diff --git a/src/components/ViewerControls.tsx b/src/components/ViewerControls.tsx
index 85a6b5f..644b04b 100644
--- a/src/components/ViewerControls.tsx
+++ b/src/components/ViewerControls.tsx
@@ -170,6 +170,7 @@ export function ViewerControls() {
           size="sm"
           className="gap-2 h-9"
           onClick={() => setMeasureMode(!measureMode)}
+          title="Clique para marcar pontos · Esc desfaz ponto pendente · Z desfaz última medição"
         >
           <Ruler className="h-3.5 w-3.5" />
           <span className="font-mono text-xs">
@@ -181,6 +182,18 @@ export function ViewerControls() {
           </span>
         </Button>
 
+        {(measurePoints.length > 0 || measurements.length > 0) && (
+          <Button
+            variant="ghost"
+            size="icon"
+            className="h-9 w-9"
+            onClick={undoLastMeasurement}
+            title="Desfazer (Z)"
+          >
+            <Undo2 className="h-3.5 w-3.5 text-muted-foreground" />
+          </Button>
+        )}
+
         {measurements.length > 0 && (
           <Button
             variant="ghost"
@@ -194,6 +207,7 @@ export function ViewerControls() {
         )}
       </div>
 
+
       {/* Screenshot */}
       <Button
         variant="outline"