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.
OpenAI's small GPT-4o model.
| Scope | pass^5 | pass@1 | E / M / H | Tools | Handoff | Final DB | TTFT | Cost/hr |
|---|---|---|---|---|---|---|---|---|
| Cross-industry | 22.8% | 46.5% | 78 / 47 / 30 | 47.7% | 79.4% | 73.0% | 748ms | $0.123 |
| Healthcare | 26.7% | 44.7% | 87 / 61 / 8 | 45.0% | 72.7% | 78.7% | 856ms | $0.125 |
| Legal | 3.3% | 36.7% | 48 / 44 / 23 | 37.0% | 85.7% | 56.0% | 611ms | $0.120 |
| Customer support | 38.3% | 58.0% | 100 / 37 / 58 | 61.0% | 79.7% | 84.3% | 811ms | $0.124 |
E / M / H is pass@1 on easy, medium, and hard tasks. Gate columns are the share of conversations that cleared each check.