Claude 4.5 Sonnet
Claude 4.5 Sonnet is a text generation model from Anthropic with a 200,000-token context window and native tool and MCP support.
AnthropicLarge-context text generation with tool use
Claude 4.5 Sonnet is a large language model developed by Anthropic, released in September 2025. It supports a 200,000-token context window and can generate responses up to 64,000 tokens in length, making it suited for tasks that involve long documents, extended conversations, or complex multi-step workflows. The model accepts image inputs alongside text and supports configurable reasoning, allowing developers to adjust how much computational effort the model applies to a given problem.
Claude 4.5 Sonnet is designed with agentic use cases in mind, offering native support for tool use and Model Context Protocol (MCP) servers. This makes it a practical choice for building AI agents that need to call external APIs, retrieve data, or coordinate across multiple services. Developers can configure reasoning depth and tool availability directly through the model's input parameters, giving fine-grained control over how the model behaves within automated pipelines.
What Claude 4.5 Sonnet supports
Large Context Window
Processes up to 200,000 tokens in a single request, enabling analysis of long documents, codebases, or extended conversation histories without truncation.
Tool Use
Supports structured tool calling, allowing the model to invoke external functions or APIs as part of a response and act on the results.
MCP Server Support
Natively integrates with Model Context Protocol servers, enabling agents to connect to external data sources and services through a standardized interface.
Configurable Reasoning
Offers a selectable reasoning mode with an adjustable max reasoning size, letting developers tune how much deliberation the model applies before responding.
Vision Input
Accepts image inputs alongside text prompts, supporting tasks like document analysis, diagram interpretation, and visual question answering.
Long Response Generation
Can produce responses up to 64,000 tokens, making it suitable for generating lengthy reports, detailed code files, or extended structured outputs.
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Get Started FreeBenchmark scores
Scores represent accuracy — the percentage of questions answered correctly on each test.
| Benchmark | What it tests | Score |
|---|---|---|
| MMLU-Pro | Expert knowledge across 14 academic disciplines | 86.0% |
| GPQA Diamond | PhD-level science questions (biology, physics, chemistry) | 72.7% |
| LiveCodeBench | Real-world coding tasks from recent competitions | 59.0% |
| HLE | Questions that challenge frontier models across many domains | 7.1% |
| SciCode | Scientific research coding and numerical methods | 42.8% |
| SWE-bench Verified | Real GitHub issues requiring multi-file code fixes | 77.2% |
| Terminal-Bench | Agentic coding and terminal command tasks | 50.0% |
| OSWorld | Autonomous computer use and desktop tasks | 61.4% |
| τ²-bench Retail | Agentic tool use in retail scenarios | 86.2% |
| τ²-bench Telecom | Agentic tool use in telecom scenarios | 98.0% |
Common questions about Claude 4.5 Sonnet
What is the context window size for Claude 4.5 Sonnet?
Claude 4.5 Sonnet supports a context window of 200,000 tokens, meaning it can process very long documents or conversation histories in a single request.
What is the maximum response length?
The model can generate responses up to 64,000 tokens in a single output, which is suitable for long-form content, detailed code, or extended structured documents.
Does Claude 4.5 Sonnet support image inputs?
Yes, the model accepts image inputs alongside text, allowing it to analyze visual content such as diagrams, screenshots, or documents.
What is MCP support and how does it work with this model?
MCP stands for Model Context Protocol. Claude 4.5 Sonnet can connect to MCP servers, which provide a standardized way for the model to access external data sources and tools within agentic workflows.
What is the reasoning input used for?
The reasoning input lets developers enable extended thinking mode and set a maximum reasoning token budget. This allows the model to spend more effort on complex problems before producing a final answer.
When was Claude 4.5 Sonnet released?
Claude 4.5 Sonnet was released in September 2025 and became available on MindStudio on September 29, 2025.
What people think about Claude 4.5 Sonnet
Community reception to Claude 4.5 Sonnet has been largely positive, with the model's launch generating significant discussion across Reddit. Users noted it reached the top position on LMArena shortly after release, and the r/singularity announcement thread drew over 1,300 upvotes and nearly 200 comments.
Some users raised questions about whether benchmark rankings matched real-world performance, and pricing relative to competing models was a recurring concern in later threads. Discussion of coding use cases and comparisons to other models were common topics in the community.
Claude 4.5 Sonnet takes #1 in LMArena, the first Anthropic model since Sonnet 3.5 to be #1
Claude 4.5 Sonnet is here
I tested GPT-5.1 Codex against Sonnet 4.5, and it's about time Anthropic bros take pricing seriously.
Claude 4.5 Sonnet: lots of hype, middling ranks. What gives?
Google Gemini 3.1 Pro Preview Soon?
Documentation & links
Parameters & options
When enabled, the model will explain its thought process step-by-step before providing a final answer. This can help users understand how the model arrived at its conclusions, but may result in longer responses.
You can allocate a larger thinking budget to support more thorough reasoning. Must be less than max. response size
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