From 3cc7f6a4b672ce0be57f11a077a32d60433f073e Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:32:05 +0530
Subject: [PATCH 1/8] test(spec): give the fake dom a real tree and a walking
 querySelectorAll

---
 pkg/spec/test/web-dom-harness.ts | 237 +++++++++++++++++++++++++++----
 1 file changed, 213 insertions(+), 24 deletions(-)

diff --git a/pkg/spec/test/web-dom-harness.ts b/pkg/spec/test/web-dom-harness.ts
index cc0e671..f35a094 100644
--- a/pkg/spec/test/web-dom-harness.ts
+++ b/pkg/spec/test/web-dom-harness.ts
@@ -1,8 +1,21 @@
-// A minimal stand-in for the DOM surface the web host reads, shared by the web
-// runtime's own tests and the cross-host eligibility test. The host asks the
-// document for three things -- every element, the tappable set, the editable set
-// -- and reads geometry, `disabled` and the scroll extents off each element, so
-// that is all a fake has to answer.
+// A small DOM the web runtime can be driven over, shared by the web runtime's
+// own tests and the cross-host eligibility test.
+//
+// It is a fake, but the structure is real: elements nest, a host owns a shadow
+// root, and querySelectorAll WALKS the tree and stops at a shadow boundary
+// exactly as the browser's does. That is what makes the shadow descent in
+// deepQueryAll and expandShadowContent (src/web-runtime.ts) observable here at
+// all; the previous harness answered three fixed selectors from a flat list, so
+// deleting either descent changed no test result.
+//
+// What it fabricates is layout: getBoundingClientRect, scrollHeight and
+// clientHeight are handed over from the spec. No headless DOM computes those,
+// and they are precisely the facts collectTargets reads, so a real DOM
+// implementation would have to be stubbed for them anyway.
+//
+// An unsupported selector throws rather than matching nothing, so a test whose
+// selector this cannot parse fails loudly instead of quietly asserting over an
+// empty list.
 
 import { __testing__ } from "../src/web-runtime.ts";
 
@@ -23,23 +36,45 @@ export interface FakeElementSpec {
   label?: string;
   alt?: string;
   title?: string;
-  // clickable/editable place the element in the selector sets the host queries;
-  // the fake answers those queries directly rather than matching CSS.
+  // text is what an ax element handle reports as `text`, the same field the
+  // goja host reads off a hierarchy node, so a test can name WHICH of two
+  // same-id elements a lookup resolved to.
+  text?: string;
+  attrs?: Record<string, string>;
+  // clickable/editable place the element in the two fact sets the host queries
+  // by selector. They are answered from these flags rather than by matching
+  // their CSS: the cross-host golden (fixtures/host-parity-golden.json, built
+  // row for row in internal/verifier/host_parity_test.go) pins fact
+  // combinations no CSS can produce, such as an <input> that is editable and
+  // not clickable. A test states the facts there; this harness reports them.
   clickable?: boolean;
   editable?: boolean;
   disabled?: boolean;
   // overflows makes the element's content taller than its box, which is how the
   // host decides an element is scrollable.
   overflows?: boolean;
+  children?: FakeElementSpec[];
+  shadow?: FakeElementSpec[];
 }
 
-export interface FakeElement extends FakeElementSpec {
+export interface FakeRoot {
+  children: FakeElement[];
+  querySelectorAll(selector: string): FakeElement[];
+}
+
+export interface FakeElement extends Omit<FakeElementSpec, "children" | "shadow"> {
   tagName: string;
   type: string;
   isContentEditable: boolean;
   id: string;
+  className: string;
+  textContent: string;
   dataset: Record<string, string | undefined>;
+  parentElement: FakeElement | null;
+  children: FakeElement[];
+  shadowRoot: FakeRoot | null;
   getAttribute(name: string): string | null;
+  querySelectorAll(selector: string): FakeElement[];
   scrollHeight: number;
   clientHeight: number;
   scrollWidth: number;
@@ -56,15 +91,26 @@ export interface FakeElement extends FakeElementSpec {
 
 export function fakeElement(spec: FakeElementSpec): FakeElement {
   const editable = spec.editable ?? false;
-  return {
+  const attributes: Record<string, string> = { ...spec.attrs };
+  if (spec.id !== undefined) attributes.id = spec.id;
+  if (spec.testid !== undefined) attributes["data-testid"] = spec.testid;
+  if (spec.label !== undefined) attributes["aria-label"] = spec.label;
+  if (spec.alt !== undefined) attributes.alt = spec.alt;
+  if (spec.title !== undefined) attributes.title = spec.title;
+  const element: FakeElement = {
     ...spec,
     tagName: spec.tag.toUpperCase(),
     type: spec.tag === "input" ? "text" : "",
     isContentEditable: editable && spec.tag !== "input" && spec.tag !== "textarea",
     id: spec.id ?? "",
+    className: attributes.class ?? "",
+    textContent: spec.text ?? "",
     dataset: { testid: spec.testid },
-    getAttribute: (name: string) =>
-      ({ "aria-label": spec.label, alt: spec.alt, title: spec.title })[name] ?? null,
+    parentElement: null,
+    children: (spec.children ?? []).map(fakeElement),
+    shadowRoot: null,
+    getAttribute: (name: string) => attributes[name] ?? null,
+    querySelectorAll: (selector: string) => queryScope(element, selector),
     scrollHeight: spec.overflows ? spec.height * 2 : spec.height,
     clientHeight: spec.height,
     scrollWidth: spec.width,
@@ -78,27 +124,170 @@ export function fakeElement(spec: FakeElementSpec): FakeElement {
       bottom: spec.y + spec.height,
     }),
   };
+  for (const child of element.children) child.parentElement = element;
+  if (spec.shadow) element.shadowRoot = fakeRoot(spec.shadow.map(fakeElement));
+  return element;
 }
 
