fix(capture): bound scroll/evaluate timeouts so heavy pages keep capturing (#3236)

* fix(capture): bound scroll/evaluate timeouts so heavy pages keep capturing Fonts/Vercel-class sites were failing after navigation when a single in-page scroll/evaluate hung until protocolTimeout. Drive lazy scroll from Node, degrade on evaluate timeouts, and stop labeling those failures as bot blocks. Co-authored-by: Cursor <cursoragent@cursor.com> * fix(capture): enforce stage budgets and surface evaluate degradation Bound each scroll/content evaluate with remaining stage time so a wedged page.evaluate cannot outlive the advertised 15s/8s budgets, skip recovery CDP calls after expiry, and return/propagate timed-out animation and screenshot work so caller warnings are reachable. Co-authored-by: Cursor <cursoragent@cursor.com> * fix(capture): prefer TimeoutError instanceof for timeout classification Use puppeteer-core TimeoutError as the primary signal for navigation vs evaluate/protocol timeouts, with message checks only as a fallback for string formatting and non-TimeoutError cases. Co-authored-by: Cursor <cursoragent@cursor.com> --------- Co-authored-by: Cursor <cursoragent@cursor.com>
2026-09-11 14:50:02 +00:00 · 2026-08-11 18:26:22 -07:00
parent 93fbb6d7fd
commit 43dba22057
12 changed files with 621 additions and 106 deletions
@@ -0,0 +1,22 @@
+import { describe, expect, it, vi } from "vitest";
+import { collectAnimationCatalog } from "./animationCataloger.js";
+
+describe("collectAnimationCatalog degradation", () => {
+  it("surfaces evaluate timeouts via timedOut instead of silent empty success", async () => {
+    const page = {
+      evaluate: vi.fn(() => new Promise(() => undefined)),
+    };
+    const cdp = {
+      send: vi.fn(async () => undefined),
+    };
+
+    const outcome = await collectAnimationCatalog(page as never, [], cdp as never, {
+      scrollBudgetMs: 20,
+      evaluateBudgetMs: 20,
+    });
+
+    expect(outcome.timedOut).toBe(true);
+    expect(outcome.catalog.summary.webAnimations).toBe(0);
+    expect(cdp.send).toHaveBeenCalledWith("Animation.disable");
+  });
+});
@@ -16,6 +16,8 @@
 */

 import type { Page, CDPSession } from "puppeteer-core";
+import { isDegradableEvaluateTimeoutError, withRemainingBudget } from "./captureTimeout.js";
+import { lazyScrollForCapture } from "./lazyScrollForCapture.js";

 export interface AnimationCatalog {
  /** Active animations via document.getAnimations() — includes keyframes */
@@ -127,32 +129,36 @@ export async function startCdpAnimationCapture(
  return { cdp, animations };
 }

-/**
- * Collect the full animation catalog after page has loaded and settled.
- * Should be called after scrolling through the page to trigger all animations.
- */
+const EMPTY_ANIMATION_SCAN = {
+  webAnimations: [] as WebAnimationEntry[],
+  cssDeclarations: [] as CssAnimationEntry[],
+  scrollTargets: [] as ScrollTarget[],
+  canvasCount: 0,
+};
+
+export interface CollectAnimationCatalogOutcome {
+  catalog: AnimationCatalog;
+  timedOut: boolean;
+}
+
 export async function collectAnimationCatalog(
  page: Page,
  cdpAnimations: CdpAnimationEntry[],
  cdp: CDPSession,
-): Promise<AnimationCatalog> {
-  // Scroll through page to trigger scroll-based animations
-  await page.evaluate(`(async () => {
-    var height = document.body.scrollHeight;
-    for (var y = 0; y < height; y += window.innerHeight * 0.5) {
-      window.scrollTo(0, y);
-      await new Promise(function(r) { setTimeout(r, 400); });
-    }
-    window.scrollTo(0, 0);
-    await new Promise(function(r) { setTimeout(r, 1000); });
-  })()`);
+  opts: { scrollBudgetMs?: number; evaluateBudgetMs?: number } = {},
+): Promise<CollectAnimationCatalogOutcome> {
+  const scrollBudgetMs = opts.scrollBudgetMs ?? 8_000;
+  const evaluateBudgetMs = opts.evaluateBudgetMs ?? 15_000;
+  const scroll = await lazyScrollForCapture(page, scrollBudgetMs);
+  let timedOut = scroll.degraded || scroll.timedOut;

-  // Collect from Web Animations API + computed styles + IO targets
-  const result = (await page.evaluate(`(() => {
+  let result = EMPTY_ANIMATION_SCAN;
+  try {
+    result = (await withRemainingBudget(
+      page.evaluate(`(() => {
    var webAnimations = [];
    var cssDeclarations = [];

