Claude Fable 5.1 is Anthropic's generally available, production-safeguarded deployment for demanding reasoning and long-horizon agentic work, sharing underlying weights with Claude Mythos 5.1. It extends Claude Fable 5 with stronger long-running agentic coding, multistep research, and document, spreadsheet, and slide work, plus per-message effort control, turn-scoped system messages, readable in-progress tool-call updates, and content provenance. Adaptive thinking is always on, with the effort parameter controlling reasoning depth (default: high).

Claude Opus 5.5 is the first model in Anthropic's Claude 5.5 family, performing at the level of Claude Fable 5.1 on most work while costing roughly 40% less to run than Claude Opus 5 on typical workloads, with output generated over 30% faster. It supports text and image input with a 1M-token context window, adaptive thinking that is always on (default effort: medium, and cannot be disabled as an anti-distillation measure), and incorporates Fable 5.1's safeguards for cybersecurity, biology, and distillation, detailed in a 230-page system card. Recommended as a daily driver for coding, financial and document workflows, and computer use.

Claude Sonnet 5.5 offers the best combination of speed and intelligence in the Claude lineup, with a 1M-token context window and fast comparative latency. It accepts text and images and returns text, with adaptive thinking on by default at high effort — the lowest setting, between_tools, turns off up-front thinking rather than disabling reasoning entirely, unlike Sonnet 5 where thinking could be fully turned off. Five breaking changes apply versus Sonnet 5: forced tool use now returns an error, thinking blocks are tied to the model and conversation, the older computer_20251124 tool is no longer accepted, the advisor tool rejects older models as advisors, and text between tool calls now arrives in thinking blocks unless a display value or between_tools is set.

Claude Haiku 4.5 is Anthropic’s October 2025 release of its newest compact AI language model, designed to offer near-premium intelligence, ultra-fast responses, and low operational cost. Positioned as the lightweight sibling to Claude Sonnet 4.5 and Opus 4.1, Haiku 4.5 enables “near‑frontier‑level” performance suitable for enterprise-scale workloads, free-tier operations, and real-time applications.

Anthropic/Claude Fable 5 is Anthropic’s newest generally available, public-facing Mythos-class model, positioned as its most capable model for complex, long-running work. According to Anthropic and reporting on the launch, it is built for software engineering, knowledge work, vision, research, analysis, and long-horizon autonomy, with strong safety guardrails that block or route some high-risk requests to Claude Opus 4.8.

Claude Opus 5 is Anthropic’s latest flagship reasoning model in the Claude Opus family, offering near-frontier intelligence with strong performance on complex analysis, coding, and multi-step reasoning tasks. It supports very long-context interactions (up to around 1M tokens) and is designed as a general-purpose assistant for enterprise and developer use via the Claude API. Pricing matches the prior Opus 4.8 generation, with significantly higher quality per dollar than earlier Opus models.

Claude Opus 4.8 is Anthropic's most capable generally available Opus-family model, built for complex reasoning, long-horizon agentic coding, advanced analysis, knowledge work, vision understanding, and memory-heavy workflows. It supports text, image, and file inputs with text output, includes reasoning support, and offers a 1M-token context window for handling very large prompts, documents, and multi-step tasks.

Opus 4.7 is Anthropic’s next-generation Opus model, designed for long-running, asynchronous agents. Building on the coding and agentic capabilities of Opus 4.6, it offers improved performance across complex tasks.

Sonnet 4.6 is Anthropic’s strongest Sonnet-tier model to date, delivering near-frontier performance for coding, agentic workflows, and professional tasks. It’s especially good at iterative build cycles, navigating large codebases, managing end-to-end projects with memory, producing polished documents, and reliably using computers for web QA and workflow automation.

Claude Sonnet 4.5 is Anthropic’s most advanced Sonnet model to date, optimized for real-world agents and coding workflows. It delivers state-of-the-art performance on coding benchmarks such as SWE-bench Verified, with improvements across system design, code security, and specification adherence. The model is designed for extended autonomous operation, maintaining task continuity across sessions and providing fact-based progress tracking. Sonnet 4.5 also introduces stronger agentic capabilities, including improved tool orchestration, speculative parallel execution, and more efficient context and memory management. With enhanced context tracking and awareness of token usage across tool calls, it is particularly well-suited for multi-context and long-running workflows. Use cases span software engineering, cybersecurity, financial analysis, research agents, and other domains requiring sustained reasoning and tool use.

Claude Opus 4.1, a direct replacement for Opus 4, excels in real-world coding and agentic tasks with enhanced performance and precision. It autonomously handles complex, end-to-end development tasks, adapting to user styles while maintaining high-quality output, particularly in frontend code generation and intricate logic. With superior long-horizon task management and problem-solving, it serves as an ideal virtual collaborator for sustained reasoning and multi-step actions. Opus 4.1 also boosts AI agent capabilities, enabling accurate execution of complex tasks and shining in agentic search, research, content creation, and context management for comprehensive insights and high-quality summarization.

anthropic/claude-opus-4.5 is Anthropic’s latest frontier reasoning model, optimized for complex software engineering, agentic workflows, and long-running computer-use tasks such as multi-step automation and tool use. It is positioned as the most capable model in the Claude Opus family, offering state-of-the-art performance on challenging coding and enterprise benchmarks while being significantly more efficient than earlier Opus versions.

Opus 4.6 is Anthropic’s new top-end Claude model, optimized for complex reasoning, coding, and high‑stakes professional work. It excels at agentic workflows, breaking down multi-step tasks, calling tools, and running for longer with fewer errors and less hand-holding. The model introduces a 1M‑token context window (in beta), stronger long-context retrieval, and up to 128k output tokens for large code and document workloads. It also adds “adaptive thinking” and adjustable effort levels, letting it dynamically choose when to think deeply versus respond quickly.