--- a/sys/kern/kern_resource.c	2026-06-29 12:51:19.000000000 +0000
+++ b/sys/kern/kern_resource.c	2026-10-26 00:25:42.773043131 +0000
@@ -588,9 +588,18 @@
 	if (uap->tid == -1) {
 		/*
 		 * sadly, tid can be 0 so we can't use 0 here
-		 * like sys_rtprio()
+		 * like sys_rtprio().  Resolve the first LWP of the
+		 * TARGET process, not the caller.
 		 */
-		lp = curthread->td_lwp;
+		if (p == curproc) {
+			lp = curthread->td_lwp;
+		} else {
+			lp = RB_ROOT(&p->p_lwp_tree);
+			if (lp == NULL) {
+				error = ESRCH;
+				goto done;
+			}
+		}
 	} else {
 		lp = lwp_rb_tree_RB_LOOKUP(&p->p_lwp_tree, uap->tid);
 		if (lp == NULL) {