3 files changed, 65 insertions, 1 deletions
diff --git a/.changeset/funny-lobsters-promise.md b/.changeset/funny-lobsters-promise.md
new file mode 100644
index 000000000..6b77e442c
--- /dev/null
+++ b/.changeset/funny-lobsters-promise.md
@@ -0,0 +1,5 @@
+---
+"astro": patch
+---
+
+Fixes an issue where configuring trailingSlash had no effect on API routes.
diff --git a/packages/astro/src/core/routing/manifest/create.ts b/packages/astro/src/core/routing/manifest/create.ts
index f87d5fcd2..247a01ad1 100644
--- a/packages/astro/src/core/routing/manifest/create.ts
+++ b/packages/astro/src/core/routing/manifest/create.ts
@@ -328,7 +328,7 @@ export function createRouteManifest(
 			} else {
 				components.push(item.file);
 				const component = item.file;
-				const trailingSlash = item.isPage ? settings.config.trailingSlash : 'never';
+				const { trailingSlash } = settings.config;
 				const pattern = getPattern(segments, settings.config, trailingSlash);
 				const generate = getRouteGenerator(segments, trailingSlash);
 				const pathname = segments.every((segment) => segment.length === 1 && !segment[0].dynamic)
diff --git a/packages/astro/test/units/routing/trailing-slash.test.js b/packages/astro/test/units/routing/trailing-slash.test.js
new file mode 100644
index 000000000..c707c7215
--- /dev/null
+++ b/packages/astro/test/units/routing/trailing-slash.test.js
@@ -0,0 +1,59 @@
+import {
+	createBasicSettings,
+	createFs,
+	createRequestAndResponse,
+	defaultLogger,
+} from '../test-utils.js';
+import { fileURLToPath } from 'node:url';
+import { expect } from 'chai';
+import { createContainer } from '../../../dist/core/dev/container.js';
+import testAdapter from '../../test-adapter.js';
+
+const root = new URL('../../fixtures/api-routes/', import.meta.url);
+const fileSystem = {
+	'/src/pages/api.ts': `export const GET = () => Response.json({ success: true })`,
+};
+
+describe('trailingSlash', () => {
+	let container;
+	let settings;
+
+	before(async () => {
+		const fs = createFs(fileSystem, root);
+		settings = await createBasicSettings({
+			root: fileURLToPath(root),
+			trailingSlash: 'always',
+			output: 'server',
+			adapter: testAdapter(),
+		});
+		container = await createContainer({
+			fs,
+			settings,
+			logger: defaultLogger,
+		});
+	});
+
+	after(async () => {
+		await container.close();
+	});
+
+    it('should match the API route when request has a trailing slash', async () => {
+        const { req, res, text } = createRequestAndResponse({
+            method: 'GET',
+            url: '/api/',
+        });
+        container.handle(req, res);
+        const json = await text();
+        expect(json).to.equal('{"success":true}');
+    });
+
+    it('should NOT match the API route when request lacks a trailing slash', async () => {
+        const { req, res, text } = createRequestAndResponse({
+            method: 'GET',
+            url: '/api',
+        });
+        container.handle(req, res);
+        expect(await text()).to.equal('');
+        expect(res.statusCode).to.equal(404);
+    });
+});