-    // 1. Web Animations API
    try {
      var anims = document.getAnimations();
      webAnimations = anims.map(function(anim) {
@@ -180,7 +186,6 @@ export async function collectAnimationCatalog(
      });
    } catch(e) {}

-    // 2. CSS animation/transition scan
    var allEls = document.querySelectorAll('*');
    for (var i = 0; i < allEls.length && i < 5000; i++) {
      var el = allEls[i];
@@ -202,31 +207,44 @@ export async function collectAnimationCatalog(
      } catch(e) {}
    }

-    // 3. IO targets (collected by monkey-patch)
    var scrollTargets = (window.__hf_io_targets || []).map(function(t) {
      return { selector: t.selector, rect: t.rect };
    });

-    // 4. Canvas summary
    var canvasCount = document.querySelectorAll('canvas').length;

    return { webAnimations: webAnimations, cssDeclarations: cssDeclarations, scrollTargets: scrollTargets, canvasCount: canvasCount };
-  })()`)) as any;
+  })()`),
+      evaluateBudgetMs,
+      "animation-catalog",
+    )) as typeof EMPTY_ANIMATION_SCAN;
+  } catch (err) {
+    if (!isDegradableEvaluateTimeoutError(err)) {
+      throw err;
+    }
+    timedOut = true;
+  }

-  // Stop CDP listener
-  await cdp.send("Animation.disable");
+  try {
+    await cdp.send("Animation.disable");
+  } catch {
+    /* session may already be closed */
+  }

