Claude Opus 5.5

Anthropic, closed weights, released Sep 2026, run at provider defaults through the Anthropic API. It built the same five pages as every model on season 0.5 of the Rams Index, and Rams graded each one at desktop and phone size.

Rams Index, 0 to 100

60.4

95% interval 52.9–70.2

Rank: 8of 14 models by Index; the paired intervals allow 2 to 13
Cost per page: $0.28Generation only, list price on run day
Second judge: 70.7GPT-5.6 Terra places it 11th of 14. The Claude judge: eighth.
Grade sum: 23.90Seven 1–5 grades, out of 35
Pages judged: 1010 judge passes, 2 builds per brief
Defects per page: 3.2Content wider than the phone (9 of 10)

Rank 8 of 14; the data allows anywhere from 2 to 13. Within noise of Grok 4.7, GPT-6.1 Sol, Claude Sonnet 5.5, GPT-6 Luna, Gemini 4 Argon, Muse Wonder, GPT-5.6 Sol, Claude Fable 5.1, Claude Fable 5, Gemini 3.8 Flash and DeepSeek V4 Pro: the gap to each sits inside the noise, so the board can't order them yet. Clearly behind GPT-6 Astra. Clearly ahead of Claude Opus 4.8.

Designer check pending · read Nov 6Season 0.5Provisional: 1.0 judge passes per page, protocol 2

Grades by dimension

The seven grades behind the Index, 1 to 5, mean of desktop and phone. The tick is the mean across all 14 models.

Hierarchy3.607 of 14
Typography3.405 of 14
Spacing3.157 of 14
Color3.507 of 14
Components3.408 of 14
Composure3.458 of 14
Craft3.406 of 14

Bars start at 2.8 and end at 4.2, the range the board uses, so small differences show.

Index by brief

The same Index on each of the five briefs, and where the model places on that brief among all 14.

Landing62.510 of 14
Dashboard58.96 of 14
Settings51.86 of 14
Pricing50.98 of 14
Article77.73 of 14

Bars run from 40 to 90.

How it ran

Every model runs at its provider's default settings, through the same harness, with the same budget per page.

Effort: Default (medium)The provider’s default. We send no effort or thinking setting
Time per page: 102sMedian over every build, broken ones included
Output tokens: 13.2kMedian per page, reasoning included
Reasoning tokens: n/aIts API doesn’t report them separately
Broken pages: 0 of 10Every build came back as a whole page
Criticals: 10%1 of 10 scored pages had a critical issue in their first Rams code review
Built through: Anthropic APIServed by Anthropic

Best and worst page

Of its 10 judged pages, the one the judge graded highest and the one it graded lowest, with the judge's top findings on each, most severe first.

Best: Article85.7
Index on this page, one judge pass. Brief mean 77.7.
- Meta line broken across two rows without visual groupingModerate
- Uneven vertical rhythm between dek and meta separatorModerate
- 12 distinct font sizes render in one componentModerate
Worst: Pricing48.2
Index on this page, one judge pass. Brief mean 50.9.
- Lede text clips at right edgeSerious
- Pro card vertical misalignment: badge disrupts price baselineModerate
- Inconsistent CTA button treatment: Free card uses outline, paid cards use filledModerate

All 10 of its pages sit beside every other model's in the gallery.

Head to head

Claude Opus 5.5 against every other model: the paired difference in Index points, and whether the 95% interval on it clears zero.

vs GPT-6 Astra-6.1Clearly behind
vs Grok 4.7-5.7Inside the noise
vs GPT-6.1 Sol-5.0Inside the noise
vs Claude Sonnet 5.5-1.4Inside the noise
vs GPT-6 Luna-1.4Inside the noise
vs Gemini 4 Argon-1.2Inside the noise
vs Muse Wonder-0.2Inside the noise
vs GPT-5.6 Sol+1.4Inside the noise
vs Claude Fable 5.1+1.4Inside the noise
vs Claude Fable 5+2.8Inside the noise
vs Gemini 3.8 Flash+4.8Inside the noise
vs DeepSeek V4 Pro+5.7Inside the noise
vs Claude Opus 4.8+7.5Clearly better

The other models

Season 0.5 of the Rams Index, in board order, then the unranked.

Rams Index v0.5 · updated 2026-10-17Judged by Rams eyes · Claude Sonnet 4.6