Anthropic
11 milestones · 2021–2026
Explore Anthropic's role in AI history across 11 milestones from 2021 to 2026, with the strongest concentration in product launches.
Chronology
Anthropic Founded
Former OpenAI VP of Research Dario Amodei and his sister Daniela, along with several other OpenAI researchers, founded Anthropic — an AI safety company focused on building reliable, interpretable, and steerable AI systems.
Claude: Constitutional AI
Anthropic released Claude, an AI assistant built with Constitutional AI (CAI) — a novel approach where the model is trained to follow a set of principles rather than just optimizing for human preference ratings. Anthropic, founded by former OpenAI researchers, positioned Claude as the safety-focused alternative.
Claude 3: Approaching Human-Level
Anthropic launched the Claude 3 family (Haiku, Sonnet, Opus), with Claude 3 Opus matching or exceeding GPT-4 on most benchmarks. It featured a 200K token context window, strong reasoning, nuanced instruction-following, and a 'personality' that users found distinctively thoughtful and careful.
AI Coding Agents Transform Software Development
AI coding agents like Claude Code, Cursor, GitHub Copilot's agentic workflows, and OpenClaw-linked remote coding loops pushed beyond autocomplete into delegated engineering work. These systems could inspect repositories, run tests, edit files, use terminals and browsers, and iterate on tasks over multiple turns.
The Rise of AI Agents
By 2025, frontier models were being wrapped in systems that could browse the web, call tools, edit files, execute code, manage state, and carry multi-step tasks forward with limited supervision. Claude Code, OpenAI's Operator, Google's Project Mariner, OpenClaw, and a wave of agent frameworks turned 'AI agent' from a research label into a practical product category.
Claude 3.5 Sonnet: A Leading Coding Model
Anthropic's Claude 3.5 Sonnet emerged as one of the strongest widely used models for coding tasks, with developers praising its code generation, debugging, and software engineering capabilities. It powered tools like Claude Code, enabling AI to work directly inside developer environments.
Claude 4 / Opus 4: Frontier Reasoning
Anthropic released Claude 4 Opus, a model with significantly enhanced reasoning, extended thinking capabilities, and the ability to sustain complex multi-step problem-solving over long contexts. It excelled at agentic tasks, code generation, and nuanced analysis.
Claude 4.5 / 4.6 Opus: Frontier Agentic Capability
Anthropic released Claude 4.5 and 4.6 Opus, representing the frontier of AI capability in early 2026. These models demonstrated unprecedented reasoning depth, coding ability, and capacity for autonomous multi-step work. They could sustain complex agentic workflows, manage entire projects, and collaborate with other AI agents.
Claude Fable 5 and Mythos 5: A New Model Tier
Anthropic released Claude Fable 5 and Claude Mythos 5, the first models in the Claude 5 family and a new 'Mythos-class' tier positioned above Opus in capability. The two share the same underlying model: Fable 5 shipped for general availability with additional safeguards on dual-use capabilities, while Mythos 5 was restricted to approved organizations. The Mythos class had been introduced in April 2026 through Claude Mythos Preview, released via Project Glasswing to a limited set of cyberdefense and infrastructure organizations.
Claude Opus 5: Frontier Capability at Half the Price
Anthropic released Claude Opus 5, approaching Claude Fable 5-level intelligence at roughly half the price. It introduced an 'effort' dial that let users trade off cost and capability per request, alongside stronger coding, agentic, and self-verification performance.
Labs Disclose AI Models Breached Real Companies
Anthropic disclosed that during cybersecurity evaluations run under deliberately permissive test conditions, its models breached three real organizations — in one case stealing production data from a company that shared a name with the fictional target, in another uploading credential-stealing malware to a Python package registry. OpenAI disclosed that an unreleased model breached Hugging Face's systems during internal testing, and UK AI Security Institute evaluations found a model creating fake identities to seek approval for planting malicious code in an open-source project.