  return {
-    webAnimations: result.webAnimations,
-    cssDeclarations: result.cssDeclarations,
-    scrollTargets: result.scrollTargets,
-    cdpAnimations,
-    summary: {
-      webAnimations: result.webAnimations.length,
-      cssDeclarations: result.cssDeclarations.length,
-      scrollTargets: result.scrollTargets.length,
-      cdpAnimations: cdpAnimations.length,
-      canvases: result.canvasCount,
+    catalog: {
+      webAnimations: result.webAnimations,
+      cssDeclarations: result.cssDeclarations,
+      scrollTargets: result.scrollTargets,
+      cdpAnimations,
+      summary: {
+        webAnimations: result.webAnimations.length,
+        cssDeclarations: result.cssDeclarations.length,
+        scrollTargets: result.scrollTargets.length,
+        cdpAnimations: cdpAnimations.length,
+        canvases: result.canvasCount,
+      },
    },
+    timedOut,
  };
 }
@@ -0,0 +1,107 @@
+import { describe, expect, it } from "vitest";
+import { TimeoutError } from "puppeteer-core";
+import {
+  PUPPETEER_DEFAULT_PROTOCOL_TIMEOUT_MS,
+  StageBudgetTimeoutError,
+  captureProtocolTimeoutMs,
+  formatCaptureFailureReason,
+  isNavigationTimeoutError,
+  isProtocolEvaluateTimeoutError,
+  withRemainingBudget,
+} from "./captureTimeout.js";
+
+describe("captureProtocolTimeoutMs", () => {
+  it("uses the larger of nav timeout and post-nav budget", () => {
+    expect(captureProtocolTimeoutMs(120_000, 90_000)).toBe(120_000);
+    expect(captureProtocolTimeoutMs(30_000, 120_000)).toBe(120_000);
+  });
+
+  it("floors at 60s", () => {
+    expect(captureProtocolTimeoutMs(5_000, 5_000)).toBe(60_000);
+  });
+
+  it("uses puppeteer default when inputs are non-finite", () => {
+    expect(captureProtocolTimeoutMs(Number.POSITIVE_INFINITY, 120_000)).toBe(
+      PUPPETEER_DEFAULT_PROTOCOL_TIMEOUT_MS,
+    );
+  });
+});
+
+describe("isNavigationTimeoutError", () => {
+  it("matches Puppeteer TimeoutError navigation timeouts", () => {
+    expect(
+      isNavigationTimeoutError(new TimeoutError("Navigation timeout of 30000 ms exceeded")),
+    ).toBe(true);
+  });
+
+  it("does not treat plain Error as navigation timeout", () => {
+    expect(isNavigationTimeoutError(new Error("Navigation timeout of 30000 ms exceeded"))).toBe(
+      false,
+    );
+  });
+
+  it("still classifies message strings for BLOCKED.md formatting", () => {
+    expect(isNavigationTimeoutError("Navigation timeout of 30000 ms exceeded")).toBe(true);
+  });
+});
+
+describe("isProtocolEvaluateTimeoutError", () => {
+  it("matches Puppeteer TimeoutError evaluate timeouts by instanceof", () => {
+    expect(
+      isProtocolEvaluateTimeoutError(
+        new TimeoutError(
+          "Runtime.evaluate timed out. Increase the 'protocolTimeout' setting in launch/connect calls for a higher timeout if needed.",
+        ),
+      ),
+    ).toBe(true);
+  });
+
+  it("treats non-navigation TimeoutError as evaluate/protocol timeout even if wording drifts", () => {
+    expect(
+      isProtocolEvaluateTimeoutError(new TimeoutError("Timed out after waiting 180000ms")),
+    ).toBe(true);
+  });
+
+  it("ignores navigation TimeoutErrors", () => {
+    expect(
+      isProtocolEvaluateTimeoutError(new TimeoutError("Navigation timeout of 30000 ms exceeded")),
+    ).toBe(false);
+  });
+});
+
+describe("withRemainingBudget", () => {
+  it("returns before a never-resolving promise when the budget elapses", async () => {
+    const never = new Promise<string>(() => undefined);
+    const started = Date.now();
+    await expect(withRemainingBudget(never, 20, "never-resolve")).rejects.toBeInstanceOf(
+      StageBudgetTimeoutError,
+    );
+    expect(Date.now() - started).toBeLessThan(200);
+  });
+
+  it("resolves when work finishes inside the budget", async () => {
+    await expect(withRemainingBudget(Promise.resolve("ok"), 100, "fast")).resolves.toBe("ok");
+  });
+
+  it("fails immediately when no budget remains", async () => {
+    await expect(withRemainingBudget(Promise.resolve("ok"), 0, "empty")).rejects.toBeInstanceOf(
+      StageBudgetTimeoutError,
+    );
+  });
+});
+
+describe("formatCaptureFailureReason", () => {
+  it("describes evaluate/protocol timeouts as extraction failures", () => {
+    const reason = formatCaptureFailureReason(
