GPT-5.5 Pro
Highest-accuracy GPT-5.5 tier for slower, precision-heavy reasoning and coding
ECI STANDING#5 of 266
SCORE162.25159.32–165.76 CI
FRONTIER LAGLaunched in the leadNothing released before it had scored higher.
SCORES LIKE THESE MODELSClaude Fable 5.1Anthropic · Sep 2026164.47Claude Fable 5Anthropic · Jun 2026163.27Claude Opus 5Anthropic · Jul 2026162.3GPT-5.6 SolOpenAI · Jul 2026161.81
Full Epoch Capabilities Index ranking ↗RELEASE DATEApr 23, 2026
WEIGHTSClosed weights
CONTEXT WINDOW1.05M
MAX OUTPUT128K
REASONINGYes
TOOL CALLINGYes
INPUTStext, image, pdf
OUTPUTStext
Specifications from Models.dev. Availability and limits may differ by provider. Benchmark scores come from Epoch AI under CC BY 4.0.