diff --git a/deployment/modules/gcp/gce/tesseract/main.tf b/deployment/modules/gcp/gce/tesseract/main.tf
index d2d7b07c..6af7dc13 100644
--- a/deployment/modules/gcp/gce/tesseract/main.tf
+++ b/deployment/modules/gcp/gce/tesseract/main.tf
@@ -198,6 +198,11 @@ resource "google_compute_region_instance_template" "tesseract" {
     source_image = data.google_compute_image.cos.self_link
     auto_delete  = true
     boot         = true
+    // Gen 4+ machine series require hyperdisk-balanced; Gen 3 (plus t2a/g2) require pd-balanced;
+    // Gen 1/2 default to pd-standard.
+    disk_type = can(regex("(?i)^[a-z]+[4-9][a-z]*-", var.machine_type)) ? "hyperdisk-balanced" : (
+      can(regex("(?i)^([a-z]+3[a-z]*|t2a|g2)-", var.machine_type)) ? "pd-balanced" : "pd-standard"
+    )
   }
 
   network_interface {