+      "Runtime.evaluate timed out. Increase the 'protocolTimeout' setting in launch/connect calls for a higher timeout if needed.",
+    );
+    expect(reason).toMatch(/extraction timed out/i);
+    expect(reason).not.toMatch(/navigation timed out/i);
+  });
+
+  it("keeps navigation timeout wording for nav failures", () => {
+    expect(formatCaptureFailureReason("Navigation timeout of 30000 ms exceeded")).toMatch(
+      /navigation timed out/i,
+    );
+  });
+});
@@ -0,0 +1,97 @@
+import { TimeoutError } from "puppeteer-core";
+
+export const PUPPETEER_DEFAULT_PROTOCOL_TIMEOUT_MS = 180_000;
+
+export class StageBudgetTimeoutError extends Error {
+  readonly budgetMs: number;
+
+  constructor(label: string, budgetMs: number) {
+    super(`stage budget exceeded while ${label} (${budgetMs}ms)`);
+    this.name = "StageBudgetTimeoutError";
+    this.budgetMs = budgetMs;
+  }
+}
+
+export function captureProtocolTimeoutMs(navTimeoutMs: number, postNavBudgetMs: number): number {
+  if (!Number.isFinite(navTimeoutMs) || !Number.isFinite(postNavBudgetMs)) {
+    return PUPPETEER_DEFAULT_PROTOCOL_TIMEOUT_MS;
+  }
+  return Math.max(60_000, Math.max(0, navTimeoutMs), Math.max(0, postNavBudgetMs));
+}
+
+function errorMessage(err: unknown): string {
+  return err instanceof Error ? err.message : String(err);
+}
+
+function hasNavigationTimeoutMessage(msg: string): boolean {
+  return /navigation timeout/i.test(msg);
+}
+
+function hasProtocolEvaluateTimeoutMessage(msg: string): boolean {
+  return /Runtime\.evaluate timed out|protocolTimeout|protocol timeout/i.test(msg);
+}
+
+export function isNavigationTimeoutError(err: unknown): boolean {
+  if (err instanceof TimeoutError) {
+    return hasNavigationTimeoutMessage(err.message);
+  }
+  // String path used by BLOCKED.md formatting.
+  return typeof err === "string" && hasNavigationTimeoutMessage(err);
+}
+
+function isStageBudgetTimeoutError(err: unknown): boolean {
+  return err instanceof StageBudgetTimeoutError;
+}
+
+export function isProtocolEvaluateTimeoutError(err: unknown): boolean {
+  if (err instanceof TimeoutError) {
+    return !hasNavigationTimeoutMessage(err.message);
+  }
+  return hasProtocolEvaluateTimeoutMessage(errorMessage(err));
+}
+
+export function isDegradableEvaluateTimeoutError(err: unknown): boolean {
+  return isStageBudgetTimeoutError(err) || isProtocolEvaluateTimeoutError(err);
+}
+
+export async function withRemainingBudget<T>(
+  work: Promise<T>,
+  remainingMs: number,
+  label: string,
+): Promise<T> {
+  if (!(remainingMs > 0)) {
+    throw new StageBudgetTimeoutError(label, Math.max(0, remainingMs));
+  }
+
+  let timer: ReturnType<typeof setTimeout> | undefined;
+  try {
+    return await Promise.race([
+      work,
+      new Promise<never>((_resolve, reject) => {
+        timer = setTimeout(() => {
+          reject(new StageBudgetTimeoutError(label, remainingMs));
+        }, remainingMs);
+      }),
+    ]);
+  } finally {
+    if (timer !== undefined) {
+      clearTimeout(timer);
+    }
+  }
+}
+
+export function formatCaptureFailureReason(errMsg: string): string {
+  if (hasProtocolEvaluateTimeoutMessage(errMsg) || /stage budget exceeded/i.test(errMsg)) {
+    return (
+      `Page extraction timed out while running in-page script (${errMsg}). ` +
+      "The page likely opened, but a later capture step hung."
+    );
+  }
+  if (hasNavigationTimeoutMessage(errMsg)) {
+    return "Page navigation timed out — the site may be blocking headless browsers or requires authentication.";
+  }
+  if (/timeout|timed out/i.test(errMsg)) {
+    return `Capture timed out: ${errMsg}`;
+  }
+  return `Capture failed: ${errMsg}`;
+}
@@ -43,6 +43,12 @@ import type { VisionCaptionOutcome } from "./contentExtractor.js";
 import { loadEnvFile, generateProjectScaffold } from "./scaffolding.js";
 import { detectBlockedPage } from "./pageBlockDetection.js";
 import { navigateForCapture } from "./navigateForCapture.js";
+import {
+  captureProtocolTimeoutMs,
+  isDegradableEvaluateTimeoutError,
+  withRemainingBudget,
+} from "./captureTimeout.js";
+import { lazyScrollForCapture } from "./lazyScrollForCapture.js";
 import type { CaptureOptions, CapturePhase, CapturePhaseProgress, CaptureResult } from "./types.js";

