diff --git a/packages/playground/personal-wp/index.html b/packages/playground/personal-wp/index.html
index c2b95cc524..26ff933500 100644
--- a/packages/playground/personal-wp/index.html
+++ b/packages/playground/personal-wp/index.html
@@ -92,6 +92,50 @@
 		/>
 	</head>
 	<body>
+		<template id="load-error-fallback">
+			<!-- Use inline styles in case we are having trouble loading other resources -->
+			<div
+				style="
+					max-width: 520px;
+					margin: 80px auto;
+					font-family: system-ui, sans-serif;
+					text-align: center;
+					padding: 0 20px;
+				"
+			>
+				<h1 style="font-size: 1.4rem; margin-bottom: 12px">
+					Could not load Your WordPress
+				</h1>
+				<p style="line-height: 1.5">
+					The application failed to load. This is often caused by a
+					network issue.
+				</p>
+				<p style="line-height: 1.5; margin-top: 8px">
+					Check your internet connection, disable any VPN or ad
+					blocker that might interfere, and try again.
+				</p>
+				<button
+					onclick="location.reload()"
+					style="
+						margin-top: 15px;
+						margin-bottom: 15px;
+						font-size: 20px;
+						padding: 5px 10px;
+						cursor: pointer;
+					"
+				>
+					Try again
+				</button>
+				<p>
+					If the problem persists, please
+					<a
+						href="https://github.com/WordPress/wordpress-playground/issues/new"
+						target="_blank"
+						>report an issue on GitHub</a
+					>.
+				</p>
+			</div>
+		</template>
 		<!--
 			Shown before React loads when an iOS WKWebView (in-app browser) is
 			detected. The detection script below reveals this and skips the
@@ -250,7 +294,7 @@ <h1>Open in your browser</h1>
 				 * Therefore, we're bypassing the cached import by adding a cache busting query parameter
 				 * if the original import fails.
 				 */
-				import('./src/main').catch((e) => {
+				import('./src/main').catch(async (e) => {
 					console.error('Failed to load main module:', e);
 					try {
 						/**
@@ -273,14 +317,23 @@ <h1>Open in your browser</h1>
 								'_ts',
 								String(Date.now())
 							);
-							return import(
+							return await import(
 								/* @vite-ignore */ moduleUrl.toString()
 							);
 						}
 					} catch {
 						// Fall back to the original error
 					}
-					throw e;
+					/**
+					 * If we get here, the app module completely failed to load.
+					 * React is not available, so render a plain HTML
+					 * error message.
+					 */
+					const root = document.getElementById('root');
+					const template = document.getElementById(
+						'load-error-fallback'
+					);
+					root.replaceChildren(template.content.cloneNode(true));
 				});
 			}
 		</script>
diff --git a/packages/playground/personal-wp/src/components/site-error-modal/get-site-error-view.tsx b/packages/playground/personal-wp/src/components/site-error-modal/get-site-error-view.tsx
index f72fd84f39..b125d22b3d 100644
--- a/packages/playground/personal-wp/src/components/site-error-modal/get-site-error-view.tsx
+++ b/packages/playground/personal-wp/src/components/site-error-modal/get-site-error-view.tsx
@@ -33,7 +33,11 @@ export function getSiteErrorView(
 	// Show specific error views for certain error types, even if they occurred
 	// during a blueprint step. These errors have dedicated user-friendly views
 	// that provide better guidance than the generic step error view.
-	if (blueprintStepError && error !== 'network-firewall-interference') {
+	if (
+		blueprintStepError &&
+		error !== 'network-firewall-interference' &&
+		error !== 'resource-download-failed'
+	) {
 		return blueprintStepExecutionView(context);
 	}
 
@@ -55,6 +59,8 @@ export function getSiteErrorView(
 			return directoryHandleUnknownErrorView();
 		case 'network-firewall-interference':
 			return networkFirewallInterferenceView(context);
+		case 'resource-download-failed':
+			return resourceDownloadFailedView();
 		case 'site-boot-failed':
 		default:
 			return genericSiteBootFailedView(context);
@@ -461,6 +467,42 @@ function networkFirewallInterferenceView({
 	};
 }
 
+function resourceDownloadFailedView(): SiteErrorViewConfig {
+	return {
+		title: 'Could not download required files',
+		isDeveloperError: false,
+		hideReportButton: true,
+		detailSummaryOverride: 'Technical details',
+		body: (
+			<>
+				<p className={css.errorLead}>
+					Playground could not download one or more files it needs to
+					run. This is usually caused by a network problem.
