diff --git a/src/cmd/ksh93/include/jobs.h b/src/cmd/ksh93/include/jobs.h
index 6de9e2917f4d..9d16be540204 100644
--- a/src/cmd/ksh93/include/jobs.h
+++ b/src/cmd/ksh93/include/jobs.h
@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1982-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2025 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2026 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 2.0                  *
 *                                                                      *
@@ -31,7 +31,10 @@
 #ifndef SIGINT
 #   include	<signal.h>
 #endif /* !SIGINT */
-#include	<aso.h>
+#if !_std_atomic
+#   include	<aso.h>
+#   define	atomic_uint uint32_t
+#endif
 #include	"terminal.h"
 
 #ifndef SIGCHLD
@@ -65,7 +68,7 @@ struct jobs
 	pid_t		mypgid;		/* process group ID of shell */
 	pid_t		mytgid;		/* terminal group ID of shell */
 	int		curjobid;
-	unsigned int	in_critical;	/* >0 => in critical region */
+	atomic_uint	in_critical;	/* >0 => in critical region */
 	int		savesig;	/* active signal */
 	int		numpost;	/* number of posted jobs */
 #if SHOPT_BGX
@@ -88,6 +91,18 @@ struct jobs
 
 extern struct jobs job;
 
+#if _std_atomic
+/* locking functions used when C11's atomic_uint is available */
+#define job_lock()	(job.in_critical++)
+#define job_unlock()	\
+	do { \
+		int	_sig; \
+		if (job.in_critical == 1 && (_sig = job.savesig)) \
+			job_reap(_sig); \
+		job.in_critical--; \
+	} while(0)
+#else
+/* fallbacks using the ASO functions provided by libast */
 #define job_lock()	asoincint(&job.in_critical)
 #define job_unlock()	\
 	do { \
@@ -96,6 +111,7 @@ extern struct jobs job;
 		    job_reap(_sig); \
 		asodecint(&job.in_critical); \
 	} while(0)
+#endif
 
 extern const char	e_jobusage[];
 extern const char	e_done[];
diff --git a/src/lib/libast/comp/eaccess.c b/src/lib/libast/comp/eaccess.c
index 3690ed5806f8..8a919c6df4d5 100644
--- a/src/lib/libast/comp/eaccess.c
+++ b/src/lib/libast/comp/eaccess.c
@@ -18,7 +18,9 @@
 *                                                                      *
 ***********************************************************************/
 /*
- * access() EUID/EGID implementation
+ * AST eaccess() implementation
+ * Uses POSIX faccessat() for better portability and performance
+ * Fallbacks include native eaccess(), euidaccess(), EFF_ONLY_OK, and a custom implementation
  */
 
 #include <ast.h>
@@ -26,19 +28,21 @@
 
 #include "FEATURE/eaccess"
 
-#if _lib_eaccess
-
-NoN(eaccess)
-
-#else
+#if _lib_eaccess && !(_lib_faccessat && defined(AT_EACCESS))
+#undef eaccess
+extern int eaccess(const char* path, int flags);
+#endif
 
-extern int
-eaccess(const char* path, int flags)
+int
+_ast_eaccess(const char* path, int flags)
 {
-#ifdef EFF_ONLY_OK
+#if _lib_faccessat && defined(AT_EACCESS)
+	return faccessat(AT_FDCWD, path, flags, AT_EACCESS);
+#elif _lib_eaccess
+	return eaccess(path, flags);
+#elif defined(EFF_ONLY_OK)
 	return access(path, flags|EFF_ONLY_OK);
-#else
-#if _lib_euidaccess
+#elif _lib_euidaccess
 	return euidaccess(path, flags);
 #else
 	int		mode;
@@ -125,7 +129,4 @@ eaccess(const char* path, int flags)
 	errno = EACCES;
 	return -1;
 #endif
-#endif
 }
-
-#endif
diff --git a/src/lib/libast/features/common b/src/lib/libast/features/common
index b74a7413330d..10d4ef421d4a 100644
--- a/src/lib/libast/features/common
+++ b/src/lib/libast/features/common
@@ -10,6 +10,13 @@ std	noreturn note{ noreturn ok }end compile{
 	int main(void) { foo(); }
 }end
 
+std	atomic note{ _Atomic ok }end compile{
+	#include <stdlib.h>
+	#include <stdatomic.h>
+	static atomic_uint i = 0;
+	int main(void) { return i; }
+}end
+
 cat{
 	#if __clang__
 	#pragma clang diagnostic ignored "-Wmissing-braces"
@@ -66,6 +73,9 @@ cat{
 	#else
 	#define noreturn /* empty */
 	#endif /* _std_noreturn */
+	#if _std_atomic
+	#include <stdatomic.h>
+	#endif /* _std_atomic */
 }end
 
 if	tst - note{ <stdarg.h>+<wchar.h> works }end compile{
diff --git a/src/lib/libast/features/eaccess b/src/lib/libast/features/eaccess
index bf9710a2e67e..8076a4194951 100644
--- a/src/lib/libast/features/eaccess
+++ b/src/lib/libast/features/eaccess
@@ -1,4 +1,4 @@
-lib	eaccess,euidaccess
+lib	faccessat,eaccess,euidaccess
 macro{
 	#include <sys/types.h>
 	#include <unistd.h>
diff --git a/src/lib/libast/features/map.c b/src/lib/libast/features/map.c
index 7e3bb62b82f4..03090db4f653 100644
--- a/src/lib/libast/features/map.c
+++ b/src/lib/libast/features/map.c
@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1985-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2025 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2026 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 2.0                  *
 *                                                                      *
@@ -47,6 +47,10 @@ main(void)
 	/* do the same with sigunblock(), just to be sure (e.g., native QNX sigunblock() is different) */
 	printf("#undef	sigunblock\n");
 	printf("#define sigunblock      _ast_sigunblock\n");
+	/* use AST eaccess(3) (which will prefer faccessat over native eaccess) */
+	printf("#undef	eaccess\n");
+	printf("#define eaccess         _ast_eaccess\n");
+	printf("extern int              eaccess(const char*, int);\n");
 	/* Override the native regex library in favor of libast's regex functions */
 	printf("#undef	regaddclass\n");
 	printf("#define regaddclass	_ast_regaddclass\n");