Core concepts

Architecture

Voxa is a Next.js app paired with a Supabase Postgres, an n8n orchestration backbone on Railway, and four external service providers (Twilio, ElevenLabs, Stripe, Anthropic). The four flows below are the only paths a request takes through the system — anything not on these diagrams is helper code.

Interactive

Each diagram is rendered with React Flow — pan and zoom are disabled for legibility, but the node positions and edge animations are live.

System overview

The browser talks to Next.js. Next.js verifies webhooks and forwards payloads to n8n. n8n owns every external API call from there — Stripe Meter Events, Twilio calls + WhatsApp, ElevenLabs Conv AI, Cal.com, Anthropic Claude. Supabase Postgres + Realtime is the single source of truth that the dashboard subscribes to.

System overview

Inbound calls fan into the n8n backbone; outbound writes land in Supabase, where Realtime pushes them to the dashboard.

Workflow 1 — Onboarding

Triggered by checkout.session.completed on the Stripe webhook. Provisions the Twilio number, clones the owner's voice on ElevenLabs, creates an EL agent with the canonical 6-tool template, imports the Twilio number into EL, and WhatsApps the owner an activation message — all in one workflow.

W1 — Onboarding

From Checkout completion to a live, callable AI receptionist in five n8n steps.

Workflow 2 — Live tool calls

The EL agent calls one of six webhook tools during a live call. Each branch in W2 must respond in <2 seconds — the EL tool timeout is ~5 seconds, and a slow branch means dead air on the call.

W2 — Live tool calls

Six branches share a single Webhook trigger and a Switch node keyed on the tool name. Each branch ends in a Respond-to-Webhook node.

Workflow 3 — Post-call processing

ElevenLabs fires a post-call webhook 5–15 seconds after the caller hangs up. W3 computes the billable minutes, sends a Stripe Meter Event, runs Claude over the transcript for structured lead extraction, upserts the call + lead in Supabase, and (if the lead scored ≥ 7 or the sentiment is angry) WhatsApps the owner an alert.

W3 — Post-call

Single workflow handles billing, AI summary, persistence, and hot-lead alerts in parallel branches.

Workflows 4 & 5

W4 — Stripe events handles invoice.payment_failed (pauses the agent + WhatsApps the owner) and customer.subscription.deleted (releases the Twilio number, deletes the EL agent, archives the row). W5 — Daily digest runs on a cron at 18:00 IST and WhatsApps each business owner a one-line summary of their day. Both are simpler than W1–W3 and are documented inline in their respective JSON files (n8n/04-stripe-webhooks.json, n8n/05-daily-digest.json).

Why n8n?

n8n earns its place because every external API call sits in one place. Adding a new tool means dragging a node in. Swapping Twilio for Plivo means editing one HTTP node. Without n8n, every Voxa feature would require shipping a code change to Vercel.