+				</p>
+				<ul className={css.errorList}>
+					<li>Check your internet connection and try again.</li>
+					<li>
+						A firewall, proxy, or VPN may be blocking the download.
+					</li>
+					<li>
+						Browser extensions such as ad blockers can sometimes
+						interfere with downloads.
+					</li>
+				</ul>
+			</>
+		),
+		actions: [
+			<Button
+				variant="primary"
+				key="reload"
+				onClick={() => window.location.reload()}
+			>
+				Reload page
+			</Button>,
+		],
+	};
+}
+
 function genericSiteBootFailedView({
 	blueprintStepError,
 	helpers,
diff --git a/packages/playground/personal-wp/src/lib/state/redux/boot-site-client.ts b/packages/playground/personal-wp/src/lib/state/redux/boot-site-client.ts
index 06134f224c..47d7f42bcf 100644
--- a/packages/playground/personal-wp/src/lib/state/redux/boot-site-client.ts
+++ b/packages/playground/personal-wp/src/lib/state/redux/boot-site-client.ts
@@ -31,7 +31,10 @@ import {
 } from './slice-sites';
 // @ts-ignore
 import { corsProxyUrl } from 'virtual:cors-proxy-url';
-import { findFirewallErrorInCauseChain } from './error-utils';
+import {
+	findFirewallErrorInCauseChain,
+	findDownloadErrorInCauseChain,
+} from './error-utils';
 import {
 	initTabCoordinator,
 	checkForExistingTabs,
@@ -456,6 +459,13 @@ export function bootSiteClient(
 						details: firewallError,
 					})
 				);
+			} else if (findDownloadErrorInCauseChain(e)) {
+				dispatch(
+					setActiveSiteError({
+						error: 'resource-download-failed',
+						details: e,
+					})
+				);
 			} else {
 				dispatch(
 					setActiveSiteError({
diff --git a/packages/playground/personal-wp/src/lib/state/redux/error-utils.ts b/packages/playground/personal-wp/src/lib/state/redux/error-utils.ts
index 94fdeeeceb..4ab9d6f7d1 100644
--- a/packages/playground/personal-wp/src/lib/state/redux/error-utils.ts
+++ b/packages/playground/personal-wp/src/lib/state/redux/error-utils.ts
@@ -1,5 +1,7 @@
 import { FirewallInterferenceError } from '@php-wasm/web-service-worker';
 
+const MAX_CAUSE_CHAIN_DEPTH = 100;
+
 /**
  * Search through an error's cause chain to find a FirewallInterferenceError.
  * Checks both instanceof and the error's name property to handle cases where
@@ -11,7 +13,15 @@ export function findFirewallErrorInCauseChain(
 	error: unknown
 ): FirewallInterferenceError | Error | undefined {
 	let current: unknown = error;
-	while (current) {
+	const seen = new Set<Error>();
+	let depth = 0;
+	while (current && depth < MAX_CAUSE_CHAIN_DEPTH) {
+		if (current instanceof Error) {
+			if (seen.has(current)) {
+				break;
+			}
+			seen.add(current);
+		}
 		if (current instanceof FirewallInterferenceError) {
 			return current;
 		}
@@ -23,6 +33,73 @@ export function findFirewallErrorInCauseChain(
 		}
 		current =
 			current instanceof Error ? (current as Error).cause : undefined;
+		depth++;
+	}
+	return undefined;
+}
+
+/**
+ * Known error message patterns that indicate a network/download failure.
+ * These cover fetch failures, dynamic import failures, and WebAssembly
+ * compile errors (which happen when a non-WASM response like an HTML
+ * error page is returned).
