gpt5-router-selects-between-fast-and-reasoning-model

IN premise — summaries/2026/08/24/wiki-Generative_pre-trained_transformer-chunk-1.md

Created 2026-08-24T17:11:10+00:00

GPT-5 (August 2025) introduced a router that selects between a faster model and a slower reasoning model per task, representing a distinct architectural departure from prior GPT generations.

Summary

Rather than forcing every request through one big model, GPT-5 uses a routing layer that decides per task whether a quick, lightweight model will suffice or whether the request needs to be escalated to a slower, more deliberate reasoning model. This marks a real architectural break from earlier generations, which treated "bigger and slower" as the only path to better answers, and it implies that inference speed is now a first-class design variable rather than an afterthought.