Mail merge fields and bulk tag updates restored

Two features in the campaign builder stopped working silently: the mail merge field picker showed nothing, and bulk tag updates on contacts didn't apply. Both are fixed.

What was broken

The problems affected anyone using the template editor or managing contacts in bulk:

• In the campaign builder's template editor, the Insert toolbar showed "No fields found" even when your contact list had plenty of standard and custom fields. Mail merge variables like {{first_name}} or any custom field you'd added were effectively unreachable from the editor — leaving personalization gaps you may not have noticed until after sending.
• Bulk tag updates from the contacts table — adding, removing, or replacing tags across many contacts at once — failed silently. The operation appeared to complete but the tags weren't applied. Segmentation that depended on those tags couldn't be trusted.

Neither failure showed a useful error message, which made them hard to spot and easy to mistake for user error.

Root cause

Both requests were being captured by the wrong API route on the server, so they never reached the right handler. The fix moved the two endpoints onto unambiguous paths and added an automated guard that prevents this class of routing conflict from shipping again.

Why it matters

Mail merge personalization is one of the highest-leverage levers in cold outreach. An email that opens with a prospect's real name, company, or a tailored detail outperforms a generic blast — and custom fields let you go further, pulling in any signal you've collected on a lead. Losing the field picker during template editing meant either hand-typing variables (and risking typos that render as broken placeholders) or sending less personalized emails.

Bulk tag management is equally load-bearing. Tags control which contacts enter which campaigns and which are excluded. Silent failures there meant your segmentation logic wasn't actually being applied — contacts you meant to exclude could receive emails they shouldn't, or contacts you meant to target were being missed.

What you'll see now

1. Open a campaign → Builder → template editor: the Insert toolbar lists every standard field plus the custom fields found on your selected lists — click any chip to insert it.
2. If field loading ever fails for any reason, the toolbar now shows a clear error instead of pretending the list is empty.
3. Bulk tag operations from the contacts table apply correctly again.

If you were working around the broken Insert toolbar by typing merge tags manually, you can stop — the picker is back and includes every custom field on your account. No campaign changes are needed; the fix is live across all template editors.