GPT-6 Astra vs Claude Fable 5.1 Tested: Same 3D Game Task, Different Results SandBase's GPT-6 Astra vs Claude Fable 5.1 test: the same 3D game prompt, original code, startup failures, completion checks, response times and actual API charges. Model Comparison September 7, 2026 gpt-6-astraclaude-fable-5-1coding-agents