+ */
+const DOWNLOAD_ERROR_PATTERNS = [
+	// Standard fetch API failure
+	'Failed to fetch',
+	// Safari module import failure
+	'Importing a module script failed',
+	// Chrome/Firefox dynamic import failure
+	'error loading dynamically imported module',
+	// Firefox fetch failure
+	'NetworkError when attempting to fetch',
+	// Safari fetch failure
+	'Load failed',
+];
+
+/**
+ * Error class names that indicate a download/network problem.
+ * WebAssembly.CompileError and LinkError occur when the browser tries
+ * to compile a non-WASM response (e.g. an HTML error page) as WASM.
+ */
+const DOWNLOAD_ERROR_CLASS_NAMES = ['CompileError', 'LinkError'];
+
+/**
+ * Search through an error's cause chain to find a network/download error.
+ * Checks error messages against known patterns and error class names
+ * against WebAssembly compilation errors.
+ *
+ * Handles both native Error objects and Comlink-serialized errors
+ * (which use `originalErrorClassName` instead of the native class name).
+ *
+ * Returns the matching error if found, or undefined if not.
+ */
+export function findDownloadErrorInCauseChain(
+	error: unknown
+): Error | undefined {
+	let current: unknown = error;
+	const seen = new Set<Error>();
+	let depth = 0;
+	while (current && depth < MAX_CAUSE_CHAIN_DEPTH) {
+		if (current instanceof Error) {
+			if (seen.has(current)) {
+				break;
+			}
+			seen.add(current);
+			const message = current.message || '';
+			for (const pattern of DOWNLOAD_ERROR_PATTERNS) {
+				if (message.toLowerCase().includes(pattern.toLowerCase())) {
+					return current;
+				}
+			}
+			const className =
+				(current as any).originalErrorClassName || current.name;
+			if (className && DOWNLOAD_ERROR_CLASS_NAMES.includes(className)) {
+				return current;
+			}
+		}
+		current = current instanceof Error ? current.cause : undefined;
+		depth++;
 	}
 	return undefined;
 }
diff --git a/packages/playground/personal-wp/src/lib/state/redux/slice-ui.ts b/packages/playground/personal-wp/src/lib/state/redux/slice-ui.ts
index e955fda4d5..383adcbc85 100644
--- a/packages/playground/personal-wp/src/lib/state/redux/slice-ui.ts
+++ b/packages/playground/personal-wp/src/lib/state/redux/slice-ui.ts
@@ -14,6 +14,7 @@ export type SiteError =
 	| 'blueprint-filesystem-required'
 	| 'blueprint-validation-failed'
 	| 'network-firewall-interference'
+	| 'resource-download-failed'
 	| 'tab-superseded';
 
 export type SiteManagerSection = 'sidebar' | 'site-details' | 'blueprints';
diff --git a/packages/playground/remote/remote.html b/packages/playground/remote/remote.html
index 5e852e8634..bea61dc93c 100644
--- a/packages/playground/remote/remote.html
+++ b/packages/playground/remote/remote.html
@@ -125,7 +125,7 @@
 				const reportIssues = document.createElement('p');
 				reportIssues.innerHTML = `
 					If the problem persists, please
-					<a href="https://github.com/WordPress/playground-tools/issues/new"
+					<a href="https://github.com/WordPress/wordpress-playground/issues/new"
 						target="_blank"
 						>report an issue on GitHub</a>.
 				`;
@@ -213,7 +213,7 @@ <h3>Did you refuse to grant Playground storage access?</h3>
 								</p>
 								<p>
 									If neither method helped, please
-									<a href="https://github.com/WordPress/playground-tools/issues/new"
+									<a href="https://github.com/WordPress/wordpress-playground/issues/new"
 										target="_blank">
 										report an issue on GitHub
 									</a>.
diff --git a/packages/playground/website/index.html b/packages/playground/website/index.html
index 982bc16bd4..ee23c2b58c 100644
--- a/packages/playground/website/index.html
+++ b/packages/playground/website/index.html
@@ -92,6 +92,50 @@
 		/>
 	</head>
 	<body>
+		<template id="load-error-fallback">
+			<!-- Use inline styles in case we are having trouble loading other resources -->
+			<div
+				style="
+					max-width: 520px;
+					margin: 80px auto;
+					font-family: system-ui, sans-serif;
+					text-align: center;
+					padding: 0 20px;
+				"
+			>
+				<h1 style="font-size: 1.4rem; margin-bottom: 12px">
+					Could not load WordPress Playground
+				</h1>
+				<p style="line-height: 1.5">
+					The application failed to load. This is often caused by a
+					network issue.
