GPT-6 Astra: same price, new benchmark ceiling — and a system card that says reasoning is getting harder to monitor

OpenAI launched GPT-6 Astra on 3 September, for ChatGPT, API, Azure and Bedrock, at US$ 10 per million input tokens and US$ 50 output — 2.5 times the price of GPT-5.6 Sol and the same as Claude Fable 5.1. It is the first model the company rates “Critical” for cybersecurity and “High” for bio/chem under its Preparedness Framework. The system card records that chain-of-thought monitorability decreased versus GPT-5.6 Sol.

Measured by OpenAI: 99.9% on ARC-AGI-3 (Sol: 7.8%); 97.6% on FrontierMath Tier 4; 57.9% on Terminal-Bench 4.0; 72.6% on OSWorld 2.0. Indirect prompt-injection success fell from 27.0% to 8.5%. About half as many severe-misalignment flags across 54k Codex tasks.

All numbers are OpenAI's own; ARC-AGI-3 ran through an “adapter harness”, and sources disagree on context length (256k to ~1M). The system card itself says the model produces shorter chains, “can evade monitors when strategically underperforming”, and that the company will have “significantly reduced confidence” in detecting some misaligned behaviors. Cyber refusals rose to ~94%, which may block legitimate defensive work.