diff --git a/packages/engine/src/services/frameCapture.test.ts b/packages/engine/src/services/frameCapture.test.ts
index 1b280c8b4..01dce0596 100644
--- a/packages/engine/src/services/frameCapture.test.ts
+++ b/packages/engine/src/services/frameCapture.test.ts
@@ -1,5 +1,11 @@
 import { describe, it, expect } from "vitest";
-import { isFontResourceError } from "./frameCapture.js";
+import {
+  formatHttpErrorDiagnostic,
+  formatNavigationFailureDiagnostic,
+  formatRequestFailureDiagnostic,
+  isFontResourceError,
+  sanitizeDiagnosticUrl,
+} from "./frameCapture.js";
 
 describe("isFontResourceError", () => {
   it("matches Google Fonts CSS load failures via location.url", () => {
@@ -110,3 +116,62 @@ describe("isFontResourceError", () => {
     ).toBe(true);
   });
 });
+
+describe("navigation diagnostics", () => {
+  it("redacts credentials, query strings, and fragments from diagnostic URLs", () => {
+    expect(
+      sanitizeDiagnosticUrl("https://user:pass@example.com/assets/video.mp4?token=secret#frag"),
+    ).toBe("https://example.com/assets/video.mp4");
+  });
+
+  it("redacts data and blob URLs", () => {
+    expect(sanitizeDiagnosticUrl("data:image/png;base64,abc123")).toBe("data:<redacted>");
+    expect(sanitizeDiagnosticUrl("blob:https://example.com/abc123")).toBe("blob:<redacted>");
+  });
+
+  it("redacts query strings from relative URLs", () => {
+    expect(sanitizeDiagnosticUrl("/relative/path.png?token=secret#frag")).toBe(
+      "/relative/path.png",
+    );
+  });
+
+  it("formats page.goto failures with mode, timeout, elapsed time, and sanitized URL", () => {
+    const diagnostic = formatNavigationFailureDiagnostic({
+      captureMode: "screenshot",
+      url: "http://127.0.0.1:4173/index.html?claim_token=secret",
+      timeoutMs: 60_000,
+      elapsedMs: 60_123,
+      error: new Error("Navigation timeout of 60000 ms exceeded"),
+    });
+
+    expect(diagnostic).toContain("[FrameCapture:ERROR] page.goto failed");
+    expect(diagnostic).toContain("mode=screenshot");
+    expect(diagnostic).toContain("timeoutMs=60000");
+    expect(diagnostic).toContain("elapsedMs=60123");
+    expect(diagnostic).toContain("url=http://127.0.0.1:4173/index.html");
+    expect(diagnostic).not.toContain("claim_token");
+  });
+
+  it("formats request and HTTP failures with sanitized URLs", () => {
+    expect(
+      formatRequestFailureDiagnostic({
+        method: "GET",
+        resourceType: "media",
+        url: "https://cdn.example.com/video.mp4?token=secret",
+        failureText: "net::ERR_FAILED",
+      }),
+    ).toBe(
+      "[Browser:REQUESTFAILED] GET https://cdn.example.com/video.mp4 resource=media error=net::ERR_FAILED",
+    );
+
+    expect(
+      formatHttpErrorDiagnostic({
+        method: "GET",
+        resourceType: "image",
+        url: "https://cdn.example.com/frame.png?token=secret",
+        status: 403,
+        statusText: "Forbidden",
+      }),
+    ).toBe("[Browser:HTTP403] GET https://cdn.example.com/frame.png resource=image Forbidden");
+  });
+});
diff --git a/packages/engine/src/services/frameCapture.ts b/packages/engine/src/services/frameCapture.ts
index d02ed650c..3210b6c36 100644
--- a/packages/engine/src/services/frameCapture.ts
+++ b/packages/engine/src/services/frameCapture.ts
@@ -79,6 +79,79 @@ export interface CaptureSession {
 const BROWSER_CONSOLE_BUFFER_SIZE = 200;
 const CAPTURE_SESSION_CLOSE_TIMEOUT_MS = 5_000;
 