+				</p>
+				<p style="line-height: 1.5; margin-top: 8px">
+					Check your internet connection, disable any VPN or ad
+					blocker that might interfere, and try again.
+				</p>
+				<button
+					onclick="location.reload()"
+					style="
+						margin-top: 15px;
+						margin-bottom: 15px;
+						font-size: 20px;
+						padding: 5px 10px;
+						cursor: pointer;
+					"
+				>
+					Try again
+				</button>
+				<p>
+					If the problem persists, please
+					<a
+						href="https://github.com/WordPress/wordpress-playground/issues/new"
+						target="_blank"
+						>report an issue on GitHub</a
+					>.
+				</p>
+			</div>
+		</template>
 		<!--
 			Shown before React loads when an iOS WKWebView (in-app browser) is
 			detected. The detection script below reveals this and skips the
@@ -256,7 +300,7 @@ <h1>Open in your browser</h1>
 				 * Therefore, we're bypassing the cached import by adding a cache busting query parameter
 				 * if the original import fails.
 				 */
-				import('./src/main').catch((e) => {
+				import('./src/main').catch(async (e) => {
 					console.error('Failed to load main module:', e);
 					try {
 						/**
@@ -279,14 +323,22 @@ <h1>Open in your browser</h1>
 								'_ts',
 								String(Date.now())
 							);
-							return import(
+							return await import(
 								/* @vite-ignore */ moduleUrl.toString()
 							);
 						}
 					} catch {
 						// Fall back to the original error
 					}
-					throw e;
+					/**
+					 * If we get here, the app module completely failed to load.
+					 * React is not available, so render a plain HTML error message.
+					 */
+					const root = document.getElementById('root');
+					const template = document.getElementById(
+						'load-error-fallback'
+					);
+					root.replaceChildren(template.content.cloneNode(true));
 				});
 			}
 		</script>
diff --git a/packages/playground/website/playwright/e2e/error-handling.spec.ts b/packages/playground/website/playwright/e2e/error-handling.spec.ts
new file mode 100644
index 0000000000..a490dc06a1
--- /dev/null
+++ b/packages/playground/website/playwright/e2e/error-handling.spec.ts
@@ -0,0 +1,59 @@
+import { test, expect } from '@playwright/test';
+
+test('should show inline fallback when the main module fails to load', async ({
+	page,
+}) => {
+	// Block all requests for the main app module (initial + cache-busted retry).
+	// In dev mode Vite serves `/src/main.tsx`; in production builds
+	// it becomes `/assets/main-[hash].js`.
+	await page.route(/\/(src|assets)\/main/, (route) => route.abort('failed'));
+
+	await page.goto('./');
+
+	const heading = page.locator('h1', {
+		hasText: 'Could not load WordPress Playground',
+	});
+	await expect(heading).toBeVisible();
+
+	const reloadButton = page.locator('button', {
+		hasText: 'Try again',
+	});
+	await expect(reloadButton).toBeVisible();
+});
+
+test('should show download error modal when a resource download fails', async ({
+	page,
+}) => {
+	// Patch fetch so that any request to downloads.wordpress.org
+	// rejects with a TypeError. Using addInitScript rather than
+	// page.route because the CORS proxy puts the target URL in
+	// the query string and WebKit's page.route does not match
+	// regex patterns against query parameters.
+	await page.addInitScript(() => {
+		const originalFetch = window.fetch;
+		window.fetch = function (input: RequestInfo | URL, init?: RequestInit) {
+			const url = input instanceof Request ? input.url : String(input);
+			if (url.includes('downloads.wordpress.org')) {
+				return Promise.reject(new TypeError('Failed to fetch'));
+			}
+			return originalFetch.call(this, input, init);
+		} as typeof fetch;
+	});
+
+	// The ?plugin param adds an installPlugin blueprint step that
+	// fetches the zip from downloads.wordpress.org via the CORS
+	// proxy, triggering the resource-download-failed error through
+	// the normal pipeline.
