diff --git a/main.go b/main.go
index df5924f..618d96d 100644
--- a/main.go
+++ b/main.go
@@ -114,6 +114,10 @@ func main() {
 		}
 
 		if *latestPtr || *cleanPtr {
+			if err := app.validateVersionExists(versions, cfg.Version); err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+				os.Exit(1)
+			}
 			app.updateLifecycle(versions, *latestPtr, *cleanPtr)
 		}
 	}
@@ -237,6 +241,21 @@ func (a *App) displayVersions(projects []Project) {
 	fmt.Fprintln(a.Stdout, "------------------------")
 }
 
+func (a *App) validateVersionExists(projects []Project, version string) error {
+	var available []string
+	for _, p := range projects {
+		if p.Name != a.Config.ProjectName {
+			continue
+		}
+		if p.Version == version {
+			return nil
+		}
+		available = append(available, p.Version)
+	}
+	return fmt.Errorf("version %q not found in project %q. Available versions: %s",
+		version, a.Config.ProjectName, strings.Join(available, ", "))
+}
+
 func (a *App) updateLifecycle(projects []Project, updateLatest bool, cleanInactive bool) {
 	fmt.Fprintln(a.Stdout, "Updating Lifecycle...")
 	for _, p := range projects {
diff --git a/main_test.go b/main_test.go
index be3668f..f4456f7 100644
--- a/main_test.go
+++ b/main_test.go
@@ -408,3 +408,88 @@ func TestDisplayVersions(t *testing.T) {
 		t.Errorf("expected projects with different name to be filtered out; got: %s", out)
 	}
 }
+
+func TestValidateVersionExists_Found(t *testing.T) {
+	app, _, _ := newTestApp(t, func(w http.ResponseWriter, r *http.Request) {})
+	projects := []Project{
+		{Name: "test-project", Version: "v0.9.0"},
+		{Name: "test-project", Version: "v1.0.0"},
+	}
+	if err := app.validateVersionExists(projects, "v1.0.0"); err != nil {
+		t.Fatalf("expected nil error, got %v", err)
+	}
+}
+
+func TestValidateVersionExists_NotFound(t *testing.T) {
+	app, _, _ := newTestApp(t, func(w http.ResponseWriter, r *http.Request) {})
+	projects := []Project{
+		{Name: "test-project", Version: "v1.5.7"},
+		{Name: "test-project", Version: "v1.5.8"},
+	}
+	err := app.validateVersionExists(projects, "1.5.8")
+	if err == nil {
+		t.Fatal("expected error for missing version")
+	}
+	msg := err.Error()
+	if !strings.Contains(msg, `"1.5.8"`) {
+		t.Errorf("expected requested version %q in error, got: %s", "1.5.8", msg)
+	}
+	if !strings.Contains(msg, "not found") {
+		t.Errorf("expected 'not found' in error, got: %s", msg)
+	}
+	if !strings.Contains(msg, "v1.5.8") {
+		t.Errorf("expected available version 'v1.5.8' in error to make typo obvious, got: %s", msg)
+	}
+}
+
+func TestValidateVersionExists_IgnoresOtherProjects(t *testing.T) {
+	app, _, _ := newTestApp(t, func(w http.ResponseWriter, r *http.Request) {})
+	projects := []Project{
+		{Name: "other-project", Version: "v1.0.0"},
+	}
+	err := app.validateVersionExists(projects, "v1.0.0")
+	if err == nil {
+		t.Fatal("expected error: matching version under a different project name should not satisfy validation")
+	}
+	if !strings.Contains(err.Error(), "test-project") {
+		t.Errorf("expected configured project name in error, got: %s", err.Error())
+	}
+}
+
+func TestUpdateLifecycle_VersionNotInList(t *testing.T) {
+	projects := []Project{
+		{UUID: "u-1", Name: "test-project", Version: "v1.5.7", Active: true, IsLatest: false},
+		{UUID: "u-2", Name: "test-project", Version: "v1.5.8", Active: true, IsLatest: true},
+	}
+
+	{
+		app, _, _ := newTestApp(t, func(w http.ResponseWriter, r *http.Request) {
+			t.Fatalf("validation phase must not send any HTTP requests; got %s %s", r.Method, r.URL.Path)
+		})
+		app.Config.Version = "1.5.8"
+		if err := app.validateVersionExists(projects, app.Config.Version); err == nil {
+			t.Fatal("expected validateVersionExists to reject typo'd version")
+		}
+	}
+
+	handler, records, mu := newPatchRecorder()
+	app, _, _ := newTestApp(t, handler)
+	app.Config.Version = "1.5.8"
+
+	app.updateLifecycle(projects, true, true)
+
+	mu.Lock()
+	defer mu.Unlock()
+	if len(*records) != 2 {
+		t.Fatalf("expected 2 destructive PATCHes (one per project) when validation is bypassed; got %d: %+v",
+			len(*records), *records)
+	}
+	for _, r := range *records {
+		if r.payload["active"] != false {
+			t.Errorf("expected active=false in destructive PATCH for %s, got %+v", r.uuid, r.payload)
+		}
+		if r.payload["isLatest"] != false && r.uuid == "u-2" {
+			t.Errorf("expected isLatest=false in destructive PATCH for %s, got %+v", r.uuid, r.payload)
+		}
+	}
+}