diff --git a/.changeset/full-ties-add.md b/.changeset/full-ties-add.md
new file mode 100644
index 000000000000..f261c0bf5fd4
--- /dev/null
+++ b/.changeset/full-ties-add.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixed an issue where the API fetch in the frontmatter was not triggered when modifying external CMS content while the development server was running.
diff --git a/packages/astro/src/vite-plugin-app/app.ts b/packages/astro/src/vite-plugin-app/app.ts
index 0a401aff78e5..ff282dd200bb 100644
--- a/packages/astro/src/vite-plugin-app/app.ts
+++ b/packages/astro/src/vite-plugin-app/app.ts
@@ -182,6 +182,9 @@ export class AstroServerApp extends BaseApp<RunnablePipeline> {
 
 		const self = this;
 		await self.#loadFetchHandler();
+		// Clear the route cache on every dev request so that getStaticPaths()
+		// re-runs when external data (e.g. a headless CMS) changes between requests.
+		self.pipeline.clearRouteCache();
 
 		let handled = true;
 		await runWithErrorHandling({
diff --git a/packages/astro/test/dev-route-cache.test.ts b/packages/astro/test/dev-route-cache.test.ts
new file mode 100644
index 000000000000..00df95c8a7ed
--- /dev/null
+++ b/packages/astro/test/dev-route-cache.test.ts
@@ -0,0 +1,40 @@
+import * as assert from 'node:assert/strict';
+import { after, before, describe, it } from 'node:test';
+import * as cheerio from 'cheerio';
+import { type DevServer, type Fixture, loadFixture } from './test-utils.ts';
+
+// getStaticPaths() results were cached indefinitely during `astro dev`,
+// so external data changes (e.g. headless CMS) were never reflected without restarting the dev server.
+describe('dev: route cache is cleared between requests', () => {
+	let fixture: Fixture;
+	let devServer: DevServer;
+
+	before(async () => {
+		fixture = await loadFixture({ root: './fixtures/hmr-route-cache/' });
+		devServer = await fixture.startDevServer();
+	});
+
+	after(async () => {
+		await devServer?.stop();
+	});
+
+	it('re-runs getStaticPaths() on each request', async () => {
+		const res1 = await fixture.fetch('/test');
+		assert.equal(res1.status, 200);
+		const time1 = Number.parseInt(
+			cheerio
+				.load(await res1.text())('#time')
+				.text(),
+		);
+		await new Promise((r) => setTimeout(r, 10));
+		const res2 = await fixture.fetch('/test');
+		assert.equal(res2.status, 200);
+		const time2 = Number.parseInt(
+			cheerio
+				.load(await res2.text())('#time')
+				.text(),
+		);
+
+		assert.notEqual(time1, time2);
+	});
+});
diff --git a/packages/astro/test/fixtures/hmr-route-cache/package.json b/packages/astro/test/fixtures/hmr-route-cache/package.json
new file mode 100644
index 000000000000..05219118a03b
--- /dev/null
+++ b/packages/astro/test/fixtures/hmr-route-cache/package.json
@@ -0,0 +1,8 @@
+{
+	"name": "@test/hmr-route-cache",
+	"version": "0.0.0",
+	"private": true,
+	"dependencies": {
+		"astro": "workspace:*"
+	}
+}
diff --git a/packages/astro/test/fixtures/hmr-route-cache/src/pages/[id].astro b/packages/astro/test/fixtures/hmr-route-cache/src/pages/[id].astro
new file mode 100644
index 000000000000..d6e261ed2752
--- /dev/null
+++ b/packages/astro/test/fixtures/hmr-route-cache/src/pages/[id].astro
@@ -0,0 +1,7 @@
+---
+export async function getStaticPaths() {
+	return [{ params: { id: 'test' }, props: { callTime: Date.now() } }];
+}
+const { callTime } = Astro.props;
+---
+<p id="time">{callTime}</p>
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 0ca8c9a01909..73169eb52a8b 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -3202,6 +3202,12 @@ importers:
         specifier: workspace:*
         version: link:../../..
 
+  packages/astro/test/fixtures/hmr-route-cache:
+    dependencies:
+      astro:
+        specifier: workspace:*
+        version: link:../../..
+
   packages/astro/test/fixtures/hmr-slots-render:
     dependencies:
       astro: