What comes back after an Agent reads your code.

The handler takes account_id straight from the query string and hands it to the store. The identity that requireSession put in the request context is never read in this function, so nothing here constrains the requested account to the caller's own.

// exportInvoices streams every invoice row that belongs to the account_id
// supplied in the query string.
func (s *Server) exportInvoices(w http.ResponseWriter, r *http.Request) {
	accountID := r.URL.Query().Get("account_id")
	if accountID == "" {
		writeError(w, http.StatusBadRequest, "account_id is required")
		return
	}
	rows, err := s.invoices.Export(r.Context(), accountID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "export failed")
		return

The query filters on the supplied identifier and returns every matching row. The store is given no session, so the only way to keep a caller inside their own account is for the caller above it to check first.

import "context"

// Export returns every invoice that belongs to accountID. The identifier is a
// caller-supplied argument; this layer has no session to compare it with.
func (s *Store) Export(ctx context.Context, accountID string) ([]Invoice, error) {
	rows, err := s.db.QueryContext(ctx, `
		SELECT id, number, total_cents, issued_at
		FROM invoices
		WHERE account_id = $1
		ORDER BY issued_at DESC`, accountID)
	if err != nil {
		return nil, err

Checked as counterevidence: the codebase does contain an account comparison, on the refund route, and it returns 404 before touching the ledger. That is the check the export path is missing, and it shows the omission is specific to export rather than a codebase that never compares accounts.

Checked as counterevidence. It was found, and it does not disprove the claim.

	invoice, err := s.invoices.Get(r.Context(), r.PathValue("id"))
	if err != nil {
		writeError(w, http.StatusNotFound, "invoice not found")
		return
	}
	if invoice.AccountID != identity.AccountID {
		writeError(w, http.StatusNotFound, "invoice not found")
		return
	}

The reported endpoint exists in this commit and sits behind requireSession and requireScope("invoices:read"). Both middleware run before the handler; neither receives the account_id from the query string.

// requireSession; each route also declares the scope it needs.
func (s *Server) RegisterRoutes(mux *http.ServeMux) {
	mux.Handle("GET /v1/invoices/export",
		s.requireSession(s.requireScope("invoices:read")(http.HandlerFunc(s.exportInvoices))))
	mux.Handle("GET /v1/invoices",
		s.requireSession(s.requireScope("invoices:read")(http.HandlerFunc(s.listInvoices))))

This is the control a reader would expect to find. It answers "may this session call this endpoint" and not "which account may this session act on". The identity in the context does carry AccountID; the export path simply never compares it.

// requireScope checks that the session carries the named scope. It says
// nothing about which account the session may act on.
func (s *Server) requireScope(scope string) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			identity := identityFrom(r.Context())
			if !identity.HasScope(scope) {
				writeError(w, http.StatusForbidden, "missing scope")
				return
			}
			next.ServeHTTP(w, r)
		})
	}
}