+function appendBrowserDiagnostic(session: CaptureSession, text: string): void {
+  session.browserConsoleBuffer.push(text);
+  if (session.browserConsoleBuffer.length > BROWSER_CONSOLE_BUFFER_SIZE) {
+    session.browserConsoleBuffer.shift();
+  }
+}
+
+export function sanitizeDiagnosticUrl(input: string): string {
+  if (!input) return "(empty)";
+  if (input.startsWith("data:")) return "data:<redacted>";
+  if (input.startsWith("blob:")) return "blob:<redacted>";
+  if (input.startsWith("/")) {
+    try {
+      const url = new URL(input, "http://hyperframes.local");
+      return url.pathname;
+    } catch {
+      return input;
+    }
+  }
+
+  try {
+    const url = new URL(input);
+    url.username = "";
+    url.password = "";
+    url.search = "";
+    url.hash = "";
+    return url.toString();
+  } catch {
+    return input;
+  }
+}
+
+export function formatNavigationFailureDiagnostic(input: {
+  captureMode: CaptureMode;
+  url: string;
+  timeoutMs: number;
+  elapsedMs: number;
+  error: unknown;
+}): string {
+  const message = input.error instanceof Error ? input.error.message : String(input.error);
+  return (
+    `[FrameCapture:ERROR] page.goto failed ` +
+    `mode=${input.captureMode} timeoutMs=${input.timeoutMs} elapsedMs=${input.elapsedMs} ` +
+    `url=${sanitizeDiagnosticUrl(input.url)} error=${message}`
+  );
+}
+
+export function formatRequestFailureDiagnostic(input: {
+  method: string;
+  resourceType: string;
+  url: string;
+  failureText: string;
+}): string {
+  return (
+    `[Browser:REQUESTFAILED] ${input.method} ${sanitizeDiagnosticUrl(input.url)} ` +
+    `resource=${input.resourceType} error=${input.failureText}`
+  );
+}
+
+export function formatHttpErrorDiagnostic(input: {
+  method: string;
+  resourceType: string;
+  url: string;
+  status: number;
+  statusText: string;
+}): string {
+  const statusText = input.statusText ? ` ${input.statusText}` : "";
+  return (
+    `[Browser:HTTP${input.status}] ${input.method} ${sanitizeDiagnosticUrl(input.url)} ` +
+    `resource=${input.resourceType}${statusText}`
+  );
+}
+
 /**
  * Fixed warmup-loop iteration count used when `CaptureOptions.lockWarmupTicks`
  * is `true`. Picked to roughly match the median tick count observed by the
@@ -721,10 +794,7 @@ export async function initializeSession(session: CaptureSession): Promise<void>
       console.log(`${prefix} ${text}`);
     }
 
-    session.browserConsoleBuffer.push(`${prefix} ${text}`);
-    if (session.browserConsoleBuffer.length > BROWSER_CONSOLE_BUFFER_SIZE) {
-      session.browserConsoleBuffer.shift();
-    }
+    appendBrowserDiagnostic(session, `${prefix} ${text}`);
   });
 
   page.on("pageerror", (err) => {
@@ -738,10 +808,36 @@ export async function initializeSession(session: CaptureSession): Promise<void>
       console.error(text);
     }
 
-    session.browserConsoleBuffer.push(text);
-    if (session.browserConsoleBuffer.length > BROWSER_CONSOLE_BUFFER_SIZE) {
-      session.browserConsoleBuffer.shift();
-    }
+    appendBrowserDiagnostic(session, text);
+  });
+
+  page.on("requestfailed", (request) => {
+    appendBrowserDiagnostic(
+      session,
+      formatRequestFailureDiagnostic({
+        method: request.method(),
+        resourceType: request.resourceType(),
+        url: request.url(),
+        failureText: request.failure()?.errorText ?? "unknown",
+      }),
+    );
+  });
+
+  page.on("response", (response) => {
+    const status = response.status();
+    if (status < 400) return;
+
+    const request = response.request();
+    appendBrowserDiagnostic(
+      session,
+      formatHttpErrorDiagnostic({
+        method: request.method(),
+        resourceType: request.resourceType(),
+        url: response.url(),
+        status,
+        statusText: response.statusText(),
+      }),
+    );
   });
 
