Retell AI vs Vapi for AI voice agents: choosing the platform before you pay for it

By Edward Pinela · Founder, Lightray AI · 14 September 2026

Almost every write-up on this question is published by one of the two vendors, or by an agency that resells one of them. This one is neither. Lightray AI holds no partner badge, no reseller agreement and no affiliate relationship with either company, and nothing on this page is an affiliate link — we are paid the same to build your phone agent whichever platform it ends up on.

Everything below was checked against each vendor's own current documentation on 14 September 2026 and is linked so you can check it yourself. Two deliberate omissions: no per-minute figures, because both vendors revise them and a stale number in a comparison is worse than no number at all, and no Lightray price, because ours follows a scoped conversation rather than a page.

What are you actually buying from each one?

The same five parts, packaged differently. A phone call has to be received, turned into text, understood by a language model, turned back into speech, and managed so both sides can interrupt each other. Retell AI sells that stack assembled and billed on its own rate card. Vapi sells it as swappable parts with a platform fee charged over the top.

Two terms are worth defining, because both vendors use them constantly. Orchestration is the layer that decides whose turn it is to speak, when to stop talking because the caller has started, and when to call one of your systems mid-conversation. A tool call is that reach into your systems — check the diary, hold the slot, write the contact — expressed as a function the model is allowed to invoke. Both platforms do both. The difference is how much of it you are expected to specify.

This is a platform-choice question, not a product-category question. If you are still deciding whether you need a conversational agent at all rather than a scripted flow, that is settled first in the difference between an AI agent and a chatbot, and it is the more expensive decision to get wrong.

Which one gets a working agent live faster?

Retell, for the common case. Its dashboard is built around getting a configured agent onto a phone number in one sitting, with the model, voice and telephony choices pre-wired. Vapi assumes you will assemble the same result from parts, which costs an afternoon at the start and buys control you may or may not need later.

Be careful what you conclude from that. The demo is not the build. On either platform, the fortnight of real work is the same fortnight: tool calls into your calendar and CRM that behave when a record is missing, a transfer path that fires before the caller gets annoyed, spelled-back confirmation of addresses and emails, and a test suite that proves the agent still books correctly after someone edits the prompt. Platform choice moves the first day. It barely moves the last week.

How do the two pricing models differ?

Structurally, not just numerically. Vapi charges a platform fee per minute and passes provider costs through at cost, and its documentation states that when you supply your own provider key you are charged directly by that provider instead. Retell publishes a rate card that itemises its own per-minute platform rate alongside model, voice, telephony and optional feature charges, and bills them together.

One correction worth making, because the comparison posts repeat it: Retell is often described as a single bundled all-in rate. Its current pricing page itemises the components — platform, model, text-to-speech, telephony, and per-minute add-ons for things like knowledge bases and PII removal — plus monthly line items for phone numbers and for concurrent-call capacity beyond the included allowance. Read both vendors' pricing pages on the day you decide, not a blog's summary of them.

The durable difference is where the money lives. With Retell, one vendor sets every rate and sends one bill, which is easy to forecast and easy to approve. With Vapi's own-keys route, your model and voice spend sits in accounts you already hold, so you see provider pricing directly, keep those relationships if you leave, and accept that the total arrives in pieces. Neither is cheaper by nature. Platform fees are also rarely the largest line in a voice project, which what AI automation actually costs goes through in detail.

What does each platform require for HIPAA?

Both document a route, and the paperwork differs. Retell's compliance documentation states a signed BAA is needed before transmitting protected health information, and that its BAA and DPA can be self-signed at no additional fee. Vapi's documentation states it requires a signed BAA and that HIPAA mode needs an Enterprise subscription or a separately purchased add-on.

A BAA — business associate agreement — is the contract that lets a vendor handle protected health information on a covered entity's behalf. The practical consequence of the difference is commercial rather than technical: on one platform the compliant configuration is a form you sign, on the other it is a plan you buy. Read both current pages directly — Retell's security and compliance documentation (opens in new window) and Vapi's HIPAA documentation (opens in new window) — because this is exactly the sort of thing that changes without a press release.

Two things neither vendor does for you. Recording consent varies by state and a synthetic voice on an outbound campaign sits under telemarketing rules regardless of which platform dialled it, so that remains your obligation. And a compliance certificate is not a risk assessment: what the agent is allowed to say, what it must never promise, and who reviews the transcripts are decisions you make. The NIST AI Risk Management Framework (opens in new window) is the vocabulary we use for that conversation, and the questions worth putting to any vendor are collected in security questions to ask an AI automation vendor.

How hard is it to leave either platform?

Harder than the sales page implies, and the cost is the same shape on both. Your prompt and conversation design travel fine. What does not travel is the platform-specific wiring: tool definitions, webhook payload shapes, call-event handling, and whatever logic you built inside the dashboard rather than in your own systems.

Three decisions make a future move cheap, and all three are yours rather than the vendor's. Keep the phone number with a carrier account in your name, so switching platforms is a routing change instead of a port and a reprint of every van and business card. Put your integrations behind one endpoint you own, so the platform calls your service and your service talks to the CRM — then a migration rewrites one caller, not five integrations. And keep transcripts and recordings flowing into your own storage on a schedule, because a cancelled account takes its call history with it. Vapi's own-keys route helps with a fourth: the model and voice accounts stay yours by construction.

So which should you build on?

Pick Retell if you want one vendor, one bill and one rate card, if the agent's job is bounded — answer, qualify, book, transfer — and if a self-signed BAA is the difference between starting this month and waiting on procurement. Pick Vapi if you want to choose and swap providers, keep model spend in accounts you already own, and drive the whole thing from code.

If the honest answer is that you do not know yet, build the first version on whichever gets you to a real call fastest, but build it with the number and the integration endpoint under your own control from day one. That is what makes the choice reversible, and a reversible choice does not deserve six weeks of evaluation. What we would push back on is picking a platform on a per-minute rate quoted in a blog post, or picking one for a healthcare line before anyone has read the BAA terms.

Where this page stops and a build starts

Choosing the platform is roughly a tenth of the work. What the agent should be allowed to do, how it hands off to a person, and how it writes back to your systems is the rest, and our AI voice agent development page covers what that build actually involves — including the parts that are identical on both platforms. Where the point of the call is filling the diary, the mechanics behind it are on AI appointment scheduling: reminders, rescheduling, and the waitlist backfill that decides whether the agent pays for itself. How a scope gets agreed before anything is built is set out on how it works.

Common questions about choosing between the two