fix(geometry): preserve OOPIF scale with occupied scrollbars

fix(observation): validate DOM identity across capture phases | 校验跨采集阶段的 DOM 身份一致性

apps/extension/src/browser-driver/__tests__/chromium-cdp.test.ts

@@ -29,6 +29,24 @@ function fakeApi() {
 }
 
 describe("ChromiumCdp", () => {
+  it("changes attachment identity only across real debugger attachments", async () => {
+    const { api, onEvent, onDetach } = fakeApi();
+    const cdp = new ChromiumCdp(api);
+    expect(cdp.getAttachmentId(4)).toBeUndefined();
+    await cdp.ensureAttached(4);
+    const first = cdp.getAttachmentId(4);
+    expect(first).toBeTruthy();
+    await cdp.ensureAttached(4);
+    onEvent.fire({ tabId: 4 }, "Target.attachedToTarget", { sessionId: "child" });
+    expect(cdp.getAttachmentId(4)).toBe(first);
+    onDetach.fire({ tabId: 4 }, "target_closed");
+    expect(cdp.getAttachmentId(4)).toBeUndefined();
+    await cdp.ensureAttached(4);
+    expect(cdp.getAttachmentId(4)).not.toBe(first);
+    await cdp.detach(4);
+    expect(cdp.getAttachmentId(4)).toBeUndefined();
+  });
+
   it("discovers multiple iframe targets and recursively routes nested OOPIF commands", async () => {
     const { api, onEvent } = fakeApi();
     (api.sendCommand as ReturnType<typeof vi.fn>).mockImplementation(

apps/extension/src/browser-driver/chromium-cdp.ts

@@ -164,6 +164,7 @@ async function settleBeforeDeadline(promises: Promise<void>[], deadline: number)
 export class ChromiumCdp {
   private readonly api: CdpDebuggerApi;
   private readonly attachedTabs = new Set<number>();
+  private readonly attachmentIds = new Map<number, string>();
   private readonly attachInFlight = new Map<number, Promise<void>>();
   private readonly detachInFlight = new Map<number, Promise<void>>();
   private readonly tabOwners = new Map<number, Set<string>>();
@@ -198,6 +199,11 @@ export class ChromiumCdp {
     this.bindFrameTargetHandler();
   }
 
+  /** Identity of this actual debugger attachment, independent of frame topology. */
+  getAttachmentId(tabId: number): string | undefined {
+    return this.attachmentIds.get(tabId);
+  }
+
   /** Attach to `tabId` if we haven't already in this driver. */
   async ensureAttached(tabId: number): Promise<void> {
     // Returning a tab clears the cache before Chrome finishes detaching.
@@ -217,6 +223,7 @@ export class ChromiumCdp {
         await this.enableConsoleDomains(tabId);
         await this.enableNetworkDomainBestEffort(tabId);
         this.attachedTabs.add(tabId);
+        this.attachmentIds.set(tabId, crypto.randomUUID());
         await this.enableFrameDiscovery({ tabId }).catch((err) => {
           console.debug("[bsk cdp] frame discovery unavailable", { tabId, err });
         });
@@ -444,6 +451,7 @@ export class ChromiumCdp {
     this.attachInFlight.delete(tabId);
     if (!this.attachedTabs.has(tabId)) return;
     this.attachedTabs.delete(tabId);
+    this.attachmentIds.delete(tabId);
     this.clearDialogState(tabId);
     this.clearConsoleState(tabId);
     this.clearNetworkState(tabId);
@@ -502,6 +510,7 @@ export class ChromiumCdp {
     this.attachInFlight.clear();
     this.tabOwners.clear();
     this.attachedTabs.clear();
+    this.attachmentIds.clear();
     this.dialogBuffers.clear();
     this.dialogSequences.clear();
     this.consoleBuffers.clear();
@@ -848,6 +857,7 @@ export class ChromiumCdp {
     const listener = (source: chrome.debugger.Debuggee, _reason: string) => {
       if (typeof source.tabId === "number") {
         this.attachedTabs.delete(source.tabId);
+        this.attachmentIds.delete(source.tabId);
         this.attachInFlight.delete(source.tabId);
         this.tabOwners.delete(source.tabId);
         this.clearDialogState(source.tabId);

apps/extension/src/tools/__tests__/file-transfer.test.ts

@@ -436,6 +436,8 @@ describe("file transfer tools", () => {
         if (method === "DOM.getContentQuads") {
           return { quads: [[10, 20, 210, 20, 210, 120, 10, 120]] };
         }
+        if (method === "Runtime.evaluate")
+          return { result: { value: { width: 400, height: 300 } } };
         if (method === "Page.getLayoutMetrics") {
           return { cssLayoutViewport: { clientWidth: 400, clientHeight: 300 } };
         }

apps/extension/src/tools/__tests__/frame-geometry.test.ts

@@ -13,7 +13,138 @@ import {
 import { GeometryContext } from "../geometry/frame-context";
 import type { CdpRunner } from "../shared";
 
+function scrollbarDriver(
+  visible = { width: 185, height: 89 },
+  frameSize: unknown = { width: 200, height: 100 },
+) {
+  const send = vi.fn(async (target: { sessionId?: string }, method: string) => {
+    if (method === "Runtime.evaluate") return { result: { value: frameSize } };
+    if (method === "Page.getLayoutMetrics")
+      return {
+        cssLayoutViewport: {
+          clientWidth: target.sessionId ? visible.width : 800,
+          clientHeight: target.sessionId ? visible.height : 600,
+        },
+      };
+    if (method === "DOM.getBoxModel")
+      return {
+        model: {
+          content: target.sessionId
+            ? [0, 0, 200, 0, 200, 100, 0, 100]
+            : [100, 100, 500, 100, 500, 300, 100, 300],
+        },
+      };
+    if (method === "DOM.getContentQuads")
+      return { quads: [[180, 80, 230, 80, 230, 120, 180, 120]] };
+    throw new Error(`unexpected ${method}`);
+  });
+  const cdp: CdpRunner = {
+    send: (tabId, method) => send({ tabId } as never, method) as never,
+    sendToTarget: send as CdpRunner["sendToTarget"],
+    getFrameGraph: async () => ({
+      rootFrameId: "main",
+      frames: [
+        { frameId: "main", target: { tabId: 4 } },
+        {
+          frameId: "child",
+          parentFrameId: "main",
+          ownerBackendNodeId: 10,
+          target: { tabId: 4, sessionId: "child" },
+        },
+        {
+          frameId: "same-child",
+          parentFrameId: "child",
+          ownerBackendNodeId: 20,
+          target: { tabId: 4, sessionId: "child" },
+        },
+      ],
+    }),
+  };
+  return { cdp, send };
+}
+
 describe("frame geometry projection", () => {
+  it.each([
+    { width: 200, height: 100 },
+    { width: 185, height: 100 },
+    { width: 200, height: 89 },
+    { width: 185, height: 89 },
+  ])("preserves scale and clips scrollbar strips for visible viewport $width × $height", async (visible) => {
+    const { cdp, send } = scrollbarDriver(visible);
+    const geometry = await resolveNodeGeometry(cdp, 4, {
+      target: { tabId: 4, sessionId: "child" },
+      frameId: "child",
+      backendNodeId: 101,
+    });
+    expect(geometry).toMatchObject({
+      topBounds: {
+        x: 460,
+        y: 260,
+        width: (visible.width - 180) * 2,
+        height: (visible.height - 80) * 2,
+      },
+      actionPoint: { x: 460 + visible.width - 180, y: 260 + visible.height - 80 },
+      targetActionPoint: { x: (180 + visible.width) / 2, y: (80 + visible.height) / 2 },
+    });
+    expect(send.mock.calls.filter(([, method]) => method === "Runtime.evaluate")).toHaveLength(1);
+    expect(send.mock.calls.filter(([, method]) => method === "Page.getLayoutMetrics")).toHaveLength(
+      2,
+    );
+  });
+
+  it("shares the full viewport read across same-target frames, and refreshes it next operation", async () => {
+    const { cdp, send } = scrollbarDriver();
+    const context = new GeometryContext(cdp, 4);
+    await Promise.all([context.targetProjection("child"), context.targetProjection("same-child")]);
+    expect(send.mock.calls.filter(([, method]) => method === "Runtime.evaluate")).toHaveLength(1);
+    await new GeometryContext(cdp, 4).targetProjection("child");
+    expect(send.mock.calls.filter(([, method]) => method === "Runtime.evaluate")).toHaveLength(2);
+  });
+
+  it.each([
+    null,
+    {},
+    { width: 0, height: 100 },
+    { width: 200, height: NaN },
+  ])("rejects unavailable full viewport dimensions: %j", async (size) => {
+    const { cdp } = scrollbarDriver(undefined, size);
+    expect(await new GeometryContext(cdp, 4).targetProjection("child")).toBeNull();
+  });
+
+  it("clips an inner OOPIF against an intermediate OOPIF's occupied scrollbar strips", async () => {
+    const { cdp } = scrollbarDriver();
+    const outer = cdp.sendToTarget!;
+    cdp.sendToTarget = async (target, method, params) => {
+      if (method === "DOM.getBoxModel")
+        return { model: { content: [150, 60, 250, 60, 250, 120, 150, 120] } } as never;
+      if (target.sessionId !== "inner") return outer(target, method, params);
+      if (method === "Runtime.evaluate")
+        return { result: { value: { width: 100, height: 60 } } } as never;
+      if (method === "Page.getLayoutMetrics")
+        return { cssLayoutViewport: { clientWidth: 90, clientHeight: 50 } } as never;
+      if (method === "DOM.getContentQuads")
+        return { quads: [[0, 0, 100, 0, 100, 60, 0, 60]] } as never;
+      throw new Error(`unexpected ${method}`);
+    };
+    const graph = await cdp.getFrameGraph!(4);
+    graph.frames[2] = {
+      frameId: "inner",
+      parentFrameId: "child",
+      ownerBackendNodeId: 20,
+      target: { tabId: 4, sessionId: "inner" },
+    };
+    cdp.getFrameGraph = async () => graph;
+    expect(
+      await resolveNodeGeometry(cdp, 4, {
+        target: { tabId: 4, sessionId: "inner" },
+        frameId: "inner",
+        backendNodeId: 101,
+      }),
+    ).toMatchObject({
+      topBounds: { x: 400, y: 220, width: 70, height: 58 },
+    });
+  });
+
   it("keeps region bounds separate from polygon area", () => {
     const region = [
       rectPolygon({ x: 0, y: 0, w: 10, h: 10 }),
@@ -77,6 +208,8 @@ describe("frame geometry projection", () => {
     const cdp: CdpRunner = {
       send: send as CdpRunner["send"],
       sendToTarget: vi.fn(async (_target, method) => {
+        if (method === "Runtime.evaluate")
+          return { result: { value: { width: 200, height: 100 } } };
         if (method === "Page.getLayoutMetrics") {
           return { cssLayoutViewport: { clientWidth: 200, clientHeight: 100 } };
         }
@@ -135,6 +268,8 @@ describe("frame geometry projection", () => {
         throw new Error(`unexpected root command ${method}`);
       }) as CdpRunner["send"],
       sendToTarget: vi.fn(async (_target, method) => {
+        if (method === "Runtime.evaluate")
+          return { result: { value: { width: 200, height: 100 } } };
         if (method === "Page.getLayoutMetrics") {
           return { cssLayoutViewport: { clientWidth: 200, clientHeight: 100 } };
         }
@@ -196,6 +331,8 @@ describe("frame geometry projection", () => {
       }) as CdpRunner["send"],
       sendToTarget: vi.fn(async (_target, method) => {
         if (method === "DOM.scrollIntoViewIfNeeded") return {};
+        if (method === "Runtime.evaluate")
+          return { result: { value: { width: 200, height: 100 } } };
         if (method === "Page.getLayoutMetrics") {
           return { cssLayoutViewport: { clientWidth: 200, clientHeight: 100 } };
         }

