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 open-weights mixture-of-experts Gemma 4 model (4B active parameters), thinking off.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 27.8% | 56.8% | 83 / 55 / 46 | 57.5% | 84.1% | 82.5% | 399ms | $0.058 |
| Healthcare | 31.7% | 47.7% | 88 / 56 / 19 | 48.0% | 85.0% | 88.7% | 412ms | $0.053 |
| Legal | 15.0% | 62.7% | 68 / 63 / 59 | 63.7% | 93.3% | 75.7% | 384ms | $0.061 |
| Customer support | 36.7% | 60.0% | 92 / 45 / 59 | 60.7% | 74.0% | 83.0% | 404ms | $0.061 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.