Claude Opus 5.5 vs union-alpha
Wins 4 of 4 areas
Coding · Reasoning · Math · Following instructions
Wins 0 of 4 areas
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Claude Opus 5.5 is the stronger all-rounder.
Scores updated · 7 tests both models report · How we compare
Where each one wins
Tests won in each of the four areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
Reasoning, math and following instructions rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where Claude Opus 5.5 pulls ahead
- Fixes real GitHub issues, working as an agentLiveBench · Agentic Coding+17points ahead
- Fresh logic puzzles that change regularlyLiveBench · Reasoning+11.4points ahead
- Programming problems, refreshed regularlyLiveBench · Coding+7.1points ahead
Where union-alpha pulls ahead
No clear win on a test scored out of 100.
Every test, side by side
All 7 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Opus 5.5
- LiveBench · Agentic CodingClaude Opus 5.5 by 1771.754.7+17
- LiveBench · CodingClaude Opus 5.5 by 7.189.382.2+7.1
ReasoningClaude Opus 5.5
- LiveBench · ReasoningClaude Opus 5.5 by 11.492.280.8+11.4
Following instructionsClaude Opus 5.5
- LiveBench · Instruction FollowingClaude Opus 5.5 by 6.265.759.5+6.2
Other results2 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- livebench_data_analysisClaude Opus 5.5 by 5.780.374.6+5.7
- livebench_languagetie86.385.9tie
Questions people ask
Which is better, Claude Opus 5.5 or union-alpha?
Claude Opus 5.5 wins all four areas where both have results: coding, reasoning, math and following instructions. union-alpha wins none.
Which is better for coding?
Claude Opus 5.5. It wins 2 of the 2 coding tests both models report; union-alpha wins none.
How do you compare the two?
We use the 7 benchmark tests both models have published scores on. The verdict counts the 5 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 2 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.