How 2 Cross-Account Leak Bugs Surfaced
(and 5 BFFs Got Properly Wired)

The headline

How we found them

The W13 SANDBOX-PARITY-AUDIT (May 11) flagged that the canvas was sending user_id: "" to ep 8506 — meaning Zep memory was session-ephemeral per page-load, not per user. That was the entry point. The fix wired useAuth().user.id into the canvas dispatch payload (commit 64a847c).

That alone wasn’t the bug. The audit prompted a wider sweep across all 9 AE BFF wrappers to find sister sites that needed the same wire-up. Halfway through that sweep:

// chat-shell.tsx, line 1495 — the gut punch
const result = (await dispatchAction({
  data: {
    query,
    thread_id: threadIdRef.current,
    user_id: "15",  // ← Robert's WorkOS id, hardcoded
    ...(classOverride ? { class_override: classOverride } : {}),
    count: requestedN,
    ...(suggestionRequestIdRef.current
      ? { suggestion_request_id: suggestionRequestIdRef.current }
      : {}),
    ...(toolCalls ? { tool_calls: toolCalls } : {}),
  },
})) as DispatchResult;

Then later, deeper in the upload pipeline:

// upload-files-fn.ts, line 67 — the second one
const form = new FormData();
form.append("suggestion_request_id", String(data.suggestion_request_id));
form.append("user_id", "15");  // ← same id, different file
form.append("mode", "suggestion_request");

for (const f of data.files) {
  const bytes = Uint8Array.from(atob(f.base64), (c) => c.charCodeAt(0));
  const blob = new Blob([bytes], { type: f.mime_type });
  form.append("files[]", blob, f.filename);
}

useAuth().user.id wired into every BFF call site

The fix is the same shape everywhere: import useAuth from the WorkOS adapter, read user.id with an empty-string fallback, pass it through. The empty-string fallback preserves dev-without-auth behavior and keeps existing test setups working.

import { useAuth } from "@workos/authkit-tanstack-react-start/client";

// inside the component:
const { user } = useAuth();
const authedUserId = user?.id ?? "";

// every BFF call:
const result = (await dispatchAction({
  data: {
    query,
    thread_id: threadIdRef.current,
    user_id: authedUserId,  // ← from useAuth, not hardcoded
    ...
  },
})) as DispatchResult;

useCallback dependency arrays were updated everywhere this lands so React doesn’t close over a stale id when a different user signs in.

BFF wrapper coverage matrix

Every Anything Engine BFF wrapper, what Xano endpoint it hits, whether it touches user state, and the user_id status before / after this audit.

9 call sites wired across 3 component files

How we verified

Backend follow-up (Mark territory)