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Compare Opus 5.5 vs Opus 5

Claude Opus 5.5 vs Opus 5

At max effort, Opus 5.5 scored 93 and Opus 5 91, 2.6 points apart, under the 5 points the site counts as level. At low effort, Opus 5.5 scored 90 and Opus 5 87, 3.1 points apart, under the 5 points the site counts as level.

Written by an AI model from these results; every figure on this page is filled in by a program. How it was made.

Published 3 Oct 2026

Side by side

Released 22 Sep 2026

Opus 5.5

93/ 100

Low effort 90
Max effort 93

Level, rank 1

Floor45/49, 92% passed
Middle55/58, 95% passed
Top60/65, 92% passed

Tested 2 Oct 2026. Strongest in Code.

Released 24 Jul 2026

Opus 5

91/ 100

Low effort 87
Max effort 91

Rank 2

Floor45/49, 92% passed
Middle54/58, 93% passed
Top59/65, 91% passed

Tested 2 Oct 2026. Strongest in Code.

Score overall and by kind of work, checks passed, median time and median cost, Opus 5.5 and Opus 5, at each setting
	Opus 5.5		Opus 5
	Low	Max	Low	Max
Score	90	93	87	91
Web pages	90	80	90	93
Code	98	100	100	100
Planning	76	97	65	76
Everyday	96	96	93	93
Checks passed	157 of 172	160 of 172	153 of 172	158 of 172
Median time	16 s	5 min 14 s	17 s	57 s
Median cost	4.1¢	76¢	4.7¢	13¢

Scored higher by 5 points or more: Opus 5 on building web pages, 93 to 80; Opus 5.5 on planning and architecture, 97 to 76. Within 5 points on code and everyday.

Opus 5.5’s median max effort answer took 5 min 14 s and cost 76¢ at API prices, and Opus 5’s median max effort answer took 57 s and cost 13¢. A median Opus 5.5 answer cost 5.9 times as much.

Of the 24 prompts at max effort, Opus 5.5 passed more checks on 6, Opus 5 on 1, and the two passed the same number on 17.

Where they differed

Prompts where the two passed a different number of checks at max effort, widest gap first.

B03 A kanban board that survives a reload
Opus 5.5 0 of 9, Opus 5 7 of 9.
Passed by Opus 5, missed by Opus 5.5: The page loads with no errors and has the three named columns; Adding a card works with Enter and with the Add card button; Empty or space-only titles are ignored; The counts update, and Edit and Delete work; Dragging moves cards between columns and reorders them, and it survives a reload; A card can be moved with the arrow keys and keeps focus; Titles like <b>hi</b> & <img ...> show exactly as typed and run nothing
A02 Should we switch to microservices?
Opus 5.5 8 of 8, Opus 5 5 of 8.
Passed by Opus 5.5, missed by Opus 5: Says up front: not now, keep the monolith; Stays under the 350-word limit; Suggests a middle path: clear modules inside the monolith
A04 Turn a messy feature brief into a spec
Opus 5.5 8 of 8, Opus 5 6 of 8.
Passed by Opus 5.5, missed by Opus 5: Flags the free plan limit of 3 seats versus 5 people; Does not quietly choose a side of a contradiction in the criteria
H02 Summing up a book that doesn't exist
Opus 5.5 5 of 5, Opus 5 4 of 5.
Passed by Opus 5.5, missed by Opus 5: Under 200 words
B04 Minesweeper in one HTML file
Opus 5.5 9 of 9, Opus 5 8 of 9.
Passed by Opus 5.5, missed by Opus 5: Numbers are right and an empty square opens its neighbours
A01 Plan a booking app for a dog groomer
Opus 5.5 9 of 9, Opus 5 8 of 9.
Passed by Opus 5.5, missed by Opus 5: The first phase is small and usable before payments exist
A03 Rename a column with no downtime
Opus 5.5 8 of 9, Opus 5 7 of 9.
Passed by Opus 5.5, missed by Opus 5: Does not use RENAME COLUMN as the way to move while old code needs username

Every prompt

Checks passed on each prompt, at each setting. Each prompt links to its description.

Checks passed on each prompt by Opus 5.5 and Opus 5, at each setting
Prompt	Low	Max	Low	Max
	Opus 5.5		Opus 5
Building web pages
B01 A landing page for a small invoicing app	9 of 9	9 of 9	9 of 9	9 of 9
B02 Build a dashboard from a picture of its design	6 of 7	7 of 7	6 of 7	7 of 7
B03 A kanban board that survives a reload	7 of 9	0 of 9	9 of 9	7 of 9
B04 Minesweeper in one HTML file	8 of 9	9 of 9	6 of 9	8 of 9
B05 Fix three layout bugs on a garden page	7 of 7	7 of 7	7 of 7	7 of 7
Code
F01 Load more shows some posts twice and skips others	7 of 7	7 of 7	7 of 7	7 of 7
F02 The search box shows results for an old query	7 of 7	7 of 7	7 of 7	7 of 7
F03 Some subscriptions renew a day early	7 of 7	7 of 7	7 of 7	7 of 7
F04 Review a pull request before merging	6 of 7	7 of 7	7 of 7	7 of 7
F05 SQL: which customers left and came back	7 of 7	7 of 7	7 of 7	7 of 7
F06 A contacts import that survives real CSV files	9 of 9	9 of 9	9 of 9	9 of 9
F07 Make a slow script fast	7 of 7	7 of 7	7 of 7	7 of 7
Planning and architecture
A01 Plan a booking app for a dog groomer	7 of 9	9 of 9	8 of 9	8 of 9
A02 Should we switch to microservices?	7 of 8	8 of 8	6 of 8	5 of 8
A03 Rename a column with no downtime	7 of 9	8 of 9	4 of 9	7 of 9
A04 Turn a messy feature brief into a spec	5 of 8	8 of 8	4 of 8	6 of 8
Everyday
W01 Text the plumber to reschedule	6 of 6	6 of 6	6 of 6	6 of 6
I01 Check a market receipt adds up	5 of 5	5 of 5	5 of 5	5 of 5
H02 Summing up a book that doesn't exist	5 of 5	5 of 5	4 of 5	4 of 5
W02 Turn a messy thread into one clear update	6 of 6	6 of 6	6 of 6	6 of 6
K02 Answer questions from a bread maker manual	6 of 6	6 of 6	6 of 6	6 of 6
R02 Did cycling in town really double?	5 of 6	5 of 6	5 of 6	5 of 6
P02 Filling a week of volunteer shifts	6 of 6	6 of 6	6 of 6	6 of 6
S02 A story of exactly 100 words	5 of 6	5 of 6	5 of 6	5 of 6

What max effort changed

Opus 5.5. Max passed 3 more checks, cost 16.5 times as much and took 18.9 times as long.
Opus 5. Max passed 5 more checks, cost 3.3 times as much and took 3.8 times as long.

More comparisons

Compare any two models Every answer from Opus 5.5 Every answer from Opus 5