-// withFakeDocument installs a document answering the host's three queries over
-// `elements`, resets the host's per-tick cache, and restores the real document
-// afterwards.
+// A shadow root's children have no parentElement, as in a real DOM, so a
+// descendant selector cannot reach across the boundary from either side.
+function fakeRoot(children: FakeElement[]): FakeRoot {
+  const root: FakeRoot = {
+    children,
+    querySelectorAll: (selector: string) => queryScope(root, selector),
+  };
+  return root;
+}
+
+function queryScope(scope: { children: FakeElement[] }, selector: string): FakeElement[] {
+  const found: FakeElement[] = [];
+  const walk = (nodes: FakeElement[]): void => {
+    for (const node of nodes) {
+      if (matchesQuery(node, selector)) found.push(node);
+      walk(node.children);
+    }
+  };
+  walk(scope.children);
+  return found;
+}
+
+function matchesQuery(element: FakeElement, selector: string): boolean {
+  if (selector === TAPPABLE_SELECTOR) return element.clickable === true;
+  if (selector === EDITABLE_SELECTOR) return element.editable === true;
+  return matchesSelectorList(element, selector);
+}
+
+function matchesSelectorList(element: FakeElement, selector: string): boolean {
+  return splitTopLevel(selector, ",").some((complex) => matchesComplex(element, complex));
+}
+
+function matchesComplex(element: FakeElement, complex: string): boolean {
+  const compounds = splitTopLevel(complex, " ");
+  const subject = compounds.pop();
+  if (subject === undefined) return false;
+  if (!matchesCompound(element, subject)) return false;
+  let ancestor = element.parentElement;
+  for (const compound of compounds.reverse()) {
+    while (ancestor && !matchesCompound(ancestor, compound)) ancestor = ancestor.parentElement;
+    if (!ancestor) return false;
+    ancestor = ancestor.parentElement;
+  }
+  return true;
+}
+
+const TAG_NAME = /^[a-zA-Z][a-zA-Z0-9-]*/;
+const ATTRIBUTE = /^([a-zA-Z][\w-]*)(?:([~^]?)=(.+))?$/;
+
+function matchesCompound(element: FakeElement, compound: string): boolean {
+  let rest = compound;
+  while (rest.length > 0) {
+    if (rest.startsWith("*")) {
+      rest = rest.slice(1);
+      continue;
+    }
+    if (rest.startsWith("[")) {
+      const end = closingIndex(rest, "[", "]");
+      if (!matchesAttribute(element, rest.slice(1, end))) return false;
+      rest = rest.slice(end + 1);
+      continue;
+    }
+    if (rest.startsWith(":is(") || rest.startsWith(":not(")) {
+      const end = closingIndex(rest, "(", ")");
+      const inner = rest.slice(rest.indexOf("(") + 1, end);
+      const anyMatched = splitTopLevel(inner, ",").some((part) =>
+        matchesSelectorList(element, part),
+      );
+      if (rest.startsWith(":is(") ? !anyMatched : anyMatched) return false;
+      rest = rest.slice(end + 1);
+      continue;
+    }
+    const tag = TAG_NAME.exec(rest);
+    if (!tag) throw new Error(`web-dom-harness cannot parse selector ${JSON.stringify(compound)}`);
+    if (element.tagName !== tag[0].toUpperCase()) return false;
+    rest = rest.slice(tag[0].length);
+  }
+  return true;
+}
+
+function matchesAttribute(element: FakeElement, body: string): boolean {
+  const parsed = ATTRIBUTE.exec(body);
+  if (!parsed) throw new Error(`web-dom-harness cannot parse attribute [${body}]`);
+  const [, name, operator, quoted] = parsed;
+  const actual = element.getAttribute(name!);
+  if (actual === null) return false;
+  if (quoted === undefined) return true;
+  const value = unescapeCss(quoted.replace(/^"(.*)"$/, "$1").replace(/^'(.*)'$/, "$1"));
+  if (operator === "~") return actual.split(/\s+/).includes(value);
+  if (operator === "^") return actual.startsWith(value);
+  return actual === value;
+}
+
+// Selector values reach the harness escaped by CSS.escape, so `[id="1a"]`
+// arrives as `[id="\31 a"]` and comparing it raw would never match.
+function unescapeCss(value: string): string {
+  return value.replace(/\\([0-9a-fA-F]{1,6}) ?|\\(.)/g, (_, hex: string, literal: string) =>
+    hex ? String.fromCodePoint(parseInt(hex, 16)) : literal,
+  );
+}
+
+function closingIndex(input: string, open: string, close: string): number {
+  let depth = 0;
+  let quote = "";
+  for (let index = input.indexOf(open); index < input.length; index++) {
+    const character = input[index]!;
+    if (quote) {
+      if (character === quote) quote = "";
+      continue;
+    }
+    if (character === '"' || character === "'") quote = character;
+    else if (character === open) depth++;
+    else if (character === close && --depth === 0) return index;
+  }
+  throw new Error(`web-dom-harness cannot parse selector ${JSON.stringify(input)}`);
+}
+
+function splitTopLevel(input: string, separator: string): string[] {
+  const parts: string[] = [];
+  let current = "";
+  let depth = 0;
+  let quote = "";
+  for (const character of input) {
+    if (quote) {
+      current += character;
+      if (character === quote) quote = "";
+      continue;
+    }
+    if (character === '"' || character === "'") quote = character;
+    else if (character === "(" || character === "[") depth++;
+    else if (character === ")" || character === "]") depth--;
+    else if (depth === 0 && (character === separator || (separator === " " && /\s/.test(character)))) {
+      parts.push(current);
+      current = "";
+      continue;
+    }
+    current += character;
+  }
+  parts.push(current);
+  return parts.map((part) => part.trim()).filter((part) => part.length > 0);
+}
+
+// withFakeDocument installs a document whose top-level children are `elements`,
+// resets the host's per-tick cache, and restores the real globals afterwards.
+// window goes in alongside document because buildState reads both, so an
+// extractor reaching state.ax needs it.
 export function withFakeDocument(elements: FakeElement[], run: () => void): void {
   const global = globalThis as Record<string, unknown>;
-  const original = global.document;
-  const answers: Record<string, FakeElement[]> = {
-    "*": elements,
-    [TAPPABLE_SELECTOR]: elements.filter((element) => element.clickable),
-    [EDITABLE_SELECTOR]: elements.filter((element) => element.editable),
-  };
-  global.document = {
-    querySelectorAll: (selector: string) => answers[selector] ?? [],
-  };
+  const originalDocument = global.document;
+  const originalWindow = global.window;
+  const document: FakeRoot = fakeRoot(elements);
+  global.document = document;
+  global.window = {};
   __testing__.resetTargetCache();
   try {
     run();
   } finally {
     __testing__.resetTargetCache();
-    global.document = original;
+    global.document = originalDocument;
+    global.window = originalWindow;
   }
 }

From 3fe972946d450ae0956c86731e3463c0552fa216 Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:35:05 +0530
Subject: [PATCH 2/8] fix(spec): deepQueryAll returns matches in document order

