } from "react-i18next";
 import type { StreamItem } from "@/types/stream";
 import type { Theme } from "@/styles/theme";
 import { useStableEvent } from "@/hooks/use-stable-event";
@@ -34,15 +29,11 @@ import {
   resolveBottomAnchorTransportBehavior,
 } from "./strategy";
 import {
-  abandonHistoryStartPaginationRequest,
-  createHistoryStartPaginationState,
-  evaluateHistoryStartPagination,
   isHistoryStartLoadingOperation,
-  rearmHistoryStartPagination,
-  settleHistoryStartPagination,
   type HistoryStartPaginationInput,
-  type HistoryStartPaginationTransition,
 } from "./history-start-pagination";
+import { useHistoryStartPagination } from "./use-history-start-pagination";
+import { nativeHistoryStartGeometry } from "./native-history-start-geometry";
 import { useStreamTopOverlayInset } from "./top-overlay";
 import {
   createHistoryStartSettleScheduler,
@@ -65,6 +56,16 @@ const historyStartSlotStyle: ViewStyle = {
   flexShrink: 0,
 };
 const HISTORY_START_SETTLE_FRAMES = 2;
+const viewportStyle: ViewStyle = { flex: 1 };
+const initialFillStyle: ViewStyle = {
+  position: "absolute",
+  top: 0,
+  right: 0,
+  bottom: 0,
+  left: 0,
+  alignItems: "center",
+  justifyContent: "center",
+};
 const NATIVE_STREAM_WINDOW_SIZE = 10;
 
 function keyExtractor(item: { id: string }): string {
@@ -83,6 +84,8 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     viewportRef,
     routeBottomAnchorRequest,
     isAuthoritativeHistoryReady,
+    isInitialHistoryLoading,
+    revealInitialHistory,
     onNearBottomChange,
     onNearHistoryStart,
     isLoadingOlderHistory,
@@ -93,6 +96,8 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     baseListContentContainerStyle,
     strategy,
   } = props;
+  const isActive = useRetainedPanelActive();
+  const { t } = useTranslation();
   const { renderHistoryMountedRow, renderLiveHeadRow, renderLiveAuxiliary } = renderers;
   const flatListRef = useRef<FlatList<StreamItem>>(null);
   const streamViewportMetricsRef = useRef({
@@ -113,10 +118,6 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
   const isNativeViewportSettlingRef = useRef(false);
   const nativeViewportSettlingFrameIdRef = useRef<number | null>(null);
   const historyStartReadyRef = useRef(false);
-  const [historyStartPaginationState, setHistoryStartPaginationState] = useState(
-    createHistoryStartPaginationState,
-  );
-  const historyStartPaginationStateRef = useRef(historyStartPaginationState);
   const historyStartSettleSchedulerRef = useRef<HistoryStartSettleScheduler | null>(null);
 
   const historyItems = useMemo(() => {
@@ -132,48 +133,40 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
       metrics.viewportMeasuredForKey === metrics.containerKey &&
       metrics.contentMeasuredForKey === metrics.containerKey;
     return {
-      distanceFromHistoryStart: metrics.contentHeight - metrics.viewportHeight - metrics.offsetY,
+      ...nativeHistoryStartGeometry({
+        contentHeight: metrics.contentHeight,
+        viewportHeight: metrics.viewportHeight,
+        offsetY: metrics.offsetY,
+        topOverlayInset,
+        bottomPadding: streamKeyboardInset.contentContainerPaddingBottom,
+      }),
       hasOlderHistory,
       isLoadingOlderHistory,
-      isReady: historyStartReadyRef.current && hasMeasuredViewport,
+      isReady:
+        isActive &&
+        isAuthoritativeHistoryReady &&
+        historyStartReadyRef.current &&
+        hasMeasuredViewport,
       progressKey: olderHistoryProgressKey,
     };
   });
-  const applyHistoryStartPaginationTransition = useStableEvent(
-    (transition: HistoryStartPaginationTransition) => {
-      const previousState = historyStartPaginationStateRef.current;
-      historyStartPaginationStateRef.current = transition.state;
-      if (transition.state !== previousState) {
-        setHistoryStartPaginationState(transition.state);
-      }
-      if (transition.shouldLoad) {
-        const requestedProgressKey = olderHistoryProgressKey;
-        if (requestedProgressKey === null) {
-          return;
-        }
-        void (async () => {
-          const started = await onNearHistoryStart();
-          if (started === true) {
-            return;
-          }
-          applyHistoryStartPaginationTransition({
-            state: abandonHistoryStartPaginationRequest(
-              historyStartPaginationStateRef.current,
-              requestedProgressKey,
-            ),
-            shouldLoad: false,
-          });
-        })();
-      }
-    },
+  const { state: historyStartPaginationState, controller: historyStartPagination } =
+    useHistoryStartPagination({
+      initiallyVisible: !isInitialHistoryLoading,
+      read: getHistoryStartPaginationInput,
+      load: async () => onNearHistoryStart(),
+      scheduleSettle: () => scheduleHistoryStartSettle(),
+    });
+  const evaluateHistoryStart = useStableEvent(() => historyStartPagination.update());
+  const resetHistoryStart = useStableEvent(() =>
+    historyStartPagination.reset(!isInitialHistoryLoading),
   );
-  const evaluateHistoryStart = useStableEvent(() => {
-    const transition = evaluateHistoryStartPagination(
-      historyStartPaginationStateRef.current,
-      getHistoryStartPaginationInput(),
-    );
-    applyHistoryStartPaginationTransition(transition);
-  });
+  const disposeHistoryStart = useStableEvent(() => historyStartPagination.dispose());
+  const isHistoryStartSettling = useStableEvent(
+    () => historyStartPagination.state.status === "settling",
+  );
+  const finishInitialFill = useStableEvent(() => historyStartPagination.reveal());
+  const retryHistoryStart = useStableEvent(() => historyStartPagination.rearm());
   const scheduleHistoryStartSettle = useStableEvent(() => {
     let scheduler = historyStartSettleSchedulerRef.current;
     if (!scheduler) {
@@ -181,15 +174,9 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
         settleFrames: HISTORY_START_SETTLE_FRAMES,
         requestFrame: requestAnimationFrame,
         cancelFrame: cancelAnimationFrame,
-        isSettling: () => historyStartPaginationStateRef.current.status === "settling",
+        isSettling: () => isHistoryStartSettling(),
         isLoading: () => getHistoryStartPaginationInput().isLoadingOlderHistory,
-        onSettle: () => {
-          const transition = settleHistoryStartPagination(
-            historyStartPaginationStateRef.current,
-            getHistoryStartPaginationInput(),
-          );
-          applyHistoryStartPaginationTransition(transition);
-        },
+        onSettle: () => historyStartPagination.settle(),
       });
       historyStartSettleSchedulerRef.current = scheduler;
     }
@@ -328,9 +315,7 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     clearNativeViewportSettling();
     isNativeViewportSettlingRef.current = false;
     historyStartReadyRef.current = false;
-    const initialHistoryStartState = createHistoryStartPaginationState();
-    historyStartPaginationStateRef.current = initialHistoryStartState;
-    setHistoryStartPaginationState(initialHistoryStartState);
+    resetHistoryStart();
     const frame = requestAnimationFrame(() => {
       historyStartReadyRef.current = true;
       evaluateHistoryStart();
@@ -338,10 +323,18 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     return () => {
       cancelAnimationFrame(frame);
       clearPendingUserScrollEnd();
+      disposeHistoryStart();
       historyStartSettleSchedulerRef.current?.cancel();
       historyStartSettleSchedulerRef.current = null;
     };
-  }, [agentId, clearNativeViewportSettling, clearPendingUserScrollEnd, evaluateHistoryStart]);
+  }, [
+    agentId,
+    clearNativeViewportSettling,
+    clearPendingUserScrollEnd,
+    disposeHistoryStart,
+    evaluateHistoryStart,
+    resetHistoryStart,
+  ]);
 
