diff --git a/crates/ml-alpha/build.rs b/crates/ml-alpha/build.rs
index 38245e6b5..3ca33dd23 100644
--- a/crates/ml-alpha/build.rs
+++ b/crates/ml-alpha/build.rs
@@ -17,6 +17,10 @@ const KERNELS: &[&str] = &[
     "adamw_step",
 ];
 
+// Cache bust v3 (2026-05-17): batched cfc/heads kernels + transpose_3d_swap_01
+// added in commit 829ddfa62 + c3ee5e165. Force rebuild on cluster nodes whose
+// /cargo-target persistent volume still has the pre-batched cubins.
+
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");