diff --git a/src/api/routes.ts b/src/api/routes.ts
index 08114dba30..3b09447856 100644
--- a/src/api/routes.ts
+++ b/src/api/routes.ts
@@ -5698,9 +5698,13 @@ const DEFAULT_CORS_ORIGINS = [
   "http://localhost:3000",
   "http://localhost:4173",
   "http://localhost:5173",
+  // gittensory-ui's dev server (@lovable.dev/vite-tanstack-config) binds 8080, not Vite's 5173 default —
+  // without this, every local/preview dev server is CORS-blocked from /health and shows a false "API unreachable" banner.
+  "http://localhost:8080",
   "http://127.0.0.1:3000",
   "http://127.0.0.1:4173",
   "http://127.0.0.1:5173",
+  "http://127.0.0.1:8080",
 ] as const;
 
 function allowedCorsOrigin(env: Env, origin: string | undefined): string | null {
diff --git a/test/integration/api.test.ts b/test/integration/api.test.ts
index bce937d193..e78a95316d 100644
--- a/test/integration/api.test.ts
+++ b/test/integration/api.test.ts
@@ -92,6 +92,17 @@ describe("api routes", () => {
     expect(dynamicPreflight.status).toBe(204);
     expect(dynamicPreflight.headers.get("access-control-allow-origin")).toBe("https://preview.gittensory.test");
 
+    // REGRESSION: gittensory-ui's dev server (@lovable.dev/vite-tanstack-config) binds 8080, not Vite's 5173
+    // default — without this in DEFAULT_CORS_ORIGINS, every local/preview dev server is CORS-blocked from
+    // /health and the ApiStatusBanner falsely reports "API unreachable" even when the API is healthy.
+    const devPortPreflight = await app.request("/health", { method: "OPTIONS", headers: { origin: "http://localhost:8080" } }, env);
+    expect(devPortPreflight.status).toBe(204);
+    expect(devPortPreflight.headers.get("access-control-allow-origin")).toBe("http://localhost:8080");
+
+    const devPortLoopbackPreflight = await app.request("/health", { method: "OPTIONS", headers: { origin: "http://127.0.0.1:8080" } }, env);
+    expect(devPortLoopbackPreflight.status).toBe(204);
+    expect(devPortLoopbackPreflight.headers.get("access-control-allow-origin")).toBe("http://127.0.0.1:8080");
+
     const health = await app.request("/health", {}, env);
     expect(health.status).toBe(200);
     await expect(health.json()).resolves.toMatchObject({