diff --git a/crates/obscura-cdp/tests/nodefilter_constants.rs b/crates/obscura-cdp/tests/nodefilter_constants.rs
new file mode 100644
index 0000000..3ba280e
--- /dev/null
+++ b/crates/obscura-cdp/tests/nodefilter_constants.rs
@@ -0,0 +1,125 @@
+//! `NodeFilter` must expose the standard filter constants (issue #439).
+//! bootstrap.js defined NodeFilter twice — a partial live one (SHOW_ELEMENT /
+//! SHOW_TEXT / SHOW_ALL) and a complete one behind a dead `typeof === undefined`
+//! guard — so `NodeFilter.FILTER_ACCEPT` was undefined at runtime and the
+//! canonical `acceptNode() { return NodeFilter.FILTER_ACCEPT; }` idiom made the
+//! walker reject every node. These use the structured_clone_crypto_parity
+//! helper pattern.
+
+use obscura_cdp::dispatch::{dispatch, CdpContext};
+use obscura_cdp::types::CdpRequest;
+use serde_json::{json, Value};
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpListener;
+
+async fn serve_once() -> String {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let addr = listener.local_addr().unwrap();
+    tokio::spawn(async move {
+        let (mut socket, _) = listener.accept().await.unwrap();
+        tokio::spawn(async move {
+            let mut buf = [0u8; 2048];
+            let _ = socket.read(&mut buf).await.unwrap();
+            let body = "<html><body><script>window.__boot = true;</script></body></html>";
+            let resp = format!(
+                "HTTP/1.1 200 OK\r\nContent-Type: text/html\r\nContent-Length: {}\r\nConnection: close\r\n\r\n{body}",
+                body.len()
+            );
+            let _ = socket.write_all(resp.as_bytes()).await;
+        });
+    });
+    format!("http://{addr}/")
+}
+
+async fn cdp(ctx: &mut CdpContext, id: u64, method: &str, params: Value, session_id: &str) -> Value {
+    let resp = dispatch(
+        &CdpRequest {
+            id,
+            method: method.to_string(),
+            params,
+            session_id: Some(session_id.to_string()),
+        },
+        ctx,
+    )
+    .await;
+    assert!(resp.error.is_none(), "CDP {method} failed: {:?}", resp.error);
+    resp.result.unwrap_or_else(|| json!({}))
+}
+
+async fn eval(ctx: &mut CdpContext, id: u64, expr: &str, session_id: &str) -> Value {
+    cdp(
+        ctx,
+        id,
+        "Runtime.evaluate",
+        json!({"expression": expr, "returnByValue": true}),
+        session_id,
+    )
+    .await
+}
+
+async fn setup() -> (CdpContext, String) {
+    std::env::set_var("OBSCURA_ALLOW_PRIVATE_NETWORK", "1");
+    let url = serve_once().await;
+    let mut ctx = CdpContext::new();
+    let page_id = ctx.create_page();
+    let session_id = "session-1";
+    ctx.sessions.insert(session_id.to_string(), page_id.clone());
+    cdp(&mut ctx, 1, "Page.navigate", json!({"url": url, "waitUntil": "load"}), session_id).await;
+    (ctx, session_id.to_string())
+}
+
+#[tokio::test(flavor = "current_thread")]
+async fn node_filter_exposes_the_standard_constants() {
+    let (mut ctx, sid) = setup().await;
+    let v = eval(
+        &mut ctx,
+        2,
+        r#"JSON.stringify({
+            accept: NodeFilter.FILTER_ACCEPT,
+            reject: NodeFilter.FILTER_REJECT,
+            skip: NodeFilter.FILTER_SKIP,
+            showAll: NodeFilter.SHOW_ALL,
+            showElement: NodeFilter.SHOW_ELEMENT,
+            showText: NodeFilter.SHOW_TEXT,
+            showComment: NodeFilter.SHOW_COMMENT,
+        })"#,
+        &sid,
+    )
+    .await;
+    let val = serde_json::from_str::<Value>(v["result"]["value"].as_str().unwrap()).unwrap();
+    assert_eq!(val["accept"], 1, "FILTER_ACCEPT must be 1");
+    assert_eq!(val["reject"], 2, "FILTER_REJECT must be 2");
+    assert_eq!(val["skip"], 3, "FILTER_SKIP must be 3");
+    assert_eq!(val["showAll"], 0xFFFFFFFFu32, "SHOW_ALL must be 0xFFFFFFFF");
+    assert_eq!(val["showElement"], 1, "SHOW_ELEMENT must be 1");
+    assert_eq!(val["showText"], 4, "SHOW_TEXT must be 4");
+    assert_eq!(val["showComment"], 128, "SHOW_COMMENT must be 128");
+}
+
+#[tokio::test(flavor = "current_thread")]
+async fn tree_walker_filter_using_filter_accept_constant_works() {
+    let (mut ctx, sid) = setup().await;
+    // The canonical MDN idiom: acceptNode returns NodeFilter.FILTER_ACCEPT.
