Working paper / 2026
Conversational AI LLM Bench
Abstract
We define conversational AI LLMs as the language models at the center of cascaded voice pipelines, between speech recognition and speech synthesis, that return a first token within one second: a median time to first token of 1,000 ms or less. The Conversational AI LLM Bench (CALLM) benchmarks this category. Each model operates every agent of a multi-agent front desk in healthcare, legal, and customer support, with production-length prompts, executable tools, and per-call database state. A simulated caller pursues a locked task over a simulated phone line, so the model receives only what a speech recognizer would have transcribed, errors included. A deterministic verifier scores tool calls, handoffs, and final database state; pass@1 and pass5 measure single-attempt capability and five-attempt reliability.
Clone the repository, point a model at an industry pack, and reproduce the evaluation environment.
Deepgram's Think-Fast, an LLM built for Deepgram's voice agents, called through its Think API (Early Access).
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 12.8% | 35.3% | 73 / 27 / 25 | 35.6% | 63.9% | 59.1% | 285ms | N/A |
| Healthcare | 8.3% | 30.0% | 78 / 29 / 7 | 30.0% | 63.0% | 64.7% | 282ms | N/A |
| Legal | 13.3% | 37.3% | 53 / 34 / 33 | 37.7% | 70.7% | 45.3% | 275ms | N/A |
| Customer support | 16.7% | 38.7% | 87 / 17 / 37 | 39.0% | 58.0% | 67.3% | 451ms | N/A |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.