   useEffect(() => () => clearNativeViewportSettling(), [clearNativeViewportSettling]);
 
@@ -421,18 +414,18 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
   });
 
   const handleScrollBeginDrag = useStableEvent((event: NativeSyntheticEvent<NativeScrollEvent>) => {
+    finishInitialFill();
     clearPendingUserScrollEnd();
     isUserScrollActiveRef.current = true;
     scrollKeyboardDismiss.onScrollBeginDrag(event);
     bottomAnchorController.beginUserScroll();
-    const rearmed = rearmHistoryStartPagination(historyStartPaginationStateRef.current);
-    if (rearmed !== historyStartPaginationStateRef.current) {
-      historyStartPaginationStateRef.current = rearmed;
-      setHistoryStartPaginationState(rearmed);
-      evaluateHistoryStart();
-    }
+    historyStartPagination.rearm();
   });
 
+  useEffect(() => {
+    if (revealInitialHistory) finishInitialFill();
+  }, [finishInitialFill, revealInitialHistory]);
+
   // Defer drag end so momentum can take ownership, but capture the terminal
   // gesture position now because layout may move the viewport in the meantime.
   const handleScrollEndDrag = useStableEvent((event: NativeSyntheticEvent<NativeScrollEvent>) => {
@@ -506,22 +499,25 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
       contentHeight: nextContentHeight,
     });
     evaluateHistoryStart();
-    if (historyStartPaginationStateRef.current.status === "settling") {
+    if (isHistoryStartSettling()) {
       scheduleHistoryStartSettle();
     }
   });
 
   useEffect(() => {
     evaluateHistoryStart();
-    if (historyStartPaginationStateRef.current.status === "settling") {
+    if (isHistoryStartSettling()) {
       scheduleHistoryStartSettle();
     }
   }, [
     evaluateHistoryStart,
     hasOlderHistory,
+    isActive,
+    isAuthoritativeHistoryReady,
     isLoadingOlderHistory,
     olderHistoryProgressKey,
     scheduleHistoryStartSettle,
+    isHistoryStartSettling,
   ]);
 
   const renderItem = useStableEvent(
@@ -566,50 +562,64 @@ function NativeStreamViewport(props: StreamRenderInput & { strategy: StreamStrat
     const isLoadingOperation = isHistoryStartLoadingOperation(historyStartPaginationState);
     return (
       <View style={historyStartSlotStyle} testID="older-history-slot">
-        {isLoadingOperation ? (
+        {isLoadingOperation && (
           <View testID="load-older-history-spinner">
             <ThemedLoadingSpinner size="small" uniProps={foregroundMutedColorMapping} />
           </View>
-        ) : null}
+        )}
+        {!isLoadingOperation &&
+          historyStartPaginationState.status === "failed" &&
+          hasOlderHistory && (
+            <Button variant="ghost" size="sm" onPress={retryHistoryStart}>
+              {t("paneFind.retry")}
+            </Button>
+          )}
       </View>
     );
-  }, [historyStartPaginationState]);
+  }, [historyStartPaginationState, hasOlderHistory, retryHistoryStart, t]);
 