+    // Only the first accepted child is checked, so this does not depend on the
+    // separate nextNode leaf-advance fix (#432).
+    let v = eval(
+        &mut ctx,
+        2,
+        r#"(() => {
+            document.body.innerHTML = '<div id="r"><p id="target">keep</p></div>';
+            const r = document.getElementById('r');
+            const w = document.createTreeWalker(r, NodeFilter.SHOW_ELEMENT, {
+                acceptNode() { return NodeFilter.FILTER_ACCEPT; }
+            });
+            const first = w.nextNode();
+            return JSON.stringify({ id: first ? first.id : null });
+        })()"#,
+        &sid,
+    )
+    .await;
+    let val = serde_json::from_str::<Value>(v["result"]["value"].as_str().unwrap()).unwrap();
+    assert_eq!(
+        val["id"], "target",
+        "a filter returning NodeFilter.FILTER_ACCEPT must accept the node, not reject it"
+    );
+}
diff --git a/crates/obscura-js/js/bootstrap.js b/crates/obscura-js/js/bootstrap.js
index b83d603..67d421f 100644
--- a/crates/obscura-js/js/bootstrap.js
+++ b/crates/obscura-js/js/bootstrap.js
@@ -4455,7 +4455,28 @@ globalThis.ElementInternals = class ElementInternals {
   get shadowRoot() { return (this._el && this._el._shadowRoot) || null; }
   get states() { return this._states; }
 };
-globalThis.NodeFilter = { SHOW_ELEMENT: 1, SHOW_TEXT: 4, SHOW_ALL: 0xFFFFFFFF };
+// Full standard constant set (issue #439). The partial version here lacked
+// FILTER_ACCEPT/REJECT/SKIP and most SHOW_* values, so the canonical
+// `acceptNode() { return NodeFilter.FILTER_ACCEPT; }` filter idiom returned
+// undefined and TreeWalker/NodeIterator rejected every node.
+globalThis.NodeFilter = {
+  SHOW_ALL: 0xFFFFFFFF,
+  SHOW_ELEMENT: 0x1,
+  SHOW_ATTRIBUTE: 0x2,
+  SHOW_TEXT: 0x4,
+  SHOW_CDATA_SECTION: 0x8,
+  SHOW_ENTITY_REFERENCE: 0x10,
+  SHOW_ENTITY: 0x20,
+  SHOW_PROCESSING_INSTRUCTION: 0x40,
+  SHOW_COMMENT: 0x80,
+  SHOW_DOCUMENT: 0x100,
+  SHOW_DOCUMENT_TYPE: 0x200,
+  SHOW_DOCUMENT_FRAGMENT: 0x400,
+  SHOW_NOTATION: 0x800,
+  FILTER_ACCEPT: 1,
+  FILTER_REJECT: 2,
+  FILTER_SKIP: 3,
+};
 // ResizeObserver is defined earlier with real per-target firing; the stub
 // that previously lived here was a no-op that clobbered the real class.
 //
@@ -7691,11 +7712,6 @@ if (typeof Selection === 'undefined') {
   };
 }
 
-if (typeof NodeFilter === 'undefined') {
-  globalThis.NodeFilter = { SHOW_ALL:0xFFFFFFFF, SHOW_ELEMENT:1, SHOW_TEXT:4, SHOW_COMMENT:128,
-    FILTER_ACCEPT:1, FILTER_REJECT:2, FILTER_SKIP:3 };
-}
-
 if (typeof TreeWalker === 'undefined') {
   globalThis.TreeWalker = class TreeWalker {
     constructor(root){this.root=root;this.currentNode=root;this.whatToShow=0xFFFFFFFF;this.filter=null;}