Top 5 Voice AI stacks [2026]

Telnyx engineers run voice AI stacks in production every day, on our own platform and alongside customers debugging theirs. Certain combinations of LLM, STT, and TTS keep proving out. Below are the five we recommend, with the specific models we'd pick internally if you asked.

Each template is tuned for a different priority: multilingual reach, cost, latency, compliance, or audio quality. Every template names a specific LLM, STT engine, and TTS voice. Swap any component without rebuilding the application. The platform underneath stays the same.

Why the stack underneath matters

A voice AI stack is only as fast as its slowest hop and only as reliable as its weakest vendor. The standard Frankenstack stitches together five vendors (Twilio for telephony, Deepgram for STT, OpenAI for the LLM, ElevenLabs for TTS, Vapi or Retell to orchestrate), adding latency at every boundary and a margin at every vendor. Telnyx runs the full pipeline on one network: STT, LLM routing, TTS, and orchestration in the same facilities where calls terminate. One SLA. One bill. One team accountable when something breaks.

You can start with one template and swap components as priorities shift, without rebuilding the application. Because the whole pipeline runs on Telnyx-owned infrastructure, performance stays consistent no matter which models you choose.

1. Multilingual AI agents

Recommended stack:

LLM: meta-llama/Llama-3.3-70B-Instruct
STT: Deepgram Nova 3
TTS: Rime Arcana V3

Llama 3.3 natively supports 8 major languages (English, French, Spanish, German, Italian, Portuguese, Hindi, and Thai) with 70 billion parameters providing the nuanced understanding needed for cross-cultural conversations.

The real magic happens with Rime Arcana V3's code-switching capability. Your agent can start a conversation in English, seamlessly switch to Spanish when a customer prefers it, then back to English, all within the same call, using the same voice. No jarring transitions or robotic announcements about language changes.

Deepgram Nova 3 provides the accuracy needed to correctly transcribe multilingual conversations, even when customers mix languages or have strong accents.

Any business can use this stack to better connect with customers. For example, a global e-commerce company can deploy this stack for customer support. When a customer calls about a delayed shipment and says "Mi pedido no ha llegado," the agent immediately switches to Spanish, and resolves the issue, creating a naturally bilingual experience that feels effortless.

2. Cost-optimized voice AI

Recommended stack:

LLM: Groq/llama-4-maverick-17b-128e-instruct (free tier)
STT: Telnyx STT (included in base pricing)
TTS: Telnyx NaturalHD (included)

This configuration runs at Telnyx's base rate with no additional charges for the LLM or speech processing, so you get Llama-4 Maverick's reasoning capabilities without paying for them on top of telephony and TTS.

Cost in a Frankenstack is the sum of five stacked margins. Telnyx is one margin. That's where the savings come from. Structural, not promotional.

Telnyx STT is Whisper-based with support for 100+ languages and included in your base pricing. Telnyx NaturalHD provides voice synthesis without per-minute TTS charges. Volume discounts on STT and TTS are available for committed usage.

3. Low-latency voice agents

Recommended stack:

LLM: google/gemini-2.5-flash-lite
STT: Deepgram Flux
TTS: Telnyx Ultra

Gemini Flash Lite is specifically optimized for speed while maintaining intelligence, with massive 1M+ context windows for complex conversations. It's designed for real-time scenarios where inference speed matters more than maximum reasoning depth.

Deepgram Flux excels at turn detection, knowing when customers finish speaking versus when they're just pausing to think. This prevents the agent from interrupting mid-thought, which paradoxically makes conversations feel faster even though the agent waits for proper completion signals.

Telnyx Ultra runs on the same PoP as the call. No inter-provider hop between media and inference. That's how sub-200ms round-trip becomes achievable instead of aspirational.

4. Voice AI for regulated CX

Recommended stack:

LLM: anthropic/claude-sonnet-4-20250514
STT: Deepgram Nova 3
TTS: Telnyx Ultra

Claude Sonnet provides enterprise-grade safety controls and reasoning capabilities, with Anthropic's constitutional AI approach reducing hallucination risks in sensitive contexts. It's designed for scenarios where accuracy and safety matter more than pure speed.

Deepgram maintains enterprise-grade protocols and complies with PCI, SOC 2, and HIPAA. For maximum compliance rigor, Deepgram also offers a Dedicated tier with single-tenant, fully isolated infrastructure, which is ideal for heavily regulated industries.

SOC 2 Type II, HIPAA, PCI, ISO, and GDPR are included on the Telnyx platform, not upsold as an enterprise tier. One DPA covers telephony, inference, and TTS because they run on one network.

Businesses can also anchor their Voice AI to specific regions (EU, Australia, etc.) to meet data residency requirements. Telnyx gives you control over where data travels during calls, and not just where it's stored.

For example, a telehealth provider can use this stack for patient intake calls. When patients provide medical history or insurance details, every component meets HIPAA requirements, with conversation data processed in-region and automatically purged per retention policies.

5. Premium audio quality

Recommended stack:

LLM: openai/gpt-4o
STT: Deepgram Nova 3
TTS: MiniMax

GPT-4o excels at understanding context and emotional nuance, generating responses that match the sophistication your premium customers expect. Its tool usage capabilities seamlessly integrate with CRM systems to provide personalized experiences based on customer history.

Deepgram Nova 3 provides the highest accuracy for speech recognition, correctly capturing customer names, account numbers, and complex requests on the first try. No "could you repeat that?" moments that break premium experience flow.

MiniMax delivers natural clarity with premium detail, built for real-time scenarios where subtlety matters. The voice quality includes emotional range and tonal variation that sounds genuinely human, not synthetic.

This stack has diverse applications. A high-end jewelry brand can use this stack for appointment scheduling and customer service. When VIP customers call about custom pieces or exclusive events, the premium audio quality matches their $50K+ purchase experience.

All five stacks at a glance

Implementation strategy

Start cost-optimized, scale into specificity

• Start with the Cost-Optimized stack while you validate the use case.
• Swap individual components as needs sharpen: STT, LLM, or TTS independently.
• Compare configurations side-by-side on the Telnyx dashboard before promoting to production.
• Track per-call latency and cost in one place because the whole call path lives on one network.

Switching made simple

Unlike platforms that require complete rebuilds when changing providers, Telnyx lets you swap any component (Telnyx Inference for the LLM, STT, or TTS) without touching your application code. Test Deepgram vs. Telnyx STT for latency. Try MiniMax vs. Telnyx Ultra for the agent voice experience, or NaturalHD when a lower-cost or WebSocket-compatible Telnyx voice path matters. Your voice AI adapts as your business grows.

The stack is a choice. The infrastructure underneath is not.

Five model combinations, one operational domain. Pick the template that matches the priority that hurts most: cost, latency, compliance, language coverage, audio quality. Swap components later when the priority shifts. The platform underneath stays the same, which is the only reason any of those swaps are cheap.