# 7 best AI voice agent builders in 2026, compared

By Samuel Oram-Jones

The best AI voice agent builders in 2026 are Bland, Vapi, Synthflow, ElevenLabs, PolyAI, Sierra, and Retell, and Bland ranks first for enterprise calls because it is full stack. This ranking compares platforms that build and run live phone calls on who builds the AI, how a team builds a call, and what a minute costs, as of November 2026.

## What are the best AI voice agent builders?

The best AI voice agent builder overall is Bland, because one company builds and runs every AI model on a call, and the other six builders each lean on outside companies for at least one of them.

An AI voice agent builder is a platform where a team designs, tests, and launches an agent that answers or places phone calls. General frameworks for text agents sit outside this ranking.

- **Bland:** Best overall for enterprise calls
- **Vapi:** Best for developers assembling their own voice stack
- **Synthflow:** Best for sales-led teams that sign one annual contract
- **ElevenLabs:** Best for teams that already build on ElevenLabs voices
- **PolyAI:** Best for enterprises that want a managed, quoted agent
- **Sierra:** Best for customer service teams buying outcome-priced agents
- **Retell:** Best for developer teams that pick their own model and voice

| Builder | Best for | Price | Who builds the AI | iMessage |
|---|---|---|---|---|
| Bland | Enterprise calls | $0.14 per minute on self-serve Start, $0.12 on self-serve Build plus $299 a month, phone billed separately | Bland builds all of it | Native on Enterprise |
| Vapi | Developers assembling a stack | $0.05 per minute for hosting, plus providers | Other companies | No |
| Synthflow | Sales-led annual contracts | Annual agreement only | Mixed | No |
| ElevenLabs | Teams on ElevenLabs voices | $0.08 per minute past a plan's allowance, with language model usage billed on top in Custom mode | Mixed | No |
| PolyAI | Managed, quoted agents | Quote only | Mixed | No |
| Sierra | Outcome-priced customer service | No published rate | Mixed | Business Chat |
| Retell | Developer teams | $0.07 to $0.31 per minute, with the model and voice as separate lines | Other companies | No |

## What should buyers check in AI voice agent builders?

Buyers should check who assembles each part of a call, because the builders here split between ones that hand a team the parts and ones that deliver a finished agent.

Vapi takes its language model, transcription, and voice from other companies, Retell takes most of its models from other companies, ElevenLabs, Synthflow, PolyAI, and Sierra mix their own models with outside ones, and Bland builds its language, speech, and transcription models itself. Each outside company is one more name in a [security review](/blog/call-center-security-best-practices), and a headline rate rarely includes all of them.

![Bland's trust page, which reads Pass security review on day one, with voice, text to speech, transcription, and language models all owned and operated by Bland.](/images/compare/bland-trust.jpg)

Where a call may run comes next. It is worth asking each builder how it hosts calls, and Bland sets out its own answer in its [security program](https://www.bland.ai/trust-security). Enterprise customers get dedicated orchestration and dedicated GPUs run by Bland.

Compliance paperwork matters as much as the feature list.

A BAA is the contract [HIPAA](/hipaa-compliant-voice-ai) requires before a vendor handles patient information, and card payments need a clear [PCI DSS](/pci-compliant-voice-ai) statement. Bland self-attests to PCI DSS v4.0.1 and shares its attestation under NDA on Enterprise, Sierra says it holds PCI DSS Level 1 Service Provider certification, and Retell bars card data unless it agrees in writing.

A buyer who needs messaging beside voice should ask about iMessage too.

Bland runs branded iMessage agents natively on Enterprise, Sierra supports Apple Business Chat, and the other five builders here don't offer iMessage agents.

Proof at volume is the last check, such as a customer replacing an IVR (an automated phone menu) with a voice AI agent, which a demo can't show. Idaho Housing and Finance Association saves $750,000 a year by replacing its IVR with Bland, which handles 4,000 inbound calls a day and cut average call time by 20%.

> "We save thousands of dollars a day."

Greg Blake, Chief Information Officer, Idaho Housing and Finance Association

## How do the 7 best AI voice agent builders compare?

These seven builders differ most in how much of a call they build themselves, and Bland is the one that builds all of it.

![Bland's homepage, which reads Voice AI for the calls that can't go wrong.](/images/compare/bland-home.jpg)

### 1. Bland: Best overall for enterprise calls

**What does it do?** Bland is a full stack voice AI provider that builds and runs its own language, speech, and transcription models for inbound and outbound calls, with a visual builder called Pathways where teams connect steps and test them before launch. It publishes sub-200ms latency, a 99.9% uptime SLA, and it serves more than 250 enterprise customers.

