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.
Meta's open-weights Llama 4 Scout, mixture of experts with 17B active parameters.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 7.8% | 23.0% | 54 / 17 / 13 | 24.2% | 53.6% | 48.8% | 544ms | $0.093 |
| Healthcare | 10.0% | 16.3% | 68 / 7 / 0 | 16.3% | 29.3% | 48.3% | 549ms | $0.097 |
| Legal | 1.7% | 24.7% | 35 / 25 / 19 | 25.0% | 77.7% | 40.0% | 549ms | $0.086 |
| Customer support | 11.7% | 28.0% | 60 / 20 / 20 | 31.3% | 53.7% | 58.0% | 502ms | $0.096 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.