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 smallest and fastest Gemini 2.5 model.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 17.2% | 45.8% | 76 / 45 / 31 | 46.6% | 80.4% | 71.9% | 466ms | $0.047 |
| Healthcare | 23.3% | 51.0% | 92 / 56 / 26 | 51.0% | 82.0% | 79.7% | 492ms | $0.046 |
| Legal | 11.7% | 45.0% | 58 / 49 / 34 | 46.0% | 89.3% | 63.3% | 460ms | $0.048 |
| Customer support | 16.7% | 41.3% | 78 / 30 / 34 | 42.7% | 70.0% | 72.7% | 446ms | $0.047 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.