 export type { CaptureOptions, CaptureResult } from "./types.js";
@@ -123,6 +129,7 @@ export async function captureWebsite(
  const chromeBrowser = await puppeteer.default.launch({
    headless: true,
    executablePath: browser.executablePath,
+    protocolTimeout: captureProtocolTimeoutMs(timeout, budgetMs),
    args: [
      "--no-sandbox",
      "--disable-dev-shm-usage",
@@ -253,27 +260,51 @@ export async function captureWebsite(
    postNavigationDeadline = Date.now() + budgetMs;
    await new Promise((r) => setTimeout(r, settleTime));

-    // Check if the page loaded real content or an anti-bot challenge
-    // Combine structural evidence with the main response status/title. Low text
-    // alone stays non-fatal so image-led sites are not rejected.
-    const pageContentCheck = (await page1.evaluate(`(() => {
-      var text = (document.body.innerText || "").trim();
-      var title = document.title || "";
-      // Structural: Cloudflare Turnstile widget or challenge iframe
-      var hasCfTurnstile = !!document.querySelector('.cf-turnstile, [data-sitekey], iframe[src*="challenges.cloudflare.com"], #challenge-running, #challenge-form');
-      // Structural: page is almost empty (challenge pages have minimal DOM)
-      var bodyChildCount = document.body.children.length;
-      return { textLength: text.length, title: title, hasChallengeElement: hasCfTurnstile, bodyChildCount: bodyChildCount };
-    })()`)) as {
+    let pageContentCheck: {
      textLength: number;
      title: string;
      hasChallengeElement: boolean;
      bodyChildCount: number;
+    } = {
+      textLength: 0,
+      title: "",
+      hasChallengeElement: false,
+      bodyChildCount: Number.POSITIVE_INFINITY,
    };
+    let contentCheckTimedOut = false;
+    try {
+      pageContentCheck = (await withRemainingBudget(
+        page1.evaluate(`(() => {
+      var text = (document.body && document.body.innerText || "").trim();
+      var title = document.title || "";
+      var hasCfTurnstile = !!document.querySelector('.cf-turnstile, [data-sitekey], iframe[src*="challenges.cloudflare.com"], #challenge-running, #challenge-form');
+      var bodyChildCount = document.body ? document.body.children.length : 0;
+      return { textLength: text.length, title: title, hasChallengeElement: hasCfTurnstile, bodyChildCount: bodyChildCount };
+    })()`),
+        Math.min(5_000, remainingMs()),
+        "content-check",
+      )) as typeof pageContentCheck;
+    } catch (err) {
+      if (!isDegradableEvaluateTimeoutError(err)) {
+        throw err;
+      }
+      contentCheckTimedOut = true;
+      const message =
+        "post-navigation content check timed out; continuing with HTTP-status blocked-page detection only";
+      warnings.push(message);
+      progress("warn", message);
+    }