apps/extension/src/tools/__tests__/human-loop.test.ts

@@ -433,6 +433,7 @@ describe("handleRequestHelp", () => {
       if (method === "DOM.getContentQuads") {
         return { quads: [[10, 20, 110, 20, 110, 60, 10, 60]] };
       }
+      if (method === "Runtime.evaluate") return { result: { value: { width: 200, height: 100 } } };
       if (method === "Page.getLayoutMetrics") {
         return { cssLayoutViewport: { clientWidth: 200, clientHeight: 100 } };
       }

apps/extension/src/tools/__tests__/interaction.test.ts

@@ -201,6 +201,7 @@ describe("handleClick", () => {
       if (method === "DOM.getContentQuads") {
         return { quads: [[10, 20, 110, 20, 110, 60, 10, 60]] };
       }
+      if (method === "Runtime.evaluate") return { result: { value: { width: 200, height: 100 } } };
       if (method === "Page.getLayoutMetrics") {
         return { cssLayoutViewport: { clientWidth: 200, clientHeight: 100 } };
       }
@@ -220,6 +221,7 @@ describe("handleClick", () => {
       { sessionId: "child-session", method: "DOM.scrollIntoViewIfNeeded" },
       { sessionId: "child-session", method: "DOM.getContentQuads" },
       { sessionId: "child-session", method: "Page.getLayoutMetrics" },
+      { sessionId: "child-session", method: "Runtime.evaluate" },
     ]);
     expect(fake.sent.filter((call) => call.method === "Input.dispatchMouseEvent")).toHaveLength(3);
   });

apps/extension/src/tools/__tests__/observation.test.ts

@@ -3380,6 +3380,7 @@ describe("handleSnapshot", () => {
       throw new Error(`unexpected root CDP method ${method}`);
     });
     const sendToTarget = vi.fn(async (_target, method: string) => {
+      if (method === "Runtime.evaluate") return { result: { value: { width: 400, height: 300 } } };
       if (method === "Page.getLayoutMetrics" && ownerGeometry !== "unavailable")
         return {
           visualViewport: { clientWidth: 1000 },
@@ -3695,7 +3696,8 @@ describe("handleSnapshot", () => {
     const result = await captureVomObservation(makeFrameAwareDeps().cdp, 4, "https://example.com", {
       maxTokens,
     });
-    expect(result.text.match(/@warning/g)).toHaveLength(1);
+    expect(result.text.match(/@warning/g)).toHaveLength(2);
+    expect(result.text).toContain("document identity unverified");
     expect(result.text).toContain("geometry incomplete");
     expect(result.text.startsWith("@vom 1\n")).toBe(true);
     if (maxTokens === undefined) {
@@ -3722,7 +3724,8 @@ describe("handleSnapshot", () => {
     for (const maxTokens of [undefined, 100, 0]) {
       const result = await captureVomObservation(cdp, 4, "https://example.com", { maxTokens });
       expect(result.text).toContain(`@warning observation incomplete: some ${stage} data`);
-      expect(result.text.match(/@warning/g)).toHaveLength(1);
+      expect(result.text.match(/@warning/g)).toHaveLength(2);
+      expect(result.text).toContain("document identity unverified");
       expect(result.text.startsWith("@vom 1\n")).toBe(true);
       if (maxTokens === undefined) {
         expect(result.frames.map((frame) => frame.frameId)).toEqual(["main", "child"]);
@@ -3770,7 +3773,8 @@ describe("handleSnapshot", () => {
       4,
       "https://example.com",
     );
-    expect(result.text).not.toContain("@warning");
+    expect(result.text).not.toContain("iframe geometry incomplete");
+    expect(result.text).toContain("document identity unverified");
     const node = result.matchNodes.find((item) => item.backendNodeId === 22);
     if (ownerGeometry === "clipped") expect(node?.rect).toBeNull();
     else expect(node?.rect).toEqual({ x: 120, y: 130, w: 120, h: 40 });

apps/extension/src/tools/__tests__/snapshot-coordinates.browser.test.ts

@@ -1,6 +1,7 @@
 // @vitest-environment node
 import { describe, expect, it } from "vitest";
 import type { CdpFrame, CdpFrameGraph, CdpTarget } from "@/browser-driver/frame-graph";
+import { resolveNodeGeometry } from "../frame-geometry";
 import type { CdpRunner } from "../shared";
 import { captureObservationFacts } from "../vom/capture-coordinator";
 
@@ -11,12 +12,28 @@ type Send = <T = Record<string, unknown>>(
 ) => Promise<T>;
 type Tree = { frame: { id: string; parentId?: string; name?: string }; childFrames?: Tree[] };
 type Rect = { x: number; y: number; w: number; h: number };
-type Oracle = { probe: Rect; owners: Record<string, { x: number; y: number; scale: number }> };
+type Oracle = {
+  probes: Record<string, Rect>;
+  viewport: { width: number; height: number };
+  owners: Record<string, { x: number; y: number; scale: number }>;
+};
+
+function clip(rect: Rect, viewport: Oracle["viewport"]): Rect | null {
+  const x = Math.max(0, rect.x),
+    y = Math.max(0, rect.y);
+  const right = Math.min(viewport.width, rect.x + rect.w);
+  const bottom = Math.min(viewport.height, rect.y + rect.h);
+  return right > x && bottom > y ? { x, y, w: right - x, h: bottom - y } : null;
+}
 