+	await page.goto('./?plugin=hello-dolly');
+
+	const title = page.getByText('Could not download required files');
+	await expect(title).toBeVisible();
+
+	const body = page.getByText('usually caused by a network problem');
+	await expect(body).toBeVisible();
+
+	const reloadButton = page.getByRole('button', {
+		name: 'Reload page',
+	});
+	await expect(reloadButton).toBeVisible();
+});
diff --git a/packages/playground/website/src/components/site-error-modal/get-site-error-view.tsx b/packages/playground/website/src/components/site-error-modal/get-site-error-view.tsx
index f72fd84f39..b125d22b3d 100644
--- a/packages/playground/website/src/components/site-error-modal/get-site-error-view.tsx
+++ b/packages/playground/website/src/components/site-error-modal/get-site-error-view.tsx
@@ -33,7 +33,11 @@ export function getSiteErrorView(
 	// Show specific error views for certain error types, even if they occurred
 	// during a blueprint step. These errors have dedicated user-friendly views
 	// that provide better guidance than the generic step error view.
-	if (blueprintStepError && error !== 'network-firewall-interference') {
+	if (
+		blueprintStepError &&
+		error !== 'network-firewall-interference' &&
+		error !== 'resource-download-failed'
+	) {
 		return blueprintStepExecutionView(context);
 	}
 
@@ -55,6 +59,8 @@ export function getSiteErrorView(
 			return directoryHandleUnknownErrorView();
 		case 'network-firewall-interference':
 			return networkFirewallInterferenceView(context);
+		case 'resource-download-failed':
+			return resourceDownloadFailedView();
 		case 'site-boot-failed':
 		default:
 			return genericSiteBootFailedView(context);
@@ -461,6 +467,42 @@ function networkFirewallInterferenceView({
 	};
 }
 
+function resourceDownloadFailedView(): SiteErrorViewConfig {
+	return {
+		title: 'Could not download required files',
+		isDeveloperError: false,
+		hideReportButton: true,
+		detailSummaryOverride: 'Technical details',
+		body: (
+			<>
+				<p className={css.errorLead}>
+					Playground could not download one or more files it needs to
+					run. This is usually caused by a network problem.
+				</p>
+				<ul className={css.errorList}>
+					<li>Check your internet connection and try again.</li>
+					<li>
+						A firewall, proxy, or VPN may be blocking the download.
+					</li>
+					<li>
+						Browser extensions such as ad blockers can sometimes
+						interfere with downloads.
+					</li>
+				</ul>
+			</>
+		),
+		actions: [
+			<Button
+				variant="primary"
+				key="reload"
+				onClick={() => window.location.reload()}
+			>
+				Reload page
+			</Button>,
+		],
+	};
+}
+
 function genericSiteBootFailedView({
 	blueprintStepError,
 	helpers,
diff --git a/packages/playground/website/src/lib/state/redux/boot-site-client.ts b/packages/playground/website/src/lib/state/redux/boot-site-client.ts
index 7813eaf2c4..2ea7c8fb62 100644
--- a/packages/playground/website/src/lib/state/redux/boot-site-client.ts
+++ b/packages/playground/website/src/lib/state/redux/boot-site-client.ts
@@ -34,7 +34,10 @@ import {
 	createGitAuthHeaders,
 	shouldShowGitHubAuthModal,
 } from '../../../github/git-auth-helpers';
-import { findFirewallErrorInCauseChain } from './error-utils';
+import {
+	findFirewallErrorInCauseChain,
+	findDownloadErrorInCauseChain,
+} from './error-utils';
 import { PHPMYADMIN_INSTALL_PATH } from '@wp-playground/tools';
 
 export function bootSiteClient(
@@ -208,6 +211,13 @@ export function bootSiteClient(
 						details: firewallError,
 					})
 				);
+			} else if (findDownloadErrorInCauseChain(e)) {
+				dispatch(
+					setActiveSiteError({
+						error: 'resource-download-failed',
+						details: e,
+					})
+				);
 			} else if (
 				(e as any).name === 'GitAuthenticationError' ||
 				(e as any).originalErrorClassName ===
diff --git a/packages/playground/website/src/lib/state/redux/error-utils.spec.ts b/packages/playground/website/src/lib/state/redux/error-utils.spec.ts
new file mode 100644
index 0000000000..5dd1c5a9a4
--- /dev/null
+++ b/packages/playground/website/src/lib/state/redux/error-utils.spec.ts
@@ -0,0 +1,206 @@
+import { FirewallInterferenceError } from '@php-wasm/web-service-worker';
+import {
+	findDownloadErrorInCauseChain,
+	findFirewallErrorInCauseChain,
+} from './error-utils';
+
+describe('findDownloadErrorInCauseChain', () => {
+	it('should detect TypeError with "Failed to fetch"', () => {
+		const error = new TypeError('Failed to fetch');
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect TypeError with "Importing a module script failed"', () => {
+		const error = new TypeError('Importing a module script failed.');
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect "error loading dynamically imported module"', () => {
+		const error = new TypeError(
+			'error loading dynamically imported module: https://example.com/foo.js'
+		);
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect Firefox "NetworkError when attempting to fetch"', () => {
+		const error = new TypeError(
+			'NetworkError when attempting to fetch resource.'
