Claude 3.5 Sonnet vs Claude Sonnet 4.5

Overview Claude 3.5 Sonnet and Claude Sonnet 4.5 are both large language models developed by Anthropic. They share the same architectural family, are closed‑weight, multimodal, and provide a 200 000‑token context window. Their release dates differ, with the 3.5 version arriving in mid‑2024 and the 4.5 version arriving over a year later in September 2025. The later model is positioned as a flagship within the Claude 4 line, while the earlier model sits as a mid‑tier offering in the 3.5 series.

Where they differ The most concrete distinctions are in the *Released* field, the *Capabilities* listed, and the *Description* provided by Anthropic. Claude 3.5 Sonnet was released on 2024‑06‑20 and emphasizes coding, agentic tool use, and vision. Claude Sonnet 4.5 appeared on 2025‑09‑29 and highlights agentic coding and computer use as its core strengths. These capability sets suggest different focal points: the earlier model includes visual understanding alongside general tool use, whereas the later model concentrates on coding‑centric agentic behavior and the ability to drive computer‑based workflows. The description fields reinforce this: the 3.5 Sonnet is described as a mid‑tier model that out‑performed Claude 3 Opus on many tasks, while the 4.5 Sonnet is termed Anthropic’s coding‑ and agent‑focused flagship in the Claude 4 family. All other attributes—Developer, Type, Open weights, Modality, and Context window—are identical between the two models.

Which to choose When deciding between the two, consider the primary tasks you intend to automate. If your workflow benefits from visual input—such as interpreting diagrams, screenshots, or images—or requires a broad set of tool‑use abilities beyond coding, Claude 3.5 Sonnet offers those capabilities. If your goal is to build or deploy autonomous coding agents that can write, debug, and refactor code, or to orchestrate computer‑use automation where the model drives UI interactions, Claude Sonnet 4.5’s emphasis on agentic coding and computer use may be a better fit. Both models provide the same extensive context window, so length‑dependent tasks are supported equally. The choice ultimately hinges on whether visual understanding and general tool use (3.5 Sonnet) or advanced agentic coding and computer‑use automation (4.5 Sonnet) align more closely with your application’s requirements.