HealthBench Professional

Anthropic logoClaude Fable 5 (September card) on HealthBench Professional

rank 6 of 31 · updated September 30, 2026

Claude Fable 5 (September card) scores 0.633 on HealthBench Professional, rank 6 of 31 models on the board. Anthropic's top-tier model, positioned above the Opus line for the hardest reasoning work. 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

rank6 of 31
score0.633
labAnthropic
context window1.0M tokens
API price per 1M tokens$10.00 in / $50.00 out
licenseproprietary
sourceClaude Fable 5.1 and Claude Mythos 5.1 System Card (system card)
released2026-06-09

Position in the field

The gap to the leader, GPT-6 Astra (Anthropic run) at 0.703, is 0.070. Directly above sits GPT-6 Astra at 0.647. Directly below sits Claude Fable 5.1 at 0.621. The scores on this page are compiled from published documents rather than from one controlled run, so a small gap between 2 models can reflect a difference in grader version, reasoning effort, or deployment setting as well as a difference in capability.

Source of this score

Read from Claude Fable 5.1 and Claude Mythos 5.1 System Card (system card, Anthropic, 2026-09-01). Vendor-reported. Confidence: verified. Configuration: Measured as Claude Fable 5; Anthropic September card; length-adjusted; adaptive max effort; Opus 4.8 grader; five trials; no tools or custom system prompt; raw 68.9%.

HealthBench Professional | Length-adjusted score | Claude Fable 5 | 63.3%

p. 199, Figure 8.17.2.A, Claude Fable 5 length-adjusted bar (visually read printed labels). · full entry on the sources page

What does Claude Fable 5 (September card) score on HealthBench Professional?

Claude Fable 5 (September card) scores 0.633 on HealthBench Professional, which places it at rank 6 of 31 models on the board as of September 30, 2026. The number was read from Claude Fable 5.1 and Claude Mythos 5.1 System Card, listed on the sources page.

How much does Claude Fable 5 (September card) cost to run?

Claude Fable 5 (September card) is priced at $10.00 per million input tokens and $50.00 per million output tokens through Anthropic's API.

Head to head

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

Where the scores come from and how they are read is on the methodology page. The full ranking is on the leaderboard.