+		);
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect Safari "Load failed"', () => {
+		const error = new TypeError('Load failed');
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect WebAssembly.CompileError', () => {
+		const error = new WebAssembly.CompileError(
+			'expected magic word 00 61 73 6d'
+		);
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect CompileError via originalErrorClassName (Comlink)', () => {
+		const error = new Error('expected magic word 00 61 73 6d');
+		(error as any).originalErrorClassName = 'CompileError';
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect LinkError', () => {
+		const error = new WebAssembly.LinkError(
+			'import object field is not a Function'
+		);
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should find download error nested in cause chain', () => {
+		const downloadError = new TypeError('Failed to fetch');
+		const wrapper = new Error('Boot failed', {
+			cause: downloadError,
+		});
+		expect(findDownloadErrorInCauseChain(wrapper)).toBe(downloadError);
+	});
+
+	it('should find download error deeply nested in cause chain', () => {
+		const downloadError = new TypeError('Failed to fetch');
+		const mid = new Error('Step failed', {
+			cause: downloadError,
+		});
+		const outer = new Error('Boot failed', { cause: mid });
+		expect(findDownloadErrorInCauseChain(outer)).toBe(downloadError);
+	});
+
+	it('should return undefined for non-network errors', () => {
+		const error = new Error('Something else went wrong');
+		expect(findDownloadErrorInCauseChain(error)).toBeUndefined();
+	});
+
+	it('should return undefined for null/undefined', () => {
+		expect(findDownloadErrorInCauseChain(null)).toBeUndefined();
+		expect(findDownloadErrorInCauseChain(undefined)).toBeUndefined();
+	});
+
+	it('should return undefined for non-Error objects', () => {
+		expect(
+			findDownloadErrorInCauseChain('Failed to fetch')
+		).toBeUndefined();
+	});
+
+	it('should be case-insensitive for message matching', () => {
+		const error = new TypeError('FAILED TO FETCH');
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect LinkError via originalErrorClassName (Comlink)', () => {
+		const error = new Error('import object field is not a Function');
+		(error as any).originalErrorClassName = 'LinkError';
+		expect(findDownloadErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should return the first matching error in the chain', () => {
+		const deeper = new TypeError('Load failed');
+		const shallower = new TypeError('Failed to fetch', {
+			cause: deeper,
+		});
+		const outer = new Error('Boot failed', { cause: shallower });
+		expect(findDownloadErrorInCauseChain(outer)).toBe(shallower);
+	});
+
+	it('should return undefined for an error with non-Error cause', () => {
+		const error = new Error('Wrapper');
+		(error as any).cause = 'not an error object';
+		expect(findDownloadErrorInCauseChain(error)).toBeUndefined();
+	});
+});
+
+describe('findFirewallErrorInCauseChain', () => {
+	it('should detect FirewallInterferenceError via instanceof', () => {
+		const error = new FirewallInterferenceError(
+			'https://example.com',
+			403,
+			'Forbidden'
+		);
+		expect(findFirewallErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should detect FirewallInterferenceError by name property', () => {
+		const error = new Error('Could not fetch https://example.com');
