Matt Shumer's GPT-6 Astra review: Manager Loop sustains a week-long Manhattan build in Unreal

mattshumer_ · x · 2026-09-04

Matt Shumer published a 19-minute hands-on review of GPT-6 Astra. Key points:

Daily driver: Plain-English replies, strong intent understanding and ambiguity handling; medium reasoning for everyday work, Ultra for big experiments. Claude still wins on visual taste and design assets.
Manager Loop: The biggest surprise—a coordinator keeps the project moving while an implementer works in a separate Codex session, spawning sub-agents as needed. He used it to build a simulated civilization and make real progress on a GTA-like New York City.
Manhattan build: Astra constructed a Manhattan world in Unreal Engine street by street over a week—work that would take humans months. Finding the setup that allowed such long runs took considerable iteration.
Caveats: Long-running autonomy isn't solved; Astra can get absorbed in details and ambitious runs need careful coordination or they asymptote. It's the first model where he feels the right prompting can get it there.
Cost: His large experiments consumed enormous token amounts.

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