diff --git a/tool/shelltool/localshell.go b/tool/shelltool/localshell.go
index 3fdc9063..95f015ab 100644
--- a/tool/shelltool/localshell.go
+++ b/tool/shelltool/localshell.go
@@ -594,37 +594,40 @@ func shellKindDescription(shell resolvedShell) string {
 }
 
 func (s resolvedShell) statelessArgvForCommand(command string) []string {
-	var suffix []string
 	switch s.kind {
 	case shellKindPowerShell:
-		suffix = []string{"-NoProfile", "-NoLogo", "-NonInteractive", "-Command", command}
+		return s.argvWithExtra([]string{"-NoProfile", "-NoLogo", "-NonInteractive", "-Command", command})
 	case shellKindCmd:
-		suffix = []string{"/d", "/c", command}
+		return s.argvWithExtra([]string{"/d", "/c", command})
 	case shellKindBash:
-		suffix = []string{"--noprofile", "--norc", "-c", command}
+		return s.argvWithExtra([]string{"--noprofile", "--norc", "-c", command})
 	default:
-		suffix = []string{"-c", command}
+		return s.argvWithExtra([]string{"-c", command})
 	}
-	return combineArgv(s.extraArgv, suffix)
 }
 
 func (s resolvedShell) persistentArgv() ([]string, error) {
-	var suffix []string
 	switch s.kind {
 	case shellKindPowerShell:
-		suffix = []string{"-NoProfile", "-NoLogo", "-NonInteractive", "-Command", "-"}
+		return s.launchArgv([]string{"-NoProfile", "-NoLogo", "-NonInteractive", "-Command", "-"}), nil
 	case shellKindCmd:
 		return nil, fmt.Errorf("persistent mode is not supported for cmd.exe; use pwsh, powershell, or a POSIX shell")
 	case shellKindBash:
-		suffix = []string{"--noprofile", "--norc"}
+		return s.launchArgv([]string{"--noprofile", "--norc"}), nil
 	default:
-		suffix = nil
+		return s.launchArgv(nil), nil
 	}
-	return append([]string{s.binary}, combineArgv(s.extraArgv, suffix)...), nil
 }
 
-func combineArgv(extra, suffix []string) []string {
-	return slices.Concat(extra, suffix)
+func (s resolvedShell) launchArgv(suffix []string) []string {
+	return append([]string{s.binary}, s.argvWithExtra(suffix)...)
+}
+
+func (s resolvedShell) argvWithExtra(suffix []string) []string {
+	if len(s.extraArgv) == 0 {
+		return suffix
+	}
+	return append(slices.Clone(s.extraArgv), suffix...)
 }
 
 func classifyShellKind(shell string) shellKind {
diff --git a/tool/shelltool/localshell_internal_test.go b/tool/shelltool/localshell_internal_test.go
index 9f8d6c12..fcc8a3a3 100644
--- a/tool/shelltool/localshell_internal_test.go
+++ b/tool/shelltool/localshell_internal_test.go
@@ -2,7 +2,10 @@
 
 package shelltool
 
-import "testing"
+import (
+	"slices"
+	"testing"
+)
 
 func TestPreserveEnvironmentValuesKeepsOnlyAllowlist(t *testing.T) {
 	source := []string{
@@ -11,6 +14,7 @@ func TestPreserveEnvironmentValuesKeepsOnlyAllowlist(t *testing.T) {
 		"AF_SHELL_PARENT_VAR=should-not-leak",
 		"tmp=/tmp/test",
 	}
+
 	env := make(map[string]string)
 
 	preserveEnvironmentValues(env, source)
@@ -28,3 +32,23 @@ func TestPreserveEnvironmentValuesKeepsOnlyAllowlist(t *testing.T) {
 		t.Fatal("unexpected non-preserved variable copied")
 	}
 }
+
+func TestResolvedShellArgvIncludesExtraArgv(t *testing.T) {
+	shell := resolvedShell{
+		binary:    "/custom/bash",
+		kind:      shellKindBash,
+		extraArgv: []string{"--login"},
+	}
+
+	if got, want := shell.statelessArgvForCommand("echo hi"), []string{"--login", "--noprofile", "--norc", "-c", "echo hi"}; !slices.Equal(got, want) {
+		t.Fatalf("statelessArgvForCommand = %v, want %v", got, want)
+	}
+
+	got, err := shell.persistentArgv()
+	if err != nil {
+		t.Fatalf("persistentArgv: %v", err)
+	}
+	if want := []string{"/custom/bash", "--login", "--noprofile", "--norc"}; !slices.Equal(got, want) {
+		t.Fatalf("persistentArgv = %v, want %v", got, want)
+	}
+}