OpenAI

GPT-5.5 Pro

• Released 23 April 2026
• Framework: Preparedness Framework
• 1 independent or government test
• 2 source documents

Independent and government tests

• BioTier · SecureBio, independent evaluator · Chemical, biological, radiological and nuclear

  at the same time, we saw gpt-5.5 pro and grok 4.20 drop in performance on biotier-refuse, while claude opus 4.8 showed little change at all.

  SecureBio · 16 July 2026 · Read the source

No document we read states: whether a capability level was crossed, a test by the provider, a safeguard. No incident on record names this version.

Some documents we hold are stored in lower case only, so their quotes are shown in lower case. The source link opens the original.

Previous version: GPT-5.4 Thinking · Compare the two