   // RN's FlatList strictMode keeps its internal renderItem wrapper stable when
   // data or the live header changes, preserving the row identities above.
   return (
-    <FlatList
-      {...listInsetProps}
-      ref={flatListRef}
-      data={historyRows}
-      renderItem={renderItem}
-      keyExtractor={keyExtractor}
-      strictMode
-      testID="agent-chat-scroll"
-      nativeID="agent-chat-scroll-native-virtualized"
-      ListHeaderComponent={liveHeaderContent ?? undefined}
-      ListFooterComponent={historyFooterContent ?? undefined}
-      contentContainerStyle={listContentContainerStyle}
-      style={listStyle}
-      onLayout={handleListLayout}
-      onScroll={handleScroll}
-      onScrollBeginDrag={handleScrollBeginDrag}
-      onScrollEndDrag={handleScrollEndDrag}
-      onMomentumScrollBegin={handleMomentumScrollBegin}
-      onMomentumScrollEnd={handleMomentumScrollEnd}
-      scrollEventThrottle={16}
-      onContentSizeChange={handleContentSizeChange}
-      maintainVisibleContentPosition={maintainVisibleContentPosition}
-      // Tall Markdown rows exhaust a shallow window during flings. Keep the initial
-      // render small, then refill a deeper window in batches large enough to keep up.
-      initialNumToRender={2}
-      maxToRenderPerBatch={10}
-      windowSize={NATIVE_STREAM_WINDOW_SIZE}
-      removeClippedSubviews={false}
-      scrollEnabled={scrollEnabled}
-      showsVerticalScrollIndicator
-      inverted
-    />
+    <View style={viewportStyle}>
+      <FlatList
+        {...listInsetProps}
+        ref={flatListRef}
+        data={historyRows}
+        renderItem={renderItem}
+        keyExtractor={keyExtractor}
+        strictMode
+        testID="agent-chat-scroll"
+        nativeID="agent-chat-scroll-native-virtualized"
+        ListHeaderComponent={liveHeaderContent ?? undefined}
+        ListFooterComponent={historyFooterContent ?? undefined}
+        contentContainerStyle={listContentContainerStyle}
+        style={[listStyle, { opacity: historyStartPaginationState.visible ? 1 : 0 }]}
+        onLayout={handleListLayout}
+        onScroll={handleScroll}
+        onScrollBeginDrag={handleScrollBeginDrag}
+        onScrollEndDrag={handleScrollEndDrag}
+        onMomentumScrollBegin={handleMomentumScrollBegin}
+        onMomentumScrollEnd={handleMomentumScrollEnd}
+        scrollEventThrottle={16}
+        onContentSizeChange={handleContentSizeChange}
+        maintainVisibleContentPosition={maintainVisibleContentPosition}
+        // Tall Markdown rows exhaust a shallow window during flings. Keep the initial
+        // render small, then refill a deeper window in batches large enough to keep up.
+        initialNumToRender={2}
+        maxToRenderPerBatch={10}
+        windowSize={NATIVE_STREAM_WINDOW_SIZE}
+        removeClippedSubviews={false}
+        scrollEnabled={scrollEnabled}
+        showsVerticalScrollIndicator
+        inverted
+      />
+      {!historyStartPaginationState.visible ? (
+        <View pointerEvents="none" testID="agent-initial-fill" style={initialFillStyle}>
+          <ThemedLoadingSpinner size="large" uniProps={foregroundMutedColorMapping} />
+        </View>
+      ) : null}
+    </View>
   );
 }
 

packages/app/src/agent-stream/strategy-web.test.tsx

@@ -152,7 +152,7 @@ describe("createWebStreamStrategy", () => {
         routeBottomAnchorRequest: null,
         isAuthoritativeHistoryReady: true,
         onNearBottomChange: () => {},
-        onNearHistoryStart: () => true,
+        onNearHistoryStart: async () => true,
         isLoadingOlderHistory: false,
         hasOlderHistory: false,
         olderHistoryProgressKey: null,
@@ -274,7 +274,7 @@ describe("createWebStreamStrategy", () => {
       routeBottomAnchorRequest: null,
       isAuthoritativeHistoryReady: true,
       onNearBottomChange: () => {},
-      onNearHistoryStart: () => true,
+      onNearHistoryStart: async () => true,
       isLoadingOlderHistory: false,
       hasOlderHistory: false,
       olderHistoryProgressKey: null,

packages/app/src/agent-stream/strategy-web.tsx

@@ -20,6 +20,7 @@ import { withUnistyles } from "react-native-unistyles";
 import { useRetainedPanelActive } from "@/components/retained-panel";
 import { LoadingSpinner } from "@/components/ui/loading-spinner";
 import { useStableEvent } from "@/hooks/use-stable-event";
+import { useTranslation } from "react-i18next";
 import { getStreamItemMessageId, type StreamItem } from "@/types/stream";
 import type { Theme } from "@/styles/theme";
 import { WEB_SCROLLBAR_SIZE_PX } from "@/styles/web-scrollbar";
@@ -30,15 +31,10 @@ import type { StreamRenderInput, StreamStrategy, StreamViewportHandle } from "./
 import { useRevisedHistoryRows } from "./history-row-revision";
 import { createStreamStrategy } from "./strategy";
 import {
-  abandonHistoryStartPaginationRequest,
-  createHistoryStartPaginationState,
-  evaluateHistoryStartPagination,
   isHistoryStartLoadingOperation,
-  rearmHistoryStartPagination,
-  settleHistoryStartPagination,
   type HistoryStartPaginationInput,
-  type HistoryStartPaginationTransition,
 } from "./history-start-pagination";
+import { useHistoryStartPagination } from "./use-history-start-pagination";
 import {
   createHistoryStartSettleScheduler,
   type HistoryStartSettleScheduler,
@@ -77,6 +73,14 @@ const historyStartSlotStyle: CSSProperties = {
 };
 
 const streamRowsHostStyle: CSSProperties = { position: "relative", width: "100%" };
+const initialFillStyle: CSSProperties = {
+  position: "absolute",
+  inset: 0,
+  display: "flex",
+  alignItems: "center",
+  justifyContent: "center",
+  pointerEvents: "none",
+};
 