 // The independent oracle uses DOM border boxes and this fixture's axis-aligned
 // iframe transforms. No production snapshot conversion/projection builds expectations.
 const oracleExpression = `(() => {
-  const box = document.querySelector('#probe').getBoundingClientRect();
+  const probes = {};
+  for (const node of document.querySelectorAll('[data-geometry-probe]')) {
+    const box = node.getBoundingClientRect();
+    probes[node.id] = { x: box.x, y: box.y, w: box.width, h: box.height };
+  }
   const owners = {};
   for (const frame of document.querySelectorAll('iframe')) {
     const rect = frame.getBoundingClientRect();
@@ -28,17 +45,31 @@ const oracleExpression = `(() => {
       scale,
     };
   }
-  return { probe: { x: box.x, y: box.y, w: box.width, h: box.height }, owners };
+  return { probes, viewport: { width: document.documentElement.clientWidth, height: document.documentElement.clientHeight }, owners };
 })()`;
 
 describe.skipIf(!process.env.BSK_GEOMETRY_CHROME)("real DOMSnapshot coordinate contract", () => {
-  it.each([
-    { deviceScale: 1, zoom: 1 },
-    { deviceScale: 0.8, zoom: 1 },
-    { deviceScale: 1, zoom: 1.25 },
-    { deviceScale: 2, zoom: 1 },
-    { deviceScale: 2, zoom: 0.8 },
-  ])("matches DOM geometry at device scale $deviceScale and zoom $zoom", async (configuration) => {
+  it.each(
+    [
+      { deviceScale: 1, zoom: 1 },
+      { deviceScale: 0.8, zoom: 1 },
+      { deviceScale: 1, zoom: 1.25 },
+      { deviceScale: 2, zoom: 1 },
+      { deviceScale: 2, zoom: 0.8 },
+    ]
+      .flatMap((configuration) => [
+        { ...configuration, fixture: "snapshot-coordinates", scrollbars: "none" },
+        { ...configuration, fixture: "oopif-scrollbars", scrollbars: "both" },
+      ])
+      .concat(
+        ["vertical", "horizontal", "none"].map((scrollbars) => ({
+          deviceScale: 1,
+          zoom: 1,
+          fixture: "oopif-scrollbars",
+          scrollbars,
+        })),
+      ),
+  )("$fixture: device scale $deviceScale, zoom $zoom, scrollbars $scrollbars", async (configuration) => {
     const evalRoot = new URL("../../../../../evals/browser/", import.meta.url);
     const { createEvalServer } = await import(new URL("lib/server.mjs", evalRoot).href);
     const { withChrome } = await import(
@@ -59,7 +90,9 @@ describe.skipIf(!process.env.BSK_GEOMETRY_CHROME)("real DOMSnapshot coordinate c
           );
           await send(
             "Page.navigate",
-            { url: `${baseUrl}/snapshot-coordinates?run=coordinates` },
+            {
+              url: `${baseUrl}/${configuration.fixture}?run=coordinates&scrollbars=${configuration.scrollbars}`,
+            },
             rootSession,
           );
           await expect
@@ -86,7 +119,7 @@ describe.skipIf(!process.env.BSK_GEOMETRY_CHROME)("real DOMSnapshot coordinate c
             });
             sessions.push(sessionId);
           }
-          expect(sessions.length).toBe(2); // The cross-site fixture must actually be an OOPIF.
+          expect(sessions.length).toBe(configuration.fixture === "oopif-scrollbars" ? 3 : 2);
           const frames: CdpFrame[] = [];
           const names = new Map<string, string>();
           const sessionFor = (target: CdpTarget) => target.sessionId ?? rootSession;
@@ -107,7 +140,7 @@ describe.skipIf(!process.env.BSK_GEOMETRY_CHROME)("real DOMSnapshot coordinate c
             };
             visit(frameTree);
           }
-          expect(frames).toHaveLength(5);
+          expect(frames).toHaveLength(configuration.fixture === "oopif-scrollbars" ? 3 : 5);
           for (const frame of frames) {
             if (!frame.parentFrameId) continue;
             const parent = frames.find((item) => item.frameId === frame.parentFrameId)!;
@@ -127,9 +160,15 @@ describe.skipIf(!process.env.BSK_GEOMETRY_CHROME)("real DOMSnapshot coordinate c
             },
             sendToTarget: (target, method, params) => {
               calls.push(`${target.sessionId ?? target.tabId}:${method}`);
+              if (
+                method === "Runtime.evaluate" &&
+                (params as { expression?: string })?.expression?.includes("window.innerWidth")
+              )
+                calls.push(`${target.sessionId ?? target.tabId}:viewport-size`);
               return send(method, params, sessionFor(target));
             },
             getFrameGraph: async () => graph,
+            getAttachmentId: () => rootSession,
           };
           const oracles = new Map<string, Oracle>();
           for (const frame of frames) {
@@ -178,47 +217,130 @@ describe.skipIf(!process.env.BSK_GEOMETRY_CHROME)("real DOMSnapshot coordinate c
             );
             oracles.set(frame.frameId, reply.result.value);
           }
+          const childViewport = await send<{
+            result: {
+              value: { width: number; height: number; clientWidth: number; clientHeight: number };
+            };
+          }>(
+            "Runtime.evaluate",
+            {
+              expression:
+                "({ width: innerWidth, height: innerHeight, clientWidth: document.documentElement.clientWidth, clientHeight: document.documentElement.clientHeight })",
+              returnByValue: true,
+            },
+            sessions[1],
+          );
+          for (const dimension of ["Width", "Height"] as const) {
+            const occupied =
+              childViewport.result.value[dimension === "Width" ? "width" : "height"] -
+              childViewport.result.value[`client${dimension}`];
+            if (
+              configuration.scrollbars === "both" ||
+              configuration.scrollbars === (dimension === "Width" ? "vertical" : "horizontal")
+            )
+              expect(occupied).toBeGreaterThan(0);
+            else expect(occupied).toBe(0);
+          }
           const facts = await captureObservationFacts(cdp, 1);
           expect(facts.issues).toEqual([]);
-          for (const frame of frames) {
-            const node = facts.documents
-              .find((doc) => doc.frame.frameId === frame.frameId)
-              ?.domNodes.find((node) => node.attrs.id === "probe");
-            expect(node, `missing probe in ${names.get(frame.frameId) || "root"}`).toBeDefined();
-            const local = oracles.get(frame.frameId)!.probe;
-            const top = { ...local };
-            let current = frame;
-            while (current.parentFrameId) {
-              const owner = oracles.get(current.parentFrameId)!.owners[names.get(current.frameId)!];
-              top.x = owner.x + top.x * owner.scale;
-              top.y = owner.y + top.y * owner.scale;
-              top.w *= owner.scale;
-              top.h *= owner.scale;
-              current = frames.find((item) => item.frameId === current.parentFrameId)!;
-            }
-            expect(
-              node!.rect,
-              JSON.stringify({
-                frame: names.get(frame.frameId),
-                local,
-                top,
-                viewport: facts.viewport,
-              }),
-            ).not.toBeNull();
-            for (const key of ["x", "y", "w", "h"] as const) {
-              expect(
-                Math.abs(node!.localRect![key] - local[key]),
-                `${names.get(frame.frameId)} local ${key}`,
-              ).toBeLessThan(2);
-              expect(
-                Math.abs(node!.rect![key] - top[key]),
-                `${names.get(frame.frameId)} top ${key}`,
-              ).toBeLessThan(2);
-            }
-          }
           expect(calls.filter((call) => call.endsWith(":Page.getLayoutMetrics"))).toHaveLength(
             sessions.length,
           );
+          // Identity verification also uses Runtime.evaluate; count the full viewport reads separately.
+          const viewportReadsBeforeLive = calls.filter((call) => call.endsWith(":viewport-size"));
+          expect(new Set(viewportReadsBeforeLive).size).toBe(viewportReadsBeforeLive.length);
+          expect(viewportReadsBeforeLive.length).toBeLessThanOrEqual(sessions.length - 1);
+          for (const frame of frames) {
+            for (const [id, local] of Object.entries(oracles.get(frame.frameId)!.probes)) {
+              const node = facts.documents
+                .find((doc) => doc.frame.frameId === frame.frameId)
+                ?.domNodes.find((node) => node.attrs.id === id);
+              expect(node, `missing ${id} in ${names.get(frame.frameId) || "root"}`).toBeDefined();
+              let top = clip(local, oracles.get(frame.frameId)!.viewport);
+              let current = frame;
+              while (top && current.parentFrameId) {
+                const parentOracle = oracles.get(current.parentFrameId)!;
+                const owner = parentOracle.owners[names.get(current.frameId)!];
+                top = clip(
+                  {
+                    x: owner.x + top.x * owner.scale,
+                    y: owner.y + top.y * owner.scale,
+                    w: top.w * owner.scale,
+                    h: top.h * owner.scale,
+                  },
+                  parentOracle.viewport,
+                );
+                current = frames.find((item) => item.frameId === current.parentFrameId)!;
+              }
+              for (const key of ["x", "y", "w", "h"] as const)
+                expect(
+                  Math.abs(node!.localRect![key] - local[key]),
+                  `${names.get(frame.frameId)} ${id} local ${key}`,
+                ).toBeLessThan(2);
+              if (!top) {
+                expect(node!.rect, `${id} must be clipped out`).toBeNull();
+                if (configuration.fixture === "oopif-scrollbars")
+                  expect(
+                    await resolveNodeGeometry(cdp, 1, {
+                      target: frame.target,
+                      frameId: frame.frameId,
+                      backendNodeId: node!.backendNodeId,
+                    }),
+                  ).toMatchObject({ code: "permission_denied" });
+                continue;
+              }
+              expect(node!.rect).not.toBeNull();
+              for (const key of ["x", "y", "w", "h"] as const)
+                expect(
+                  Math.abs(node!.rect![key] - top[key]),
+                  `${names.get(frame.frameId)} ${id} top ${key}`,
+                ).toBeLessThan(2);
+              if (configuration.fixture !== "oopif-scrollbars") continue;
+              const live = await resolveNodeGeometry(cdp, 1, {
+                target: frame.target,
+                frameId: frame.frameId,
+                backendNodeId: node!.backendNodeId,
+              });
+              if ("code" in live) throw new Error(live.message);
+              for (const [key, liveKey] of [
+                ["x", "x"],
+                ["y", "y"],
+                ["w", "width"],
+                ["h", "height"],
+              ] as const)
+                expect(
+                  Math.abs(live.topBounds[liveKey] - top[key]),
+                  `${id} live ${key}`,
+                ).toBeLessThan(2);
+              const before = server.snapshot("coordinates").events.length;
+              for (const type of ["mousePressed", "mouseReleased"])
+                await send(
+                  "Input.dispatchMouseEvent",
+                  { type, ...live.actionPoint, button: "left", clickCount: 1 },
+                  rootSession,
+                );
+              await expect
+                .poll(
+                  () =>
+                    server
+                      .snapshot("coordinates")
+                      .events.slice(before)
+                      .some(
+                        (event: { type: string; path: string; data: { probe?: string } }) =>
+                          event.type === "geometry.clicked" &&
+                          event.data.probe === id &&
+                          event.path ===
+                            (frame.parentFrameId
+                              ? names.get(frame.frameId) === "nested"
+                                ? "/oopif-scrollbars/nested"
+                                : "/oopif-scrollbars/frame"
+                              : "/oopif-scrollbars"),
+                      ),
+                  { timeout: 3000 },
+                )
+                .toBe(true);
+            }
+          }
           const metrics = await send<{
             cssVisualViewport: { zoom: number };
             visualViewport: { clientWidth: number };

