GPT-5.5 Instant on HealthBench Professional

rank 8 of 9 · updated August 16, 2026

GPT-5.5 Instant scores 0.384 on HealthBench Professional, rank 8 of 9 evaluated models. The fast variant that became ChatGPT's default model in May 2026. HealthBench Professional scores models on 525 tasks drawn from real clinician conversations, graded criterion by criterion against physician-written rubrics on a 0 to 1 scale.

Result and API facts

Position in the field

The gap to the leader, Claude Fable 5 at 0.660, is 0.276. Directly above sits GPT-5.6 Luna at 0.557. Directly below sits MAI-Thinking-1 at 0.350. Scores on this page come from the same evaluation run, so differences between models are differences on identical tasks, not across configurations.

Head to head

Pairings with a dedicated comparison page are linked; every other difference is in the score-difference matrix.

• GPT-5.5 Instant vs Claude Fable 5
  0.384 vs 0.660 · Claude Fable 5 by 0.276
• GPT-5.5 Instant vs GPT-5.6 Sol
  0.384 vs 0.605 · GPT-5.6 Sol by 0.221
• GPT-5.5 Instant vs Claude Opus 5
  0.384 vs 0.598 · Claude Opus 5 by 0.214
• GPT-5.5 Instant vs Claude Sonnet 5
  0.384 vs 0.578 · Claude Sonnet 5 by 0.194
• GPT-5.5 Instant vs GPT-5.6 Terra
  0.384 vs 0.577 · GPT-5.6 Terra by 0.193
• GPT-5.5 Instant vs Claude Opus 4.8
  0.384 vs 0.558 · Claude Opus 4.8 by 0.174
• GPT-5.5 Instant vs GPT-5.6 Luna
  0.384 vs 0.557 · GPT-5.6 Luna by 0.173
• GPT-5.5 Instant vs MAI-Thinking-1
  0.384 vs 0.350 · GPT-5.5 Instant by 0.034

How tasks are selected and graded is on the methodology page. The full ranking is on the leaderboard.