    const blockedReason = detectBlockedPage({
      httpStatus: navigationResponse?.status() ?? null,
-      ...pageContentCheck,
+      ...(contentCheckTimedOut
+        ? {
+            title: "",
+            textLength: 0,
+            bodyChildCount: 0,
+            hasChallengeElement: false,
+          }
+        : pageContentCheck),
    });
    if (blockedReason) {
      phase("navigation", "degraded", "blocked");
@@ -283,7 +314,7 @@ export async function captureWebsite(
    phase("navigation", "completed");
    phase("core-extraction", "started");

-    if (pageContentCheck.textLength < 100) {
+    if (!contentCheckTimedOut && pageContentCheck.textLength < 100) {
      const reason =
        "Page has very little text content (" +
        pageContentCheck.textLength +
@@ -292,42 +323,18 @@ export async function captureWebsite(
      progress("warn", reason);
    }

-    // Scroll through page to trigger lazy-loaded images and Lottie animations
-    // Framer and other modern sites use IntersectionObserver — images only load
-    // when scrolled into view. We scroll the full page, then wait for all images
-    // to finish loading before proceeding.
    const lazyLoadBudgetMs = Math.min(15_000, remainingMs());
-    if (lazyLoadBudgetMs > 0) {
-      await page1.evaluate(`(async () => {
-      var lazyLoadDeadline = Date.now() + ${lazyLoadBudgetMs};
-      var h = document.body.scrollHeight;
-      for (var y = 0; y < h; y += window.innerHeight * 0.7) {
-        if (Date.now() >= lazyLoadDeadline) break;
-        window.scrollTo(0, y);
-        await new Promise(function(r) { setTimeout(r, 400); });
-      }
-      // Scroll to very bottom to catch footer lazy-loads
-      if (Date.now() < lazyLoadDeadline) {
-        window.scrollTo(0, document.body.scrollHeight);
-        await new Promise(function(r) { setTimeout(r, Math.min(800, Math.max(0, lazyLoadDeadline - Date.now()))); });
-      }
-      // Wait for all images to finish loading
-      var imgs = Array.from(document.querySelectorAll('img'));
-      var pending = imgs.filter(function(img) { return !img.complete; });
-      var imageWaitMs = Math.min(5000, Math.max(0, lazyLoadDeadline - Date.now()));
-      if (pending.length > 0 && imageWaitMs > 0) {
-        await Promise.race([
-          Promise.all(pending.map(function(img) {
-            return new Promise(function(r) { img.onload = r; img.onerror = r; });
-          })),
-          new Promise(function(r) { setTimeout(r, imageWaitMs); })
-        ]);
-      }
-      window.scrollTo(0, 0);
-    })()`);
+    const lazyScroll = await lazyScrollForCapture(page1, lazyLoadBudgetMs, {
+      onWarning: (message) => {
+        warnings.push(message);
+        progress("warn", message);
+      },
+    });
+    if (lazyScroll.timedOut && !lazyScroll.degraded) {
+      const message = `lazy-scroll stopped after ${lazyScroll.steps} steps (budget ${lazyLoadBudgetMs}ms)`;
+      warnings.push(message);
+      progress("warn", message);
    }
-
-    await page1.evaluate(`window.scrollTo(0, 0)`);
    await new Promise((r) => setTimeout(r, 300));

    // Save discovered Lottie animations
@@ -434,15 +441,47 @@ export async function captureWebsite(
      warnings.push(`Design style extraction failed: ${errMsg}`);
    }

-    // Collect animation catalog
    progress("animations", "Cataloging animations...");
-    animationCatalog = await collectAnimationCatalog(page1, cdpAnims, cdp);
+    try {
+      const animationOutcome = await collectAnimationCatalog(page1, cdpAnims, cdp, {
+        scrollBudgetMs: Math.min(8_000, remainingMs()),
+        evaluateBudgetMs: Math.min(15_000, remainingMs()),
+      });
+      animationCatalog = animationOutcome.catalog;
+      if (animationOutcome.timedOut) {
+        const message =
+          "animation catalog evaluate timed out; continuing without animation catalog";
+        warnings.push(message);
+        progress("warn", message);
+      }
+    } catch (err) {
+      if (!isDegradableEvaluateTimeoutError(err)) {
+        throw err;
+      }
+      const message = "animation catalog evaluate timed out; continuing without animation catalog";
+      warnings.push(message);
+      progress("warn", message);
+      try {
+        await cdp.send("Animation.disable");
+      } catch {
+        /* ignore */
+      }
+    }

