diff --git a/src/deployment/viteConfig.test.mjs b/src/deployment/viteConfig.test.mjs
new file mode 100644
index 0000000..4d576ed
--- /dev/null
+++ b/src/deployment/viteConfig.test.mjs
@@ -0,0 +1,9 @@
+import assert from 'node:assert/strict'
+import { readFileSync } from 'node:fs'
+import test from 'node:test'
+
+const configSource = readFileSync(new URL('../../vite.config.ts', import.meta.url), 'utf8')
+
+test('fails fast when the dedicated client development port is occupied', () => {
+  assert.match(configSource, /server:\s*\{\s*strictPort: true,/)
+})
diff --git a/vite.config.ts b/vite.config.ts
index 59bf850..7889d72 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -27,6 +27,7 @@ export default defineConfig(({ mode }) => {
       },
     },
     server: {
+      strictPort: true,
       proxy: {
         '/api': {
           target: proxyTarget,