   // Navigate to the file server
@@ -752,10 +848,27 @@ export async function initializeSession(session: CaptureSession): Promise<void>
   const logInitPhase = (phase: string) => {
     console.log(`[initSession:${session.captureMode}] ${phase} (${Date.now() - initStart}ms)`);
   };
+  const gotoEntryPage = async (): Promise<void> => {
+    try {
+      await page.goto(url, { waitUntil: "domcontentloaded", timeout: pageNavigationTimeout });
+    } catch (error) {
+      appendBrowserDiagnostic(
+        session,
+        formatNavigationFailureDiagnostic({
+          captureMode: session.captureMode,
+          url,
+          timeoutMs: pageNavigationTimeout,
+          elapsedMs: Date.now() - initStart,
+          error,
+        }),
+      );
+      throw error;
+    }
+  };
 
   if (session.captureMode === "screenshot") {
     // Screenshot mode: standard navigation, rAF works normally
-    await page.goto(url, { waitUntil: "domcontentloaded", timeout: pageNavigationTimeout });
+    await gotoEntryPage();
     logInitPhase("page.goto complete");
 
     const pageReadyTimeout =
@@ -894,7 +1007,7 @@ export async function initializeSession(session: CaptureSession): Promise<void>
   warmupLoopPromise.catch(() => {});
   logInitPhase("warmup loop started");
 
-  await page.goto(url, { waitUntil: "domcontentloaded", timeout: pageNavigationTimeout });
+  await gotoEntryPage();
   logInitPhase("page.goto complete");
 
   // Poll for window.__hf readiness using manual evaluate loop (waitForFunction
diff --git a/packages/engine/src/services/parallelCoordinator.test.ts b/packages/engine/src/services/parallelCoordinator.test.ts
index 3cf266c1f..523a51442 100644
--- a/packages/engine/src/services/parallelCoordinator.test.ts
+++ b/packages/engine/src/services/parallelCoordinator.test.ts
@@ -2,6 +2,8 @@ import { describe, it, expect } from "vitest";
 import {
   calculateOptimalWorkers,
   distributeFrames,
+  formatWorkerFailure,
+  selectWorkerDiagnostics,
   shouldVerifyWorkerGpu,
 } from "./parallelCoordinator.js";
 import type { EngineConfig } from "../config.js";
@@ -74,6 +76,42 @@ describe("calculateOptimalWorkers", () => {
   });
 });
 
+describe("worker failure diagnostics", () => {
+  it("keeps only actionable worker diagnostics and caps the tail", () => {
+    const diagnostics = selectWorkerDiagnostics(
+      [
+        "[Browser] harmless log",
+        "[Browser:WARN] noisy warning",
+        "[Browser:REQUESTFAILED] GET https://cdn.example.com/a.mp4 resource=media error=net::ERR_FAILED",
+        "[Browser:HTTP404] GET https://cdn.example.com/missing.png resource=image Not Found",
+        "[FrameCapture:ERROR] page.goto failed mode=screenshot timeoutMs=60000 elapsedMs=60001 url=http://127.0.0.1:4173/index.html error=timeout",
+      ],
+      2,
+    );
+
+    expect(diagnostics).toEqual([
+      "[Browser:HTTP404] GET https://cdn.example.com/missing.png resource=image Not Found",
+      "[FrameCapture:ERROR] page.goto failed mode=screenshot timeoutMs=60000 elapsedMs=60001 url=http://127.0.0.1:4173/index.html error=timeout",
+    ]);
+  });
+
+  it("adds compact diagnostics to the worker failure message", () => {
+    expect(
+      formatWorkerFailure({
+        workerId: 1,
+        framesCaptured: 0,
+        startFrame: 0,
+        endFrame: 30,
+        durationMs: 60_100,
+        error: "Navigation timeout of 60000 ms exceeded",
+        diagnostics: ["[FrameCapture:ERROR] page.goto failed\n  mode=screenshot timeoutMs=60000"],
+      }),
+    ).toBe(
+      "Worker 1: Navigation timeout of 60000 ms exceeded; diagnostics: [FrameCapture:ERROR] page.goto failed mode=screenshot timeoutMs=60000",
+    );
+  });
+});
+
 describe("shouldVerifyWorkerGpu", () => {
   const softwareConfig: Partial<EngineConfig> = { browserGpuMode: "software" };
 
