Claude Opus 5.5 vs GPT-6.1 Terra
| Spec | Claude Opus 5.5 | GPT-6.1 Terra |
|---|---|---|
| Respan Index | 73.7 (#1) | 68.9 (#9) |
| Blended price per 1M | $4 | $1 |
| Context window | 1M | 1.1M |
| Input / output per 1M | $2 / $10 | $0.5 / $2.5 |
| Max output | 128K | 128K |
| Input | text, vision | text, vision |
| Released | 2026-09-22 | 2026-10-26 |
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 | GPT-6.1 Terra |
|---|---|---|
| Coding | 66.8 Claude Opus 5.5 | 57.9 GPT-6.1 Terra |
| Agents | 79.2 Claude Opus 5.5 | 77.0 GPT-6.1 Terra |
| Reasoning | 83.9 Claude Opus 5.5 | 83.0 GPT-6.1 Terra |
| Knowledge & language | 70.4 Claude Opus 5.5 | 57.4 GPT-6.1 Terra |
| Human preference | 61.4 Claude Opus 5.5 | 57.9 GPT-6.1 Terra |
Benchmarks both report
Claude Opus 5.5 leads on 10 of the 14 benchmarks both report. Higher is better. Each score links to where it was published.
| Benchmark | Claude Opus 5.5 | GPT-6.1 Terra |
|---|---|---|
| LMArena Agent (LMArena) | 0.2094 | 0.1057 |
| LMArena WebDev (LMArena) | 1810 | 1673 |
| APEX-Agents (Mercor) | 73.5% | 68.3% |
| EBR-bench (Epoch AI) | 71.4% | 78.1% |
| FrontierMath Tier 4 v2 (Epoch AI) | 95% | 92.7% |
| FrontierMath Tiers 1-3 v2 (Epoch AI) | 91.2% | 90.9% |
| Furniture Assembly (Epoch AI) | 83.3% | 79.2% |
| GPQA Diamond | 90.6% | 94.3% |
| Mystery Game Puzzles (Epoch AI) | 71% | 74% |
| OTIS Mock AIME 2024-2025 (Epoch AI) | 100% | 100% |
| SimpleQA Verified | 72.2% | 57.3% |
| Terminal-Bench 4.0 (Vals AI) | 65.2% | 49.5% |
| Vending-Bench 2 (Andon Labs) | 9235.25 | 9107.46 |
| Terminal-Bench 4.0 | 66.4% | 50.3% |
FAQ
Is Claude Opus 5.5 better than GPT-6.1 Terra?
Claude Opus 5.5 scores 73.7 on the Respan Index (#1), ahead of GPT-6.1 Terra at 68.9 (#9). Claude Opus 5.5 leads on 10 of the 14 benchmarks both report.
Which is cheaper, Claude Opus 5.5 or GPT-6.1 Terra?
Claude Opus 5.5 lists at $2 input and $10 output per 1M tokens; GPT-6.1 Terra at $0.5 and $2.5. GPT-6.1 Terra is 4.0x cheaper per token at list price.
Which has the larger context window?
Claude Opus 5.5 accepts 1M tokens and GPT-6.1 Terra 1.1M tokens.