---
 pkg/spec/src/web-runtime.ts       |  11 ++-
 pkg/spec/test/web-runtime.test.ts | 150 +++++++++++++++++++++---------
 2 files changed, 113 insertions(+), 48 deletions(-)

diff --git a/pkg/spec/src/web-runtime.ts b/pkg/spec/src/web-runtime.ts
index 24deca8..a607758 100644
--- a/pkg/spec/src/web-runtime.ts
+++ b/pkg/spec/src/web-runtime.ts
@@ -193,13 +193,18 @@ function selectorFromString(selector: string): { css?: string; xpath?: string }
 // (Compose for Web mounts its canvas and its whole accessibility tree inside a
 // shadow root on the mount element) keeps its entire UI on the far side of one:
 // without this a spec sees four nodes and can neither enumerate a target nor
-// resolve a testTag. Light-DOM matches come first, then shadow content in walk
-// order. XPath has no equivalent, so `text:` selectors stop at the boundary.
+// resolve a testTag. Matches come back in the order expandShadowContent walks
+// and buildTree (internal/driver/chrome/driver.go) emits: a host, then that
+// host's shadow content, then the host's light children. Sweeping the light DOM
+// first and descending afterwards put a shadow-hosted match behind a later
+// light-DOM one, so find() answered with a different element on each host.
+// XPath has no equivalent, so `text:` selectors stop at the boundary.
 function deepQueryAll(selector: string, root: ParentNode): Element[] {
   const found: Element[] = [];
   const visit = (scope: ParentNode): void => {
-    for (const element of Array.from(scope.querySelectorAll(selector))) found.push(element);
+    const matched = new Set<Element>(Array.from(scope.querySelectorAll(selector)));
     for (const element of Array.from(scope.querySelectorAll<HTMLElement>("*"))) {
+      if (matched.has(element)) found.push(element);
       if (element.shadowRoot) visit(element.shadowRoot);
     }
   };
diff --git a/pkg/spec/test/web-runtime.test.ts b/pkg/spec/test/web-runtime.test.ts
index a5ac7e6..5316fc9 100644
--- a/pkg/spec/test/web-runtime.test.ts
+++ b/pkg/spec/test/web-runtime.test.ts
@@ -84,6 +84,7 @@ test("installRuntime defined the host-invoked globals", () => {
 });
 
 const { fakeElement, withFakeDocument } = await import("./web-dom-harness.ts");
+type FakeElementSpec = Parameters<typeof fakeElement>[0];
 
 // The host reports facts and never routes verbs: which of these a verb may act
 // on is decided by the shared rule in src/targets.ts, exercised across both
@@ -175,6 +176,55 @@ test("queryTargets leaves duplicated identities unnamed", () => {
   });
 });
 
+// The enumeration ORDER is the parity contract. buildTree in
+// internal/driver/chrome/driver.go emits a host's shadow children before its
+// light ones, and TestHierarchy_DerivesTheSameFactsAsTheWebRuntime compares the
+// two enumerations position by position.
+test("queryTargets splices shadow content in before the host's light children", () => {
+  const page = fakeElement({
+    tag: "div", x: 0, y: 0, width: 400, height: 800, id: "page",
+    children: [
+      {
+        tag: "div", x: 0, y: 0, width: 400, height: 100, id: "mount",
+        shadow: [
+          { tag: "button", x: 0, y: 0, width: 40, height: 20, id: "shadow-save", clickable: true },
+        ],
+        children: [{ tag: "div", x: 0, y: 20, width: 40, height: 20, id: "mount-light-child" }],
+      },
+      { tag: "div", x: 0, y: 100, width: 400, height: 100, id: "after" },
+    ],
+  });
+  withFakeDocument([page], () => {
+    assert.deepEqual(
+      host.queryTargets().map((target) => target.selector),
+      ["id:page", "id:mount", "id:shadow-save", "id:mount-light-child", "id:after"],
+    );
+  });
+});
+
+// The tappable set is resolved by selector, and querySelectorAll stops dead at
+// a shadow boundary, so a control inside a shadow root carries the clickable
+// fact only if the selector sweep descends. A Compose for Web app keeps every
+// control it has on the far side of one boundary.
+test("queryTargets reports a shadow-hosted control as clickable", () => {
+  const mount = fakeElement({
+    tag: "div", x: 0, y: 0, width: 400, height: 100, id: "mount",
+    shadow: [
+      { tag: "button", x: 0, y: 0, width: 40, height: 20, id: "shadow-save", clickable: true },
+      { tag: "input", x: 0, y: 20, width: 40, height: 20, id: "shadow-amount", editable: true },
+    ],
+  });
+  withFakeDocument([mount], () => {
+    const targets = host.queryTargets();
+    assert.deepEqual(
+      targets.map((target) => target.selector),
+      ["id:mount", "id:shadow-save", "id:shadow-amount"],
+    );
+    assert.equal(targets[1]!.clickable, true);
+    assert.equal(targets[2]!.editable, true);
+  });
+});
+
 test("queryTargets caches within a tick until reset", () => {
   const button = fakeElement({ tag: "button", x: 0, y: 0, width: 10, height: 10, clickable: true });
   withFakeDocument([button], () => {
@@ -473,28 +523,23 @@ test("selectorTag renders the selector shapes the goja host renders", () => {
 // accounts/totalBalance extractors (findAll([{HomeScreen}, {AccountCard}]))
 // were empty on every web step and the properties over them checked nothing.
 test("ax.findAll resolves a selector path segment by segment", () => {
-  const rect = { left: 0, top: 0, right: 10, bottom: 10, width: 10, height: 10 };
-  const node = (id: string, answers: Record<string, unknown[]> = {}) => ({
-    id,
-    tagName: "DIV",
-    className: "",
-    textContent: id,
-    dataset: {},
-    getAttribute: () => null,
-    getBoundingClientRect: () => rect,
-    querySelectorAll: (selector: string) => answers[selector] ?? [],
+  const card = (id: string, y: number): FakeElementSpec => ({
+    tag: "div", x: 0, y, width: 10, height: 10, testid: "AccountCard", text: id,
+  });
+  // The stray card is outside HomeScreen, so a document-wide sweep for the
+  // second segment picks it up and the scoping assertion below fails.
+  const page = fakeElement({
+    tag: "div", x: 0, y: 0, width: 100, height: 100,
+    children: [
+      {
+        tag: "div", x: 0, y: 0, width: 100, height: 50, testid: "HomeScreen",
+        children: [card("first", 0), card("second", 10)],
+      },
+      card("stray", 60),
+    ],
   });
-  const cardCss = `:is([data-testid="AccountCard"], [id="AccountCard"])`;
-  const screenCss = `:is([data-testid="HomeScreen"], [id="HomeScreen"])`;
-  const cards = [node("first"), node("second")];
-  const home = node("HomeScreen", { [cardCss]: cards });
 
