GPT-5.5
OpenAI's latest flagship with noticeably stronger reasoning and autonomy than GPT-5.4. Available in standard and Pro variants. 1M context window, $5/$30 per 1M tokens for standard.
- Stronger reasoning vs GPT-5.4
- GPT-5.5 Pro variant
- 1M context window
- Codex integration
- $5/$30 API pricing
GPT-5.5
Identity
GPT-5.5 is a flagship reasoning-class artificial intelligence model developed by OpenAI, released on April 23, 2026 (Source 1, 2). It serves as the successor to the GPT-5.4 lineage, maintaining per-token latency parity with its predecessor while increasing intelligence and autonomous capabilities (Source 6). The model is deployed in several variants, including GPT-5.5 Standard, GPT-5.5 Pro, and GPT-5.5 Instant, the latter of which serves as the default model for ChatGPT (Source 1, 9, 20). In June 2026, OpenAI acquired the cloud platform Ona to provide managed runtimes for the model's agentic workflows (Source 4). The model features tightened integration with NVIDIA hardware specifically for Codex and agentic execution (Source 6). A specialized version, GPT-5.5-Cyber, is utilized for state-level infrastructure protection and the "Patch the Planet" initiative, a partnership with Trail of Bits to remediate open-source software bugs (Source 10, 1