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 small dense open-weights Qwen3.5 model, thinking off.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 7.2% | 24.5% | 54 / 19 / 16 | 25.0% | 61.0% | 57.9% | 410ms | $0.100 |
| Healthcare | 8.3% | 27.7% | 65 / 29 / 8 | 27.7% | 63.3% | 74.0% | 421ms | $0.109 |
| Legal | 1.7% | 18.0% | 25 / 17 / 16 | 18.7% | 65.7% | 32.3% | 391ms | $0.091 |
| Customer support | 11.7% | 27.7% | 72 / 10 / 23 | 28.7% | 54.0% | 67.3% | 410ms | $0.100 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.