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 largest open-weights Qwen3.5 model, mixture of experts with 17B active parameters, thinking off.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 39.4% | 68.8% | 88 / 66 / 62 | 70.1% | 90.9% | 89.4% | 395ms | $0.234 |
| Healthcare | 50.0% | 72.3% | 100 / 77 / 54 | 72.3% | 93.3% | 92.7% | 408ms | $0.259 |
| Legal | 25.0% | 64.3% | 68 / 64 / 63 | 65.7% | 95.3% | 82.7% | 387ms | $0.206 |
| Customer support | 43.3% | 69.7% | 97 / 57 / 69 | 72.3% | 84.0% | 92.7% | 393ms | $0.238 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.