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.
DeepSeek's open-weights V4.1 Flash, thinking off.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 57.8% | 81.1% | 93 / 82 / 75 | 82.7% | 95.7% | 92.4% | 476ms | $0.031 |
| Healthcare | 61.7% | 83.3% | 98 / 88 / 71 | 83.3% | 97.7% | 94.3% | 485ms | $0.032 |
| Legal | 53.3% | 81.7% | 83 / 88 / 74 | 83.0% | 98.3% | 89.0% | 454ms | $0.028 |
| Customer support | 58.3% | 78.3% | 97 / 68 / 79 | 81.7% | 91.0% | 94.0% | 485ms | $0.033 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.