+		error.name = 'FirewallInterferenceError';
+		expect(findFirewallErrorInCauseChain(error)).toBe(error);
+	});
+
+	it('should find FirewallInterferenceError nested in cause chain', () => {
+		const firewallError = new FirewallInterferenceError(
+			'https://example.com',
+			403,
+			'Forbidden'
+		);
+		const wrapper = new Error('Boot failed', {
+			cause: firewallError,
+		});
+		expect(findFirewallErrorInCauseChain(wrapper)).toBe(firewallError);
+	});
+
+	it('should find FirewallInterferenceError deeply nested', () => {
+		const firewallError = new FirewallInterferenceError(
+			'https://example.com',
+			403,
+			'Forbidden'
+		);
+		const mid = new Error('Step failed', { cause: firewallError });
+		const outer = new Error('Boot failed', { cause: mid });
+		expect(findFirewallErrorInCauseChain(outer)).toBe(firewallError);
+	});
+
+	it('should find by name when deeply nested', () => {
+		const firewallError = new Error('Could not fetch');
+		firewallError.name = 'FirewallInterferenceError';
+		const mid = new Error('Step failed', { cause: firewallError });
+		const outer = new Error('Boot failed', { cause: mid });
+		expect(findFirewallErrorInCauseChain(outer)).toBe(firewallError);
+	});
+
+	it('should return undefined for non-firewall errors', () => {
+		const error = new Error('Something else went wrong');
+		expect(findFirewallErrorInCauseChain(error)).toBeUndefined();
+	});
+
+	it('should return undefined for null/undefined', () => {
+		expect(findFirewallErrorInCauseChain(null)).toBeUndefined();
+		expect(findFirewallErrorInCauseChain(undefined)).toBeUndefined();
+	});
+
+	it('should return undefined for non-Error objects', () => {
+		expect(
+			findFirewallErrorInCauseChain('FirewallInterferenceError')
+		).toBeUndefined();
+	});
+
+	it('should not match errors with similar but different names', () => {
+		const error = new Error('Some error');
+		error.name = 'NotAFirewallInterferenceError';
+		expect(findFirewallErrorInCauseChain(error)).toBeUndefined();
+	});
+
+	it('should not match errors that mention firewall in the message', () => {
+		const error = new Error('firewall blocked the request');
+		expect(findFirewallErrorInCauseChain(error)).toBeUndefined();
+	});
+
+	it('should return the first match when both instanceof and name matches exist in the chain', () => {
+		const namedError = new Error('fake');
+		namedError.name = 'FirewallInterferenceError';
+		const realFirewall = new FirewallInterferenceError(
+			'https://example.com',
+			403,
+			'Forbidden'
+		);
+		// Chain: outer → namedError → realFirewall
+		// namedError is encountered first while walking the chain
+		(realFirewall as any).cause = undefined;
+		(namedError as any).cause = realFirewall;
+		const outer = new Error('top', { cause: namedError });
+		expect(findFirewallErrorInCauseChain(outer)).toBe(namedError);
+	});
+});
diff --git a/packages/playground/website/src/lib/state/redux/error-utils.ts b/packages/playground/website/src/lib/state/redux/error-utils.ts
index 94fdeeeceb..4ab9d6f7d1 100644
--- a/packages/playground/website/src/lib/state/redux/error-utils.ts
+++ b/packages/playground/website/src/lib/state/redux/error-utils.ts
@@ -1,5 +1,7 @@
 import { FirewallInterferenceError } from '@php-wasm/web-service-worker';
 
+const MAX_CAUSE_CHAIN_DEPTH = 100;
+
 /**
  * Search through an error's cause chain to find a FirewallInterferenceError.
