Register Bias in Complexity-Based Large Language Model Routing
Large language model services increasingly route each query to one of several models of differing capability, using a cheap estimate of query complexity to send easy queries to small models and hard queries to large ones. I show that this routing step is not register neutral: text written in a non-standard English register, African American English or the English of second-language writers, is systematically assigned a lower-capacity tier than a meaning-equivalent standard-English version of the same query. The effect is driven by a specific, common routing signal, input length, because non-standard registers omit function words and thus look shorter and therefore simpler; other complexit...
| Authors | Simran Koul |
|---|---|
| Primary category | cs.CL |
| Published | 14 July 2026 |
| Last updated at source | 14 July 2026 |
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