What is GPT-5.5?

GPT-5.5 is an AI model from OpenAI, discussed in May 2026 as a leading model for agentic tasks and tool calling, with strong benchmark performance.

• May 2026 - Nathaniel Whittemore reported GPT-5.5 scored 69.3% on Terminal Bench 2.0, behind Opus 4.7, and scored 77.8% on SweBench multilingual, comparable to Opus 4.7 at 80.5%.
• May 2026 - Greg Isenberg stated GPT-5.5 is the best model for Hermes agents or OpenClaw, being efficient with tool calls and not consuming tokens like Opus 4.7.
• May 2026 - Dan Shipper noted a 30-point bump in score for GPT-5.5, reaching 60 out of 100.
• May 2026 - Nathaniel Whittemore said Gemini 3.2 Flash hits 92% of GPT-5.5’s coding and reasoning performance while being 15-20x cheaper on inference.