Best AI Coding Models for Vellum

Claude Fable 5.1 is a frontier AI model from Anthropic built for demanding coding, research, knowledge work, and autonomous multi-step workflows. It delivers higher performance than Claude Fable 5 across benchmarks covering scientific research, terminal-based coding, business automation, computer use, multidisciplinary reasoning, and agentic software development. The model is particularly suited to long-running tasks where it must investigate problems, use tools, maintain context, verify intermediate work, and continue operating with limited supervision. Early evaluations highlighted improvements in areas such as root-cause analysis, code review, browser automation, financial research, document drafting, slide creation, and complex engineering workflows. Fable 5.1 also introduces lower cache-read pricing, which Anthropic says can reduce costs by roughly 25% for typical workloads and considerably more for context-heavy agentic tasks. Enterprise customers can use new privacy-oriented safeguard options that are designed to support zero-data-retention-style deployments while still maintaining misuse protections. Cybersecurity safeguards have also been refined to intervene less often on legitimate defensive work while continuing to restrict higher-risk activities such as exploit generation. Anthropic offers the model through Claude Code, Claude Cowork, Claude.ai, the Claude API, and supported cloud platforms. Claude Fable 5.1 is intended for developers, researchers, enterprises, and professional teams that need strong reasoning and coding performance without relying on Anthropic’s most restricted-access model tier.

Claude Mythos 5 is a frontier AI model from Anthropic created for highly trusted users working on advanced cybersecurity, infrastructure protection, and scientific research. It is based on the same core model as Claude Fable 5, but certain safeguards are lifted for approved partners operating under restricted access programs. The model offers exceptional performance across software engineering, cybersecurity analysis, autonomous development workflows, scientific reasoning, visual understanding, and long-context tasks. In cybersecurity, Claude Mythos 5 is positioned for cyberdefenders and critical infrastructure providers who need advanced AI support for securing complex systems. In life sciences, the model has demonstrated strong capabilities in drug design, protein research, molecular biology, and genomics. Claude Mythos 5 can perform long-running research and technical workflows with minimal high-level human input. Anthropic designed the model for controlled deployment because its advanced capabilities could create misuse risks if broadly available without safeguards. Access is initially limited to Project Glasswing partners, with broader trusted access programs planned for cybersecurity and select biology researchers. Claude Mythos 5 helps approved organizations apply powerful AI to high-impact technical and scientific challenges while operating within a stricter governance model.

Claude is an advanced AI assistant created by Anthropic to help users think, create, and work more efficiently. It is built to handle tasks such as content creation, document editing, coding, data analysis, and research with a strong focus on safety and accuracy. Claude enables users to collaborate with AI in real time, making it easy to draft websites, generate code, and refine ideas through conversation. The platform supports uploads of text, images, and files, allowing users to analyze and visualize information directly within chat. Claude includes powerful tools like Artifacts, which help organize and iterate on creative and technical projects. Users can access Claude on the web as well as on mobile devices for seamless productivity. Built-in web search allows Claude to surface relevant information when needed. Different plans offer varying levels of usage, model access, and advanced research features. Claude is designed to support both individual users and teams at scale. Anthropic’s commitment to responsible AI ensures Claude is secure, reliable, and aligned with real-world needs.

Claude Opus 4.7 is an advanced AI model built to push the boundaries of software engineering, automation, and complex reasoning tasks. Compared to Opus 4.6, it delivers notable improvements in handling challenging coding workflows and executing long-duration tasks with consistency. The model excels at strictly following user instructions, reducing ambiguity and improving output accuracy. It also introduces stronger self-verification capabilities, allowing it to check and refine its own results before presenting them. One of its key upgrades is enhanced multimodal functionality, particularly its ability to process higher-resolution images with greater clarity. This enables more precise analysis of visuals such as technical diagrams, dense screenshots, and structured data layouts. Opus 4.7 is also more refined in generating professional content, including polished documents, presentations, and interface designs. In real-world applications, it performs effectively across domains like finance, legal analysis, and business workflows. The model incorporates improved memory features, allowing it to retain context across extended sessions and reduce repetitive input requirements. It also introduces built-in safeguards to detect and prevent misuse, especially in sensitive cybersecurity scenarios. With broad availability across APIs and cloud platforms, Opus 4.7 offers developers and enterprises a powerful, scalable AI solution.

Claude Sonnet 4.6 represents a comprehensive upgrade to Anthropic’s Sonnet model line, delivering expanded capabilities across coding, reasoning, computer interaction, and professional knowledge tasks. With a beta 1M token context window, the model can process massive datasets such as full repositories, extended legal agreements, or multi-document research projects in a single request. Developers report improved reliability, better instruction adherence, and fewer hallucinations, making long working sessions smoother and more predictable. Early users preferred Sonnet 4.6 over its predecessor in the majority of tests and often selected it over Opus 4.5 for practical coding work. The model’s computer-use skills have advanced significantly, enabling it to navigate spreadsheets, complete web forms, and manage multi-tab workflows with near human-level competence in many cases. Benchmark evaluations show consistent performance gains across reasoning, coding, and long-horizon planning tasks. In competitive simulations like Vending-Bench Arena, Sonnet 4.6 demonstrated strategic capacity-building and profit optimization over time. On the developer platform, it supports adaptive and extended thinking modes, context compaction, and improved tool integration for greater efficiency. Claude’s API tools now automatically execute filtering and code-processing steps to enhance search and token optimization. Sonnet 4.6 is available across Claude.ai, Cowork, Claude Code, the API, and major cloud providers at the same starting price as Sonnet 4.5.

Anthropic has introduced Claude Haiku 4.5, its newest small language model aimed at achieving near-frontier capabilities at a significantly reduced cost. This model mirrors the coding and reasoning abilities of the company's mid-tier Sonnet 4, yet operates at approximately one-third of the expense while delivering over double the processing speed. According to benchmarks highlighted by Anthropic, Haiku 4.5 either matches or surpasses the performance of Sonnet 4 in critical areas such as code generation and intricate "computer use" workflows. The model is specifically optimized for scenarios requiring real-time, low-latency performance, making it ideal for applications like chat assistants, customer support, and pair-programming. Available through the Claude API under the designation “claude-haiku-4-5,” Haiku 4.5 is designed for large-scale implementations where cost-effectiveness, responsiveness, and advanced intelligence are essential. Now accessible on Claude Code and various applications, this model's efficiency allows users to achieve greater productivity within their usage confines while still enjoying top-tier performance. Moreover, its launch marks a significant step forward in providing businesses with affordable yet high-quality AI solutions.