 const streamRowStyle: CSSProperties = {
   display: "flex",
@@ -298,6 +302,8 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
     viewportRef,
     routeBottomAnchorRequest,
     isAuthoritativeHistoryReady,
+    isInitialHistoryLoading,
+    revealInitialHistory,
     onNearBottomChange,
     onReadingPositionChange,
     onNearHistoryStart,
@@ -318,6 +324,9 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
     [historyMounted, historyVirtualized, inputSegments],
   );
   const isActive = useRetainedPanelActive();
+  const { t } = useTranslation();
+  const rowsHostRef = useRef<HTMLDivElement | null>(null);
+  const auxiliaryRef = useRef<HTMLDivElement | null>(null);
   const isActiveRef = useRef(isActive);
   const scrollContainerRef = useRef<HTMLElement | null>(null);
   const contentRef = useRef<HTMLElement | null>(null);
@@ -351,10 +360,6 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
   const pendingAutoScrollFrameRef = useRef<number | null>(null);
   const pendingAutoScrollTimeoutRef = useRef<number | null>(null);
   const historyStartReadyRef = useRef(false);
-  const [historyStartPaginationState, setHistoryStartPaginationState] = useState(
-    createHistoryStartPaginationState,
-  );
-  const historyStartPaginationStateRef = useRef(historyStartPaginationState);
   const readingAnchor = useMemo(createReadingAnchor, []);
   const measuredRowHeights = useRef(new Map<string, { width: number; height: number }>());
   const historyStartSettleSchedulerRef = useRef<HistoryStartSettleScheduler | null>(null);
@@ -479,60 +484,39 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
       !followOutputRef.current || isScrollContainerNearBottom(scrollContainer);
     return {
       distanceFromHistoryStart: scrollContainer.scrollTop,
+      isUnderfilled:
+        (rowsHostRef.current?.getBoundingClientRect().height ?? 0) +
+          (auxiliaryRef.current?.getBoundingClientRect().height ?? 0) <
+        scrollContainer.clientHeight,
       hasOlderHistory,
       isLoadingOlderHistory,
       // An explicit jump owns the landing position. Revealing another local
       // page here changes the virtual index before the target has mounted.
-      isReady: historyStartReadyRef.current && bottomAnchorSettled && !isJumpSettling(),
+      isReady:
+        historyStartReadyRef.current &&
+        isAuthoritativeHistoryReady &&
+        bottomAnchorSettled &&
+        !isJumpSettling(),
       progressKey: olderHistoryProgressKey,
     };
   });
-  const applyHistoryStartPaginationTransition = useStableEvent(
-    (transition: HistoryStartPaginationTransition) => {
-      const previousState = historyStartPaginationStateRef.current;
-      historyStartPaginationStateRef.current = transition.state;
-      if (transition.state !== previousState) {
-        setHistoryStartPaginationState(transition.state);
-      }
-      if (!transition.shouldLoad || olderHistoryProgressKey === null) {
-        return;
-      }
-      const requestedProgressKey = olderHistoryProgressKey;
-      void (async () => {
-        const started = await onNearHistoryStart();
-        if (started === true) {
-          return;
-        }
-        applyHistoryStartPaginationTransition({
-          state: abandonHistoryStartPaginationRequest(
-            historyStartPaginationStateRef.current,
-            requestedProgressKey,
-          ),
-          shouldLoad: false,
-        });
-      })();
-    },
+  const { state: historyStartPaginationState, controller: historyStartPagination } =
+    useHistoryStartPagination({
+      initiallyVisible: !isInitialHistoryLoading,
+      read: getHistoryStartPaginationInput,
+      load: async () => onNearHistoryStart(),
+      scheduleSettle: () => scheduleHistoryStartPrependSettle(),
+    });
+  const evaluateHistoryStart = useStableEvent(() => historyStartPagination.update());
+  const resetHistoryStart = useStableEvent(() =>
+    historyStartPagination.reset(!isInitialHistoryLoading),
   );
-  const evaluateHistoryStart = useStableEvent(() => {
-    const input = getHistoryStartPaginationInput();
-    if (!input) {
-      return;
-    }
-    const transition = evaluateHistoryStartPagination(
-      historyStartPaginationStateRef.current,
-      input,
-    );
-    applyHistoryStartPaginationTransition(transition);
-  });
-  const rearmHistoryStartFromUserIntent = useStableEvent(() => {
-    const rearmed = rearmHistoryStartPagination(historyStartPaginationStateRef.current);
-    if (rearmed === historyStartPaginationStateRef.current) {
-      return;
-    }
-    historyStartPaginationStateRef.current = rearmed;
-    setHistoryStartPaginationState(rearmed);
-    evaluateHistoryStart();
-  });
+  const disposeHistoryStart = useStableEvent(() => historyStartPagination.dispose());
+  const isHistoryStartSettling = useStableEvent(
+    () => historyStartPagination.state.status === "settling",
+  );
+  const finishInitialFill = useStableEvent(() => historyStartPagination.reveal());
+  const rearmHistoryStartFromUserIntent = useStableEvent(() => historyStartPagination.rearm());
   const scheduleHistoryStartPrependSettle = useStableEvent(() => {
     let scheduler = historyStartSettleSchedulerRef.current;
     if (!scheduler) {
@@ -540,22 +524,12 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
         settleFrames: HISTORY_START_SETTLE_FRAMES,
         requestFrame: (callback) => window.requestAnimationFrame(callback),
         cancelFrame: (frame) => window.cancelAnimationFrame(frame),
-        isSettling: () => historyStartPaginationStateRef.current.status === "settling",
+        isSettling: () => isHistoryStartSettling(),
         isLoading: () => {
           const input = getHistoryStartPaginationInput();
           return !input || input.isLoadingOlderHistory;
         },
-        onSettle: () => {
-          const input = getHistoryStartPaginationInput();
-          if (!input) {
-            return;
-          }
-          const transition = settleHistoryStartPagination(
-            historyStartPaginationStateRef.current,
-            input,
-          );
-          applyHistoryStartPaginationTransition(transition);
-        },
+        onSettle: () => historyStartPagination.settle(),
       });
       historyStartSettleSchedulerRef.current = scheduler;
     }
@@ -782,6 +756,7 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
   ]);
 
   const stopFollowingOutputFromUserIntent = useStableEvent(() => {
+    finishInitialFill();
     cancelPendingStickToBottom();
     if (followOutputRef.current) {
       setFollowOutput(false);
@@ -789,6 +764,10 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
     rearmHistoryStartFromUserIntent();
   });
 