**Who is it for?** Bland suits enterprises and contact centers in any industry that run high-stakes calls at volume.

<div class="cmp-proscons cmp-proscons-own"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>No outside AI lab in the call path, so a security team reviews one AI company</li><li>Dedicated orchestration and dedicated GPUs run by Bland, on Enterprise</li><li>BAA on Enterprise, PCI DSS self-attested, FedRAMP 20x Class A</li><li>Bland Speech v3 ranked first of 13 AI voices on Audio Realism Bench on 4 August 2026</li><li>Forward-deployed engineers on Enterprise</li><li>Native iMessage agents on Enterprise, sharing pathways with voice</li><li>Staged releases that pause a new agent version when it performs worse than the last</li><li>Its own SIP and media servers, with no outside telephony provider in the call path</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>Overkill for a small prototype, because Bland is built for production calls at volume</li></ul></div></div>

**Pricing:** Self-serve Start is $0.14 per minute with no platform fee, self-serve Build is $0.12 per minute with a $299 monthly platform fee, and [Enterprise](https://www.bland.ai/pricing) is priced to volume. Phone is billed separately at carrier cost. Enterprise adds native iMessage agents, warm transfers, a BAA, SSO, data residency, dedicated GPUs run by Bland, and forward-deployed engineers, alongside SMS and web chat.

### 2. Vapi: Best for developers assembling their own voice stack

**What does it do?** Vapi is a developer platform that hosts voice agents and bills the language model, transcription, and voice from other companies on top at cost. Vapi says it passes these through with "no markup", so a team picks and wires every provider itself.

**Who is it for?** Vapi suits developers who want to pick and swap each AI provider themselves and can run a stack of several vendors.

<div class="cmp-proscons" data-rival="vapi"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>A team can choose every model and voice</li><li>Imported numbers are billed by a customer's own phone provider</li><li>Vapi says it is SOC 2 Type II attested</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>Language model, transcription, and voice bill from other companies on top of $0.05 hosting</li><li>HIPAA is a $2,000 monthly add-on</li><li>No iMessage agents</li></ul></div></div>

**Pricing:** $0.05 per minute for hosting, plus a language model, transcription, and voice at provider cost, which Vapi's pricing calculator puts at up to $0.0452, $0.0099, and $0.0238 a minute, before phone.

### 3. Synthflow: Best for sales-led teams that sign one annual contract

**What does it do?** Synthflow sells voice agents through one annual enterprise agreement that scopes in telephony, integrations, and launch support, and it offers WhatsApp and SMS chat beside voice. Synthflow says it is built on "proprietary orchestration and models from OpenAI, ElevenLabs, Deepgram, and custom in-house logic".

**Who is it for?** Synthflow suits mid-market and enterprise teams that want a sales-scoped platform and are happy to sign an annual agreement before they launch.

<div class="cmp-proscons" data-rival="synthflow"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>Has SOC 2 Type 2, ISO/IEC 27001, HIPAA, and GDPR coverage</li><li>Forward-deployed engineers launch agents with a customer's team where the agreement includes launch support</li><li>WhatsApp and SMS chat channels</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>Annual enterprise agreement only, with no free plan or trial and no rate by the minute</li><li>No iMessage agents</li></ul></div></div>

**Pricing:** Annual agreement only, with no public per-minute rate, and purchased phone numbers cost $1.50 a month.

### 4. ElevenLabs: Best for teams that already build on ElevenLabs voices

**What does it do?** ElevenLabs sells ElevenAgents, a platform for voice and text agents built on its own speech and transcription models, with a choice between its Realtime models and an outside language model. ElevenLabs charges no telephony fee, and a connected provider such as Twilio bills its own carrier charges.

**Who is it for?** ElevenLabs suits developer and enterprise teams that want ElevenLabs voices inside an agent platform and will pick a language model themselves.

<div class="cmp-proscons" data-rival="elevenlabs"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>Runs its own speech and transcription models</li><li>Plans from $6 a month with a call allowance</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>Language model usage billed on top in Custom mode</li><li>ElevenLabs says "HIPAA support is available when Zero Retention Mode is enabled and a Business Associate Agreement (BAA) is in place"</li><li>Eleven v3 ranked 12th of 13 AI voices on Audio Realism Bench on 4 August 2026</li><li>No iMessage agents</li></ul></div></div>

**Pricing:** $0.08 per minute past a plan's allowance, with plans from $6 a month and language model usage billed on top in Custom mode.

