6 files changed, 48 insertions, 5 deletions
diff --git a/.changeset/thin-deers-sin.md b/.changeset/thin-deers-sin.md
new file mode 100644
index 000000000..25cb79b2b
--- /dev/null
+++ b/.changeset/thin-deers-sin.md
@@ -0,0 +1,5 @@
+---
+"astro": patch
+---
+
+Fixes an issue where error pages did not have access to the `Astro.locals` fields provided by the adapter.
diff --git a/packages/astro/src/core/app/index.ts b/packages/astro/src/core/app/index.ts
index 0e2d745ef..5c163005d 100644
--- a/packages/astro/src/core/app/index.ts
+++ b/packages/astro/src/core/app/index.ts
@@ -66,6 +66,7 @@ export interface RenderOptions {
 }
 
 export interface RenderErrorOptions {
+	locals?: App.Locals,
 	routeData?: RouteData;
 	response?: Response;
 	status: 404 | 500;
@@ -295,7 +296,7 @@ export class App {
 			routeData = this.match(request);
 		}
 		if (!routeData) {
-			return this.#renderError(request, { status: 404 });
+			return this.#renderError(request, { locals, status: 404 });
 		}
 		const pathname = this.#getPathnameFromRequest(request);
 		const defaultStatus = this.#getDefaultStatusCode(routeData, pathname);
@@ -314,7 +315,7 @@ export class App {
 			response = await renderContext.render(await mod.page());
 		} catch (err: any) {
 			this.#logger.error(null, err.stack || err.message || String(err));
-			return this.#renderError(request, { status: 500 });
+			return this.#renderError(request, { locals, status: 500 });
 		}
 
 		if (
@@ -322,6 +323,7 @@ export class App {
 			response.headers.get(REROUTE_DIRECTIVE_HEADER) !== 'no'
 		) {
 			return this.#renderError(request, {
+				locals,
 				response,
 				status: response.status as 404 | 500,
 			});
@@ -374,7 +376,7 @@ export class App {
 	 */
 	async #renderError(
 		request: Request,
-		{ status, response: originalResponse, skipMiddleware = false }: RenderErrorOptions
+		{ locals, status, response: originalResponse, skipMiddleware = false }: RenderErrorOptions
 	): Promise<Response> {
 		const errorRoutePath = `/${status}${this.#manifest.trailingSlash === 'always' ? '/' : ''}`;
 		const errorRouteData = matchRoute(errorRoutePath, this.#manifestData);
@@ -397,6 +399,7 @@ export class App {
 			const mod = await this.#getModuleForRoute(errorRouteData);
 			try {
 				const renderContext = RenderContext.create({
+					locals,
 					pipeline: this.#pipeline,
 					middleware: skipMiddleware ? (_, next) => next() : undefined,
 					pathname: this.#getPathnameFromRequest(request),
@@ -410,6 +413,7 @@ export class App {
 				// Middleware may be the cause of the error, so we try rendering 404/500.astro without it.
 				if (skipMiddleware === false) {
 					return this.#renderError(request, {
+						locals,
 						status,
 						response: originalResponse,
 						skipMiddleware: true,
diff --git a/packages/astro/test/fixtures/ssr-locals/src/pages/404.astro b/packages/astro/test/fixtures/ssr-locals/src/pages/404.astro
new file mode 100644
index 000000000..66b1f7a04
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-locals/src/pages/404.astro
@@ -0,0 +1,4 @@
+---
+const { foo } = Astro.locals;
+---
+<h1 id="foo">{ foo }</h1>
diff --git a/packages/astro/test/fixtures/ssr-locals/src/pages/500.astro b/packages/astro/test/fixtures/ssr-locals/src/pages/500.astro
new file mode 100644
index 000000000..66b1f7a04
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-locals/src/pages/500.astro
@@ -0,0 +1,4 @@
+---
+const { foo } = Astro.locals;
+---
+<h1 id="foo">{ foo }</h1>
diff --git a/packages/astro/test/fixtures/ssr-locals/src/pages/go-to-error-page.astro b/packages/astro/test/fixtures/ssr-locals/src/pages/go-to-error-page.astro
new file mode 100644
index 000000000..ee962857d
--- /dev/null
+++ b/packages/astro/test/fixtures/ssr-locals/src/pages/go-to-error-page.astro
@@ -0,0 +1,3 @@
+---
+throw new Error
+---
+\ No newline at end of file
diff --git a/packages/astro/test/ssr-locals.test.js b/packages/astro/test/ssr-locals.test.js
index 9fea1fed9..e4dee5025 100644
--- a/packages/astro/test/ssr-locals.test.js
+++ b/packages/astro/test/ssr-locals.test.js
@@ -7,6 +7,8 @@ import { loadFixture } from './test-utils.js';
 describe('SSR Astro.locals from server', () => {
 	/** @type {import('./test-utils').Fixture} */
 	let fixture;
+	/** @type {import('./test-utils.js').App} */
+	let app;
 
 	before(async () => {
 		fixture = await loadFixture({
@@ -15,10 +17,10 @@ describe('SSR Astro.locals from server', () => {
 			adapter: testAdapter(),
 		});
 		await fixture.build();
+		app = await fixture.loadTestAdapterApp();
 	});
 
 	it('Can access Astro.locals in page', async () => {
-		const app = await fixture.loadTestAdapterApp();
 		const request = new Request('http://example.com/foo');
 		const locals = { foo: 'bar' };
 		const response = await app.render(request, { locals });
@@ -29,7 +31,6 @@ describe('SSR Astro.locals from server', () => {
 	});
 
 	it('Can access Astro.locals in api context', async () => {
-		const app = await fixture.loadTestAdapterApp();
 		const request = new Request('http://example.com/api');
 		const locals = { foo: 'bar' };
 		const response = await app.render(request, undefined, locals);
@@ -38,4 +39,26 @@ describe('SSR Astro.locals from server', () => {
 
 		assert.equal(body.foo, 'bar');
 	});
+
+	it('404.astro can access locals provided to app.render()', async () => {
+		const request = new Request('http://example.com/slkfnasf');
+		const locals = { foo: 'par' };
+		const response = await app.render(request, { locals });
+		assert.equal(response.status, 404);
+
+		const html = await response.text();
+		const $ = cheerio.load(html);
+		assert.equal($('#foo').text(), 'par');
+	});
+
+	it('500.astro can access locals provided to app.render()', async () => {
+		const request = new Request('http://example.com/go-to-error-page');
+		const locals = { foo: 'par' };
+		const response = await app.render(request, { locals });
+		assert.equal(response.status, 500);
+
+		const html = await response.text();
+		const $ = cheerio.load(html);
+		assert.equal($('#foo').text(), 'par');
+	});
 });