fix(observation): validate document consistency during capture

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/__tests__/frame-graph.test.ts

@@ -2,6 +2,24 @@ import { describe, expect, it } from "vitest";
 import { buildFrameGraph, type CdpFrameTreeNode, type CdpFrameTreeSource } from "../frame-graph";
 
 describe("buildFrameGraph", () => {
+  it("preserves the owning target's loader identity", () => {
+    const graph = buildFrameGraph([
+      {
+        target: { tabId: 4 },
+        tree: {
+          frame: { id: "root", loaderId: "root-loader" },
+          childFrames: [{ frame: { id: "child", loaderId: "stale-placeholder" } }],
+        },
+      },
+      {
+        target: { tabId: 4, sessionId: "child-session" },
+        tree: { frame: { id: "child", loaderId: "child-loader" } },
+      },
+    ]);
+    expect(graph?.frames.find((frame) => frame.frameId === "root")?.loaderId).toBe("root-loader");
+    expect(graph?.frames.find((frame) => frame.frameId === "child")?.loaderId).toBe("child-loader");
+  });
+
   it("keeps sibling frames distinct and routes nested OOPIFs to their child sessions", () => {
     const graph = buildFrameGraph([
       {

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/browser-driver/frame-graph.ts

@@ -8,6 +8,7 @@ export interface CdpFrame {
   parentFrameId?: string;
   ownerBackendNodeId?: number;
   url?: string;
+  loaderId?: string;
   target: CdpTarget;
 }
 
@@ -21,6 +22,7 @@ export interface CdpFrameTreeNode {
     id: string;
     parentId?: string;
     url?: string;
+    loaderId?: string;
   };
   childFrames?: CdpFrameTreeNode[];
 }
@@ -48,6 +50,7 @@ function mergeFrame(
     frameId: node.frame.id,
     ...(parentFrameId ? { parentFrameId } : {}),
     ...(url ? { url } : {}),
+    ...(node.frame.loaderId ? { loaderId: node.frame.loaderId } : {}),
     target,
   });
 }

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/document-identity.ts

@@ -0,0 +1,69 @@
+import type { CdpFrame } from "@/browser-driver/frame-graph";
+import type { CdpRunner } from "../shared";
+import { sendToCdpTarget } from "../shared";
+import {
+  isAbortError as isCaptureAbort,
+  throwIfAborted as throwCaptureAborted,
+} from "./capture-abort";
+import type { DocumentIdentity } from "./facts";
+
+/** Fresh, frame-scoped identity read. An isolated world supplies the owning
+ * document without querying each node or installing a page observer. */
+export async function readDocumentIdentity(
+  cdp: CdpRunner,
+  frame: CdpFrame,
+  signal?: AbortSignal,
+): Promise<DocumentIdentity | undefined> {
+  const attachmentId = cdp.getAttachmentId?.(frame.target.tabId);
+  if (!attachmentId || !frame.loaderId) return undefined;
+  let objectId: string | undefined;
+  const send = <T>(method: string, params: object) => {
+    throwCaptureAborted(signal);
+    return sendToCdpTarget<T>(cdp, frame.target, method, params);
+  };
+  try {
+    const world = await send<{ executionContextId: number }>("Page.createIsolatedWorld", {
+      frameId: frame.frameId,
+      worldName: "bsk-document-identity",
+    });
+    const element = await send<{ result?: { objectId?: string } }>("Runtime.evaluate", {
+      expression: "document.documentElement",
+      contextId: world.executionContextId,
+    });
+    objectId = element.result?.objectId;
+    if (!objectId) return undefined;
+    const reply = await send<{ node?: { backendNodeId?: number } }>("DOM.describeNode", {
+      objectId,
+      depth: 0,
+    });
+    const backendNodeId = reply.node?.backendNodeId;
+    if (!backendNodeId || cdp.getAttachmentId?.(frame.target.tabId) !== attachmentId)
+      return undefined;
+    return {
+      attachmentId,
+      target: frame.target,
+      frameId: frame.frameId,
+      loaderId: frame.loaderId,
+      documentElementBackendNodeId: backendNodeId,
+    };
+  } catch (error) {
+    if (isCaptureAbort(error)) throw error;
+    return undefined;
+  } finally {
+    if (objectId)
+      await sendToCdpTarget(cdp, frame.target, "Runtime.releaseObject", { objectId }).catch(
+        () => {},
+      );
+  }
+}
+
+export function sameDocument(a: DocumentIdentity, b: DocumentIdentity): boolean {
+  return (
+    a.attachmentId === b.attachmentId &&
+    a.target.tabId === b.target.tabId &&
+    a.target.sessionId === b.target.sessionId &&
+    a.frameId === b.frameId &&
+    a.loaderId === b.loaderId &&
+    a.documentElementBackendNodeId === b.documentElementBackendNodeId
+  );
+}

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

@@ -1,3 +1,4 @@
+import type { CdpTarget } from "@/browser-driver/frame-graph";
 import { isOverlayHostNode } from "@/lib/overlay-bridge";
 import { createCaptureCheckpoint } from "./capture-abort";
 import type { CapturedNode } from "./capture-types";
@@ -92,3 +93,11 @@ export async function buildDocumentIndex<T extends DecodedNode>(
   }
   return { nodes, excludedBackendNodeIds };
 }
+
+export interface DocumentIdentity {
+  attachmentId: string;
+  target: CdpTarget;
+  frameId: string;
+  loaderId: string;
+  documentElementBackendNodeId: number;
+}

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

@@ -20,6 +20,7 @@ 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. */
@@ -69,5 +70,11 @@ 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,
   };
 }