apps/extension/src/tools/frame-geometry.ts

@@ -161,7 +161,8 @@ export async function resolveNodeGeometry(
         return geometryError(`could not resolve frame geometry for ${address.frameId}`);
       topVisibleRegions = projectRegionToViewport(localRegion, projection);
       if (address.target.sessionId) {
-        const localViewport = projection.edges[0]?.sourceViewport ?? projection.topViewport;
+        const localViewport = await context.viewport(address.target);
+        if (!localViewport) return geometryError("could not resolve target viewport geometry");
         const localVisibleRegions = localRegion
           .map((polygon) =>
             clipPolygon(

apps/extension/src/tools/geometry/frame-context.ts

@@ -9,8 +9,10 @@ import {
   type Polygon,
   type ProjectiveEdge,
   parseCdpQuad,
+  projectPolygon,
   type Quad,
   type Size,
+  viewportPolygon,
 } from "../geometry";
 import { type CdpRunner, sendToCdpTarget } from "../shared";
 import type { CoordinateOwner, CssViewport, SnapshotProjectionResult } from "./coordinate-types";
@@ -67,6 +69,7 @@ export function cssViewport(metrics: LayoutMetrics): CssViewport {
 /** One read-only measurement phase. Discard after scrolling or any later operation. */
 export class GeometryContext {
   private readonly metrics = new Map<string, Promise<LayoutMetrics>>();
+  private readonly frameViewports = new Map<string, Promise<Size | null>>();
   private readonly owners = new Map<string, Promise<Quad | null>>();
   private readonly projections = new Map<string, Promise<GeometryProjection | null>>();
   private readonly snapshotOwners = new Map<string, Promise<{ quad: Quad; size: Size } | null>>();
@@ -157,6 +160,35 @@ export class GeometryContext {
       : null;
   }
 
+  /** The full OOPIF viewport maps to its owner's content quad. Layout metrics
+   * exclude occupied scrollbars and remain the clipping boundary, not the scale. */
+  private frameViewport(target: CdpTarget): Promise<Size | null> {
+    const key = cdpTargetKey(target);
+    let promise = this.frameViewports.get(key);
+    if (!promise) {
+      promise = this.request<{ result?: { value?: Size }; exceptionDetails?: unknown }>(
+        target,
+        "Runtime.evaluate",
+        {
+          expression: "({ width: window.innerWidth, height: window.innerHeight })",
+          returnByValue: true,
+        },
+      ).then(({ result, exceptionDetails }) => {
+        const size = result?.value;
+        return !exceptionDetails &&
+          size &&
+          Number.isFinite(size.width) &&
+          Number.isFinite(size.height) &&
+          size.width > 0 &&
+          size.height > 0
+          ? size
+          : null;
+      });
+      this.frameViewports.set(key, promise);
+    }
+    return promise;
+  }
+
   ownerContent(target: CdpTarget, backendNodeId: number): Promise<Quad | null> {
     const key = `${cdpTargetKey(target)}:${backendNodeId}`;
     let promise = this.owners.get(key);
@@ -342,12 +374,19 @@ export class GeometryContext {
       const parent = frames.get(root.parentFrameId);
       if (!parent || root.ownerBackendNodeId === undefined) return null;
       const destinationQuad = await this.ownerContent(parent.target, root.ownerBackendNodeId);
-      const source = await this.viewport(root.target);
+      if (!destinationQuad) return null;
+      const source = await this.frameViewport(root.target);
+      const visible = await this.viewport(root.target);
       const parentRoot = this.targetRoot(frames, parent);
-      if (!destinationQuad || !source || !parentRoot) return null;
+      if (!source || !visible || !parentRoot) return null;
       const destinationClips = await this.clips(frames, parent, parentRoot);
       if (!destinationClips) return null;
-      edges.push({ sourceViewport: source, destinationQuad, destinationClips });
+      const edge = { sourceViewport: source, destinationQuad, destinationClips };
+      // Keep scrollbar strips clipped at every target boundary, including
+      // intermediate OOPIFs. Project the clip with the same full-viewport scale.
+      if (source.width !== visible.width || source.height !== visible.height)
+        destinationClips.push(projectPolygon(viewportPolygon(visible), edge));
+      edges.push(edge);
       root = parentRoot;
     }
     const topViewport = await this.viewport(root.target);

apps/extension/src/tools/observation.ts

@@ -938,6 +938,18 @@ export async function captureVomObservation(
     notices.push(
       `@warning observation incomplete: some ${incompleteStages.join(", ")} data is unavailable or omitted.`,
     );
+  if (
+    facts.issues.some(
+      (issue) => issue.stage === "identity" && issue.reason !== "identity-unverified",
+    )
+  )
+    notices.push(
+      "@warning observation incomplete: some documents were omitted because their identity changed or could not be revalidated.",
+    );
+  if (facts.issues.some((issue) => issue.reason === "identity-unverified"))
+    notices.push(
+      "@warning document identity unverified: some retained documents could not be checked for changes during capture.",
+    );
   const captureNotice = notices.join("\n");
   const rendered = renderVom(decoratedScene, {
     maxDepth: options.maxDepth,

apps/extension/src/tools/shared.ts

@@ -55,6 +55,7 @@ export interface CdpRunner {
   sendToTarget?<T = unknown>(target: CdpTarget, method: string, params?: object): Promise<T>;
   detach?(tabId: number): Promise<void>;
   getFrameGraph?(tabId: number): Promise<CdpFrameGraph>;
+  getAttachmentId?(tabId: number): string | undefined;
   ensureAttachedToUrl?(tabId: number, expectedUrl: string | undefined): Promise<void>;
   trackSessionTab?(sessionId: string, tabId: number): void;
   releaseSessionTab?(sessionId: string, tabId: number): Promise<void>;

apps/extension/src/tools/vom/__tests__/capture-coordinator.test.ts

@@ -2,13 +2,22 @@ import { describe, expect, it, vi } from "vitest";
 import type { CdpFrame, CdpTarget } from "@/browser-driver/frame-graph";
 import { cdpTargetKey } from "@/browser-driver/frame-graph";
 import { OVERLAY_HOST_MARKER_ATTR } from "@/lib/overlay-bridge";
+import { captureVomObservation } from "../../observation";
 import type { CdpRunner } from "../../shared";
 import { captureObservationFacts, semanticCapture } from "../capture-coordinator";
 import { buildSemanticGraph } from "../semantic-graph/build";
 import { REQUESTED_STYLES, type SnapshotReply } from "../snapshot";
 
