Claude Opus 4.5 is a proprietary Large language model developed by Anthropic, released in November 2025. It is part of the Claude (AI model family) model family, succeeding Claude Opus 4 and preceding later Opus iterations. The model is designed for high-complexity tasks, including coding, instruction following, and creative writing, and is available in multiple configurations on public benchmark platforms.
As of the November 2025 benchmark snapshot from wikiprompt.org, Claude Opus 4.5 appears on the LMArena leaderboard with six distinct variants, reflecting different sampling settings (e.g., 'High' reasoning, 32K context) and evaluation dates. All variants are attributed to Anthropic and carry a proprietary license. The model's performance varies by category, with its strongest rankings in document-based overall evaluation and coding tasks.
Benchmark Performance
In the aggregated LMArena leaderboard snapshot dated November 1, 2025, the variant 'claude-opus-4-5-20251101' achieved an overall document ranking of 21, with a score of 1462.20. This places it in the upper tier of models, though not at the very top, indicating competitive but not leading performance in general document understanding.
For coding tasks, the variant 'Claude Opus 4.5 (High, 32K, 20251101)' ranked 22nd with a score of 1503.22, while the standard variant 'Claude Opus 4.5 (20251101)' ranked 26th with a score of 1498.24. These results suggest that enabling high reasoning effort and a larger context window improves coding performance, a common pattern in modern LLMs.
In instruction following, the High, 32K variant ranked 23rd (score 1478.03), while the standard variant ranked 30th (score 1472.37). This indicates that the enhanced configuration also benefits adherence to complex user instructions, though the gap is smaller than in coding.
Category-Specific Rankings
For longer queries, the standard variant ranked 32nd (score 1478.87), and the High, 32K variant ranked 34th (score 1478.24). The near-identical scores suggest that context length and reasoning effort have minimal impact on handling extended prompts, with both variants performing similarly.
In the hard prompts (English) category, the standard variant ranked 35th with a score of 1481.59. This category tests robustness against challenging or adversarial prompts, where Claude Opus 4.5 shows moderate performance relative to other models.
The weakest ranking for the model appears in creative writing, where the High, 32K variant ranked 39th (score 1444.95). This suggests that while the model is capable in technical domains, its creative writing output is less competitive compared to other leading models on the leaderboard.
Variants and Configurations
The benchmark snapshot lists six variants of Claude Opus 4.5, all dated November 1, 2025. These include the base 'claude-opus-4-5-20251101' and 'Claude Opus 4.5 (High, 32K, 20251101)', with the latter appearing in multiple categories. The 'High' setting likely refers to a higher reasoning effort or sampling temperature, and '32K' indicates a 32,000-token context window. These configurations are typical for evaluating model performance under different inference conditions.
All variants are proprietary, meaning the underlying weights and architecture are not publicly released. This is consistent with Anthropic's commercial approach to its Claude models, which are available through API and consumer products.
Context and Significance
Claude Opus 4.5 is part of Anthropic's rapid iteration cycle, following the release of Claude 3.5 Sonnet and Claude 3 7 Sonnet and preceding later models like Claude Opus 4.6 and Claude Opus 5. The model's appearance on public leaderboards provides a transparent, third-party assessment of its capabilities, which is valuable for researchers and developers comparing LLMs.
While the model does not top any category, its consistent top-40 rankings across diverse tasks indicate a balanced performance profile. This makes it a viable option for applications requiring reliable coding assistance, instruction adherence, and handling of complex queries, though specialized models may outperform it in niche areas like creative writing.
As of the snapshot date, Claude Opus 4.5 had not been officially announced by Anthropic, and its presence on LMArena was an anonymous or early entry. Consequently, public information is limited to benchmark data, and details about its architecture, training data, and exact release date remain undisclosed. The model is expected to be superseded by subsequent Opus versions, reflecting the fast-paced evolution of Generative AI technology.