-  const g = globalThis as Record<string, unknown>;
-  const originalDocument = g.document;
-  const originalWindow = g.window;
-  g.document = { querySelectorAll: (selector: string) => (selector === screenCss ? [home] : []) };
-  g.window = {};
-  try {
+  withFakeDocument([page], () => {
     __testing__.extractors.length = 0;
     __testing__.runtime.extract((state) => {
       const ax = (state as { ax: { findAll(s: unknown): Record<string, unknown>[] } }).ax;
@@ -506,30 +551,14 @@ test("ax.findAll resolves a selector path segment by segment", () => {
     // Scoped to the head match: the cards come from the HomeScreen node, not
     // from a document-wide sweep for AccountCard.
     assert.deepEqual(readingOf(values, 0), ["first", "second"]);
-  } finally {
-    g.document = originalDocument;
-    g.window = originalWindow;
-  }
+  });
 });
 
 test("ax.find and ax.findAll label the element with its selector", () => {
-  const rect = { left: 0, top: 0, right: 10, bottom: 10, width: 10, height: 10 };
-  const submit = {
-    id: "TxnSubmit",
-    tagName: "DIV",
-    className: "",
-    textContent: "Submit",
-    dataset: {},
-    getAttribute: () => null,
-    getBoundingClientRect: () => rect,
-  };
-  const matches = `:is([data-testid="TxnSubmit"], [id="TxnSubmit"])`;
-  const g = globalThis as Record<string, unknown>;
-  const originalDocument = g.document;
-  const originalWindow = g.window;
-  g.document = { querySelectorAll: (selector: string) => (selector === matches ? [submit] : []) };
-  g.window = {};
-  try {
+  const submit = fakeElement({
+    tag: "div", x: 0, y: 0, width: 10, height: 10, id: "TxnSubmit", text: "Submit",
+  });
+  withFakeDocument([submit], () => {
     __testing__.extractors.length = 0;
     __testing__.runtime.extract((state) => {
       const ax = (state as { ax: { find(s: unknown): Record<string, unknown> | undefined } }).ax;
@@ -546,8 +575,39 @@ test("ax.find and ax.findAll label the element with its selector", () => {
     // reference would hand the array INDEX to the runtime as the selector.
     const all = readingOf(values, 1) as Record<string, unknown>[];
     assert.equal(all[0]!.__sanderlingSelector, "testTag:TxnSubmit");
-  } finally {
-    g.document = originalDocument;
-    g.window = originalWindow;
-  }
+  });
+});
+
+// One page, one selector, two hosts. The goja host resolves a selector against
+// the hierarchy dump, whose buildTree (internal/driver/chrome/driver.go) emits
+// a host's shadow children BEFORE its light ones, so a pre-order search there
+// reaches a shadow-hosted match first. deepQueryAll swept the whole light DOM
+// first and only then descended, so this page answered find({id:"x"}) with the
+// light node in V8 and the shadow node in goja, and on web V8's answer is the
+// one that reaches the properties.
+test("ax.find resolves the shadow-hosted match the hierarchy dump reaches first", () => {
+  const page = fakeElement({
+    tag: "div", x: 0, y: 0, width: 400, height: 800, id: "page",
+    children: [
+      {
+        tag: "div", x: 0, y: 0, width: 400, height: 100, id: "mount",
+        shadow: [{ tag: "span", x: 0, y: 0, width: 40, height: 20, id: "x", text: "shadow" }],
+      },
+      { tag: "span", x: 0, y: 100, width: 40, height: 20, id: "x", text: "light" },
+    ],
+  });
+  withFakeDocument([page], () => {
+    __testing__.extractors.length = 0;
+    __testing__.runtime.extract((state) => {
+      const ax = (state as { ax: { find(s: unknown): Record<string, unknown> | undefined } }).ax;
+      return ax.find({ id: "x" })?.text;
+    });
+    __testing__.runtime.extract((state) => {
+      const ax = (state as { ax: { findAll(s: unknown): Record<string, unknown>[] } }).ax;
+      return ax.findAll({ id: "x" }).map((element) => element.text);
+    });
+    const values = __testing__.evaluateExtractors();
+    assert.equal(readingOf(values, 0), "shadow");
+    assert.deepEqual(readingOf(values, 1), ["shadow", "light"]);
+  });
 });

From e62b08dffd08650889b945558e883da9425876cb Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:39:18 +0530
Subject: [PATCH 3/8] test(browser): compare ax.find across both hosts on one
 page

---
 test/browser/browser_test.go                | 78 +++++++++++++++++++++
 test/browser/testdata/find-order/index.html | 16 +++++
 test/browser/testdata/find-order/spec.ts    | 17 +++++
 3 files changed, 111 insertions(+)
 create mode 100644 test/browser/testdata/find-order/index.html
 create mode 100644 test/browser/testdata/find-order/spec.ts