diff --git a/packages/engine/src/services/parallelCoordinator.ts b/packages/engine/src/services/parallelCoordinator.ts
index f7d892bad..45a3ffbbc 100644
--- a/packages/engine/src/services/parallelCoordinator.ts
+++ b/packages/engine/src/services/parallelCoordinator.ts
@@ -51,6 +51,7 @@ export interface WorkerResult {
   durationMs: number;
   perf?: CapturePerfSummary;
   error?: string;
+  diagnostics?: string[];
 }
 
 export interface ParallelProgress {
@@ -76,6 +77,7 @@ export interface WorkerSizingConfig extends Partial<
 
 const MEMORY_PER_WORKER_MB = 256;
 const MIN_WORKERS = 1;
+const MAX_WORKER_DIAGNOSTIC_LINES = 8;
 // Hard ceiling on explicit `--workers N` requests. Above this, the cost of
 // CDP-protocol dispatch through Node's main event loop and OS scheduling
 // noise overwhelms any further parallelism. Bumped from 10 → 24 in hf#732
@@ -95,6 +97,31 @@ function defaultSafeMaxWorkers(): number {
 }
 const MIN_FRAMES_PER_WORKER = 30;
 
+export function selectWorkerDiagnostics(
+  lines: readonly string[],
+  maxLines: number = MAX_WORKER_DIAGNOSTIC_LINES,
+): string[] {
+  return lines
+    .filter((line) =>
+      /\[(FrameCapture:ERROR|Browser:ERROR|Browser:PAGEERROR|Browser:REQUESTFAILED|Browser:HTTP\d{3})\]/.test(
+        line,
+      ),
+    )
+    .slice(-maxLines);
+}
+
+function compactDiagnosticLine(line: string): string {
+  return line.replace(/\s+/g, " ").trim();
+}
+
+export function formatWorkerFailure(result: WorkerResult): string {
+  const base = `Worker ${result.workerId}: ${result.error ?? "unknown error"}`;
+  if (!result.diagnostics || result.diagnostics.length === 0) return base;
+
+  const diagnostics = result.diagnostics.map(compactDiagnosticLine).join(" | ");
+  return `${base}; diagnostics: ${diagnostics}`;
+}
+
 export function calculateOptimalWorkers(
   totalFrames: number,
   requested?: number,
@@ -287,6 +314,7 @@ async function executeWorkerTask(
     };
   } catch (error) {
     const errMsg = error instanceof Error ? error.message : String(error);
+    const diagnostics = session ? selectWorkerDiagnostics(session.browserConsoleBuffer) : [];
     return {
       workerId: task.workerId,
       framesCaptured,
@@ -295,6 +323,7 @@ async function executeWorkerTask(
       durationMs: Date.now() - startTime,
       perf,
       error: errMsg,
+      diagnostics: diagnostics.length > 0 ? diagnostics : undefined,
     };
   } finally {
     if (session) await closeCaptureSession(session).catch(() => {});
@@ -351,7 +380,7 @@ export async function executeParallelCapture(
 
   const errors = results.filter((r) => r.error);
   if (errors.length > 0) {
-    const errorMessages = errors.map((e) => `Worker ${e.workerId}: ${e.error}`).join("; ");
+    const errorMessages = errors.map(formatWorkerFailure).join("; ");
     throw new Error(`[Parallel] Capture failed: ${errorMessages}`);
   }
 
diff --git a/packages/producer/src/services/renderOrchestrator.ts b/packages/producer/src/services/renderOrchestrator.ts
index cb8739cbd..0b86f4a7a 100644
--- a/packages/producer/src/services/renderOrchestrator.ts
+++ b/packages/producer/src/services/renderOrchestrator.ts
@@ -2184,7 +2184,13 @@ export async function executeRenderJob(
       workers: job.config.workers ?? "auto",
       protocolTimeout: cfg.protocolTimeout,
       browserConsoleErrors: lastBrowserConsole
-        .filter((l) => l.includes("ERROR") || l.includes("PAGEERROR"))
+        .filter(
+          (l) =>
+            l.includes("ERROR") ||
+            l.includes("PAGEERROR") ||
+            l.includes("REQUESTFAILED") ||
+            /\[Browser:HTTP\d{3}\]/.test(l),
+        )
         .slice(-5),
     });