+  useEffect(() => {
+    if (revealInitialHistory) finishInitialFill();
+  }, [finishInitialFill, revealInitialHistory]);
+
   const handleDomScroll = useCallback(() => {
     const scrollContainer = scrollContainerRef.current;
     if (!isActiveRef.current || !scrollContainer || !isScrollContainerMeasurable(scrollContainer)) {
@@ -827,9 +806,7 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
   ]);
 
   useEffect(() => {
-    const initialHistoryStartState = createHistoryStartPaginationState();
-    historyStartPaginationStateRef.current = initialHistoryStartState;
-    setHistoryStartPaginationState(initialHistoryStartState);
+    resetHistoryStart();
     readingAnchor.reset();
     const frame = window.requestAnimationFrame(() => {
       historyStartReadyRef.current = true;
@@ -838,10 +815,11 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
     return () => {
       window.cancelAnimationFrame(frame);
       historyStartReadyRef.current = false;
+      disposeHistoryStart();
       historyStartSettleSchedulerRef.current?.cancel();
       historyStartSettleSchedulerRef.current = null;
     };
-  }, [evaluateHistoryStart, props.agentId, readingAnchor]);
+  }, [disposeHistoryStart, evaluateHistoryStart, props.agentId, readingAnchor, resetHistoryStart]);
 
   useLayoutEffect(() => {
     if (!isActiveRef.current || !isActivationReady) {
@@ -930,16 +908,18 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
       updateScrollMetrics();
     }
     evaluateHistoryStart();
-    if (historyStartPaginationStateRef.current.status === "settling") {
+    if (isHistoryStartSettling()) {
       scheduleHistoryStartPrependSettle();
     }
   }, [
     evaluateHistoryStart,
     hasOlderHistory,
     isActive,
+    isAuthoritativeHistoryReady,
     isLoadingOlderHistory,
     olderHistoryProgressKey,
     scheduleHistoryStartPrependSettle,
+    isHistoryStartSettling,
     segments.historyMounted.length,
     segments.historyVirtualized.length,
     segments.liveHead.length,
@@ -978,7 +958,7 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
         lastObservedViewportGeometryRef.current = nextGeometry;
       }
       reconcileReadingPosition();
-      if (historyStartPaginationStateRef.current.status === "settling") {
+      if (isHistoryStartSettling()) {
         scheduleHistoryStartPrependSettle();
       }
       updateScrollMetrics();
@@ -1012,6 +992,7 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
     isActive,
     reportReadingPosition,
     scheduleHistoryStartPrependSettle,
+    isHistoryStartSettling,
     forceStickToBottom,
     updateScrollMetrics,
     measureVirtualizedRows,
@@ -1229,8 +1210,9 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
       // Detached reading has one owner: reconcileReadingPosition.
       overflowAnchor: followOutput ? "auto" : "none",
       scrollbarWidth: overlayScrollbarEnabled ? "none" : undefined,
+      opacity: historyStartPaginationState.visible ? 1 : 0,
     };
-  }, [followOutput, isMobileBreakpoint, scrollEnabled]);
+  }, [followOutput, historyStartPaginationState.visible, isMobileBreakpoint, scrollEnabled]);
   const viewportStyle = useMemo(
     (): CSSProperties => ({
       position: "relative",
@@ -1307,14 +1289,21 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
     const isLoadingOperation = isHistoryStartLoadingOperation(historyStartPaginationState);
     return (
       <div style={historyStartSlotStyle} data-testid="older-history-slot">
-        {isLoadingOperation ? (
+        {isLoadingOperation && (
           <div data-testid="load-older-history-spinner">
             <ThemedLoadingSpinner size="small" uniProps={foregroundMutedColorMapping} />
           </div>
-        ) : null}
+        )}
+        {!isLoadingOperation &&
+          historyStartPaginationState.status === "failed" &&
+          hasOlderHistory && (
+            <button type="button" onClick={rearmHistoryStartFromUserIntent}>
+              {t("paneFind.retry")}
+            </button>
+          )}
       </div>
     );
-  }, [historyStartPaginationState]);
+  }, [historyStartPaginationState, hasOlderHistory, rearmHistoryStartFromUserIntent, t]);
   const shouldRenderEmpty =
     !boundary.hasMountedHistory &&
     !boundary.hasVirtualizedHistory &&
@@ -1334,7 +1323,7 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
       >
         <div ref={handleContentRef} style={contentContainerStyle}>
           {historyStartSlot}
-          <div style={streamRowsHostStyle}>
+          <div ref={rowsHostRef} style={streamRowsHostStyle}>
             <div style={virtualRowsContainerStyle} />
             {[
               ...virtualRows.map((virtualRow) => {
@@ -1362,10 +1351,15 @@ function WebStreamViewport(props: StreamRenderInput & { isMobileBreakpoint: bool
               ...mountedRows,
             ]}
           </div>
-          {liveAuxiliary}
+          <div ref={auxiliaryRef}>{liveAuxiliary}</div>
           {shouldRenderEmpty ? listEmptyComponent : null}
         </div>
       </div>
+      {!historyStartPaginationState.visible ? (
+        <div data-testid="agent-initial-fill" style={initialFillStyle}>
+          <ThemedLoadingSpinner size="large" uniProps={foregroundMutedColorMapping} />
+        </div>
+      ) : null}
       {scrollEnabled && !isMobileBreakpoint ? (
         <DomOverlayScrollbar
           scrollContainerRef={scrollContainerRef}