diff --git a/test/browser/browser_test.go b/test/browser/browser_test.go
index 3cae9cd..1cab5d4 100644
--- a/test/browser/browser_test.go
+++ b/test/browser/browser_test.go
@@ -23,6 +23,7 @@ import (
 	"github.com/priyanshujain/sanderling/internal/bundler"
 	"github.com/priyanshujain/sanderling/internal/driver"
 	"github.com/priyanshujain/sanderling/internal/driver/chrome"
+	"github.com/priyanshujain/sanderling/internal/hierarchy"
 	chromerunner "github.com/priyanshujain/sanderling/internal/runner"
 	"github.com/priyanshujain/sanderling/internal/trace"
 	"github.com/priyanshujain/sanderling/internal/verifier"
@@ -222,3 +223,80 @@ func TestBrowserUndefinedExtractorStaysUndefined(t *testing.T) {
 		t.Fatalf("nothing was ever tapped, so the property above held vacuously; violations=%v", violations)
 	}
 }
+
+// One page, one selector, two hosts, two answers.
+//
+// The V8 host resolves state.ax.find against the live DOM; the goja host
+// resolves the same selector against the hierarchy dump. The fixture puts a
+// shadow-hosted #x above a light-DOM #x, the one shape where the two walks can
+// disagree, and on web it is V8's answer that reaches the properties. Each host
+// is driven through its production path (EvaluateExtractors in the page,
+// PushSnapshot over the dump) and neither is asked what the other said, so the
+// comparison is evidence rather than an assertion about one of them.
+func TestBrowserAxFindAgreesAcrossHosts(t *testing.T) {
+	server := httptest.NewServer(http.FileServer(http.Dir(testdataDir(t))))
+	t.Cleanup(server.Close)
+
+	gojaBundle, webBundle := bundleSpec(t, filepath.Join(testdataDir(t), "find-order", "spec.ts"))
+
+	driverInstance := chrome.New()
+	t.Cleanup(func() {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		_ = driverInstance.Terminate(ctx)
+	})
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+
+	if err := driverInstance.Launch(ctx, server.URL+"/find-order/", false, nil); err != nil {
+		t.Fatalf("launch: %v", err)
+	}
+	if err := driverInstance.InstallBundle(ctx, webBundle); err != nil {
+		t.Fatalf("install web bundle: %v", err)
+	}
+	readings, err := driverInstance.EvaluateExtractors(ctx)
+	if err != nil {
+		t.Fatalf("evaluate extractors in the page: %v", err)
+	}
+	fromV8 := string(readings[0])
+
+	dump, err := driverInstance.Hierarchy(ctx)
+	if err != nil {
+		t.Fatalf("hierarchy: %v", err)
+	}
+	tree, err := hierarchy.Parse(dump)
+	if err != nil {
+		t.Fatalf("parse hierarchy: %v", err)
+	}
+	verifierInstance, err := verifier.New(
+		verifier.WithSeed(fixtureSeed),
+		verifier.WithPlatform("web"),
+	)
+	if err != nil {
+		t.Fatalf("verifier: %v", err)
+	}
+	if err := verifierInstance.Load(string(gojaBundle)); err != nil {
+		t.Fatalf("load spec: %v", err)
+	}
+	if err := verifierInstance.PushSnapshot(verifier.SnapshotInput{Tree: tree}); err != nil {
+		t.Fatalf("push snapshot: %v", err)
+	}
+	change, ok := verifierInstance.ChangedExtractors()["found"]
+	if !ok {
+		t.Fatal("the goja host recorded no reading for the found extractor")
+	}
+	fromGoja := string(change.Curr)
+
+	// Pinned, not just compared: two hosts that both resolved nothing would
+	// agree on undefined and prove nothing about the walk.
+	if fromGoja != `"shadow"` {
+		t.Errorf("the goja host read %s off the dump, want the shadow-hosted %q", fromGoja, "shadow")
+	}
+	if fromV8 != fromGoja {
+		t.Fatalf(
+			"one page, one selector, two answers: the V8 host read %s and the goja host read %s",
+			fromV8,
+			fromGoja,
+		)
+	}
+}
diff --git a/test/browser/testdata/find-order/index.html b/test/browser/testdata/find-order/index.html
new file mode 100644
index 0000000..9e81425
--- /dev/null
+++ b/test/browser/testdata/find-order/index.html
@@ -0,0 +1,16 @@
+<!doctype html>
+<html>
+  <body>
+    <!-- Two elements share the id, one inside a shadow root on the mount and
+         one later in the light DOM. The hierarchy dump orders a host's shadow
+         children before its light ones, so a pre-order search there reaches the
+         shadow one first; a light-DOM sweep that only descends afterwards
+         reaches the other. The page exists to make the two walks disagree. -->
+    <div id="mount" style="width: 200px; height: 80px"></div>
+    <span id="x">light</span>
+    <script>
+      document.getElementById("mount").attachShadow({ mode: "open" }).innerHTML =
+        '<span id="x">shadow</span>';
+    </script>
+  </body>
+</html>
diff --git a/test/browser/testdata/find-order/spec.ts b/test/browser/testdata/find-order/spec.ts
new file mode 100644
index 0000000..854c367
--- /dev/null
+++ b/test/browser/testdata/find-order/spec.ts
@@ -0,0 +1,17 @@
+import { always, extract, taps } from "@sanderling/spec";
+
+// Which of the two #x a selector means is the whole fixture. The reading is
+// compared between the two hosts by TestBrowserAxFindAgreesAcrossHosts, which
+// drives each host's production path and never asks one what the other said.
+//
+// Written in the "k:v" string grammar because that is the one form both hosts
+// resolve the same way: the object form {id: "x"} reaches the goja host as a
+// plain attribute filter, and a web hierarchy dump carries the id under
+// resource-id, so it matches nothing there.
+const found = extract((s) => s.ax.find("id:x")?.text).named("found");
+
+const findsTheShadowMatch = always(() => found.current === "shadow");
+
+export const properties = { findsTheShadowMatch };
+
+export const actionsRoot = taps;

From 0cef5bd1d3999bbdac1efc7b6b5f634084b22bd0 Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:39:21 +0530
Subject: [PATCH 4/8] test(spec): name the shadow match in the grammar both
 hosts parse

---
 pkg/spec/test/web-runtime.test.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pkg/spec/test/web-runtime.test.ts b/pkg/spec/test/web-runtime.test.ts
index 5316fc9..d325871 100644
--- a/pkg/spec/test/web-runtime.test.ts
+++ b/pkg/spec/test/web-runtime.test.ts
@@ -600,11 +600,11 @@ test("ax.find resolves the shadow-hosted match the hierarchy dump reaches first"
     __testing__.extractors.length = 0;
     __testing__.runtime.extract((state) => {
       const ax = (state as { ax: { find(s: unknown): Record<string, unknown> | undefined } }).ax;
-      return ax.find({ id: "x" })?.text;
+      return ax.find("id:x")?.text;
     });
     __testing__.runtime.extract((state) => {
       const ax = (state as { ax: { findAll(s: unknown): Record<string, unknown>[] } }).ax;
-      return ax.findAll({ id: "x" }).map((element) => element.text);
+      return ax.findAll("id:x").map((element) => element.text);
     });
     const values = __testing__.evaluateExtractors();
     assert.equal(readingOf(values, 0), "shadow");

From 56d6aa53f150ab1689b4643b61cdfcee586d717b Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:42:36 +0530
Subject: [PATCH 5/8] test: pin that a nested undefined does not survive the
 wire