-    // Capture scroll-position viewport screenshots
    progress("screenshots", "Capturing scroll screenshots...");
    const { captureScrollScreenshots } = await import("./screenshotCapture.js");
-    const screenshots = await captureScrollScreenshots(page1, outputDir, { remainingMs });
-    progress("screenshots", `${screenshots.length} scroll screenshots captured`);
+    let screenshots: string[] = [];
+    try {
+      screenshots = await captureScrollScreenshots(page1, outputDir, { remainingMs });
+      progress("screenshots", `${screenshots.length} scroll screenshots captured`);
+    } catch (err) {
+      if (!isDegradableEvaluateTimeoutError(err)) {
+        throw err;
+      }
+      const message = "scroll screenshots timed out; continuing without screenshots";
+      warnings.push(message);
+      progress("warn", message);
+    }

    // Catalog all assets (must run before extractHtml which converts img src to data URLs)
    progress("design", "Cataloging assets...");
@@ -0,0 +1,61 @@
+import { describe, expect, it, vi } from "vitest";
+import { lazyScrollForCapture } from "./lazyScrollForCapture.js";
+
+describe("lazyScrollForCapture", () => {
+  it("no-ops when budget is empty", async () => {
+    const evaluate = vi.fn();
+    const result = await lazyScrollForCapture({ evaluate }, 0);
+    expect(result).toEqual({ steps: 0, timedOut: false, degraded: false });
+    expect(evaluate).not.toHaveBeenCalled();
+  });
+
+  it("scrolls in node-driven steps until the bottom", async () => {
+    const heights = [{ atBottom: false }, { atBottom: false }, { atBottom: true }];
+    const evaluate = vi.fn(async (expr: string) => {
+      if (expr.includes("atBottom")) {
+        return heights.shift() ?? { atBottom: true };
+      }
+      return 0;
+    });
+    const sleep = vi.fn(async () => undefined);
+
+    const result = await lazyScrollForCapture({ evaluate }, 15_000, { stepDelayMs: 10, sleep });
+
+    expect(result.steps).toBe(3);
+    expect(result.timedOut).toBe(false);
+    expect(result.degraded).toBe(false);
+  });
+
+  it("returns within the stage budget when evaluate never resolves", async () => {
+    const evaluate = vi.fn(() => new Promise(() => undefined));
+    const started = Date.now();
+    const warnings: string[] = [];
+
+    const result = await lazyScrollForCapture({ evaluate }, 25, {
+      onWarning: (message) => warnings.push(message),
+      sleep: async () => undefined,
+    });
+
+    expect(result.degraded).toBe(true);
+    expect(result.timedOut).toBe(true);
+    expect(Date.now() - started).toBeLessThan(250);
+    expect(warnings[0]).toMatch(/lazy-scroll evaluate timed out/i);
+  });
+
+  it("does not issue a recovery evaluate after the budget is exhausted", async () => {
+    let now = 1_000_000;
+    const dateSpy = vi.spyOn(Date, "now").mockImplementation(() => now);
+    const evaluate = vi.fn(() => {
+      now += 100;
+      return new Promise(() => undefined);
+    });
+
+    try {
+      const result = await lazyScrollForCapture({ evaluate }, 30, { sleep: async () => undefined });
+      expect(result.degraded).toBe(true);
+      expect(evaluate).toHaveBeenCalledTimes(1);
+    } finally {
+      dateSpy.mockRestore();
+    }
+  });
+});
@@ -0,0 +1,141 @@
+import { isDegradableEvaluateTimeoutError, withRemainingBudget } from "./captureTimeout.js";
+
+const LAZY_SCROLL_STEP_DELAY_MS = 400;
+const LAZY_SCROLL_MAX_IMAGE_WAIT_MS = 5_000;
+const LAZY_SCROLL_BOTTOM_SETTLE_MS = 800;
+const LAZY_SCROLL_IMAGE_POLL_MS = 250;
+
+export interface LazyScrollPage {
+  evaluate(pageFunction: string): Promise<unknown>;
+}
+
+export interface LazyScrollResult {
+  steps: number;
+  timedOut: boolean;
+  degraded: boolean;
+}
+
+async function evaluateWithinBudget(
+  page: LazyScrollPage,
+  expression: string,
+  deadline: number,
+  label: string,
+): Promise<unknown> {
+  return withRemainingBudget(page.evaluate(expression), deadline - Date.now(), label);
+}
+
+async function settleAfterScroll(
+  page: LazyScrollPage,
+  deadline: number,
+  sleep: (ms: number) => Promise<void>,
+): Promise<void> {
+  const bottomSettleMs = Math.min(LAZY_SCROLL_BOTTOM_SETTLE_MS, Math.max(0, deadline - Date.now()));
+  if (bottomSettleMs > 0) {
+    await evaluateWithinBudget(
+      page,
+      `window.scrollTo(0, document.body.scrollHeight)`,
+      deadline,
+      "lazy-scroll-bottom",
+    );
+    await sleep(bottomSettleMs);
+  }
+
+  const imageDeadline = Math.min(deadline, Date.now() + LAZY_SCROLL_MAX_IMAGE_WAIT_MS);
+  while (Date.now() < imageDeadline) {
+    const pending = (await evaluateWithinBudget(
+      page,
+      `Array.from(document.images).filter(function(img) { return !img.complete; }).length`,
+      imageDeadline,
+      "lazy-scroll-image-pending",
+    )) as number;
+    if (!(pending > 0)) {
+      break;
+    }
+    const waitMs = Math.min(LAZY_SCROLL_IMAGE_POLL_MS, imageDeadline - Date.now());
+    if (waitMs <= 0) {
+      break;
+    }
+    await sleep(waitMs);
+  }
+
+  if (deadline - Date.now() > 0) {
+    await evaluateWithinBudget(page, `window.scrollTo(0, 0)`, deadline, "lazy-scroll-reset");
+  }
+}
+
+// fallow-ignore-next-line complexity
+export async function lazyScrollForCapture(
+  page: LazyScrollPage,
+  budgetMs: number,
+  opts: {
+    stepDelayMs?: number;
+    onWarning?: (message: string) => void;
+    sleep?: (ms: number) => Promise<void>;
+  } = {},
+): Promise<LazyScrollResult> {
+  if (budgetMs <= 0) {
+    return { steps: 0, timedOut: false, degraded: false };
+  }
+
+  const stepDelayMs = opts.stepDelayMs ?? LAZY_SCROLL_STEP_DELAY_MS;
+  const sleep = opts.sleep ?? ((ms: number) => new Promise((resolve) => setTimeout(resolve, ms)));
+  const deadline = Date.now() + budgetMs;
+  let steps = 0;
+  let timedOut = false;
+  let degraded = false;
+
+  try {
+    while (Date.now() < deadline) {
+      const state = (await evaluateWithinBudget(
+        page,
+        `(() => {
+        var y = window.scrollY || window.pageYOffset || 0;
+        var view = window.innerHeight || 0;
+        var height = document.body ? document.body.scrollHeight : 0;
+        var next = Math.min(y + view * 0.7, Math.max(0, height - view));
+        var atBottom = height <= view + 2 || next <= y + 1;
+        window.scrollTo(0, atBottom ? height : next);
+        return { atBottom: atBottom };
+      })()`,
+        deadline,
+        "lazy-scroll-step",
+      )) as { atBottom: boolean };
+
+      steps += 1;
+      if (state.atBottom) {
+        break;
+      }
+
+      const remaining = deadline - Date.now();
+      if (remaining <= 0) {
+        timedOut = true;
+        break;
+      }
+      await sleep(Math.min(stepDelayMs, remaining));
+    }
+
+    if (Date.now() >= deadline) {
+      timedOut = true;
+    }
+
+    if (deadline - Date.now() > 0) {
+      await settleAfterScroll(page, deadline, sleep);
+    }
+  } catch (err) {
+    if (!isDegradableEvaluateTimeoutError(err)) {
+      throw err;
+    }
+    degraded = true;
+    timedOut = true;
+    opts.onWarning?.("lazy-scroll evaluate timed out; continuing with current page state");
+    if (deadline - Date.now() > 0) {
+      try {
+        await evaluateWithinBudget(page, `window.scrollTo(0, 0)`, deadline, "lazy-scroll-recovery");
+      } catch {
+        /* page may be wedged; do not spend another unbounded protocol wait */
+      }
+    }
+  }
+
+  return { steps, timedOut, degraded };
+}
@@ -1,4 +1,5 @@
 import { describe, expect, it, vi } from "vitest";
+import { TimeoutError } from "puppeteer-core";
 import {
  isNavigationTimeoutError,
  navigateForCapture,
@@ -17,10 +18,10 @@ describe("networkIdleAttemptTimeoutMs", () => {
 });

 describe("isNavigationTimeoutError", () => {
-  it("matches Puppeteer navigation timeouts", () => {
-    expect(isNavigationTimeoutError(new Error("Navigation timeout of 30000 ms exceeded"))).toBe(
-      true,
-    );
+  it("matches Puppeteer TimeoutError navigation timeouts", () => {
+    expect(
+      isNavigationTimeoutError(new TimeoutError("Navigation timeout of 30000 ms exceeded")),
+    ).toBe(true);
  });