packages/app/src/agent-stream/strategy.ts

@@ -87,11 +87,13 @@ export interface StreamRenderInput {
   viewportRef: RefObject<StreamViewportHandle | null>;
   routeBottomAnchorRequest: BottomAnchorRouteRequest | null;
   isAuthoritativeHistoryReady: boolean;
+  isInitialHistoryLoading?: boolean;
+  revealInitialHistory?: boolean;
   onNearBottomChange: (value: boolean) => void;
   // The history row under the top of the viewport, for surfaces that mark where the reader
   // is in the transcript. Only the web viewport measures it today.
   onReadingPositionChange?: (rowId: string | null) => void;
-  onNearHistoryStart: () => boolean | Promise<boolean>;
+  onNearHistoryStart: () => Promise<boolean>;
   isLoadingOlderHistory: boolean;
   hasOlderHistory: boolean;
   olderHistoryProgressKey: string | null;

packages/app/src/agent-stream/use-history-start-pagination.ts

@@ -0,0 +1,33 @@
+import { useRef, useState } from "react";
+import { useStableEvent } from "@/hooks/use-stable-event";
+import {
+  createHistoryStartPagination,
+  type HistoryStartPaginationInput,
+  type HistoryStartPaginationState,
+} from "./history-start-pagination";
+
+export function useHistoryStartPagination(input: {
+  initiallyVisible: boolean;
+  read: () => HistoryStartPaginationInput | null;
+  load: () => Promise<boolean>;
+  scheduleSettle: () => void;
+}) {
+  const read = useStableEvent(input.read);
+  const load = useStableEvent(input.load);
+  const scheduleSettle = useStableEvent(input.scheduleSettle);
+  const [state, setState] = useState<HistoryStartPaginationState>(() => ({
+    status: "dormant",
+    visible: input.initiallyVisible,
+  }));
+  const controller = useRef<ReturnType<typeof createHistoryStartPagination> | null>(null);
+  if (!controller.current) {
+    controller.current = createHistoryStartPagination({
+      initiallyVisible: input.initiallyVisible,
+      read,
+      load,
+      scheduleSettle,
+      changed: setState,
+    });
+  }
+  return { state, controller: controller.current };
+}

packages/app/src/agent-stream/view.tsx

@@ -281,6 +281,8 @@ export interface AgentStreamViewProps {
   turnPresentation: TurnPresentation;
   routeBottomAnchorRequest?: BottomAnchorRouteRequest | null;
   isAuthoritativeHistoryReady?: boolean;
+  isInitialHistoryLoading?: boolean;
+  revealInitialHistory?: boolean;
   /** Tail space required by a transparent overlay rendered at the bottom edge. */
   bottomOverlayTailClearance?: number;
   /** Bottom offset required for controls floating above that overlay. */
@@ -337,6 +339,8 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
       turnPresentation,
       routeBottomAnchorRequest = null,
       isAuthoritativeHistoryReady = true,
+      isInitialHistoryLoading,
+      revealInitialHistory,
       bottomOverlayTailClearance = 0,
       bottomOverlayControlClearance,
       toast,
@@ -1218,6 +1222,8 @@ const AgentStreamViewComponent = forwardRef<AgentStreamViewHandle, AgentStreamVi
                   viewportRef,
                   routeBottomAnchorRequest,
                   isAuthoritativeHistoryReady,
+                  isInitialHistoryLoading,
+                  revealInitialHistory,
                   onNearBottomChange: setIsNearBottom,
                   onReadingPositionChange: handleReadingPositionChange,
                   onNearHistoryStart: loadOlder,
@@ -1369,6 +1375,12 @@ function agentStreamViewPropsEqual(
   if (left.isAuthoritativeHistoryReady !== right.isAuthoritativeHistoryReady) {
     reasons.push("isAuthoritativeHistoryReady");
   }
+  if (left.isInitialHistoryLoading !== right.isInitialHistoryLoading) {
+    reasons.push("isInitialHistoryLoading");
+  }
+  if (left.revealInitialHistory !== right.revealInitialHistory) {
+    reasons.push("revealInitialHistory");
+  }
   if (left.bottomOverlayTailClearance !== right.bottomOverlayTailClearance) {
     reasons.push("bottomOverlayTailClearance");
   }

packages/app/src/hooks/use-load-older-agent-history.test.ts

@@ -129,7 +129,7 @@ describe("loadOlderAgentHistory", () => {
 
     expect(client.calls).toEqual([]);
     expect(inFlight.values).toEqual([true]);
-    expect(started).toBe(true);
+    expect(started).toBe(false);
   });
 
   it("requests the page before the current start cursor and clears in-flight on success", async () => {
@@ -153,6 +153,7 @@ describe("loadOlderAgentHistory", () => {
           limit: TIMELINE_FETCH_PAGE_SIZE,
           projection: "projected",
           wholeTurns: true,
+          timeout: 10_000,
         },
       },
     ]);
@@ -169,7 +170,7 @@ describe("loadOlderAgentHistory", () => {
     const toast = createToast();
     const logger = createLogger();
 
-    await loadOlderAgentHistory(agentId, {
+    const applied = await loadOlderAgentHistory(agentId, {
       client,
       cursor: someCursor,
       hasOlder: true,
@@ -179,6 +180,7 @@ describe("loadOlderAgentHistory", () => {
       logger,
     });
 
