Claude Opus 5.5 vs Muse Spark Open
| Spec | Claude Opus 5.5 | Muse Spark Open |
|---|---|---|
| Respan Index | 73.7 (#1) | 42.8 (#53) |
| Blended price per 1M | $4 | $2 |
| Context window | 1M | 1.0M |
| Input / output per 1M | $2 / $10 | $1.25 / $4.25 |
| Max output | 128K | - |
| Input | text, vision | text, vision, video, audio |
| Released | 2026-09-22 | 2026-10-15 |
Respan Index by category
Each category is scored 0 to 100, and how far ahead the winner is. Leads under a point are close to even.
| Category | Claude Opus 5.5 | Muse Spark Open |
|---|---|---|
| Coding | 66.8 Claude Opus 5.5 | 21.7 Muse Spark Open |
| Agents | 79.2 Claude Opus 5.5 | 44.5 Muse Spark Open |
| Reasoning | 83.9 Claude Opus 5.5 | 50.1 Muse Spark Open |
| Knowledge & language | 70.4 Claude Opus 5.5 | 56.6 Muse Spark Open |
| Human preference | 61.4 Claude Opus 5.5 | 54.0 Muse Spark Open |
Benchmarks both report
Claude Opus 5.5 leads on 9 of the 9 benchmarks both report. Higher is better. Each score links to where it was published.
| Benchmark | Claude Opus 5.5 | Muse Spark Open |
|---|---|---|
| SAGE 1.1 (Vals AI) | 91.3% | 85.8% |
| LMArena WebDev (LMArena) | 1810 | 1526 |
| APEX-Agents (Mercor) | 73.5% | 33.4% |
| FrontierMath Tier 4 v2 (Epoch AI) | 95% | 31.7% |
| FrontierMath Tiers 1-3 v2 (Epoch AI) | 91.2% | 69.8% |
| GPQA Diamond | 90.6% | 89% |
| OTIS Mock AIME 2024-2025 (Epoch AI) | 100% | 98.1% |
| SimpleQA Verified | 72.2% | 56.6% |
| Terminal-Bench 4.0 (Vals AI) | 65.2% | 6.6% |
FAQ
Is Claude Opus 5.5 better than Muse Spark Open?
Claude Opus 5.5 scores 73.7 on the Respan Index (#1), ahead of Muse Spark Open at 42.8 (#53). Claude Opus 5.5 leads on 9 of the 9 benchmarks both report.
Which is cheaper, Claude Opus 5.5 or Muse Spark Open?
Claude Opus 5.5 lists at $2 input and $10 output per 1M tokens; Muse Spark Open at $1.25 and $4.25. Muse Spark Open is 2.0x cheaper per token at list price.
Which has the larger context window?
Claude Opus 5.5 accepts 1M tokens and Muse Spark Open 1.0M tokens.