Claude Fable 5 vs GPT 5.5: Which Frontier Model Wins for Agentic Coding?

Claude Fable 5 features a context window up to 500K tokens and improved tool-use reliability for long agentic chains, according to the comparison. GPT 5.5 is positioned as an incremental upgrade between GPT-5 and GPT-6, with both models showing strengths in different real-world coding workflows.