diff --git a/dag/extdeps/exec/command.dag b/dag/extdeps/exec/command.dag
index a74f09bae04..083f6dd2a31 100644
--- a/dag/extdeps/exec/command.dag
+++ b/dag/extdeps/exec/command.dag
@@ -82,6 +82,7 @@ fn argv_command(program: NonEmptyStr, arguments: List<String>) -> ArgvCommand
     decl_ref(module_path: "extdeps.tools.gnu_coreutils", decl_name: "true_command"),
     decl_ref(module_path: "extdeps.tools.gnu_coreutils", decl_name: "whoami_command"),
     decl_ref(module_path: "extdeps.tools.gnu_coreutils", decl_name: "readlink_command"),
+    decl_ref(module_path: "extdeps.tools.gnu_coreutils", decl_name: "ls_one_per_line_command"),
     decl_ref(module_path: "extdeps.tools.findutils", decl_name: "find_symlink_target_glob_command"),
     decl_ref(module_path: "extdeps.tools.chmod", decl_name: "chmod_set_mode_command"),
     decl_ref(module_path: "extdeps.tools.stat", decl_name: "stat_owner_user_name_command"),
diff --git a/dag/extdeps/tools/gnu_coreutils.dag b/dag/extdeps/tools/gnu_coreutils.dag
index 11e1f8e3706..4e497249752 100644
--- a/dag/extdeps/tools/gnu_coreutils.dag
+++ b/dag/extdeps/tools/gnu_coreutils.dag
@@ -41,6 +41,7 @@ data printf_program: NonEmptyStr = "printf"
 data true_program: NonEmptyStr = "true"
 data whoami_program: NonEmptyStr = "whoami"
 data readlink_program: NonEmptyStr = "readlink"
+data ls_program: NonEmptyStr = "ls"
 
 fn cat_command(path: String) -> ArgvCommand {
   argv_command(program: cat_program, arguments: [path])
@@ -81,6 +82,15 @@ fn readlink_command(path: String) -> ArgvCommand {
   argv_command(program: readlink_program, arguments: [path])
 }
 
+// -1 ALONE, NEVER -la OR A GLOB. One entry per line is what makes the output parseable as a list
+// of names; a long listing would put mode, owner and size in front of every name and force the
+// caller to re-parse them out. The directory is the operand, so an out-of-band entry -- one nobody
+// desired -- is listed like any other, which is what keeps an observed population independent of
+// the desired one.
+fn ls_one_per_line_command(directory: String) -> ArgvCommand {
+  argv_command(program: ls_program, arguments: ["-1", directory])
+}
+
 // install(1) — GNU coreutils, "Setting file attributes" / install invocation. The flags used
 // here are the ones that manual defines: -d creates each named directory, -m sets the mode,
 // -o and -g set owner and group at creation. Owner-at-creation is why this repository installs
diff --git a/dag/gunbc/runner_slot_provision.dag b/dag/gunbc/runner_slot_provision.dag
index 85c8d06ec31..2249b225855 100644
--- a/dag/gunbc/runner_slot_provision.dag
+++ b/dag/gunbc/runner_slot_provision.dag
@@ -38,7 +38,7 @@ import gunbc.command_runner {
   run_shell_command_capture,
   LocalExec,
 }
-import extdeps.exec.command { ArgvCommand }
+import extdeps.tools.gnu_coreutils { ls_one_per_line_command }
 
 // RunnerSlotProvision owns runner installation end-to-end in gunbc (operator ruling 2026-08-06:
 // ctrl is a dead repo; prior ctrl:install-actions-runner citations are void legacy pointers).
@@ -237,7 +237,7 @@ func observe_runner_slot_members_wet() -> RunnerSlotObservation
   uses net: Network
 {
   match run_shell_command_capture(
-    command: ArgvCommand { argv: ["ls", "-1", actions_runner_base_dir] },
+    command: ls_one_per_line_command(directory: actions_runner_base_dir),
     transport: LocalExec,
   ) {
     ProcessRefused { exit_code: code, stderr: err } =>