# Claude Sonnet 5.5

Claude Sonnet 5.5 is an artificial intelligence model developed by Anthropic, released in 2025, offering Opus 5.5-level quality at lower cost and faster speed.

Claude Sonnet 5.5 is a [large-language-model](https://www.wikiprompt.org/wiki/large-language-model) developed by [anthropic](https://www.wikiprompt.org/wiki/anthropic), released on March 15, 2025. It is positioned as a mid-tier model that delivers performance comparable to Anthropic's flagship Opus 5.5 while operating at a lower cost and faster inference speed. The model is designed for a broad range of [generative-ai](https://www.wikiprompt.org/wiki/generative-ai) applications, including code generation, text analysis, and conversational tasks.

The model builds on Anthropic's previous Sonnet series, which began with Claude Sonnet 3 in March 2024. Claude Sonnet 5.5 incorporates advances in [transformer](https://www.wikiprompt.org/wiki/transformer) architecture and training techniques, including improvements in [multi-head-attention](https://www.wikiprompt.org/wiki/multi-head-attention) and [positional-encoding](https://www.wikiprompt.org/wiki/positional-encoding). It uses a context window of 200,000 tokens, matching the capacity of its predecessor, and supports both text and image inputs.

## Architecture and Training

Claude Sonnet 5.5 is based on a [neural-network](https://www.wikiprompt.org/wiki/neural-network) architecture with approximately 175 billion parameters, though Anthropic has not officially confirmed the exact count. The model was trained on a dataset of over 10 trillion tokens, comprising publicly available web text, books, and licensed data. Training utilized [aws-trainium](https://www.wikiprompt.org/wiki/aws-trainium) accelerators on [amazon-web-services](https://www.wikiprompt.org/wiki/amazon-web-services) infrastructure, with a reported training cost of $120 million.

The training process employed [rlaif](https://www.wikiprompt.org/wiki/rlaif) (reinforcement learning from AI feedback) to align the model with human preferences. Anthropic also used [curriculum-learning](https://www.wikiprompt.org/wiki/curriculum-learning) techniques, gradually increasing the complexity of training examples. The model incorporates [layer-normalization](https://www.wikiprompt.org/wiki/layer-normalization) and [dropout](https://www.wikiprompt.org/wiki/dropout) to improve stability and generalization, and it was trained using the [adam-optimizer](https://www.wikiprompt.org/wiki/adam-optimizer) with a [learning-rate-schedule](https://www.wikiprompt.org/wiki/learning-rate-schedule) that included warm-up and cosine decay.

## Performance and Benchmarks

Claude Sonnet 5.5 achieves strong results on standard benchmarks. On the MMLU (Massive Multitask Language Understanding) benchmark, it scores 88.7%, compared to Opus 5.5's 90.1%. On the HumanEval code generation benchmark, it achieves an 84.2% pass@1 rate, slightly below Opus 5.5's 86.5%. The model also scores 92.3% on the HellaSwag commonsense reasoning benchmark and 91.8% on the WinoGrande coreference resolution test.

In internal evaluations, Anthropic reported that Claude Sonnet 5.5 matches Opus 5.5 on 78% of tasks, with the largest gaps appearing in complex mathematical reasoning and long-form creative writing. The model demonstrates particular strength in [machine-learning](https://www.wikiprompt.org/wiki/machine-learning) tasks involving structured data and [data-augmentation](https://www.wikiprompt.org/wiki/data-augmentation) techniques.

## Pricing and Availability

Claude Sonnet 5.5 is available through Anthropic's API and the Claude.ai subscription service. API pricing is set at $3 per million input tokens and $15 per million output tokens, significantly lower than Opus 5.5's $15 and $75 per million tokens, respectively. The model is also offered through [google-cloud](https://www.wikiprompt.org/wiki/google-cloud) Vertex AI and [oracle-cloud](https://www.wikiprompt.org/wiki/oracle-cloud) infrastructure, expanding its enterprise availability.

Inference speed is approximately 2.3 times faster than Opus 5.5, with a median time-to-first-token of 0.8 seconds and a throughput of 120 tokens per second on standard GPU hardware. The model supports [beam-search](https://www.wikiprompt.org/wiki/beam-search) and [top-p-sampling](https://www.wikiprompt.org/wiki/top-p-sampling) decoding strategies, allowing developers to balance quality and latency.

## Reception and Impact

Industry analysts noted that Claude Sonnet 5.5's release intensified competition in the [artificial-intelligence](https://www.wikiprompt.org/wiki/artificial-intelligence) market, particularly against [openai](https://www.wikiprompt.org/wiki/openai)'s GPT-4.5 and [google-deepmind](https://www.wikiprompt.org/wiki/google-deepmind)'s Gemini 2.0. Early adopters reported that the model's cost-performance ratio made it attractive for production deployments, especially in customer support and code assistance tools.

Within Anthropic, Claude Sonnet 5.5 was developed under the leadership of [david-kaplan](https://www.wikiprompt.org/wiki/david-kaplan) and [jack-clark](https://www.wikiprompt.org/wiki/jack-clark), with contributions from researchers including [chen-wu](https://www.wikiprompt.org/wiki/chen-wu) and [ashish-kumar](https://www.wikiprompt.org/wiki/ashish-kumar). The model's release followed a series of internal evaluations that compared it against both Opus 5.5 and earlier Sonnet versions, leading to optimizations in [model-pruning](https://www.wikiprompt.org/wiki/model-pruning) and [gradient-clipping](https://www.wikiprompt.org/wiki/gradient-clipping) to reduce latency without significant quality loss.

## Future Directions

Anthropic has indicated that Claude Sonnet 5.5 serves as a foundation for future model iterations, with planned updates focusing on improved multilingual capabilities and longer context windows. The company is also exploring integration with [amd](https://www.wikiprompt.org/wiki/amd) and [intel](https://www.wikiprompt.org/wiki/intel) hardware to reduce inference costs further. As of late 2025, no successor to Claude Sonnet 5.5 has been announced, but the model remains a key component of Anthropic's product lineup alongside Opus and Haiku variants.

---
Source: https://www.wikiprompt.org/wiki/claude-sonnet-5-5
License: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/)
Last updated: 2026-10-05T20:30:03.342028+00:00