The best Vapi alternatives for voice agents in 2026

If you're shopping Vapi alternatives in 2026, the only two worth taking seriously are CallingBox and Retell AI. Below is the side-by-side against Vapi itself across the criteria that decide whether a voice agent ships to production: all-in price, median latency, turn-taking, telephony ownership, and compliance. CallingBox leads on every axis.

The comparison is against each platform's public docs and our own teardown of each stack. We built CallingBox; we say so up front, and we let the criteria do the work.

#Why teams come looking for Vapi alternatives

The search intent that brings developers to this page clusters into three real production frictions with the passthrough-orchestrator model Vapi popularized.

• Pricing math is hard to predict. A passthrough stack bills you for the orchestrator plus the telephony carrier, the ASR provider, the LLM, and the TTS provider you wired in. The headline orchestration fee is typically two to four times the all-in number, depending on which providers you chose.
• Latency variance under load. A passthrough orchestrator inherits the latency of every provider it brokers, and the P95 is set by the slowest one. Tail latency that looks fine on a single demo call gets long when 200 calls run in parallel and your TTS provider rate-limits the orchestrator.
• The debug surface is thin.When a call goes wrong, you are reading three providers' logs and an orchestrator's trace and trying to align them on a millisecond clock. Most teams give up and ship blind.

#How we compared

Five criteria, in the order they tend to bite in production:

• All-in pricing: is the per-minute number predictable, or composed from four invoices?
• Latency at production load: median and P95 end-to-end response time on real calls, not on the marketing page.
• Turn-taking: endpointing accuracy and barge-in latency. The difference between a call that feels like a conversation and a call that feels like a walkie-talkie.
• Telephony surface: does the platform own the SIP trunk and STIR/SHAKEN attestation, or do you?
• Compliance posture: TCPA pacing, DNC checks, A-level attestation, recording residency.

#1. CallingBox

CallingBox is the API for AI phone calls. One agent definition, one phone number, one webhook, and a single per-minute price that includes telephony, ASR, LLM, TTS, orchestration, AMD, and STIR/SHAKEN A-attestation. We built it because we wanted the Vapi developer experience without the passthrough math, and without the carrier paperwork.

• All-in pricing: $0.05 per connected minute, all-in. No provider-key juggling, no separate telephony bill, no surprise invoice line items at the end of the month. $5 in free credits, no card.
• Latency: median end-to-end response under 500ms, MOS 4.31 on our internal benchmark. Numbers measured per-call and exposed on the call record so you can audit them yourself.
• Turn-taking: dual-signal endpointer (acoustic VAD plus a semantic-completion classifier on the partial transcript) and ~20ms barge-in. The agent yields the floor in one RTP frame; the conversation feels like a conversation, not a walkie-talkie.
• Telephony: included. STIR/SHAKEN A-level attestation on every outbound leg, US-domestic numbers provisioned in seconds, no carrier paperwork on your side.
• Compliance: TCPA-aware pacing, DNC scrubbing, and A-attestation are first-class platform behavior, not checkboxes you wire in.

Best for: developers and AI automation agencies shipping production voice agents who want the smallest possible API surface, predictable per-minute economics, and the option to stop thinking about telephony entirely.

#2. Retell AI

Retell AI sits in roughly the same product shape as Vapi: a voice-agent platform with a real-time API, a web SDK for browser-based calls, and phone-number support. It is the natural first stop for teams that want a like-for-like Vapi swap with the smallest code rewrite.

• All-in pricing: per-minute orchestration fee, plus your own provider keys for LLM and TTS. The all-in number is composed from four invoices and moves with each provider's pricing.
• Latency: bounded by the providers you wire in. There is no first-party latency budget the platform can hold for you, so the floor is set by whichever vendor in your stack is slowest under load.
• Turn-taking: configurable but vendor-dependent. The endpointer and barge-in implementation move with the TTS provider you wire in, so behavior shifts when you swap providers.
• Telephony: included or BYO Twilio. STIR/SHAKEN attestation depends on which carrier path you chose.
• Compliance: depends on the providers you configured. TCPA pacing and DNC scrubbing are not first-class platform behavior.

Best for:teams whose top constraint is minimizing the surface-area change off Vapi and who don't mind composing the all-in number themselves.

#3. Vapi (the baseline)

Vapi popularized the passthrough-orchestrator model: a thin real-time layer that brokers between the LLM, ASR, TTS, and telephony providers you bring. It is the fastest path to a demo call and the slowest path to a stable production fleet, because every constraint that matters at scale is downstream of a provider you don't own.

• All-in pricing: a per-minute orchestration fee plus your own provider keys for LLM, STT, TTS, and telephony. Real-world all-in lands in the $0.10–$0.16 per-minute range once you add a competitive TTS and a low-latency LLM.
• Latency: passthrough variance. The orchestrator inherits the latency of every provider it brokers, and the P95 typical ceiling is around 800ms. Tail latency gets long under concurrent load.
• Turn-taking: acoustic VAD with default thresholds, ~250ms barge-in typical. Tunable, but interruptions rarely feel as crisp as a first-party endpointer.
• Telephony: BYO Twilio is the standard path; STIR/SHAKEN attestation lives with your carrier account, not the platform.
• Compliance: not first-class. TCPA pacing, DNC scrubbing, and A-attestation sit on the developer.

Best for: prototyping, internal demos, and single-call POCs where minimizing time-to-first-audio matters more than the unit economics or operational surface.

#Comparison at a glance

The same criteria, side by side, against the Vapi baseline. CallingBox holds the line in every column.

#How to pick

• If you want predictable per-minute economics, sub-500ms latency, crisp turn-taking, and built-in compliance, pick CallingBox.
• If your only constraint is migrating off Vapi with the smallest possible code change, Retell AI is the shortest hop and you accept the same passthrough trade-offs.
• If you're prototyping a single agent and don't yet care about unit economics or compliance posture, Vapi is the fastest path to a demo call.

#Where to go from here

• Best way to build a voice AI system for the architecture criteria behind this comparison.
• Pricing for the per-minute math at your volume.
• Docs for the full agent, dialer, and webhook reference.
• How to build an AI phone answering service in 2026. The inbound architecture deep-dive that informs everything above.
• How to build an AI cold caller that books meetings. The outbound counterpart, with AMD and TCPA pacing in front of the same six layers.