OpenAI's new flagship model, GPT-5.6 Sol, performs almost as well as Fable 5 in benchmarks but costs only one-third as much. According to the independent AI evaluation platform Artificial Analysis, GPT-5.6 Sol (max) scores 59 points on the Intelligence Index, just one point behind Claude Fable 5 (max). In Artificial Analysis's new Coding Agent Index, Sol (max) takes the top spot with 80 points when running in OpenAI's Codex environment. In the AA-Briefcase benchmark for realistic office tasks, Sol earns the highest "Presentation Elo" of all models but still trails Fable 5 in the overall ranking. Sol costs $1.04 per task, about one-third of what Fable 5 charges at $2.75. The smaller variants, Terra and Luna, cost $0.55 and $0.21 per task, respectively. GPT-5.6 also introduces a cache-write fee for the first time, pushing prices down further. Token prices per million are $5/$30 (Sol), $2.50/$15 (Terra), and $1/$6 (Luna) for input/output. Cache reads get a 90 percent discount. Sol also burns fewer output tokens than models with similar performance, up to 54 percent fewer for agentic coding tasks, according to OpenAI CEO Sam Altman.