+    expect(applied).toBe(false);
     expect(client.calls).toHaveLength(1);
     expect(toast.shown).toEqual([
       {

packages/app/src/hooks/use-load-older-agent-history.ts

@@ -18,6 +18,7 @@ export interface LoadOlderAgentHistoryClient {
       cursor: { epoch: string; seq: number };
       limit: number;
       projection: "projected";
+      timeout: number;
     },
   ) => Promise<unknown>;
 }
@@ -44,7 +45,7 @@ export async function loadOlderAgentHistory(
   const { client, cursor, hasOlder, isLoadingOlder, setInFlight, toast, logger, failedMessage } =
     deps;
   if (isLoadingOlder) {
-    return true;
+    return false;
   }
   if (!client || !cursor || !hasOlder) {
     return false;
@@ -52,16 +53,17 @@ export async function loadOlderAgentHistory(
 
   setInFlight(true);
   try {
-    await client.fetchAgentTimeline(
-      agentId,
-      planTimelineOlderFetch({ epoch: cursor.epoch, seq: cursor.startSeq }),
-    );
+    await client.fetchAgentTimeline(agentId, {
+      ...planTimelineOlderFetch({ epoch: cursor.epoch, seq: cursor.startSeq }),
+      timeout: 10_000,
+    });
   } catch (error) {
     (logger ?? console).warn("[Timeline] failed to load older agent history", agentId, error);
     toast?.show(failedMessage ?? i18n.t("loadOlderHistory.failed"), {
       durationMs: 2200,
       testID: "agent-load-older-history-toast",
     });
+    return false;
   } finally {
     setInFlight(false);
   }

packages/app/src/panels/agent-panel.tsx

@@ -1021,6 +1021,10 @@ function ChatAgentContent({
       effectiveAgent={effectiveAgent}
       routeBottomAnchorRequest={routeBottomAnchorRequest}
       hasAppliedAuthoritativeHistory={hasAppliedAuthoritativeHistory}
+      shouldHoldInitialFill={
+        routeBottomAnchorRequest?.reason === "initial-entry" && replicaTimelineStatus !== "painted"
+      }
+      hasCachedHistory={replicaTimelineStatus === "painted"}
       toastApi={toastApi}
       toast={toastState}
       dismiss={dismissToast}
@@ -1051,6 +1055,8 @@ const ChatAgentReadyContent = memo(function ChatAgentReadyContent({
   effectiveAgent,
   routeBottomAnchorRequest,
   hasAppliedAuthoritativeHistory,
+  shouldHoldInitialFill,
+  hasCachedHistory,
   toastApi,
   toast,
   dismiss,
@@ -1077,6 +1083,8 @@ const ChatAgentReadyContent = memo(function ChatAgentReadyContent({
   effectiveAgent: AgentScreenAgent;
   routeBottomAnchorRequest: RouteBottomAnchorRequest;
   hasAppliedAuthoritativeHistory: boolean;
+  shouldHoldInitialFill: boolean;
+  hasCachedHistory: boolean;
   toastApi: ToastApi;
   toast: ToastState | null;
   dismiss: () => void;
@@ -1203,6 +1211,8 @@ const ChatAgentReadyContent = memo(function ChatAgentReadyContent({
           agent={effectiveAgent}
           routeBottomAnchorRequest={routeBottomAnchorRequest}
           hasAppliedAuthoritativeHistory={hasAppliedAuthoritativeHistory}
+          isInitialHistoryLoading={shouldHoldInitialFill && !showHistorySyncError}
+          revealInitialHistory={hasCachedHistory || showHistorySyncError}
           hasActiveComposer={hasActiveComposer}
           hasVisibleAgentTracks={hasVisibleAgentTracks}
           toast={toastApi}
@@ -1339,6 +1349,8 @@ const AgentStreamSection = memo(function AgentStreamSection({
   agent,
   routeBottomAnchorRequest,
   hasAppliedAuthoritativeHistory,
+  isInitialHistoryLoading,
+  revealInitialHistory,
   hasActiveComposer,
   hasVisibleAgentTracks,
   toast,
@@ -1351,6 +1363,8 @@ const AgentStreamSection = memo(function AgentStreamSection({
   agent: AgentScreenAgent;
   routeBottomAnchorRequest: RouteBottomAnchorRequest;
   hasAppliedAuthoritativeHistory: boolean;
+  isInitialHistoryLoading: boolean;
+  revealInitialHistory: boolean;
   hasActiveComposer: boolean;
   hasVisibleAgentTracks: boolean;
   toast: ReturnType<typeof useToastHost>["api"];
@@ -1419,6 +1433,8 @@ const AgentStreamSection = memo(function AgentStreamSection({
       pendingPermissions={pendingPermissions}
       routeBottomAnchorRequest={routeBottomAnchorRequest}
       isAuthoritativeHistoryReady={hasAppliedAuthoritativeHistory}
+      isInitialHistoryLoading={isInitialHistoryLoading}
+      revealInitialHistory={revealInitialHistory}
       bottomOverlayTailClearance={bottomOverlayTailClearance}
       bottomOverlayControlClearance={bottomOverlayControlClearance}
       toast={toast}

packages/app/src/panels/provider-subagent-panel.tsx

@@ -26,6 +26,7 @@ import {
   providerSubagentLifecycleStatus,
   refreshProviderSubagents,
   observeProviderSubagentTimeline,
+  loadOlderProviderSubagentTimeline,
   useProviderSubagentStore,
 } from "@/subagents/provider-store";
 import { useTranslation } from "react-i18next";
@@ -180,26 +181,24 @@ function ProviderSubagentPanel() {
     });
   }, [client, supported, serverId, target.parentAgentId, target.subagentId]);
 
