# Build brief — a focused alternative to Vapi

> **Verdict:** Partly, if you narrow it · **Buildability:** 53/100 · **Category:** Dev Tools
> **Source:** https://www.canitbevibecoded.com/vapi
> Independent editorial assessment from Can It Be Vibe Coded? Not affiliated with, endorsed by, or derived from Vapi. Verify current pricing and capabilities before acting.

## Context

**Vapi** — API-first platform for inbound and outbound phone and web voice agents. It currently costs Variable pricing.

A focused inbound agent is a credible contained build with LiveKit Agents or Pipecat. Replacing Vapi as a product is much larger: it combines realtime orchestration, provider abstraction, phone-number and SIP workflows, outbound campaigns, tool calls, testing, observability, scaling, support, and compliance options. Self-hosting can remove Vapi's $0.05 per-minute platform fee, but model, carrier, number, infrastructure, failed-call, monitoring, and engineering costs remain.

This brief describes a focused, single-operator replacement for the part of Vapi that is genuinely reproducible. It is deliberately narrower than the product it replaces, and it says so in writing. Build the useful core; do not pretend to have rebuilt the rest.

## What you are building

Route a SIP trunk into a realtime agent, stream speech through STT, LLM, and TTS with interruption handling, run a server-side tool, and save the call outcome.

- Build the focused developer workflow you use repeatedly, with local configuration.
- A responsive interface with real empty, loading, success, and error states.

## Requirements

### Functional

- Public Linux VM, domain, TLS, and correctly restricted SIP, WebRTC, and RTP ports.
- SIP trunk and phone number from a carrier such as Telnyx.
- Country-specific consent, recording, caller-ID, and outbound-calling review before real traffic.

### Data and integrations

- STT, LLM, and TTS provider API keys.

Each of these needs a real account, credential, or quota. Set them up before writing feature code.

### Non-functional

- Accessibility: semantic markup, labelled controls, visible focus, and reduced-motion support.
- Security: server-side secrets, validated input, and no credentials in the client bundle.
- Reliability: retries with backoff on external calls, and a clear failure state when a provider is down.
- Portability: the operator can export their data and leave without losing it.

## Implementation brief

Build me a focused, self-hosted alternative to Vapi for one inbound support number.
Requirements:

- Use Python 3.12 and livekit-agents~=1.5 with one named AgentServer worker.
  Use direct provider plugins, not LiveKit Inference or another managed agent host.
- Run LiveKit Server, Redis, and LiveKit SIP with Docker Compose on one Ubuntu VM.
  Put Caddy in front of HTTPS/WSS; expose only the documented SIP and UDP media ports.
- Provision one Telnyx DID and credential-authenticated SIP trunk. Include checked-in
  LiveKit inbound-trunk and dispatch-rule JSON that sends calls to support-agent.
- Build an AgentSession with Silero VAD, Deepgram Nova-3 STT, gpt-5-mini through
  the OpenAI plugin, and Cartesia Sonic-3 TTS. Load every secret from .env.
- Give the agent one narrow support prompt, interruption handling, and two tools:
  look up an order in SQLite and save a callback request after caller confirmation.
- Persist call id, timestamps, transcript, tool results, and outcome to SQLite.
  Add structured JSON logs and /healthz; recording is off by default.
- Include unit tests for both tools and scripted agent tests for lookup, refusal to
  invent an order, callback confirmation, and a caller interruption.
- Provide make setup, make dev, make smoke, and docker compose up -d commands.
  The smoke test must work in the LiveKit agent console before a real PSTN call.
- README: DNS, TLS, firewall, Telnyx, trunk, dispatch, provider-key, and test-call
  steps, plus common one-way-audio and SIP authentication checks.
- The cost section must say the Vapi fee is removed, while the DID, SIP minutes,
  model usage, VM, failed calls, monitoring, and operator time remain. Link the
  source-backed calculator at https://voice.oss.codes for changing rates.
- Out of scope: outbound campaigns, a multi-tenant dashboard, squads, billing,
  automatic provider failover, call recording, compliance claims, and high availability.

## Delivery standard

- Inspect the repository first, then write a short implementation plan before writing code.
- Deliver the smallest complete end-to-end workflow first; every primary control must work against persisted data.
- Use real validation and storage; never substitute fake dashboards, decorative controls, hard-coded success states, or mock integrations.
- Include responsive layouts plus genuine empty, loading, success, validation, and failure states.
- Keep secrets server-side in environment variables, provide .env.example, and never commit credentials or user data.
- Add structured logs around every external call and return actionable errors without leaking sensitive details.
- Write unit tests for the core logic and one automated test of the main user journey.
- Finish with a README covering setup, architecture, data location, backups, tests, deployment, and known limitations.

## Acceptance criteria

- [ ] A clean install starts the app using only the README and .env.example.
- [ ] The primary journey works from first visit through saved result, reload, edit, export, and deletion where applicable.
- [ ] Invalid input, missing configuration, provider failure, and an empty database each have a usable state.
- [ ] The interface works at 390px and 1440px, is keyboard navigable, and shows visible focus on every control.
- [ ] Tests, type checking, linting, and a production build all pass with no ignored failures.
- [ ] No part of the interface implies a live integration, security guarantee, or scale capability that was not actually built and verified.

## Non-goals

Do not build these, and do not claim to have replaced them:

- Managed realtime infrastructure, scaling, provider failover, and support.
- Assistant, squad, workflow, phone-number, and provider configuration APIs.
- Outbound campaigns, carrier integrations, spam mitigation, and production telephony debugging.
- Hosted simulations, evaluations, call logs, recordings, analytics, and retention controls.
- Reliability at the vendor's scale is an operations problem, not a prompt.
- Connectors, OAuth flows, and vendor API changes require constant upkeep.

## What you still own after launch

- Secure credentials, rotate secrets, and handle provider rate limits.
- Run migrations, backups, restores, and dependency updates.
- Test the critical journey after every model, API, or hosting change.
- Monitor failures and fix the edge cases a first prompt will miss.
- Maintain every third-party integration as APIs and OAuth rules change.

## Risk

**Operational risk.** The code is achievable; dependable data, integrations, and ongoing operations are the real cost.

Editorial confidence in this assessment: high. No independent one-shot implementation is linked yet.

## Prior art

Working open-source software you can read, fork, or borrow from before starting:

- [LiveKit Agents + SIP](https://github.com/livekit/agents) — Apache-2.0 realtime agent framework. Pair it with the separately deployed LiveKit Server and SIP service for a self-hosted phone stack
- [Pipecat](https://github.com/pipecat-ai/pipecat) — BSD-2-Clause Python framework with composable voice pipelines and broad model, transport, and telephony integrations. You still own deployment and carrier operations
- [Voice OSS cost planner](https://github.com/oss-codes/voice-cost) — Source-linked calculator and deployment reference for platform, model, SIP, number, infrastructure, and operational costs. It is a planning companion, not an agent runtime

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