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.
OpenAI's small non-reasoning GPT-4.1 model.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 40.0% | 66.8% | 95 / 65 / 54 | 67.5% | 90.3% | 87.1% | 653ms | $0.245 |
| Healthcare | 28.3% | 52.3% | 97 / 55 / 28 | 52.7% | 86.0% | 85.0% | 716ms | $0.257 |
| Legal | 36.7% | 75.0% | 88 / 80 / 63 | 75.7% | 98.7% | 84.7% | 580ms | $0.231 |
| Customer support | 55.0% | 73.0% | 100 / 60 / 73 | 74.0% | 86.3% | 91.7% | 665ms | $0.248 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.