Head-to-head comparison
Claude Opus 5.5 (Anthropic) and GPT-5.5 (OpenAI) compared on the ModelCap Index, API price, context window, provider availability, weight access and every public benchmark board they share. Figures are the same ones shown on the live rankings; nothing here is a hidden score.
Snapshot as of 6 November 2026
As of 6 November 2026, Claude Opus 5.5 holds the stronger ModelCap Index position (#1 vs #16); and Claude Opus 5.5 is 1.5× cheaper per output token ($20.00/1M vs $30.00/1M).
Evidence: 4 public benchmark observations across 4 boards · 4 public benchmark observations across 4 boards. Prices are the lowest listed API offer per million tokens observed on the OpenRouter catalogue.
Scores are the sources' own published figures for each model's best evaluated configuration; ModelCap never re-runs a benchmark.
Want a different pairing? Open the interactive comparison tool to swap either model for any current ranked language model.
Claude Opus 5.5 ranks higher on the ModelCap Index as of 6 November 2026: #1 against #16. That is a capability ranking built from public benchmark evidence with published uncertainty; whether it is "better" for you also depends on price, context and where you can run it. Their published uncertainty intervals overlap, so the rank difference alone does not establish a reliable capability advantage for your workload.
Claude Opus 5.5 is cheaper on output tokens: $20.00/1M against $30.00/1M. Input tokens are $4.00/1M for Claude Opus 5.5 and $5.00/1M for GPT-5.5. Prices are the lowest listed API offer ModelCap observed, in USD per million tokens. For 1,000 requests with 2,000 input and 500 output tokens each (2M input + 0.5M output), the listed-rate estimate is $18.00 for Claude Opus 5.5 versus $25.00 for GPT-5.5. Claude Opus 5.5 costs 28.0% less in this scenario. This excludes caching, batch discounts, prompt-length tiers, tool charges and retries; verify the selected endpoint before budgeting.
Both publish a 1M-token context window. OpenRouter catalogue or provider-endpoint declaration. Limits can vary by provider and prompt length; a model-wide maximum has not been independently verified.
Arena coding: Claude Opus 5.5 1551, GPT-5.5 1519 — Claude Opus 5.5 leads.
Claude Opus 5.5: No linked weights. GPT-5.5: No linked weights. Open weights mean the checkpoint can be downloaded and self-hosted under its licence. A missing weight link does not identify every API or chat product that offers a model.
ModelCap currently lists 5 API providers for Claude Opus 5.5 and 3 for GPT-5.5, from the OpenRouter catalogue snapshot the site serves; each model page lists the providers and their prices.
Every figure and ModelCap Index position comes from the same published snapshot dated 6 November 2026. Publication and page updates happen separately; use the snapshot date shown on the page.