Null-safe responsive config, defensive snapshot cast, DOM.disable cleanup

- responsive snapshot detection threw NPE when cliConfig.snapshot was missing
  or JSON-null; guard each layer before reading responsiveSnapshotCapture.
- getSerializedDOM treated a null jse return as a Map and ClassCastException'd
  deep in the snapshot path. Detect non-Map results and raise a clear error
  pointing at the @percy/dom load failure as the root cause.
- Pair every successful DOM.enable with DOM.disable in a finally block so the
  CDP session doesn't keep emitting DOM events after closed-shadow capture.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: aryanku-dev

package.json

@@ -5,5 +5,6 @@
   },
   "devDependencies": {
     "@percy/cli": "1.31.10"
-  }
+  },
+  "packageManager": "yarn@1.22.22+sha512.a6b2f7906b721bba3d67d4aff083df04dad64c399707841b7acf00f6b133b7ac24255f2652fa22ae3534329dc6180534e98d17432037ff6fd140556e2bb3137e"
 }

src/main/java/io/percy/selenium/Percy.java

@@ -339,8 +339,11 @@ private boolean isCaptureResponsiveDOM(Map<String, Object> options) {
 
         boolean responsiveSnapshotCaptureCLI = false;
         if (eligibleWidths == null) { return false; }
-        if (cliConfig.getJSONObject("snapshot").has("responsiveSnapshotCapture")) {
-            responsiveSnapshotCaptureCLI = cliConfig.getJSONObject("snapshot").getBoolean("responsiveSnapshotCapture");
+        if (cliConfig != null && cliConfig.has("snapshot") && !cliConfig.isNull("snapshot")) {
+            JSONObject snapshotCfg = cliConfig.getJSONObject("snapshot");
+            if (snapshotCfg.has("responsiveSnapshotCapture") && !snapshotCfg.isNull("responsiveSnapshotCapture")) {
+                responsiveSnapshotCaptureCLI = snapshotCfg.getBoolean("responsiveSnapshotCapture");
+            }
         }
         Object responsiveSnapshotCaptureSDK = options.get("responsiveSnapshotCapture");
 
@@ -973,7 +976,13 @@ private List<Map<String, Object>> processFrameTree(
     }
 
     private Map<String, Object> getSerializedDOM(JavascriptExecutor jse, Set<Cookie> cookies, Map<String, Object> options) {
-        Map<String, Object> domSnapshot = (Map<String, Object>) jse.executeScript(buildSnapshotJS(options));
+        Object raw = jse.executeScript(buildSnapshotJS(options));
+        if (!(raw instanceof Map)) {
+            throw new RuntimeException("PercyDOM.serialize returned null or non-object; "
+                + "the @percy/dom script likely failed to load. Aborting snapshot.");
+        }
+        @SuppressWarnings("unchecked")
+        Map<String, Object> domSnapshot = (Map<String, Object>) raw;
         Map<String, Object> mutableSnapshot = new HashMap<>(domSnapshot);
         mutableSnapshot.put("cookies", cookies);
 
@@ -1061,8 +1070,10 @@ private void exposeClosedShadowRoots(WebDriver driver) {
         if (!(driver instanceof ChromeDriver)) return;
         ChromeDriver chrome;
         try { chrome = (ChromeDriver) driver; } catch (ClassCastException e) { return; }
+        boolean domEnabled = false;
         try {
             chrome.executeCdpCommand("DOM.enable", new HashMap<>());
+            domEnabled = true;
             Map<String, Object> getDocParams = new HashMap<>();
             getDocParams.put("depth", -1);
             getDocParams.put("pierce", true);
@@ -1111,6 +1122,14 @@ private void exposeClosedShadowRoots(WebDriver driver) {
             }
         } catch (Exception ex) {
             log("Could not expose closed shadow roots via CDP: " + ex.getMessage(), "debug");
+        } finally {
+            // Release the DOM domain so subsequent commands don't keep emitting
+            // DOM events for this session. Best-effort — we don't care if this
+            // fails (e.g., session already closed).
+            if (domEnabled) {
+                try { chrome.executeCdpCommand("DOM.disable", new HashMap<>()); }
+                catch (Exception ignore) { /* defensive */ }
+            }
         }
     }