 function fixture(
-  options: { frames?: CdpFrame[]; fail?: string; omitDocument?: string; overlay?: string } = {},
+  options: {
+    frames?: CdpFrame[];
+    after?: Record<string, { element?: number; missing?: boolean; unreadable?: boolean }>;
+    fail?: string;
+    missingIdentity?: boolean;
+    omitDocument?: string;
+    attachmentChanged?: boolean;
+    overlay?: string;
+  } = {},
 ) {
   const frames = options.frames ?? [
     { frameId: "main", target: { tabId: 4 } },
@@ -34,7 +43,10 @@ function fixture(
   const elements = new Map(
     frames.map((frame, i) => [frame.frameId, frame.target.sessionId ? 1 : i * 10 + 1]),
   );
+  const contexts = new Map(frames.map((frame, i) => [i + 1, frame.frameId]));
   const logs: Array<{ target: CdpTarget; method: string; params: Record<string, unknown> }> = [];
+  let snapshots = 0;
+  const targetCount = new Set(frames.map((frame) => cdpTargetKey(frame.target))).size;
   const send = vi.fn(
     async <T>(target: CdpTarget, method: string, params: object = {}): Promise<T> => {
       logs.push({ target, method, params: params as Record<string, unknown> });
@@ -42,6 +54,27 @@ function fixture(
       if (options.fail === `${target.sessionId ?? "main"}:${method}`)
         throw new Error("fixture failure");
       let result: unknown = {};
+      if (method === "Page.createIsolatedWorld")
+        result = {
+          executionContextId: frames.findIndex((frame) => frame.frameId === args.frameId) + 1,
+        };
+      if (method === "Runtime.evaluate" && args.contextId) {
+        const id = contexts.get(Number(args.contextId))!;
+        const change = options.after?.[id];
+        result =
+          options.missingIdentity || change?.unreadable
+            ? {}
+            : {
+                result: {
+                  deepSerializedValue: change?.missing
+                    ? { type: "null" }
+                    : {
+                        type: "node",
+                        value: { backendNodeId: change?.element ?? elements.get(id) },
+                      },
+                },
+              };
+      }
       if (method === "Page.getLayoutMetrics")
         result = {
           visualViewport: { clientWidth: 1000 },
@@ -49,6 +82,7 @@ function fixture(
           cssLayoutViewport: { clientWidth: 1000, clientHeight: 800 },
         };
       if (method === "DOMSnapshot.captureSnapshot") {
+        snapshots++;
         expect((params as { computedStyles: unknown }).computedStyles).toEqual(REQUESTED_STYLES);
         result = {
           strings: [
@@ -137,6 +171,12 @@ function fixture(
     },
   );
   const cdp: CdpRunner = {
+    getAttachmentId: () =>
+      options.missingIdentity
+        ? undefined
+        : options.attachmentChanged && snapshots === targetCount
+          ? "new-attachment"
+          : "attachment",
     getFrameGraph: async () => ({ rootFrameId: frames[0].frameId, frames }),
     send: (tabId, method, params) =>
       (send as NonNullable<CdpRunner["sendToTarget"]>)({ tabId }, method, params),
@@ -181,6 +221,9 @@ describe("captureObservationFacts", () => {
     expect(logs.filter((call) => call.method === "DOMSnapshot.captureSnapshot")).toHaveLength(2);
     expect(logs.filter((call) => call.method === "Accessibility.enable")).toHaveLength(2);
     expect(logs.filter((call) => call.method === "Accessibility.getFullAXTree")).toHaveLength(4);
+    expect(facts.documents.every((doc) => doc.identity)).toBe(true);
+    expect(logs.filter((call) => call.method === "DOM.describeNode")).toHaveLength(0);
+    expect(logs.filter((call) => call.method === "Page.createIsolatedWorld")).toHaveLength(4);
     const main = facts.documents.find((doc) => doc.frame.frameId === "main")!;
     const remote = facts.documents.find((doc) => doc.frame.frameId === "remote")!;
     expect(main.index.nodes.get(2)).not.toBe(remote.index.nodes.get(2));
@@ -191,6 +234,219 @@ describe("captureObservationFacts", () => {
     expect(facts.finishedAt).toBeGreaterThanOrEqual(facts.startedAt);
   });
 
