Tutorials, deep dives and product notes — built for developers.
GPT-6 Luna vs GPT-5.4 Mini compared: rate card, context windows, knowledge cutoffs, and the shared Artificial Analysis harness where Luna leads the Intelligence Index 37 to 24 at 6.4x lower cost per task, while mini wins on speed. Vendor scorecard gaps stated honestly.
GPT-6.1 Sol replaced GPT-6 Sol after seven days: +4 index points, +12 on Terminal-Bench 4.0, and a cache rate halved to $0.10. It also dropped the "none" reasoning setting, uses 10-30% more output tokens, and is measurably slower.
GPT-6.1 Sol matches Claude Opus 5.5's default index score for 46% less per task and ties it at low effort for 76% less — then stops at index 52, below every Opus effort above default.
OpenAI shipped GPT-6 Sol 90 minutes after Claude Opus 5.5, at half the token price. Artificial Analysis ran both on the same tests: Sol is cheaper to any index score up to about 44, then runs out of headroom. Every benchmark, both effort ladders and the real bill.
Opus 5.5 matches GPT-6 Astra on Terminal-Bench 4.0 for roughly 40% of the cost per task, with 5x cheaper cache reads. Astra keeps uncontested leads in science, maths and gated offensive security — and OpenAI says it is harder to monitor.
Sixty days apart: a 29.7-point jump on scientific research, a 200,000-line codebase audit that drops from 20+ hours to under 3, and a 40% cost cut — plus four API changes that will 400 your Opus 5 integration.
Opus 5.5 wins eight of the nine benchmarks Anthropic publishes against Fable 5.1 at 2.5x lower token price - but four of those margins sit inside the disclosed error bars. Includes the HAProxy same-task test, the 16-0 research-report result and the one-way thinking-block handoff.
Anthropic's Claude Opus 5.5 matches Fable 5.1 on most work at $4/$20 per million tokens: 66.4% on Terminal-Bench 4.0, 1,846 GDPval-AA Elo, and 40% lower cost per task than Opus 5. Full benchmark table with footnotes, real tester results, the four breaking API changes, and where GPT-6 Astra still wins.
DeepSeek V4.1 Flash wins 5 of the 15 benchmarks it shares with Claude Opus 5 — by an average of 1.94 points, while undercutting it by up to 41.7× on output price. Opus 5's 10 wins average 10.19 points. Full vendor data, community test reports, pricing math, charts and a routing verdict.
Terminal-Bench 4.0 checked Oct 6, 2026: Claude Opus 5.5 (64.8%) and Sonnet 5.5 (61.8%) now top the public tbench.ai board, with GPT-6 Astra and GPT-6.1 Sol tied at 58.2%. Vendor runs and Artificial Analysis results are reported separately, with harness, tokens and cost per row.
OpenAI's GPT-6 Astra vs Anthropic's Claude Fable 5.1: every benchmark, the independent indices, real-world head-to-heads, pricing deep dive, and who actually wins your workload.
GPT-6 Astra review: every benchmark, what people built, pricing, and the Critical cybersecurity rollout — with sources.