diff --git a/workspace-server/internal/handlers/workspace_crud_helpers_test.go b/workspace-server/internal/handlers/workspace_crud_helpers_test.go
new file mode 100644
index 00000000..8d0169c5
--- /dev/null
+++ b/workspace-server/internal/handlers/workspace_crud_helpers_test.go
@@ -0,0 +1,165 @@
+package handlers
+
+// workspace_crud_helpers_test.go — tests for pure-logic helpers in workspace_crud.go.
+//
+// Covered helpers:
+//   validateWorkspaceDir — bind-mount path safety (CWE-22 defence-in-depth)
+
+import "testing"
+
+// ─────────────────────────────────────────────────────────────────────────────
+// validateWorkspaceDir
+// ─────────────────────────────────────────────────────────────────────────────
+
+func TestValidateWorkspaceDir_AcceptsValidAbsolutePath(t *testing.T) {
+	cases := []string{
+		"/home/ubuntu/workspace",
+		"/opt/myapp/data",
+		"/tmp/molecule-workspace",
+		"/Users/admin/workspace",
+		"/workspace",
+		"/mnt/volumes/data",
+		"/srv/molecule",
+		"/nix/store",
+	}
+	for _, dir := range cases {
+		err := validateWorkspaceDir(dir)
+		if err != nil {
+			t.Errorf("validateWorkspaceDir(%q) returned error: %v; want nil", dir, err)
+		}
+	}
+}
+
+func TestValidateWorkspaceDir_RejectsRelativePath(t *testing.T) {
+	cases := []string{
+		"relative/path",
+		"./local",
+		"../sibling",
+		"workspace",
+		"",
+	}
+	for _, dir := range cases {
+		err := validateWorkspaceDir(dir)
+		if err == nil {
+			t.Errorf("validateWorkspaceDir(%q) = nil; want error (relative path)", dir)
+		}
+	}
+}
+
+func TestValidateWorkspaceDir_RejectsTraversalSequence(t *testing.T) {
+	cases := []string{
+		"/etc/../../../etc/passwd",
+		"/home/user/../../root",
+		"/workspace/../../../sibling",
+		"/foo/bar/..%2f..%2fetc",
+		"/valid/../etc/passwd",
+	}
+	for _, dir := range cases {
+		err := validateWorkspaceDir(dir)
+		if err == nil {
+			t.Errorf("validateWorkspaceDir(%q) = nil; want error (traversal)", dir)
+		}
+	}
+}
+
+func TestValidateWorkspaceDir_RejectsSystemPaths(t *testing.T) {
+	// System paths must be rejected outright — a workspace binding /etc or
+	// /proc would let the agent read host secrets or inspect kernel state.
+	systemPaths := []string{
+		"/etc",
+		"/var",
+		"/proc",
+		"/sys",
+		"/dev",
+		"/boot",
+		"/sbin",
+		"/bin",
+		"/usr",
+	}
+	for _, dir := range systemPaths {
+		err := validateWorkspaceDir(dir)
+		if err == nil {
+			t.Errorf("validateWorkspaceDir(%q) = nil; want error (system path)", dir)
+		}
+	}
+}
+
+func TestValidateWorkspaceDir_RejectsDescendantsOfSystemPaths(t *testing.T) {
+	// A descendant of a system path must also be rejected — /etc/shadow,
+	// /proc/1/cmdline, /dev/null all fall in this category.
+	descendants := []string{
+		"/etc/passwd",
+		"/etc/shadow",
+		"/etc/ssh/sshd_config",
+		"/var/log/syslog",
+		"/proc/self/environ",
+		"/sys/kernel/version",
+		"/dev/null",
+		"/boot/grub/grub.cfg",
+		"/sbin/init",
+		"/bin/bash",
+		"/usr/bin/python3",
+	}
+	for _, dir := range descendants {
+		err := validateWorkspaceDir(dir)
+		if err == nil {
+			t.Errorf("validateWorkspaceDir(%q) = nil; want error (descendant of system path)", dir)
+		}
+	}
+}
+
+func TestValidateWorkspaceDir_AcceptsPathsSimilarToSystemPaths(t *testing.T) {
+	// Paths that LOOK like system paths but are NOT exact matches or
+	// descendants should be accepted. These are valid workspace directories.
+	valid := []string{
+		"/etcworkspace",
+		"/varworkspace",
+		"/procworkspace",
+		"/sysworkspace",
+		"/devworkspace",
+		"/bootworkspace",
+		"/sbinworkspace",
+		"/binworkspace",
+		"/usrworkspace",
+		"/etx",    // typo of /etc but a different path
+		"/vartmp",  // /var/tmp is different from /var
+		"/usrr",    // typo of /usr but a different path
+		"/workspace/etc",
+		"/workspace/var",
+		"/home/user/etc",
+		"/opt/etc",
+	}
+	for _, dir := range valid {
+		err := validateWorkspaceDir(dir)
+		if err != nil {
+			t.Errorf("validateWorkspaceDir(%q) returned error: %v; want nil", dir, err)
+		}
+	}
+}
+
+func TestValidateWorkspaceDir_ErrorMessages(t *testing.T) {
+	// Error messages must be descriptive enough for operators to self-diagnose.
+	relErr := validateWorkspaceDir("relative")
+	if relErr == nil {
+		t.Fatal("relative path: want error, got nil")
+	}
+	if relErr.Error() == "" {
+		t.Error("relative path error message is empty")
+	}
+
+	travErr := validateWorkspaceDir("/etc/../../../etc/passwd")
+	if travErr == nil {
+		t.Fatal("traversal: want error, got nil")
+	}
+	if travErr.Error() == "" {
+		t.Error("traversal error message is empty")
+	}
+
+	sysErr := validateWorkspaceDir("/etc")
+	if sysErr == nil {
+		t.Fatal("system path: want error, got nil")
+	}
+	if sysErr.Error() == "" {
+		t.Error("system path error message is empty")
+	}
+}