Forms API (api.hsforms.com/submissions/v3/integration/submit/...) can
return 200 OK without actually creating a contact in HubSpot \xe2\x80\x94 silent
failures triggered by anti-spam filters, form configuration, or whatever
state the form GUID was left in.
Symptom in production: E2E flow completes (welcome email sent with
ref MVA-005), but contact is never created in HubSpot CRM. Reproduced
with serge+test1@mind4solutions.com on 2026-05-07.
Fix: switch to direct CRM API POST /crm/v3/objects/contacts which is
deterministic (= returns 409 if exists, error otherwise). Falls back to
PATCH on 409 to handle duplicate-email reinscriptions.
Refs: WordPress \xe2\x86\x92 static migration, post-Phase F bugfix.
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