Cold SMS Engine — Iron Automations Build

Architecture

Lead Source (Iron ACQ / CSV / scraper)
  → Postgres/Supabase (leads table, dedupe, status)
  → Python Dispatcher (cron every 5 min)
    → Slot check: morning | midday | evening window active?
    → Pull N leads due for next touch
    → Signal House API (send SMS)
    → Log to `sms_events` table
    → Push to GHL sub-account as contact+conversation (native threading)
  → Inbound reply webhook (Signal House → FastAPI)
    → Classify: positive | negative | stop | neutral
    → Positive → create GHL opportunity, notify rep
    → Stop → blacklist, opt-out table

Why Python (not n8n)

n8n hit the wall at ~5K sends/day — visual nodes choke on batch logic, error recovery is painful, version control is JSON-in-Git hell. Python sequencer:

Cron-driven, not webhook-driven → deterministic
Slot windows prevent TCPA violations (no sends before 9am / after 8pm local)
Retries + dead-letter queue native
Git-diffable, testable

Slot Logic

SLOTS = {
    "morning":  (9, 11),
    "midday":   (12, 14),
    "evening":  (16, 19),
}
# Each lead gets rotated across slots to avoid same-hour sends
# Leads bucketed by timezone from area code lookup

Touchpoint Sequence (proven)

T+0: Permission ask ("mind if I send info?")
T+3min: Human-mimicking followup (Eugene Katsen gem — 3x reply boost)
T+1d: Value drop
T+3d: Soft CTA
T+7d: Hard CTA
T+14d: Breakup message

Telephony: Signal House

Cheaper than Twilio at volume
Pre-registered numbers with warm reputation
Native A2P submission from portal
Python SDK works; raw REST also fine

GHL Threading

Every SMS event POSTs to GHL via public API to create:

Contact (if new)
Conversation message (inbound/outbound)
Opportunity (when positive classifier fires)

This makes the GHL sub-account the source of truth for reps, while Python remains the source of truth for sending logic.

Numbers

Cost-per-interested-lead: $3.31
CPA (booked call): $29
CAC (closed deal): $234
Show rate: 12.5%
Throughput: 1000 new leads/day
Avg 5 SMS segments per conversation before decision

Cold SMS Engine — Iron Automations Architecture