### 5. PolyAI: Best for enterprises that want a managed, quoted agent

**What does it do?** PolyAI builds and runs a voice agent for a customer on quoted per-minute pricing, with its own Raven model family beside GPT and Claude models. PolyAI also sells a Dialog-RSN-1 model API at 2¢ per connected minute, without telephony or orchestration.

**Who is it for?** PolyAI suits large consumer-facing companies that want it to build and run their agent for them.

<div class="cmp-proscons" data-rival="polyai"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>PolyAI handles the build and the ongoing running</li><li>Has SOC 2 Type II and ISO/IEC 27001</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>No public rate for a managed agent</li><li>Its contract says "the total handle time is rounded up to the next 30-second increment"</li><li>No iMessage agents</li></ul></div></div>

**Pricing:** A managed agent is quoted per minute with no public rate.

### 6. Sierra: Best for customer service teams buying outcome-priced agents

**What does it do?** Sierra started as a chat-first platform for customer support, added voice later, and now covers chat, voice, email, SMS, and WhatsApp. Sierra says it builds on "a constellation of LLMs" and that it "automatically switches between LLM providers", so a customer does not pick the model behind a call.

**Who is it for?** Sierra suits enterprise customer experience teams that want a managed agent and are happy to negotiate pricing.

<div class="cmp-proscons" data-rival="sierra"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>Has SOC 2, HIPAA, GDPR, and PCI, and holds FedRAMP High through Knox Systems rather than its own authorization</li><li>Supports Apple Business Chat beside WhatsApp and SMS</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>Outcome-based pricing with no published rate</li><li>No self-serve mode</li><li>Sierra says it switches between language model providers on its own, so a team cannot fix one</li></ul></div></div>

**Pricing:** Outcome-based, with no published rate. Sierra says it gets paid when it completes a task, and that routing or greeter-style interactions may fit consumption-based pricing instead.

### 7. Retell: Best for developer teams that pick their own model and voice

**What does it do?** Retell is a platform for building and monitoring AI voice and chat agents, billed per minute with the language model and voice priced as separate lines. A customer's own SIP trunk (a connection to the phone network) carries no Retell phone charge, and phone on Twilio or Telnyx is billed on top.

**Who is it for?** Retell suits developer-led teams that want to choose their own language model and voice and pay per minute.

<div class="cmp-proscons" data-rival="retell"><div class="cmp-proscons-pros"><p><strong>Pros</strong></p><ul><li>A wide choice of language models and voices</li><li>Has SOC 2, HIPAA, and GDPR coverage</li></ul></div><div class="cmp-proscons-cons"><p><strong>Cons</strong></p><ul><li>Advertises "We guarantee >99.9% uptime", while its terms say "at least 99.5% uptime"</li><li>PII (personal data) Removal adds $0.01 a minute</li><li>No iMessage agents</li></ul></div></div>

**Pricing:** $0.07 to $0.31 per minute depending on the language model and voice, with Retell Voice Infra, GPT-4.1, and an ElevenLabs Flash voice coming to $0.14 per minute before phone.

### How were these builders ranked?

Builders were compared on who builds the AI, how a team builds and tests a call, where calls can run, price per minute before phone, compliance, and voice realism, with weight on what enterprise calls need. Every claim about a builder comes from its own public pages as read in November 2026, and voice scores come from Design Arena's chart of 4 August 2026.

Closer comparisons sit in [Bland vs Vapi](/compare/bland-vs-vapi), [Bland vs Synthflow](/compare/bland-vs-synthflow), [Bland vs ElevenLabs](/compare/bland-vs-elevenlabs), [Bland vs PolyAI](/compare/bland-vs-polyai), [Bland vs Sierra](/compare/bland-vs-sierra), and [Bland vs Retell](/compare/bland-vs-retell). Related rankings cover [Best AI phone agents](/blog/best-ai-phone-agents), [AI voice agent services](/blog/best-ai-voice-agent-services), [AI voice agents for automated phone calls](/blog/best-ai-voice-agents-automated-phone-calls), and [AI customer service agent platforms](/blog/best-ai-customer-service-agent-platforms).

## How much do AI voice agent builders cost?

Enterprise pricing is custom, set with Bland's sales team. AI voice agent builders charge per minute, but what a minute includes differs, so each price below states its basis. Bland's self-serve Start plan is $0.14 per minute for its language model, transcription, and speech together, and Bland replaced an earlier flat $0.09 rate with Start and Build in December 2025.

