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Step 5 Preview vs Claude Opus 5.5
Claude Opus 5.5 scores higher than Step 5 Preview on all 4 public leaderboards that rate both. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Step 5 Preview is at 29.5 and Claude Opus 5.5 at 90.9 (out of 100).
Scores as published by each board; table composed November 13, 2026.
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Leaderboard by leaderboard
| Board | Step 5 Preview | Claude Opus 5.5 | Higher |
|---|---|---|---|
| LMArena Elo (community votes) | 1,572.5 | 1,814.7 | Claude Opus 5.5 |
| LiveBench global average (0-100) | 54.9 | 83.4 | Claude Opus 5.5 |
| Vals AI Vals Index accuracy % · weighted finance + coding tasks | 54.8 | 70.1 | Claude Opus 5.5 |
| Artificial Analysis intelligence index · measured runs only | 28.5 | 59.1 | 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, Step 5 Preview is at 26 (#40 of 48) and Claude Opus 5.5 at 90 (#3). Claude Opus 5.5 scores higher on all 3 coding boards that rate both.
| Coding board | Step 5 Preview | Claude Opus 5.5 |
|---|---|---|
| LMArena · Coding | 1,481.7 | 1,543.4 |
| LiveBench · Coding | 67.6 | 87.1 |
| Vals Vibe Code Bench | 70.4 | 90.3 |
Step 5 Preview at a glance
- Developer
- StepFun
- Status
- Live since September 20, 2026
Live — Sep 20 · 600B total / ~27B active MoE · 1M ctx · $1.00/$2.70 per 1M, $0.05 cached input · open weights landed Oct 15, as scheduled: FP8 and BF16 checkpoints on Hugging Face and ModelScope, plus an NVFP4 build on Hugging Face (604.3B parameters in the safetensors index; about 650 GB in FP8, 1.2 TB in BF16), under the StepFun Model License 1.0, which adds a 'Powered by StepFun AI' credit past 100M monthly users or $20M monthly revenue and a separate commercial license for device makers and for model-as-a-service firms over $20M a year (license read Oct 15) · aimed at long-horizon agentic work.
StepFun opens Step 5 Preview's weights: 600B total, 27B active, 1M context, under its own license
2026-10-15 · StepFun released the weights of Step 5 Preview on October 15, the date it set when the model went on sale through its API on September 20. FP8 and BF16 checkpoints are on Hugging Face and ModelScope, and an NVFP4 build is on Hugging Face too.
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 · fast mode (speed: 'fast', up to 2.5x the output tokens per second by Anthropic's figure) at $8 / $40 per MTok, double standard, left research preview Oct 15 with no waitlist, access request or beta header; on the Claude API and on Claude in Microsoft Foundry (Azure-hosted), not on Bedrock, Google Cloud, Claude Platform on AWS, the Batch API or Priority Tier; @ClaudeDevs says Google Cloud is coming soon (Anthropic's fast mode docs, read Oct 16).
AI models go live a median of 4 months after their knowledge ends: Claude Opus 5.5 knows up to June 2026, Gemini 4 Argon only to March
2026-11-06 · Of the 22 live AI models whose labs publish a knowledge cutoff, the median went live 4 months after its training data ends, by ArtificialWatch's count. The latest published cutoff we found is June 2026, for Anthropic's four current Claude models and OpenAI's GPT-6.1 Terra.
SemiAnalysis launches GDPx: Opus 5.5 leads at 12%, Gemini 4 Carbon close behind
2026-11-02 · SemiAnalysis released GDPx on November 2, a new agentic benchmark of 206 tasks across 11 domains, and the best model it tested scores 12%. Claude Opus 5.5 leads at 12.0, Gemini 4 Carbon is second at 10.9 and GPT-6 Astra third at 9.6. We read the leaderboard directly at gdpx.semianalysis.com.
Step 5 Preview vs Claude Opus 5.5: quick answers
Which is better, Step 5 Preview or Claude Opus 5.5?
It depends on what you measure. Claude Opus 5.5 scores higher than Step 5 Preview on all 4 public leaderboards that rate both. Claude Opus 5.5's widest lead is on LiveBench. On the ArtificialWatch Index, which takes the median of each model's percentile across the boards that score it, Step 5 Preview is at 29.5 and Claude Opus 5.5 at 90.9 (out of 100).
Which is newer, Step 5 Preview or Claude Opus 5.5?
Claude Opus 5.5. It went live on September 22, 2026, 2 days after Step 5 Preview (September 20, 2026).
How do Step 5 Preview and Claude Opus 5.5 compare for coding?
On the ArtificialWatch coding index, Step 5 Preview is at 26 (#40 of 48) and Claude Opus 5.5 at 90 (#3). Claude Opus 5.5 scores higher on all 3 coding boards that rate both.
Who makes Step 5 Preview and Claude Opus 5.5?
Step 5 Preview is from StepFun; Claude Opus 5.5 is from Anthropic.
Where do these numbers come from?
Each score is the leaderboard's own published figure, read by ArtificialWatch (table composed November 13, 2026). Boards measure different things, so raw scores are only comparable within a row.
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