+  it.each([
+    { element: 99 },
+    { missing: true },
+  ])("isolates changed child identity %j and dependent descendants", async (change) => {
+    const { cdp } = fixture({ after: { same: change } });
+    const facts = await captureObservationFacts(cdp, 4);
+    expect(facts.documents.map((doc) => doc.frame.frameId)).toEqual(["main", "remote"]);
+    expect(facts.issues).toContainEqual(
+      expect.objectContaining({ frameId: "same", reason: "document-changed" }),
+    );
+  });
+
+  it.each([
+    { after: { main: { element: 99 } } },
+    { attachmentChanged: true },
+  ])("rejects a root replacement or reattachment %j", async (options) => {
+    await expect(captureObservationFacts(fixture(options).cdp, 4)).rejects.toThrow(
+      "document identity",
+    );
+  });
+
+  it.each([
+    "main",
+    "same",
+  ])("does not publish a previously identified %s document after identity reads fail", async (frameId) => {
+    const { cdp } = fixture({ after: { [frameId]: { unreadable: true } } });
+    if (frameId === "main")
+      await expect(captureObservationFacts(cdp, 4)).rejects.toThrow("document identity");
+    else {
+      const facts = await captureObservationFacts(cdp, 4);
+      expect(facts.documents.map((doc) => doc.frame.frameId)).toEqual(["main", "remote"]);
+      expect(facts.issues).toContainEqual(
+        expect.objectContaining({ frameId, reason: "identity-unavailable" }),
+      );
+    }
+  });
+
+  it("validates newly discovered snapshot documents without a pre-snapshot identity read", async () => {
+    const { cdp, logs } = fixture();
+    const graph = await cdp.getFrameGraph!(4);
+    cdp.getFrameGraph = async () => ({ ...graph, frames: graph.frames.slice(0, 1) });
+    const facts = await captureObservationFacts(cdp, 4);
+    expect(facts.documents.map((doc) => doc.frame.frameId)).toEqual(["main", "same", "nested"]);
+    expect(facts.documents.every((doc) => doc.identity)).toBe(true);
+    expect(logs.filter((call) => call.method === "Page.createIsolatedWorld")).toHaveLength(3);
+    expect(logs.findIndex((call) => call.method === "Page.createIsolatedWorld")).toBeGreaterThan(
+      logs.findIndex((call) => call.method === "Accessibility.getFullAXTree"),
+    );
+  });
+
+  it("rejects a snapshot root that no longer matches the current frame root", async () => {
+    const { cdp } = fixture();
+    const original = cdp.sendToTarget!;
+    cdp.sendToTarget = async (target, method, params) => {
+      const result = await original(target, method, params);
+      if (method === "DOMSnapshot.captureSnapshot" && !target.sessionId) {
+        const snapshot = result as {
+          documents: { frameId: string; nodes: { backendNodeId: number[] } }[];
+        };
+        snapshot.documents[0].nodes.backendNodeId[2] = 999;
+      }
+      return result as never;
+    };
+    cdp.send = (tabId, method, params) => cdp.sendToTarget!({ tabId }, method, params);
+    await expect(captureObservationFacts(cdp, 4)).rejects.toThrow("document identity");
+  });
+
+  it("starts after-identity reads only after every target finishes and propagates cancellation during identity cleanup", async () => {
+    const { cdp, logs } = fixture();
+    const controller = new AbortController();
+    const original = cdp.sendToTarget!;
+    let identityCleanup = 0;
+    cdp.sendToTarget = async (target, method, params) => {
+      if (method === "Page.createIsolatedWorld") {
+        expect(logs.filter((call) => call.method === "Accessibility.getFullAXTree")).toHaveLength(
+          4,
+        );
+      }
+      const result = await original(target, method, params);
+      if (
+        method === "Runtime.releaseObjectGroup" &&
+        String((params as { objectGroup?: string })?.objectGroup).startsWith(
+          "bsk-document-identity-",
+        ) &&
+        target.sessionId === "remote"
+      ) {
+        if (++identityCleanup === 1) controller.abort();
+      }
+      return result as never;
+    };
+    cdp.send = (tabId, method, params) => cdp.sendToTarget!({ tabId }, method, params);
+    await expect(captureObservationFacts(cdp, 4, controller.signal)).rejects.toMatchObject({
+      name: "AbortError",
+    });
+    expect(identityCleanup).toBe(1);
+  });
+
+  it.each([
+    1, 10, 100,
+  ])("bounds identity reads for %i same-target documents after snapshot and AX collection", async (count) => {
+    const frames: CdpFrame[] = Array.from({ length: count }, (_, i) => ({
+      frameId: `frame-${i}`,
+      target: { tabId: 4 },
+      ...(i ? { parentFrameId: "frame-0", ownerBackendNodeId: 90000 + i } : {}),
+    }));
+    const { cdp, logs } = fixture({ frames });
+    const original = cdp.sendToTarget!;
+    let active = 0;
+    let peak = 0;
+    let released = 0;
+    cdp.sendToTarget = async (target, method, params) => {
+      if (method === "Page.createIsolatedWorld") {
+        peak = Math.max(peak, ++active);
+        await new Promise((resolve) => setTimeout(resolve, 1));
+      }
+      if (method === "DOMSnapshot.captureSnapshot") {
+        expect(active).toBe(0);
+        expect(released).toBe(0);
+      }
+      if (method === "Page.createIsolatedWorld") {
+        expect(logs.filter((call) => call.method === "Accessibility.getFullAXTree")).toHaveLength(
+          count,
+        );
+      }
+      const result = await original(target, method, params);
+      if (
+        method === "Runtime.releaseObjectGroup" &&
+        String((params as { objectGroup?: string })?.objectGroup).startsWith(
+          "bsk-document-identity-",
+        )
+      ) {
+        active--;
+        released++;
+      }
+      return result as never;
+    };
+    cdp.send = (tabId, method, params) => cdp.sendToTarget!({ tabId }, method, params);
+    const facts = await captureObservationFacts(cdp, 4);
+    expect(facts.documents.every((doc) => doc.identity)).toBe(true);
+    expect(peak).toBe(Math.min(count, 4));
+    expect(active).toBe(0);
+    expect(released).toBe(count);
+    for (const method of [
+      "Page.createIsolatedWorld",
+      "Runtime.evaluate",
+      "Runtime.releaseObjectGroup",
+    ])
+      expect(logs.filter((call) => call.method === method)).toHaveLength(count);
+    expect(logs.filter((call) => call.method === "DOMSnapshot.captureSnapshot")).toHaveLength(1);
+    expect(logs.filter((call) => call.method === "Page.getFrameTree")).toHaveLength(0);
+  });
+
+  it("joins identity cleanup on cancellation without starting queued frames", async () => {
+    const frames: CdpFrame[] = Array.from({ length: 5 }, (_, i) => ({
+      frameId: `frame-${i}`,
+      target: { tabId: 4 },
+      ...(i ? { parentFrameId: "frame-0", ownerBackendNodeId: 90000 + i } : {}),
+    }));
+    const { cdp, logs } = fixture({ frames });
+    const original = cdp.sendToTarget!;
+    const controller = new AbortController();
+    let release!: () => void;
+    const gate = new Promise<void>((resolve) => {
+      release = resolve;
+    });
+    let ready!: () => void;
+    const blocked = new Promise<void>((resolve) => {
+      ready = resolve;
+    });
+    let held = 0;
+    cdp.sendToTarget = async (target, method, params) => {
+      const result = await original(target, method, params);
+      if (
+        method === "Runtime.releaseObjectGroup" &&
+        String((params as { objectGroup?: string })?.objectGroup).startsWith(
+          "bsk-document-identity-",
+        )
+      ) {
+        if (++held === 4) ready();
+        await gate;
+      }
+      return result as never;
+    };
+    cdp.send = (tabId, method, params) => cdp.sendToTarget!({ tabId }, method, params);
+    let settled = false;
+    const pending = captureObservationFacts(cdp, 4, controller.signal).finally(() => {
+      settled = true;
+    });
+    const rejected = expect(pending).rejects.toMatchObject({ name: "AbortError" });
+    await blocked;
+    controller.abort();
+    await Promise.resolve();
+    expect(settled).toBe(false);
+    release();
+    await rejected;
+    expect(held).toBe(4);
+    expect(logs.filter((call) => call.method === "Page.createIsolatedWorld")).toHaveLength(4);
+  });
+
+  it.each([
+    [{ after: { same: { element: 99 } } }, "omitted", false],
+    [{ after: { same: { unreadable: true } } }, "omitted", false],
+    [{ missingIdentity: true }, "document identity unverified", true],
+    [{}, "", true],
+  ] as const)("publishes identity integrity without silently losing content %j", async (options, notice, retained) => {
+    const { cdp } = fixture(options);
+    const result = await captureVomObservation(cdp, 4, "https://example.com");
+    expect(result.frames.some((frame) => frame.frameId === "same")).toBe(retained);
+    if (notice) expect(result.text).toContain(notice);
+    else expect(result.text).not.toContain("identity");
+    if (!retained) expect(result.text).not.toContain("document identity unverified");
+  });
+
   it("does not retry failed or missing documents and retains valid AX-only semantics", async () => {
     const { cdp, logs } = fixture({
       fail: "remote:DOMSnapshot.captureSnapshot",
@@ -209,6 +465,12 @@ describe("captureObservationFacts", () => {
     );
   });
 
+  it("keeps missing identity explicit without manufacturing a verified document", async () => {
+    const facts = await captureObservationFacts(fixture({ missingIdentity: true }).cdp, 4);
+    expect(facts.documents.every((doc) => !doc.identity)).toBe(true);
+    expect(facts.issues.filter((issue) => issue.reason === "identity-unverified")).toHaveLength(4);
+  });
+
   it("excludes overlay AX in its own document without excluding equal IDs elsewhere", async () => {
     const facts = await captureObservationFacts(fixture({ overlay: "remote" }).cdp, 4);
     const { documents } = semanticCapture(facts);
@@ -393,6 +655,7 @@ function childSnapshot(frameId: string, backendNodeId: number) {
 describe("OOPIF capture", () => {
   it("captures and positions multiple OOPIF documents missing from the root snapshot", async () => {
     const sendToTarget = vi.fn(async (target, method) => {
+      if (method === "Runtime.evaluate") return { result: { value: { width: 300, height: 200 } } };
       if (method === "Page.getLayoutMetrics") {
         return {
           visualViewport: { clientWidth: 1000 },
@@ -906,7 +1169,7 @@ describe("sibling frame measurement scheduling", () => {
       return original(tabId, method, params);
     };
     const captured = await captureObservationFacts(fixture.cdp, 4);
-    expect(captured.issues).toEqual([]);
+    expect(captured.issues.filter((issue) => issue.stage === "geometry")).toEqual([]);
     expect(captured.documents.map((doc) => doc.frame.frameId)).toEqual(
       Array.from({ length: 8 }, (_, i) => `frame-${i}`),
     );

