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.
Alibaba's open-weights Qwen3.5 mixture-of-experts model with 10B active parameters, thinking off.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 22.2% | 47.9% | 80 / 40 / 40 | 48.7% | 77.4% | 75.8% | 284ms | $0.221 |
| Healthcare | 26.7% | 52.0% | 97 / 56 / 26 | 52.0% | 82.7% | 89.0% | 295ms | $0.236 |
| Legal | 15.0% | 40.3% | 57 / 34 / 38 | 40.3% | 80.7% | 56.7% | 270ms | $0.196 |
| Customer support | 25.0% | 51.3% | 87 / 30 / 55 | 53.7% | 68.7% | 81.7% | 277ms | $0.231 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.