user=> (def xyzw 0)
0
user=> xy
<try completion>

W/ (message (format "%s" response)) throw into miracle-eval-string, I get (on emacs -Q, btw):

(dict (id . 16) (ns . user) (session . e810b11b-7e44-419c-b201-b4a4c73cf23c) (value . ("xyzw")))
received str: ("xyzw")
err: nil
Company: An error occurred in auto-begin
Company: backend company-miracle async timeout with args (candidates xy)

Debugger entered--Lisp error: (error "Company: backend company-miracle async timeout with args (candidates xy)")
  signal(error ("Company: backend company-miracle async timeout with args (candidates xy)"))
  error("Company: backend %s async timeout with args %s" company-miracle (candidates "xy"))
  company--force-sync(company-call-backend-raw (candidates "xy") company-miracle)
  company-call-backend(candidates "xy")
  company--fetch-candidates("xy")
  company-calculate-candidates("xy" nil)
  company--begin-new()
  company--perform()
  company-auto-begin()
  company-manual-begin()
  company-complete()
  funcall-interactively(company-complete)
  call-interactively(company-complete nil nil)
  command-execute(company-complete)