diff --git a/src/lib/env.ts b/src/lib/env.ts
index d71eb849..c5adb368 100644
--- a/src/lib/env.ts
+++ b/src/lib/env.ts
@@ -30,9 +30,11 @@ const envSchema = z.object({
   VF_VECTOR_BIN: z.string().default("vector"),
   VF_SYSTEM_CONFIG_PATH: z.string().default("/etc/vectorflow/system-vector.yaml"),
   VF_AUDIT_LOG_PATH: z.string().optional(),
+  // Accepts missing/empty/anything; only the literal "true" enables demo mode.
+  // Lenient because Next.js build-args may pass "" when the ARG is unset.
   NEXT_PUBLIC_VF_DEMO_MODE: z
-    .enum(["true", "false"])
-    .default("false")
+    .string()
+    .optional()
     .transform((v) => v === "true"),
   VF_VERSION: z.string().default("dev"),
   METRICS_CHUNK_INTERVAL: z.string().default("1 day"),