Anthropic

Claude Sonnet 5.5

Anthropic

Claude Sonnet 5.5 is the second released Claude 5.5 tier, focused on faster everyday agent work, bug fixes, visual design, and polished documents. It improves over Sonnet 5 while reducing typical token consumption. A million-token context and adaptive thinking support sustained tasks. The release changes thinking configuration, forced tool use, and computer-tool compatibility, so integrations need model-specific migration checks.

Claude Opus 5.5

Anthropic

Claude Opus 5.5 is the first released Claude 5.5 tier, designed for sustained agentic coding and professional work. Anthropic positions it near Fable 5.1 on most workloads with substantially lower cost than Opus 5, partly through token efficiency. It has always-on adaptive thinking, a million-token context, text and image input, and broad tool access. Effort settings control the latency and computation devoted to a task.

Claude Fable 5.1

Anthropic

Claude Fable 5.1 is the independent update to Fable 5 for long-running coding, knowledge work, and research. It improves grounding, root-cause debugging, and efficiency at lower effort. Claude Mythos 5.1 is the same model with more permissive safeguards for verified cybersecurity and life sciences work, represented as a variant. Adaptive thinking is always enabled, and a million-token context supports extended tool-assisted tasks.

Claude Opus 5

Anthropic

Claude Opus 5 is a major Opus-generation release for efficient coding, knowledge work, computer use, and scientific research. It emphasizes proactive problem solving, verifying results, and repairing root causes while approaching Fable 5 capability at lower cost. Its million-token context and adaptive thinking support sustained professional workflows, with text and image inputs and tools through the Claude API and partner platforms.

Claude Sonnet 5

Anthropic

Claude Sonnet 5 is the next-generation Sonnet tier, intended to narrow the gap to Opus 4.8 on coding and agent work at a lower cost. It plans multi-step jobs, uses browsers and terminals, and checks results more consistently than Sonnet 4.6. Text and image inputs, adaptive thinking, and a million-token context support both everyday assistance and longer development workflows.

Claude Fable 5

Anthropic

Claude Fable 5 is the publicly accessible Mythos-class Claude model for extended software engineering, visual reasoning, knowledge work, and research. It uses adaptive thinking and can maintain progress through tool-driven tasks with file-based memory. Claude Mythos 5 is the same underlying model with different safeguards and restricted trusted access, represented here as a variant. Fable access was suspended June 12 and restored July 1; the first release remains June 9.

Claude Opus 4.8

Anthropic

Claude Opus 4.8 is a further independent Opus update for sustained coding, agent tasks, and knowledge work. Anthropic emphasizes more dependable judgment, honesty about incomplete work, and stronger follow-through. It provides a million-token context by default and adaptive thinking, with the same tool surface as Opus 4.7. Its fast serving mode is an access option rather than a separate checkpoint.

Claude Opus 4.7

Anthropic

Claude Opus 4.7 advances Opus coding, visual understanding, and complex multi-step work. It is designed to check its own outputs more carefully and sustain difficult professional tasks. The release adds higher-resolution image handling and extra-high effort, with adaptive thinking and a million-token context. A changed tokenizer and reasoning behavior mean token consumption and prompts may differ from earlier Opus models.

Claude Mythos Preview

Anthropic

Claude Mythos Preview is Anthropic’s published frontier research model, documented in an April 2026 system card and deployed to selected Project Glasswing partners. The general-purpose model demonstrated substantial coding and vulnerability-research capabilities, motivating a restricted defensive-security program rather than general release. It is included as a substantive published research checkpoint, distinct from the later Fable/Mythos 5 family. Partner APIs existed, but no general public inference or open weights were offered.

Claude Sonnet 4.6

Anthropic

Claude Sonnet 4.6 is the independently released Sonnet update for coding, computer use, long-context reasoning, and professional work. It improved follow-through, instruction following, and visual design and launched with a million-token context in beta. The current API documentation lists that context as standard. It offers adaptive thinking and tools through the Claude API and cloud partners, with text and image inputs and text output.

Claude Opus 4.6

Anthropic

Claude Opus 4.6 is the independently released Opus update for sustained coding, reasoning, and professional agent tasks. It improves planning, code review, debugging, and work in large repositories. Adaptive thinking and effort settings control computation, while context compaction supports longer workflows. The million-token context launched in beta and is now listed as standard in current API documentation, with 128K normal output and an optional 300K batch beta. The model accepts text and images and generates text.

Claude 4.5 Opus

Anthropic

Claude 4.5 Opus is the most intelligent and capable model in the Claude 4.5 family, designed for the most demanding reasoning, research, and coding tasks. It introduces a unique 'effort' parameter (low, medium, high) that allows users to control the depth of the model's reasoning process and token usage. Opus 4.5 excels in handling ambiguity, complex problem-solving, and deep analysis, often succeeding where other models fail on multi-system bugs or intricate research questions. It is priced to be more accessible than previous Opus generations while delivering state-of-the-art performance.