apps/extension/src/tools/vom/capture-coordinator.ts

@@ -11,7 +11,8 @@ import {
   isAbortError as isCaptureAbort,
   throwIfAborted as throwCaptureAborted,
 } from "./capture-abort";
-import type { CapturedSceneInput } from "./facts";
+import { verifyDocumentIdentity } from "./document-identity";
+import type { CapturedSceneInput, DocumentIdentity } from "./facts";
 import { buildDocumentIndex, type CaptureIssue, type ObservationFacts } from "./facts";
 import { enrichFormControlStates } from "./form-capture";
 import {
@@ -26,6 +27,7 @@ import { describeSnapshotFrames, REQUESTED_STYLES, type SnapshotReply } from "./
 interface TargetBatch<T extends FrameOwnedAxNode> {
   target: CdpTarget;
   frames: CdpFrame[];
+  snapshotAttachmentId?: string;
   documents: NormalizedFrameDocument[];
   ax: FrameAxBatch<T>[];
   fallbackExcluded: Set<number>;
@@ -121,6 +123,7 @@ export async function captureObservationFacts<T extends FrameOwnedAxNode>(
         throwCaptureAborted(signal);
         await scoped.send(tabId, "DOMSnapshot.enable", {});
         throwCaptureAborted(signal);
+        batch.snapshotAttachmentId = cdp.getAttachmentId?.(tabId);
         const snapshot = await scoped.send<SnapshotReply>(tabId, "DOMSnapshot.captureSnapshot", {
           computedStyles: REQUESTED_STYLES,
           includePaintOrder: true,
@@ -246,6 +249,53 @@ export async function captureObservationFacts<T extends FrameOwnedAxNode>(
   const rootBatch = batches.find((batch) => !batch.target.sessionId);
   const rootFrameId =
     rootBatch?.rootFrameId ?? graph?.rootFrameId ?? rootBatch?.frames[0]?.frameId ?? "root";
+  const ownershipInvalid = new Set(invalid);
+  const identities = new Map<string, DocumentIdentity>();
+  const selected = new Map(currentFrames.map((frame) => [frame.frameId, frame]));
+  const checks = batches.flatMap((batch) => {
+    const docs = new Map(batch.documents.map((doc) => [doc.frame.frameId, doc]));
+    return batch.frames
+      .filter(
+        (frame) =>
+          !invalid.has(frame.frameId) &&
+          cdpTargetKey(selected.get(frame.frameId)!.target) === cdpTargetKey(batch.target),
+      )
+      .map((frame) => ({ batch, frame, doc: docs.get(frame.frameId) }));
+  });
+  await collectTasks(
+    checks,
+    async ({ batch, frame, doc }) => {
+      throwCaptureAborted(signal);
+      if (!batch.snapshotAttachmentId || doc?.documentElementBackendNodeId === undefined) {
+        issues.push({
+          target: frame.target,
+          frameId: frame.frameId,
+          stage: "identity",
+          reason: "identity-unverified",
+        });
+        return;
+      }
+      const identity: DocumentIdentity = {
+        attachmentId: batch.snapshotAttachmentId,
+        target: frame.target,
+        frameId: frame.frameId,
+        documentElementBackendNodeId: doc.documentElementBackendNodeId,
+      };
+      const verified = await verifyDocumentIdentity(cdp, identity, signal);
+      const status = cdp.getAttachmentId?.(tabId) === identity.attachmentId ? verified : "changed";
+      if (status === "current") identities.set(frame.frameId, identity);
+      else {
+        invalid.add(frame.frameId);
+        issues.push({
+          target: frame.target,
+          frameId: frame.frameId,
+          stage: "identity",
+          reason: status === "changed" ? "document-changed" : "identity-unavailable",
+        });
+      }
+    },
+    signal,
+  );
   const children = new Map<string, string[]>();
   for (const frame of currentFrames) {
     if (!frame.parentFrameId) continue;
@@ -263,7 +313,7 @@ export async function captureObservationFacts<T extends FrameOwnedAxNode>(
     }
   }
   for (const frame of currentFrames) {
-    if (invalid.has(frame.frameId))
+    if (ownershipInvalid.has(frame.frameId))
       issues.push({
         target: frame.target,
         frameId: frame.frameId,
@@ -271,7 +321,12 @@ export async function captureObservationFacts<T extends FrameOwnedAxNode>(
         reason: "frame-ownership-unresolved",
       });
   }
-  if (invalid.has(rootFrameId)) throw new Error("observation root document ownership is ambiguous");
+  if (invalid.has(rootFrameId))
+    throw new Error(
+      ownershipInvalid.has(rootFrameId)
+        ? "observation root document ownership is ambiguous"
+        : "observation document identity changed or could not be verified; observe again",
+    );
   const frames = currentFrames.filter((frame) => !invalid.has(frame.frameId));
   const frameById = new Map(frames.map((frame) => [frame.frameId, frame]));
   const belongs = (frame: CdpFrame) => {
@@ -319,6 +374,7 @@ export async function captureObservationFacts<T extends FrameOwnedAxNode>(
     } = document;
     facts.push({
       frame,
+      identity: identities.get(document.frameId),
       index: fallback?.size ? { ...index, excludedBackendNodeIds: fallback } : index,
       domNodes,
       axNodes,

apps/extension/src/tools/vom/document-identity.ts

@@ -0,0 +1,53 @@
+import type { CdpRunner } from "../shared";
+import { sendToCdpTarget } from "../shared";
+import { isAbortError, throwIfAborted } from "./capture-abort";
+import type { DocumentIdentity } from "./facts";
+
+/** Compare the snapshot root with the current root in that exact frame.
+ * Deep serialization supplies the backend ID without a separate describeNode. */
+export async function verifyDocumentIdentity(
+  cdp: CdpRunner,
+  identity: DocumentIdentity,
+  signal?: AbortSignal,
+): Promise<"current" | "changed" | "unavailable"> {
+  const attached = () => cdp.getAttachmentId?.(identity.target.tabId) === identity.attachmentId;
+  throwIfAborted(signal);
+  if (!attached()) return "changed";
+  const objectGroup = `bsk-document-identity-${crypto.randomUUID()}`;
+  const send = <T>(method: string, params: object) => {
+    throwIfAborted(signal);
+    return sendToCdpTarget<T>(cdp, identity.target, method, params);
+  };
+  try {
+    const world = await send<{ executionContextId: number }>("Page.createIsolatedWorld", {
+      frameId: identity.frameId,
+      worldName: "bsk-document-identity",
+    });
+    const reply = await send<{
+      result?: { deepSerializedValue?: { type: string; value?: { backendNodeId?: number } } };
+    }>("Runtime.evaluate", {
+      expression: "document.documentElement",
+      contextId: world.executionContextId,
+      objectGroup,
+      serializationOptions: {
+        serialization: "deep",
+        additionalParameters: { maxNodeDepth: 0, includeShadowTree: "none" },
+      },
+    });
+    if (!attached()) return "changed";
+    const root = reply.result?.deepSerializedValue;
+    if (root?.type === "null") return "changed";
+    const id = root?.type === "node" ? root.value?.backendNodeId : undefined;
+    if (id === undefined) return "unavailable";
+    return id === identity.documentElementBackendNodeId ? "current" : "changed";
+  } catch (error) {
+    throwIfAborted(signal);
+    if (isAbortError(error)) throw error;
+    return attached() ? "unavailable" : "changed";
+  } finally {
+    await sendToCdpTarget(cdp, identity.target, "Runtime.releaseObjectGroup", {
+      objectGroup,
+    }).catch(() => {});
+    throwIfAborted(signal);
+  }
+}

apps/extension/src/tools/vom/facts.ts

@@ -97,6 +97,13 @@ export async function buildDocumentIndex<T extends DecodedNode>(
   return { nodes, excludedBackendNodeIds };
 }
 
+export interface DocumentIdentity {
+  attachmentId: string;
+  target: CdpTarget;
+  frameId: string;
+  documentElementBackendNodeId: number;
+}
+
 /** Narrow input shared by the existing semantic scene/hover consumers. */
 export interface CapturedSceneInput {
   nodes: CapturedNode[];
@@ -110,12 +117,19 @@ export interface CaptureIssue {
   projectionIssue?: FrameProjectionIssue;
   target: CdpTarget;
   frameId?: string;
-  stage: "dom" | "ax" | "ownership" | "geometry" | "forms";
-  reason: "capture-unavailable" | "frame-ownership-unresolved" | "geometry-unavailable";
+  stage: "dom" | "ax" | "identity" | "ownership" | "geometry" | "forms";
+  reason:
+    | "document-changed"
+    | "identity-unavailable"
+    | "identity-unverified"
+    | "capture-unavailable"
+    | "frame-ownership-unresolved"
+    | "geometry-unavailable";
 }
 
 export interface DocumentFacts<T extends FrameOwnedAxNode> {
   readonly frame: CdpFrame;
+  readonly identity?: DocumentIdentity;
   readonly index: DocumentIndex;
   readonly domNodes: CapturedNode[];
   readonly axNodes: T[];

apps/extension/src/tools/vom/normalize.ts

@@ -38,6 +38,7 @@ export interface FrameContext {
 export interface NormalizedDocument {
   nodes: NodeFacts[];
   index: DocumentIndex;
+  documentElementBackendNodeId?: number;
 }
 
 /** Interpret one document using a supplied projection. No live reads or frame scheduling. */
@@ -98,6 +99,12 @@ export async function normalizeDocument(
       (node) => !node.tag.startsWith("#") && !index.excludedBackendNodeIds.has(node.backendNodeId),
     ),
     index,
+    documentElementBackendNodeId: nodes.find(
+      (node) =>
+        node.nodeType === 1 &&
+        node.parentBackendNodeId !== null &&
+        index.nodes.get(node.parentBackendNodeId)?.nodeType === 9,
+    )?.backendNodeId,
   };
 }
 

evals/browser/cases/regression/oopif-scrollbars/README.md

@@ -0,0 +1,41 @@
+# OOPIF occupied-scrollbar regression
+
+An iframe's content quad includes its child viewport's scrollbar space, while
+`Page.getLayoutMetrics().cssLayoutViewport` excludes that space. Mapping the latter
+onto the whole quad stretches positions and sizes. The full target-local viewport
+must determine scale; the visible viewport must still clip content at every OOPIF
+boundary and constrain target-local action points.
+
+This fixture alternates loopback hostnames across two nested OOPIFs. It includes
+scrolling, borders, padding, scaled iframe owners, a partially clipped button and
+a fully clipped button. Custom scrollbars occupy different widths and heights.
+The `scrollbars` query parameter accepts `both` (default), `vertical`, `horizontal`
+or `none`.
+
+Run the numerical regression with Node 22+ and a local Chrome executable:
+
+```sh
+BSK_GEOMETRY_CHROME=/path/to/chrome pnpm --filter @browser-skill/extension exec vitest run \
+  src/tools/__tests__/snapshot-coordinates.browser.test.ts
+```
+
+The existing browser runner is shared with the snapshot-unit regression. The test:
+
+- Verifies actual OOPIF targets and occupied scrollbar dimensions.
+- Compares snapshot and live geometry with independent DOM rectangles and clipping.
+- Dispatches real root-target clicks and verifies the intended frame/button received them.
+- Rejects fully clipped controls and checks snapshot measurement reuse per target.
+- Covers five device-scale/browser-zoom combinations plus single-axis and no-scrollbar cases.
+
+The runner creates and removes isolated browser profiles. It is opt-in and skipped
+in normal unit runs when `BSK_GEOMETRY_CHROME` is unset.
+
+Run the CLI fixture smoke with a connected test extension:
+
+```sh
+BSK_AUTO_UPDATE=off pnpm eval:browser smoke --case oopif-scrollbars --bsk ./target/debug/bsk
+```
+
+The smoke assertions verify both nested frames have occupied scrollbars, that the
+marker is observed and that the session is closed. Numeric geometry and actual
+click assertions are exercised by the browser test above, not by smoke alone.

