Architect expression regex for E.164 to NANP formatting

Architect & Flows
1

Quick question about writing an Architect expression that formats a phone number from +1XXXXXXXXXX to (XXX) XXX-XXXX.

I am building a data action to normalize outbound dial strings before passing them to a CTI connector. The source data comes in E.164 format via a REST proxy, but the legacy PBX requires NANP.

I tried this expression in the Assign step:

assign:
 - name: formatted_phone
 value: "{{REGEX_REPLACE(contact.phone, '(\\+1)(\\d{3})(\\d{3})(\\d{4})', '($2) $3-$4')}}"

It fails with a REGEX MISMATCH error. The engine seems to choke on the parentheses or the escape sequences. I know I can do this in the GraphQL gateway layer using JS, but the requirement is to handle it at the Architect level to keep the gateway logic clean.

How do I structure the regex correctly for the Architect expression evaluator? I need to strip the +1 and inject the formatting characters.

  1. Input: +14165550199
  2. Expected Output: (416) 555-0199

Any working examples?