OpenAI launches GPT-6 Astra, hits 99.9% on ARC-AGI 3 — but that score comes with a big asterisk

OpenAI 发布 GPT-6 Astra，ARC-AGI 3 得分 99.9%

OpenAI released GPT-6 Astra, rolling out today to select orgs and soon to all ChatGPT Plus, Pro, Business, Enterprise, and API users. API pricing matches Claude Fable 5/5.1 at $10/M input and $50/M output. The headline 99.9% on ARC-AGI 3 is real but inflated: it used OpenAI's custom Provider Adapter harness at $19K, while the default harness scored 62.7% at $26K. The custom harness preserves reasoning state across requests and compacts long conversations, letting the model reuse prior work. Security scores are genuinely strong — 100% on ExploitBench, 42.4% on ExploitGym, 99.2% on SRE-Bench reverse engineering. Long-context needle retrieval hit 100% at 256K–512K and 96.3% at 512K–1M. On Artificial Analysis's Intelligence Index, Astra ties GPT-5.6 Sol at 61, 5 points below Claude Fable 5.1 and behind Meta's Muse Spark 1.3. It leads the Coding Agent Index cost-efficiency frontier: same cost as Sol at max effort but 2 points higher, and less than half the per-task cost of Fable 5 for the same score. Simon hasn't tried it yet; the API label will be gpt-6-astra.

Why it matters: GPT-6 Astra is OpenAI's direct Fable competitor, priced identically and claiming higher benchmarks. The 99.9% ARC-AGI 3 score required a custom harness — default harness hit 62.7% — which is the key caveat. ExploitBench went from 78.5% to 100%, a concrete security jump. Simon ...