Quick Take

OpenAI’s GPT-5.6 Terra and Anthropic’s Claude Fable 5 represent two distinct approaches to frontier AI. Released in July 2026, GPT-5.6 Terra focuses on high-velocity, cost-effective performance. Conversely, the June 2026 release of Claude Fable 5 prioritizes raw intelligence and complex reasoning, albeit at a higher financial and latency cost.

Benchmark Read

Claude Fable 5 consistently outperforms GPT-5.6 Terra across the provided metrics. Claude achieves an intelligence index of 59.9 compared to GPT-5.6’s 45.6. In coding, Claude scores 76.5 against GPT-5.6’s 64.7.

Benchmark performance follows this trend:

• GPQA: Claude (0.926) vs. GPT-5.6 (0.872)
• HLE: Claude (0.533) vs. GPT-5.6 (0.316)
• SciCode: Claude (0.602) vs. GPT-5.6 (0.497)
• TAU2: Claude (0.985) vs. GPT-5.6 (0.728)
• LCR: Claude (0.7) vs. GPT-5.6 (0.68)
• IFBench: Claude (0.635) vs. GPT-5.6 (0.622)

Cost and Speed

GPT-5.6 Terra is significantly more affordable, with a blended cost of $5.63/1M tokens compared to Claude Fable 5’s $20.00/1M. GPT-5.6 also excels in responsiveness, delivering 133.563 tokens per second with a time-to-first-token of 1.054 seconds. Claude Fable 5 is slower, outputting 60.571 tokens per second with a substantial 54.299-second delay before the first token appears.

Best Fit

GPT-5.6 Terra is best suited for high-volume applications where speed and budget are critical. Claude Fable 5 is the preferred choice for complex, reasoning-heavy tasks where precision is more valuable than immediate response times.