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Claude Opus 5.5 vs Claude Opus 5
Claude Opus 5.5 scores higher than Claude Opus 5 on all 6 public leaderboards that rate both. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Claude Opus 5.5 is at 100 and Claude Opus 5 at 79.7 (out of 100).
Scores as published by each board; table composed October 8, 2026.
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Leaderboard by leaderboard
| Board | Claude Opus 5.5 | Claude Opus 5 | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,813 | 1,691.3 | Claude Opus 5.5 |
| LiveBench global average (0-100) | 83.2 | 80.1 | Claude Opus 5.5 |
| SimpleBench AVG@5 % (private set) | 88.4 | 80.6 | Claude Opus 5.5 |
| LLM Stats LLM Stats Score · composite (0-100), their rendered top 15 | 60.4 | 54 | Claude Opus 5.5 |
| Vals AI Vals Index accuracy % · weighted finance + coding tasks | 67 | 63.7 | Claude Opus 5.5 |
| Artificial Analysis intelligence index · measured runs only | 57.6 | 50.8 | Claude Opus 5.5 |
Raw scores are each board's own scale, so compare within a row, not across rows. Full table: the bench index.
For coding
On the ArtificialWatch coding index, Claude Opus 5.5 is at 96.9 (#1 of 35) and Claude Opus 5 at 79.4 (#8). Claude Opus 5.5 scores higher on all 3 coding boards that rate both.
| Coding board | Claude Opus 5.5 | Claude Opus 5 |
|---|---|---|
| LMArena · Coding | 1,549.5 | 1,534 |
| LiveBench · Coding | 80.5 | 73.3 |
| Vals Vibe Code Bench | 90.3 | 88.4 |
Claude Opus 5.5 at a glance
- Developer
- Anthropic
- Status
- Live since September 22, 2026
- API price
- $4 input / $20 output per 1M tokens · Anthropic, claude-opus-5-5
- Context window
- 1M tokens
Live — Sep 22 · $4/$20 per MTok, down from Opus 5 at $5/$25 · 1M ctx / 128K out · adaptive thinking always on, default effort medium · cache reads 5% of base input · Anthropic now says start here for most workloads, and Opus 5 is legacy.
Claude Opus 5.5 ships at $4/$20 - and that is LESS than the Opus 5 it replaces
2026-09-22 · Claude Opus 5.5 is live. Our sweep read the id claude-opus-5-5 at 16:24:44 UTC on September 22 and the alert went out at 16:25:45 - 61 seconds later, to 307 inboxes and one phone. The hunt that caught it was armed the previous day, before the model had a confirmed name, on the version range rather than on the rumour.
Markets put the next Claude Opus at 83% by Thursday — the name going around is 5.5
2026-09-21 · Polymarket's "Next Claude Opus released by...?" book, read directly at 06:49 UTC, September 21: 83% by September 24, 91% by September 27, 95% by September 30. Polymarket's own post about nine hours earlier had Thursday at 72%, so the number has been climbing through the day.
Claude Opus 5 at a glance
- Developer
- Anthropic
- Status
- Live since July 24, 2026
- API price
- $5 input / $25 output per 1M tokens · Anthropic, claude-opus-5
- Context window
- 1M tokens
Live — detected 16:51 UTC Jul 24, alert fired 61s later · superseded by Opus 5.5 on Sep 22 and moved to Anthropic's legacy list; still served at $5/$25, which is now MORE than its successor.
Claude Opus 5 is live — we detected it at 16:51 UTC and had alerts out 61 seconds later
2026-07-24 · Anthropic's Claude Opus 5 went live on the public API today. Our checkers saw the id appear at 16:51:33 UTC, confirmed it on the next 60-second sweep, and the alert blast went out at 16:52:34 — sixty-one seconds from first sighting to inbox.
Claude Opus 5.5 vs Claude Opus 5: quick answers
Which is better, Claude Opus 5.5 or Claude Opus 5?
It depends on what you measure. Claude Opus 5.5 scores higher than Claude Opus 5 on all 6 public leaderboards that rate both. Claude Opus 5.5's widest lead is on LLM Stats. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Claude Opus 5.5 is at 100 and Claude Opus 5 at 79.7 (out of 100).
Which is newer, Claude Opus 5.5 or Claude Opus 5?
Claude Opus 5.5. It went live on September 22, 2026, 60 days after Claude Opus 5 (July 24, 2026).
Which is cheaper, Claude Opus 5.5 or Claude Opus 5?
Claude Opus 5.5 is cheaper on both input and output. On each vendor's own API, Claude Opus 5.5 is $4 input / $20 output per million tokens and Claude Opus 5 is $5 input / $25 output per million tokens. Prices as published in the models.dev catalog, as of 2026-10-08.
Which has the bigger context window, Claude Opus 5.5 or Claude Opus 5?
Neither. Both take 1M tokens.
How do Claude Opus 5.5 and Claude Opus 5 compare for coding?
On the ArtificialWatch coding index, Claude Opus 5.5 is at 96.9 (#1 of 35) and Claude Opus 5 at 79.4 (#8). Claude Opus 5.5 scores higher on all 3 coding boards that rate both.
Who makes Claude Opus 5.5 and Claude Opus 5?
Both are from Anthropic.
Where do these numbers come from?
Each score is the leaderboard's own published figure, read by ArtificialWatch (table composed October 8, 2026). Boards measure different things, so raw scores are only comparable within a row.
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Also: the bench index · API pricing · the wire