  * Checks both instanceof and the error's name property to handle cases where
@@ -11,7 +13,15 @@ export function findFirewallErrorInCauseChain(
 	error: unknown
 ): FirewallInterferenceError | Error | undefined {
 	let current: unknown = error;
-	while (current) {
+	const seen = new Set<Error>();
+	let depth = 0;
+	while (current && depth < MAX_CAUSE_CHAIN_DEPTH) {
+		if (current instanceof Error) {
+			if (seen.has(current)) {
+				break;
+			}
+			seen.add(current);
+		}
 		if (current instanceof FirewallInterferenceError) {
 			return current;
 		}
@@ -23,6 +33,73 @@ export function findFirewallErrorInCauseChain(
 		}
 		current =
 			current instanceof Error ? (current as Error).cause : undefined;
+		depth++;
+	}
+	return undefined;
+}
+
+/**
+ * Known error message patterns that indicate a network/download failure.
+ * These cover fetch failures, dynamic import failures, and WebAssembly
+ * compile errors (which happen when a non-WASM response like an HTML
+ * error page is returned).
+ */
+const DOWNLOAD_ERROR_PATTERNS = [
+	// Standard fetch API failure
+	'Failed to fetch',
+	// Safari module import failure
+	'Importing a module script failed',
+	// Chrome/Firefox dynamic import failure
+	'error loading dynamically imported module',
+	// Firefox fetch failure
+	'NetworkError when attempting to fetch',
+	// Safari fetch failure
+	'Load failed',
+];
+
+/**
+ * Error class names that indicate a download/network problem.
+ * WebAssembly.CompileError and LinkError occur when the browser tries
+ * to compile a non-WASM response (e.g. an HTML error page) as WASM.
+ */
+const DOWNLOAD_ERROR_CLASS_NAMES = ['CompileError', 'LinkError'];
+
+/**
+ * Search through an error's cause chain to find a network/download error.
+ * Checks error messages against known patterns and error class names
+ * against WebAssembly compilation errors.
+ *
+ * Handles both native Error objects and Comlink-serialized errors
+ * (which use `originalErrorClassName` instead of the native class name).
+ *
+ * Returns the matching error if found, or undefined if not.
+ */
+export function findDownloadErrorInCauseChain(
+	error: unknown
+): Error | undefined {
+	let current: unknown = error;
+	const seen = new Set<Error>();
+	let depth = 0;
+	while (current && depth < MAX_CAUSE_CHAIN_DEPTH) {
+		if (current instanceof Error) {
+			if (seen.has(current)) {
+				break;
+			}
+			seen.add(current);
+			const message = current.message || '';
+			for (const pattern of DOWNLOAD_ERROR_PATTERNS) {
+				if (message.toLowerCase().includes(pattern.toLowerCase())) {
+					return current;
+				}
+			}
+			const className =
+				(current as any).originalErrorClassName || current.name;
+			if (className && DOWNLOAD_ERROR_CLASS_NAMES.includes(className)) {
+				return current;
+			}
+		}
+		current = current instanceof Error ? current.cause : undefined;
+		depth++;
 	}
 	return undefined;
 }
diff --git a/packages/playground/website/src/lib/state/redux/slice-ui.ts b/packages/playground/website/src/lib/state/redux/slice-ui.ts
index 6b038c1fb0..0d8a443668 100644
--- a/packages/playground/website/src/lib/state/redux/slice-ui.ts
+++ b/packages/playground/website/src/lib/state/redux/slice-ui.ts
@@ -14,7 +14,8 @@ export type SiteError =
 	| 'blueprint-fetch-failed'
 	| 'blueprint-filesystem-required'
 	| 'blueprint-validation-failed'
-	| 'network-firewall-interference';
+	| 'network-firewall-interference'
+	| 'resource-download-failed';
 
 export type SiteManagerSection = 'sidebar' | 'site-details' | 'blueprints';
 
diff --git a/packages/playground/wordpress-builds/src/sqlite-database-integration/get-sqlite-driver-module-details.ts b/packages/playground/wordpress-builds/src/sqlite-database-integration/get-sqlite-driver-module-details.ts
index ad96cde62b..895cb5ec60 100644
--- a/packages/playground/wordpress-builds/src/sqlite-database-integration/get-sqlite-driver-module-details.ts
+++ b/packages/playground/wordpress-builds/src/sqlite-database-integration/get-sqlite-driver-module-details.ts
@@ -19,7 +19,6 @@ export function getSqliteDriverModuleDetails(
 	url: string;
 } {
 	switch (version) {
-		
 		case 'trunk':
 			/** @ts-ignore */
 			return {