![Bland's pricing page, with self-serve Start at $0.14 a minute, self-serve Build at $0.12 a minute, and custom Enterprise pricing.](/images/compare/bland-pricing.jpg)

Every total below is AI before phone, with Vapi and ElevenLabs at their calculator defaults. Retell's card adds Retell Voice Infra, GPT-4.1, and an ElevenLabs Flash voice to reach $0.14 per minute, while Retell publishes a range of $0.07 to $0.31 per minute depending on the model and voice.

Vapi's card adds hosting to the top of each range on its pricing calculator, ElevenLabs' card adds the calculator's default model to a call minute, and phone is billed by whichever provider a customer connects. Synthflow, PolyAI, and Sierra publish no per-minute rate for a managed agent, so no bill can be added up for them.

| Vendor | What a minute pays for | Total per minute | Phone |
|---|---|---|---|
| Bland Start (self-serve) | All AI: model, transcription, speech $0.14 | $0.14 before phone | Billed separately at carrier cost |
| Retell | Voice infrastructure $0.055, GPT-4.1 $0.045, ElevenLabs Flash voice $0.04 | $0.14 before phone | Twilio at $0.015 a minute, billed on top |
| Vapi | Hosting $0.05, Transcription $0.0099, Language model $0.0452, Voice $0.0238 | $0.1289 before phone | Free on Vapi numbers, billed on top on Twilio at up to $0.014 a minute |
| ElevenLabs Agents | Call minute $0.08, Gemini 2.5 Flash, the calculator's default model $0.0029 | $0.0829 before phone | No ElevenLabs telephony fee, with a connected provider billing on top |

Bland Start (self-serve): Self-serve Start has no platform fee. Self-serve Build is $0.12 a minute plus $299 a month. Phone and transfers bill separately. Retell: Retell Voice Infra, GPT-4.1, and an ElevenLabs Flash voice, before Twilio phone minutes. Vapi: Hosting plus the top of each range on Vapi's pricing calculator, before phone. ElevenLabs Agents: ElevenLabs call minute plus its pricing calculator's default model, before the customer's own phone provider.

## Which AI voice agent builder sounds most like a real person?

Bland Speech v3 ranked 1st of 13 AI voices on Design Arena's Audio Realism Bench on 4 August 2026, at 1365, and every outside voice in those results that the other builders here let a customer choose scored lower.

On Retell and Vapi the highest outside voice was OpenAI's GPT Realtime 2, 4th at 1119.

ElevenLabs' Eleven v3 ranked 12th at 938, and Synthflow offers it as a voice a customer can switch to. PolyAI uses outside voice providers and no PolyAI voice was in the results. No Sierra voice was in them either. Retell's own platform voices, Vapi's own voices, and Synthflow TTS were not in the results either.

See [Design Arena's published results](https://notes.designarena.ai/audio-realism-benchmark-measuring-realism-in-audio-models/).

## Frequently asked questions

### What is the best AI voice agent builder?

Bland is the best AI voice agent builder for enterprise calls as of November 2026, because one company builds every model on a call. Enterprise customers get dedicated orchestration and dedicated GPUs run by Bland.

### Which AI voice agent builders are HIPAA compliant?

Bland is HIPAA compliant and includes its BAA on Enterprise, and Retell, Synthflow, and PolyAI offer a BAA as of November 2026. Vapi sells HIPAA mode as a $2,000 monthly add-on, ElevenLabs applies its BAA only while Zero Retention Mode is on, and Sierra has HIPAA among its standards.

### Is Bland only for outbound calls?

No, Bland runs inbound and outbound calls, including AI receptionist and contact center work, and it also runs SMS and web chat.

### Is Bland only for developers?

No, Bland isn't only for developers. Pathways gives teams a visual builder, Norm helps build agents, and on Enterprise forward-deployed engineers build alongside a customer's team.

### Does Bland use an open-source model?

No, Bland operates a closed-source model that it developed itself, so its language model isn't an open-source model and no outside AI lab sits behind it.

### Which AI voice agent builders support iMessage?

Bland runs branded iMessage agents natively on its Enterprise plan. Sierra supports Apple Business Chat, and Vapi, Synthflow, ElevenLabs, PolyAI, and Retell don't offer iMessage agents as of November 2026.

### How much does an AI voice agent builder cost per minute?

Rates run from $0.05 per minute for hosting alone on Vapi to $0.07 to $0.31 on Retell depending on the model and voice, and Synthflow, PolyAI, and Sierra publish no per-minute rate for a managed agent. Bland is $0.14 per minute on self-serve Start for all of its AI, before phone.

### Can I keep my phone carrier if I move to Bland?

Yes, Bland connects to a carrier or phone system over SIP, so numbers and routing stay in place.