  it("ignores unrelated failures", () => {
@@ -51,7 +52,7 @@ describe("navigateForCapture", () => {
    const response = { status: () => 200 };
    const goto = vi
      .fn()
-      .mockRejectedValueOnce(new Error("Navigation timeout of 30000 ms exceeded"))
+      .mockRejectedValueOnce(new TimeoutError("Navigation timeout of 30000 ms exceeded"))
      .mockResolvedValueOnce(response);

    const result = await navigateForCapture({ goto }, "https://www.yahoo.com/", 120_000);
@@ -81,7 +82,7 @@ describe("navigateForCapture", () => {
      const response = { status: () => 200 };
      const goto = vi
        .fn()
-        .mockRejectedValueOnce(new Error("Navigation timeout of 30000 ms exceeded"))
+        .mockRejectedValueOnce(new TimeoutError("Navigation timeout of 30000 ms exceeded"))
        .mockResolvedValueOnce(response);

      await navigateForCapture({ goto }, "https://www.yahoo.com/", totalTimeoutMs);
@@ -106,7 +107,7 @@ describe("navigateForCapture", () => {
  });

  it("does not fall back when the caller timeout already equals the idle attempt", async () => {
-    const err = new Error("Navigation timeout of 10000 ms exceeded");
+    const err = new TimeoutError("Navigation timeout of 10000 ms exceeded");
    const goto = vi.fn().mockRejectedValue(err);

    await expect(navigateForCapture({ goto }, "https://example.com", 10_000)).rejects.toBe(err);
@@ -1,3 +1,7 @@
+import { isNavigationTimeoutError } from "./captureTimeout.js";
+
+export { isNavigationTimeoutError };
+
 export const NETWORK_IDLE_ATTEMPT_MS = 30_000;

 export type CaptureGotoWaitUntil = "networkidle2" | "domcontentloaded";
@@ -22,11 +26,6 @@ export function networkIdleAttemptTimeoutMs(totalTimeoutMs: number): number {
  return Math.min(NETWORK_IDLE_ATTEMPT_MS, Math.max(0, totalTimeoutMs));
 }

-export function isNavigationTimeoutError(err: unknown): boolean {
-  const msg = err instanceof Error ? err.message : String(err);
-  return /navigation timeout/i.test(msg);
-}
-
 export async function navigateForCapture<TResponse>(
  page: CaptureGotoPage<TResponse>,
  url: string,
@@ -0,0 +1,25 @@
+import { describe, expect, it, vi } from "vitest";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { TimeoutError } from "puppeteer-core";
+import type { Page } from "puppeteer-core";
+import { captureScrollScreenshots } from "./screenshotCapture.js";
+
+describe("captureScrollScreenshots degradation", () => {
+  it("rethrows protocol evaluate timeouts for the caller warning path", async () => {
+    const dir = mkdtempSync(join(tmpdir(), "hf-scroll-degrade-"));
+    const page = {
+      evaluate: vi.fn(async () => {
+        throw new TimeoutError(
+          "Runtime.evaluate timed out. Increase the 'protocolTimeout' setting in launch/connect calls for a higher timeout if needed.",
+        );
+      }),
+      screenshot: vi.fn(),
+    } as unknown as Page;
+
+    await expect(
+      captureScrollScreenshots(page, dir, { remainingMs: () => 5_000 }),
+    ).rejects.toBeInstanceOf(TimeoutError);
+  });
+});
@@ -6,6 +6,7 @@
 */

 import type { Page } from "puppeteer-core";
+import { isDegradableEvaluateTimeoutError } from "./captureTimeout.js";
 import { writeFileSync, mkdirSync } from "node:fs";
 import { join } from "node:path";

@@ -197,7 +198,11 @@ export async function captureScrollScreenshots(
          node = walker.nextNode();
        }
      })
-      .catch(() => {});
+      .catch((err: unknown) => {
+        if (isDegradableEvaluateTimeoutError(err)) {
+          throw err;
+        }
+      });
    await new Promise((r) => setTimeout(r, 400));

    const scrollHeight = (await page.evaluate(
@@ -257,7 +262,10 @@ export async function captureScrollScreenshots(
      const plate = await captureFullPagePlate(page, screenshotsDir, budget);
      if (plate) filePaths.push(plate);
    }
-  } catch {
+  } catch (err) {
+    if (isDegradableEvaluateTimeoutError(err)) {
+      throw err;
+    }
    /* scroll screenshots are non-critical */
  }