-  const loadOlder = useCallback((): boolean => {
+  const loadOlder = useCallback(async (): Promise<boolean> => {
     if (!client || !supported || isLoadingOlder || !timeline?.hasOlder || !timeline.epoch) {
       return false;
     }
-    const firstSeq = timeline.cursor?.startSeq ?? null;
-    if (firstSeq === null) return false;
     setIsLoadingOlder(true);
-    void client
-      .fetchProviderSubagentTimeline(target.parentAgentId, target.subagentId, {
-        direction: "before",
-        cursor: { epoch: timeline.epoch, seq: firstSeq },
+    try {
+      return await loadOlderProviderSubagentTimeline({
+        client,
+        serverId,
+        parentAgentId: target.parentAgentId,
+        subagentId: target.subagentId,
         limit: TIMELINE_FETCH_PAGE_SIZE,
-      })
-      .then((payload) => {
-        useProviderSubagentStore.getState().replaceTimeline(serverId, payload);
-        return undefined;
-      })
-      .catch(() => undefined)
-      .finally(() => setIsLoadingOlder(false));
-    return true;
+      });
+    } catch {
+      return false;
+    } finally {
+      setIsLoadingOlder(false);
+    }
   }, [
     client,
     isLoadingOlder,

packages/app/src/subagents/provider-store.test.ts

@@ -1,7 +1,9 @@
+import { createHistoryStartPagination } from "@/agent-stream/history-start-pagination";
 import { DaemonConnectionError } from "@getpaseo/client/internal/daemon-client";
-import { afterEach, describe, expect, test } from "vitest";
+import { afterEach, describe, expect, test, vi } from "vitest";
 import type { ProviderSubagentDescriptorPayload } from "@getpaseo/protocol/messages";
 import {
+  loadOlderProviderSubagentTimeline,
   observeProviderSubagentTimeline,
   providerSubagentKey,
   refreshProviderSubagents,
@@ -565,6 +567,95 @@ describe("projected child history", () => {
       .getState()
       .replaceTimeline(SERVER_ID, response(value, seqStart, seqEnd, direction));
   }
+  test("older child history completes only after the delayed page is applied", async () => {
+    const tail = { ...response("B", 2, 2), hasOlder: true };
+    useProviderSubagentStore.getState().replaceTimeline(SERVER_ID, tail);
+    let deliver!: (payload: Payload) => void;
+    const client = {
+      fetchProviderSubagentTimeline: () =>
+        new Promise<Payload>((resolve) => {
+          deliver = resolve;
+        }),
+    };
+    let completed = false;
+    const request = loadOlderProviderSubagentTimeline({
+      client,
+      serverId: SERVER_ID,
+      parentAgentId: PARENT_ID,
+      subagentId: SUBAGENT_ID,
+      limit: 100,
+    }).then((result) => {
+      completed = true;
+      return result;
+    });
+    await Promise.resolve();
+    expect(completed).toBe(false);
+    deliver({ ...response("A", 1, 1), direction: "before" });
+    expect(await request).toBe(true);
+    expect(current().cursor?.startSeq).toBe(1);
+  });
+  test("bounds an older child request so a timeout permits another attempt", async () => {
+    vi.useFakeTimers();
+    try {
+      useProviderSubagentStore
+        .getState()
+        .replaceTimeline(SERVER_ID, { ...response("B", 2, 2), hasOlder: true });
+      const timeouts: Array<number | undefined> = [];
+      const client = {
+        fetchProviderSubagentTimeline: (
+          _parent: string,
+          _child: string,
+          options: { timeout?: number },
+        ) => {
+          timeouts.push(options.timeout);
+          return new Promise<Payload>((_resolve, reject) =>
+            setTimeout(() => reject(new Error("timeout")), options.timeout ?? 60_000),
+          );
+        },
+      };
+      let loading = false;
+      const pagination = createHistoryStartPagination({
+        initiallyVisible: true,
+        read: () => ({
+          distanceFromHistoryStart: 0,
+          isUnderfilled: true,
+          hasOlderHistory: true,
+          isLoadingOlderHistory: loading,
+          isReady: true,
+          progressKey: "e:2",
+        }),
+        load: async () => {
+          loading = true;
+          try {
+            return await loadOlderProviderSubagentTimeline({
+              client,
+              serverId: SERVER_ID,
+              parentAgentId: PARENT_ID,
+              subagentId: SUBAGENT_ID,
+              limit: 100,
+            });
+          } catch {
+            return false;
+          } finally {
+            loading = false;
+          }
+        },
+        changed: () => {},
+        scheduleSettle: () => {},
+      });
+      pagination.update();
+      expect(timeouts).toEqual([10_000]);
+      await vi.advanceTimersByTimeAsync(10_000);
+      expect(pagination.state.status).toBe("failed");
+      pagination.rearm();
+      expect(timeouts).toEqual([10_000, 10_000]);
+      expect(pagination.state.status).toBe("loading");
+      pagination.dispose();
+      await vi.advanceTimersByTimeAsync(10_000);
+    } finally {
+      vi.useRealTimers();
+    }
+  });
   test("replaces overlapping fetched text and continues live streaming", () => {
     page("AB", 1, 2);
     stream(3, "C");

packages/app/src/subagents/provider-store.ts

@@ -355,6 +355,35 @@ export const useProviderSubagentStore = create<ProviderSubagentState>((set) => (
 }));
 
 /** Owns child history bootstrap and recovery while a pane observes the child. */
+export async function loadOlderProviderSubagentTimeline({
+  client,
+  serverId,
+  parentAgentId,
+  subagentId,
+  limit,
+}: {
+  client: Pick<DaemonClient, "fetchProviderSubagentTimeline">;
+  serverId: string;
+  parentAgentId: string;
+  subagentId: string;
+  limit: number;
+}): Promise<boolean> {
+  const timeline = useProviderSubagentStore
+    .getState()
+    .timelines.get(providerSubagentKey(serverId, parentAgentId, subagentId));
+  const seq = timeline?.cursor?.startSeq;
+  if (!timeline?.hasOlder || !timeline.epoch || seq == null) return false;
+  const payload = await client.fetchProviderSubagentTimeline(parentAgentId, subagentId, {
+    direction: "before",
+    cursor: { epoch: timeline.epoch, seq },
+    limit,
+    timeout: 10_000,
+  });
+  if (payload.error) return false;
+  useProviderSubagentStore.getState().replaceTimeline(serverId, payload);
+  return true;
+}
+
 export function observeProviderSubagentTimeline({
   client,
   serverId,