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.
Google's fast Gemini 2.5 model, a common choice for low-latency voice agents.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 38.9% | 66.0% | 81 / 68 / 56 | 67.6% | 89.7% | 84.0% | 610ms | $0.132 |
| Healthcare | 36.7% | 59.7% | 100 / 74 / 25 | 59.7% | 88.3% | 86.0% | 598ms | $0.137 |
| Legal | 35.0% | 72.3% | 52 / 80 / 75 | 75.0% | 94.7% | 78.3% | 618ms | $0.120 |
| Customer support | 45.0% | 66.0% | 92 / 50 / 69 | 68.0% | 86.0% | 87.7% | 607ms | $0.139 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.