Claude 4.5 Haiku

Anthropic

Claude 4.5 Haiku is the fastest and most cost-efficient model in the Claude 4.5 family, designed to deliver near-frontier intelligence with low latency. It is optimized for high-volume tasks, real-time responses, and sub-agent orchestration. Despite its smaller size, it supports advanced features like 'extended thinking' and computer use, making it suitable for parallelized workflows where speed is critical. It is positioned as a drop-in replacement for previous mid-tier models with significantly better economics.

Claude 4.5 Sonnet

Anthropic

Claude 4.5 Sonnet is a high-intelligence frontier model designed for complex agentic workflows, coding, and computer use. It balances capability with speed and cost, positioning it as the workhorse of the Claude 4.5 family. It features 'extended thinking' capabilities (beta) and is optimized for long-horizon tasks, capable of maintaining focus for extended periods (up to 30+ hours in internal tests). It introduces significant improvements in tool use, particularly in interacting with software interfaces and executing complex multi-step plans.

Claude Opus 4.1

Anthropic

Claude Opus 4.1 is an independently released update to Opus 4, focused on agentic tasks, coding, and reasoning. The release improves multi-file refactoring and precise debugging while retaining the Opus pricing tier. It was accessible through Claude, the API, and cloud partners. Its API endpoint was subsequently retired in August 2026; the page preserves this significant historical weight update.

Claude Opus 4

Anthropic

Claude Opus 4 is Anthropic's most powerful model and the best coding model in the world, leading on SWE-bench (72.5%) and Terminal-bench (43.2%). It delivers sustained performance on long-running tasks that require focused effort and thousands of steps, with the ability to work continuously for several hours. Features include extended thinking with tool use, parallel tool execution, improved memory capabilities, and significantly reduced shortcut behaviors.

Claude Sonnet 4

Anthropic

Claude Sonnet 4 significantly improves on Sonnet 3.7's capabilities, excelling in coding with a state-of-the-art 72.7% on SWE-bench. The model balances performance and efficiency, with enhanced steerability for greater control over implementations. Features include extended thinking with tool use, parallel tool execution, improved instruction following, and significantly reduced shortcut behaviors.

Claude 3.7 Sonnet

Anthropic

Anthropic's most intelligent model to date and the first hybrid reasoning model on the market. Claude 3.7 Sonnet can produce near-instant responses or extended, step-by-step thinking that is made visible to the user. API users have fine-grained control over how long the model can think for (up to 128K tokens). Priced at $3 per million input tokens and $15 per million output tokens at launch, including thinking tokens.

Claude 3.5 Haiku

Anthropic

Anthropics fastest model at time of launch, delivering intelligence at blazing speeds. Claude 3.5 Haiku is optimized for quick responses while maintaining high quality.

Claude 3.5 Sonnet

Anthropic

Claude 3.5 Sonnet raises the industry bar for intelligence, outperforming competitor models and Claude 3 Opus on a wide range of evaluations, with the speed and cost of a mid-tier model. It operates at twice the speed of Claude 3 Opus.

Claude 3 Haiku

Anthropic

Anthropic's fastest and most compact model at the time of launch with near-instant responsiveness. Answers simple queries and requests with unmatched speed while maintaining good quality. Pricing at launch: $0.25 per million input tokens, $1.25 per million output tokens.

Claude 3 Opus

Anthropic

Anthropic's most intelligent model at release, with best-in-market performance on highly complex tasks. It can navigate open-ended prompts with remarkable fluency and human-like understanding. Pricing at launch: $15 per million input tokens, $75 per million output tokens.

Claude 3 Sonnet

Anthropic

Anthropic's balanced model that strikes an ideal balance between intelligence and speed for enterprise workloads. Delivers strong performance at a lower cost compared to its peers. Pricing at launch: $3 per million input tokens, $15 per million output tokens.

Claude 2.1

Anthropic

Major update to Claude 2 featuring an industry-leading 200K token context window (roughly 150,000 words or 500+ pages), 2x reduction in hallucination rates, system prompts support, and beta tool use capabilities for API integration.

Claude 2

Anthropic

Anthropic's most capable system at release, representing a continuous evolution from previous Claude models. Trained via unsupervised learning, RLHF, and Constitutional AI with both supervised and reinforcement learning phases. Features improved helpfulness, honesty, and harmlessness (HHH) with enhanced coding abilities, longer output generation up to 4000 tokens, and better structured data formatting capabilities.

Claude (v1)

Anthropic

Anthropic's first-generation AI assistant, built on research into training helpful, honest, and harmless AI systems. Claude was designed for conversational and text processing tasks with enhanced safety features, reduced harmful outputs, and improved steerability compared to earlier language models. Claude v1 introduced Constitutional AI training methods that became foundational to Anthropic's approach.

Claude Instant

Anthropic

Claude Instant was Anthropic’s original lighter, faster, and less expensive Claude tier, released alongside Claude. It supported conversational and text-processing work through the API and partner chat interfaces. The family progressed through 1.0, 1.1, and the significant 1.2 update, which improved coding, mathematics, reasoning, extraction, and multilingual answers. The final model supported a 100K context. All Instant API identities were retired in November 2024.