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.
Mistral AI's open-weights Mistral Small 4 (119B), reasoning off.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 11.1% | 38.5% | 69 / 29 / 33 | 39.6% | 65.1% | 64.1% | 827ms | $0.227 |
| Healthcare | 11.7% | 32.0% | 73 / 28 / 15 | 32.7% | 51.0% | 67.0% | 840ms | $0.215 |
| Legal | 1.7% | 29.7% | 40 / 23 / 31 | 30.3% | 71.3% | 48.7% | 724ms | $0.210 |
| Customer support | 20.0% | 53.7% | 93 / 36 / 52 | 55.7% | 73.0% | 76.7% | 835ms | $0.255 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.