---
 internal/verifier/extractor_encoding_test.go | 76 ++++++++++++++++++++
 pkg/spec/test/web-runtime.test.ts            | 24 +++++++
 2 files changed, 100 insertions(+)

diff --git a/internal/verifier/extractor_encoding_test.go b/internal/verifier/extractor_encoding_test.go
index a693dbf..40b9a32 100644
--- a/internal/verifier/extractor_encoding_test.go
+++ b/internal/verifier/extractor_encoding_test.go
@@ -177,3 +177,79 @@ func compactJSON(t *testing.T, source string) string {
 	}
 	return compact.String()
 }
+
+// TestExtractorEncoding_NestedUndefinedIsNotOnTheWire pins the one reading
+// shape the two hosts do NOT encode alike, rather than hiding it.
+//
+// JSON has no undefined, so the page loses the whole key (asserted in
+// pkg/spec/test/web-runtime.test.ts) while goja writes null. goja cannot mirror
+// the drop: Export reports an undefined member and a null member identically as
+// nil, so dropping those keys here would drop the genuine nulls the page keeps.
+// Mirroring the other way, by writing null on the page, would break the one
+// thing that does agree. Carrying the member across takes a wire format that
+// can express undefined, which is a change to every layer that parses a reading
+// and to the replay UI that renders one.
+//
+// So the guarantee is narrower than "the same object": both hosts answer
+// undefined when a property READS the member. Key presence (`in`, Object.keys)
+// is not part of it, and this test says so out loud, so closing the gap has to
+// be a deliberate change to both hosts at once.
+func TestExtractorEncoding_NestedUndefinedIsNotOnTheWire(t *testing.T) {
+	const reading = `({ absent: undefined, empty: null, present: 1 })`
+	const fromGoja = `{"absent":null,"empty":null,"present":1}`
+	// What the page sends for the same getter, with the key gone.
+	const fromWeb = `{"empty":null,"present":1}`
+
+	if got := encodeSpecValue(t, reading); got != fromGoja {
+		t.Errorf("goja encoded the reading as %s, want %s", got, fromGoja)
+	}
+
+	native := newVerifier(t)
+	mustLoad(t, native, "__sanderling__.extract(state => "+reading+", \"value\");\nglobalThis.properties = {};")
+	if err := native.PushSnapshot(SnapshotInput{}); err != nil {
+		t.Fatal(err)
+	}
+
+	web := newVerifier(t)
+	mustLoad(t, web, "__sanderling__.extract(state => null, \"value\");\nglobalThis.properties = {};")
+	if err := web.PushSnapshot(SnapshotInput{}); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := web.OverrideExtractorValues(map[int]json.RawMessage{0: json.RawMessage(fromWeb)}); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, probe := range []struct {
+		expression string
+		native     bool
+		web        bool
+	}{
+		{"reading.absent === undefined", true, true},
+		{"reading.empty === null", true, true},
+		{"reading.present === 1", true, true},
+		// The half that does not survive the wire.
+		{`"absent" in reading`, true, false},
+	} {
+		if got := evaluateAgainstReading(t, native, probe.expression); got != probe.native {
+			t.Errorf("goja host: %s is %v, want %v", probe.expression, got, probe.native)
+		}
+		if got := evaluateAgainstReading(t, web, probe.expression); got != probe.web {
+			t.Errorf("web host: %s is %v, want %v", probe.expression, got, probe.web)
+		}
+	}
+}
+
+// evaluateAgainstReading answers a boolean expression over the value a property
+// would read out of the first extractor, which is where the two hosts have to
+// agree.
+func evaluateAgainstReading(t *testing.T, verifier *Verifier, expression string) bool {
+	t.Helper()
+	if err := verifier.runtime.GlobalObject().Set("reading", verifier.extractors[0].currentValue); err != nil {
+		t.Fatal(err)
+	}
+	value, err := verifier.runtime.RunString(expression)
+	if err != nil {
+		t.Fatalf("evaluate %s: %v", expression, err)
+	}
+	return value.ToBoolean()
+}
diff --git a/pkg/spec/test/web-runtime.test.ts b/pkg/spec/test/web-runtime.test.ts
index d325871..105975b 100644
--- a/pkg/spec/test/web-runtime.test.ts
+++ b/pkg/spec/test/web-runtime.test.ts
@@ -611,3 +611,27 @@ test("ax.find resolves the shadow-hosted match the hierarchy dump reaches first"
     assert.deepEqual(readingOf(values, 1), ["shadow", "light"]);
   });
 });
+
+// A nested undefined is the one reading shape the two hosts do NOT encode
+// alike, and this pins the split instead of hiding it. JSON has no undefined,
+// so the key goes with the value here; goja marshals the same member as null,
+// and it cannot do otherwise, because an exported goja object reports undefined
+// and null identically, so dropping those keys there would drop the genuine
+// nulls this host keeps. Carrying the member across would take a wire format
+// that can express undefined.
+//
+// What both hosts DO agree on is the member's value: reading it answers
+// undefined either way, and that is the guarantee a property may rely on. Key
+// presence (`in`, Object.keys) is not.
+// TestExtractorEncoding_NestedUndefinedIsNotOnTheWire in
+// internal/verifier/extractor_encoding_test.go pins the other half.
+test("a nested undefined leaves the page as a dropped key, a nested null does not", () => {
+  __testing__.extractors.length = 0;
+  __testing__.runtime.extract(() => ({ absent: undefined, empty: null, present: 1 }));
+  let wire = "";
+  withState(() => {
+    // Exactly what extractorScript in internal/driver/chrome/driver.go sends.
+    wire = JSON.stringify(__testing__.evaluateExtractors());
+  });
+  assert.equal(wire, `{"0":{"value":{"empty":null,"present":1}}}`);
+});

From ad63c5eb74b2bc673934afea83c37dca4046cb09 Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:50:55 +0530
Subject: [PATCH 6/8] fix(hierarchy): object selectors resolve by the same rule
 as string ones

