--- a/sys/vfs/hpfs/hpfs_vfsops.c	2026-09-09 14:21:27.496928348 +0000
+++ b/sys/vfs/hpfs/hpfs_vfsops.c	2026-09-09 14:21:27.528927951 +0000
@@ -529,6 +529,8 @@
 	error = bread(hpmp->hpm_devvp, dbtodoff(ino), FNODESIZE, &bp);
 	if (error) {
 		kprintf("hpfs_vget: can't read ino %"PRId64"\n",ino);
+		/* DF3253 instrument: cold-I/O validation window */
+		tsleep(&hp->h_fn, 0, "df3253w", hz / 100);
 		vx_put(vp);
 		return (error);
 	}
@@ -537,6 +539,8 @@
 
 	if (hp->h_fn.fn_magic != FN_MAGIC) {
 		kprintf("hpfs_vget: MAGIC DOESN'T MATCH\n");
+		/* DF3253 instrument: cold-I/O validation window */
+		tsleep(&hp->h_fn, 0, "df3253w", hz / 100);
 		vx_put(vp);
 		return (EINVAL);
 	}