evals/browser/cases/regression/oopif-scrollbars/oopif-scrollbars.case.json

@@ -0,0 +1,39 @@
+{
+  "$schema": "../../../schemas/case.schema.json",
+  "schemaVersion": 1,
+  "id": "oopif-scrollbars",
+  "title": "Nested OOPIFs with occupied scrollbars and clipped controls",
+  "suite": "regression",
+  "tags": ["geometry", "iframe", "scroll"],
+  "fixture": { "startPath": "/oopif-scrollbars" },
+  "prompts": {
+    "en": "Open {url}, observe the page and its frames, report the OOPIF-SCROLLBARS marker, then close the session.",
+    "zh-CN": "打开 {url}，观察页面及其 iframe，报告 OOPIF-SCROLLBARS 标记，然后关闭会话。"
+  },
+  "coverage": ["session.start", "session.stop", "page.navigate", "inspect.observe"],
+  "assertions": {
+    "site": [
+      {
+        "label": "nested frame fixture settled",
+        "type": "geometry.ready",
+        "where": { "data.root": true },
+        "minCount": 1
+      },
+      {
+        "label": "both child frames have occupied scrollbars",
+        "type": "geometry.scrollbars",
+        "where": { "data.vertical": true, "data.horizontal": true },
+        "minCount": 2
+      }
+    ],
+    "response": [{ "label": "observed the fixture marker", "includes": "OOPIF-SCROLLBARS" }],
+    "adapter": [{ "label": "browser session was closed", "key": "sessionStopped" }]
+  },
+  "smoke": {
+    "steps": [
+      { "action": "navigate" },
+      { "action": "wait-site-event", "type": "geometry.ready", "where": { "root": true } },
+      { "action": "observe" }
+    ]
+  }
+}

evals/browser/cases/regression/oopif-scrollbars/oopif-scrollbars.fixture.mjs

@@ -0,0 +1,56 @@
+import { page, withRun } from "../../../lib/fixtures.mjs";
+
+export default {
+  id: "oopif-scrollbars",
+  routes: ["/oopif-scrollbars", "/oopif-scrollbars/frame", "/oopif-scrollbars/nested"],
+  render({ pathname, runId, query }) {
+    const root = pathname === "/oopif-scrollbars";
+    const nested = pathname.endsWith("/nested");
+    const mode = query.get("scrollbars") ?? "both";
+    return page({
+      title: "OOPIF scrollbar geometry regression",
+      body: `
+        <style>
+          main { margin: 0; width: auto; }
+          body { width: 2000px; height: 2400px; }
+          html { overflow-anchor: none; }
+          ${!root ? `html { overflow-x: ${mode === "vertical" || mode === "none" ? "hidden" : "scroll"}; overflow-y: ${mode === "horizontal" || mode === "none" ? "hidden" : "scroll"}; } html::-webkit-scrollbar { width: 17px; height: 11px; }` : ""}
+          button { position: absolute; padding: 0; border: 0; border-radius: 0; }
+          #probe { left: ${root ? 180 : nested ? 30 : 100}px; top: ${root ? 360 : nested ? 40 : 160}px; width: 60px; height: 20px; }
+          #edge { position: fixed; right: -20px; bottom: -15px; width: 80px; height: 60px; }
+          #outside { position: fixed; left: calc(100% + 2px); top: calc(100% + 2px); width: 10px; height: 10px; }
+          iframe { position: absolute; box-sizing: content-box; width: 420px; height: 320px;
+            left: 340px; top: 400px; border: 6px solid black; padding: 8px; transform: scale(1.2); transform-origin: 0 0; }
+          #nested { left: 150px; top: 210px; width: 200px; height: 120px; border-width: 4px; padding: 6px; transform: scale(0.8); }
+        </style>
+        <button id="probe" data-geometry-probe>OOPIF-SCROLLBARS</button>
+        ${!root ? '<button id="edge" data-geometry-probe>EDGE</button><button id="outside" data-geometry-probe>OUTSIDE</button>' : ""}
+        ${!nested ? `<iframe id="${root ? "cross" : "nested"}" name="${root ? "cross" : "nested"}" title="${root ? "outer" : "nested"} cross-site frame"></iframe>` : ""}
+      `,
+      script: `
+        history.scrollRestoration = "manual";
+        const child = document.querySelector("iframe");
+        if (child) {
+          const url = new URL(${JSON.stringify(withRun(root ? "/oopif-scrollbars/frame" : "/oopif-scrollbars/nested", runId, { scrollbars: mode }))}, location.href);
+          url.hostname = location.hostname === "127.0.0.1" ? "localhost" : "127.0.0.1";
+          child.src = url.href;
+        }
+        document.addEventListener("click", event => {
+          const probe = event.target.closest("[data-geometry-probe]");
+          if (probe) browserEval.send("geometry.clicked", { probe: probe.id });
+        });
+        window.addEventListener("load", () => {
+          scrollTo(${root ? "80, 240" : nested ? "10, 20" : "40, 100"});
+          requestAnimationFrame(() => requestAnimationFrame(() => {
+            document.documentElement.dataset.geometryReady = "true";
+            if (!${root}) browserEval.send("geometry.scrollbars", {
+              vertical: innerWidth > document.documentElement.clientWidth,
+              horizontal: innerHeight > document.documentElement.clientHeight,
+            });
+            browserEval.send("geometry.ready", { root: ${root} });
+          }));
+        });
+      `,
+    });
+  },
+};

evals/browser/cases/regression/snapshot-coordinates/README.md

@@ -33,12 +33,9 @@ BSK_AUTO_UPDATE=off pnpm eval:browser smoke --case snapshot-coordinates --bsk ./
 Smoke alone does **not** certify coordinate accuracy; CLI observations do not expose raw boxes.
 Use the geometric test above for the regression's numeric assertions.
 
-## Separate existing boundary
+## Related scrollbar regression
 
-The OOPIF root uses non-occupying scrollbars in the unit-conversion regression. Root and
-same-process frames retain normal scrollbars. Append `&classic-scrollbars` to the fixture URL
-to reproduce the separate existing OOPIF projection issue: `targetProjection()` maps the CSS
-layout viewport (which excludes occupying scrollbars) onto the entire owner content quad.
-This inflates the projected coordinates when scrollbars occupy space. Main already has that
-mapping; fixing it also changes shared live geometry and is outside this snapshot-unit fix.
-The test does not relax its numeric tolerance to absorb that error.
+The unit-conversion fixture keeps non-occupying OOPIF scrollbars by default. The same
+browser test also runs the dedicated [OOPIF scrollbar fixture](../oopif-scrollbars/README.md),
+which covers occupied scrollbars, two OOPIF boundaries, clipping and real clicks.
+Append `&classic-scrollbars` to this fixture's URL to enable its normal OOPIF scrollbars.

evals/browser/tests/eval.test.mjs

@@ -41,22 +41,23 @@ test("case manifests are discovered, ordered, and grouped into suites", () => {
       "diagnostics",
       "mobile-emulation",
       "generated-form",
+      "oopif-scrollbars",
       "snapshot-coordinates",
     ],
   );
   assert.deepEqual(repositorySummary(cases, fixtureRegistry).suites, {
     core: 6,
     matrix: 1,
-    regression: 1,
+    regression: 2,
   });
 });
 
 test("repository validation links every case to a fixture and valid workflow evidence", () => {
   assert.deepEqual(validateRepositoryCases(cases, fixtureRegistry), []);
   const summary = repositorySummary(cases, fixtureRegistry);
-  assert.equal(summary.cases, 8);
-  assert.equal(summary.fixtureModules, 9);
-  assert.equal(summary.fixtureRoutes, 15);
+  assert.equal(summary.cases, 9);
+  assert.equal(summary.fixtureModules, 10);
+  assert.equal(summary.fixtureRoutes, 18);
 });
 
 test("manifest validation rejects unknown operations and incomplete workflow steps", () => {