---
 internal/hierarchy/hierarchy.go      | 14 +++--
 internal/hierarchy/hierarchy_test.go | 80 ++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 3 deletions(-)

diff --git a/internal/hierarchy/hierarchy.go b/internal/hierarchy/hierarchy.go
index c54a052..1f1e9b4 100644
--- a/internal/hierarchy/hierarchy.go
+++ b/internal/hierarchy/hierarchy.go
@@ -11,7 +11,8 @@
 //	  descPrefix:<prefix>  - starts-with on content-desc / accessibilityText
 //
 //	Object selectors (multi-attribute AND, element-scoped or global):
-//	  { attr: value, ... } - all key/value pairs must match; substring / boolean semantics
+//	  { attr: value, ... } - all key/value pairs must match, each key resolved by
+//	                         the same rule its string form above uses
 //
 //	Path queries (global scan only, string form):
 //	  <sel> > <sel> > ...  - each segment matched within subtree of previous match
@@ -156,10 +157,17 @@ func matchAttr(element *Element, attr, value string) bool {
 	return false
 }
 
-// matchSelector returns true when all filters in sel match the element (AND semantics).
+// matchSelector returns true when all filters in sel match the element (AND
+// semantics). Each filter goes through match, the same rule the string form
+// resolves a "kind:value" segment by, so {id: "Submit"} and "id:Submit" can
+// never resolve to different elements. Applying matchAttr directly here made
+// the object form skip the kind arms entirely: id, desc and descPrefix name no
+// attribute any producer writes, so those keys matched NOTHING through an
+// object selector while the string form matched, and every property over the
+// missing element passed vacuously.
 func matchSelector(element *Element, sel Selector) bool {
 	for _, f := range sel.Filters {
-		if !matchAttr(element, f.Attr, f.Value) {
+		if !match(element, f.Attr, f.Value) {
 			return false
 		}
 	}
diff --git a/internal/hierarchy/hierarchy_test.go b/internal/hierarchy/hierarchy_test.go
index 91abd4c..395065f 100644
--- a/internal/hierarchy/hierarchy_test.go
+++ b/internal/hierarchy/hierarchy_test.go
@@ -1035,3 +1035,83 @@ func TestTreeTransitional(t *testing.T) {
 		t.Error("nil tree must not be flagged as transitional")
 	}
 }
+
+// selectorFormsDump carries one node per id shape a real dump produces, plus
+// nodes carrying a description in the ", " form the desc rule knows about and a
+// text the text rule matches on a substring.
+const selectorFormsDump = `{
+  "attributes": {"resource-id": "root", "bounds": "[0,0,400,800]"},
+  "children": [
+    {"attributes": {"resource-id": "BareThing", "bounds": "[0,0,100,50]"}, "children": []},
+    {"attributes": {"resource-id": "com.example.app:id/AndroidThing", "bounds": "[0,50,100,100]"},
+     "children": []},
+    {"attributes": {"accessibilityIdentifier": "IosThing", "bounds": "[0,100,100,150]"},
+     "children": []},
+    {"attributes": {"resource-id": "Described", "content-desc": "Save, button", "bounds": "[0,150,100,200]"},
+     "children": []},
+    {"attributes": {"resource-id": "Labelled", "text": "Total balance", "bounds": "[0,200,100,250]"},
+     "children": []}
+  ]
+}`
+
+// TestSelectorFormsResolveTheSameElement holds the two selector forms a spec can
+// write to ONE rule per key. A spec reaches these through state.ax.find: a
+// string goes to FindNode, an object to FindBySelector, and the two ran
+// different matchers. `id` has a kind arm that knows an Android resource id is
+// package-qualified (com.example.app:id/Thing) and that a spec names the bare
+// tail; the object form had no such arm and looked for a literal `id` attribute
+// no producer writes, so {id: "Thing"} silently matched nothing on every
+// platform while "id:Thing" matched. `desc` and `descPrefix` had the same
+// split. A selector that resolves nothing makes every property over it
+// vacuously true, which is the failure that reports a green run while checking
+// nothing.
+func TestSelectorFormsResolveTheSameElement(t *testing.T) {
+	tree, err := Parse(selectorFormsDump)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, test := range []struct {
+		key   string
+		value string
+		want  string
+	}{
+		{"id", "BareThing", "BareThing"},
+		// A spec names the tail; an Android dump carries the package prefix.
+		{"id", "AndroidThing", "com.example.app:id/AndroidThing"},
+		{"id", "com.example.app:id/AndroidThing", "com.example.app:id/AndroidThing"},
+		{"id", "IosThing", "IosThing"},
+		{"desc", "Save, button", "Described"},
+		// The ", " form an accessibility label takes when a role is appended.
+		{"desc", "Save", "Described"},
+		{"descPrefix", "Sav", "Described"},
+		{"text", "Total", "Labelled"},
+		{"resource-id", "BareThing", "BareThing"},
+		{"testTag", "IosThing", "IosThing"},
+	} {
+		t.Run(test.key+":"+test.value, func(t *testing.T) {
+			stringForm := test.key + ":" + test.value
+			fromString := tree.FindNode(stringForm)
+			if fromString == nil {
+				t.Fatalf("the string form %q resolved nothing", stringForm)
+			}
+			if fromString.ResourceID != test.want {
+				t.Fatalf("the string form resolved %q, want %q", fromString.ResourceID, test.want)
+			}
+			fromObject := tree.Root.FindBySelector(
+				Selector{Filters: []AttrFilter{{Attr: test.key, Value: test.value}}},
+			)
+			if fromObject == nil {
+				t.Fatalf(
+					"the object form {%s: %q} resolved nothing while %q resolved %q",
+					test.key, test.value, stringForm, fromString.ResourceID,
+				)
+			}
+			if fromObject != fromString {
+				t.Errorf(
+					"one selector, two answers: {%s: %q} resolved %q and %q resolved %q",
+					test.key, test.value, fromObject.ResourceID, stringForm, fromString.ResourceID,
+				)
+			}
+		})
+	}
+}

From 4324573d97e3cbb9a971c7c36f4ac58502b8b706 Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:51:43 +0530
Subject: [PATCH 7/8] test(verifier): both ax.find selector forms resolve the
 same element

---
 internal/verifier/ax_integration_test.go | 75 ++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/internal/verifier/ax_integration_test.go b/internal/verifier/ax_integration_test.go
index 97fd596..6a3589b 100644
--- a/internal/verifier/ax_integration_test.go
+++ b/internal/verifier/ax_integration_test.go
@@ -2,6 +2,7 @@ package verifier
 
 import (
 	"os"
+	"strconv"
 	"testing"
 
 	"github.com/priyanshujain/sanderling/internal/hierarchy"
@@ -99,3 +100,77 @@ func TestStateAxFindWorks(t *testing.T) {
 		t.Fatalf("findAll count = %d, want 1", count)
 	}
 }
+
+// axSelectorFormsTree carries one node per id shape a dump produces: the bare
+// tag Compose and the web driver emit, the package-qualified resource id
+// Android emits, and the iOS accessibility identifier.
+const axSelectorFormsTree = `{
+	"attributes": {"resource-id": "root", "bounds": "[0,0,400,800]"},
+	"children": [
+		{"attributes": {"resource-id": "BareThing", "text": "bare", "bounds": "[0,0,100,50]"},
+		 "children": []},
+		{"attributes": {"resource-id": "com.example.app:id/AndroidThing", "text": "android",
+		 "bounds": "[0,50,100,100]"}, "children": []},
+		{"attributes": {"accessibilityIdentifier": "IosThing", "text": "ios",
+		 "bounds": "[0,100,100,150]"}, "children": []}
+	]
+}`
+
+// TestStateAxSelectorFormsAgree drives both selector forms a spec can write
+// through state.ax.find and holds them to the same element. The two forms
+// dispatch to different lookups (findNodeFromJS sends a string to FindNode and
+// an object to FindBySelector), and the object one used to skip the id rule
+// that knows an Android resource id is package-qualified, so a spec that wrote
+// ax.find({id: "AddAccountSubmit"}) got undefined on Android and every property
+// reading it passed while checking nothing.
+func TestStateAxSelectorFormsAgree(t *testing.T) {
+	tree, err := hierarchy.Parse(axSelectorFormsTree)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, test := range []struct {
+		value string
+		want  string
+	}{
+		{"BareThing", "bare"},
+		{"AndroidThing", "android"},
+		{"com.example.app:id/AndroidThing", "android"},
+		{"IosThing", "ios"},
+	} {
+		t.Run(test.value, func(t *testing.T) {
+			verifier := newVerifier(t)
+			mustLoad(t, verifier, `
+				globalThis.fromObject = __sanderling__.extract(
+					state => state.ax.find({ id: `+strconv.Quote(test.value)+` })?.text, "fromObject");
+				globalThis.fromString = __sanderling__.extract(
+					state => state.ax.find("id:" + `+strconv.Quote(test.value)+`)?.text, "fromString");
+				globalThis.properties = {};
+			`)
+			if err := verifier.PushSnapshot(SnapshotInput{Tree: tree}); err != nil {
+				t.Fatal(err)
+			}
+			fromObject := readCurrent(t, verifier, "fromObject")
+			fromString := readCurrent(t, verifier, "fromString")
+			if fromString != test.want {
+				t.Fatalf(`ax.find("id:%s") read %v, want %q`, test.value, fromString, test.want)
+			}
+			if fromObject != fromString {
+				t.Errorf(
+					`one selector, two answers: ax.find({id: %q}) read %v and ax.find("id:%s") read %v`,
+					test.value, fromObject, test.value, fromString,
+				)
+			}
+		})
+	}
+}
+
+// readCurrent returns a named extractor's current value, or nil when the getter
+// returned undefined, which is what an unresolved selector produces.
+func readCurrent(t *testing.T, verifier *Verifier, name string) any {
+	t.Helper()
+	handle := verifier.runtime.GlobalObject().Get(name)
+	if handle == nil {
+		t.Fatalf("%s is not defined", name)
+	}
+	return handle.ToObject(verifier.runtime).Get("current").Export()
+}

From 047c53a2e74d1dc7f599af539d0b57ccf1c728e5 Mon Sep 17 00:00:00 2001
From: PJ <ipriyanshujain@gmail.com>
Date: Sat, 15 Aug 2026 20:52:43 +0530
Subject: [PATCH 8/8] test(browser): the cross-host fixture uses the object
 selector form

---
 test/browser/browser_test.go             | 14 ++++++++++----
 test/browser/testdata/find-order/spec.ts | 10 +++++-----
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/test/browser/browser_test.go b/test/browser/browser_test.go
index 1cab5d4..b94732d 100644
--- a/test/browser/browser_test.go
+++ b/test/browser/browser_test.go
@@ -281,11 +281,17 @@ func TestBrowserAxFindAgreesAcrossHosts(t *testing.T) {
 	if err := verifierInstance.PushSnapshot(verifier.SnapshotInput{Tree: tree}); err != nil {
 		t.Fatalf("push snapshot: %v", err)
 	}
-	change, ok := verifierInstance.ChangedExtractors()["found"]
-	if !ok {
-		t.Fatal("the goja host recorded no reading for the found extractor")
+	if count := verifierInstance.ExtractorCount(); count != 1 {
+		t.Fatalf("the goja host registered %d extractors, want the fixture's 1", count)
+	}
+	// ChangedExtractors omits an extractor whose reading is null and unchanged,
+	// which is exactly what a selector resolving nothing produces. With the
+	// count checked above, an absent entry is a null reading and not a missing
+	// extractor, so reporting it as null names the real failure.
+	fromGoja := "null"
+	if change, ok := verifierInstance.ChangedExtractors()["found"]; ok {
+		fromGoja = string(change.Curr)
 	}
-	fromGoja := string(change.Curr)
 
 	// Pinned, not just compared: two hosts that both resolved nothing would
 	// agree on undefined and prove nothing about the walk.
diff --git a/test/browser/testdata/find-order/spec.ts b/test/browser/testdata/find-order/spec.ts
index 854c367..2145321 100644
--- a/test/browser/testdata/find-order/spec.ts
+++ b/test/browser/testdata/find-order/spec.ts
@@ -4,11 +4,11 @@ import { always, extract, taps } from "@sanderling/spec";
 // compared between the two hosts by TestBrowserAxFindAgreesAcrossHosts, which
 // drives each host's production path and never asks one what the other said.
 //
-// Written in the "k:v" string grammar because that is the one form both hosts
-// resolve the same way: the object form {id: "x"} reaches the goja host as a
-// plain attribute filter, and a web hierarchy dump carries the id under
-// resource-id, so it matches nothing there.
-const found = extract((s) => s.ax.find("id:x")?.text).named("found");
+// Written in the object form on purpose. It used to reach the goja host as a
+// plain attribute filter looking for an `id` attribute a dump never carries
+// (the web dump files the DOM id under resource-id), so it resolved nothing
+// there while the V8 host resolved it against the live DOM.
+const found = extract((s) => s.ax.find({ id: "x" })?.text).named("found");
 
 const findsTheShadowMatch = always(() => found.current === "shadow");