Claude Versions

The OpenAI exodus and the founding (2021)

Anthropic was incorporated in San Francisco in early 2021 by a group of senior researchers and engineers who had just left OpenAI over a stated disagreement about the direction of safety and commercialization. The cofounders included Dario Amodei (Research VP at OpenAI; CEO at Anthropic), Daniela Amodei (President), Tom Brown (lead author of the GPT-3 paper), Sam McCandlish, Jared Kaplan (the “Scaling Laws” paper), Jack Clark, Chris Olah, Tom Henighan, Andy Jones, Nick Joseph, and several others.

The Series A in mid-2021 raised roughly $124M with Jaan Tallinn and Dustin Moskovitz as lead investors and the Center for Emerging Risk Research participating. Anthropic spent its first eighteen months as a research-only operation; the first commercial Claude product did not ship until March 2023.

For per-cofounder bios, prior-OpenAI roles, and a chronological timeline of Anthropic's founding, governance, and leadership events, see the dedicated Anthropic Leadership page.

Constitutional AI and the research direction

Anthropic's December 2022 paper “Constitutional AI: Harmlessness from AI Feedback” (Bai et al.) introduced RLAIF — reinforcement learning from AI feedback — as an alternative to RLHF. A model critiques and revises its own outputs against a written constitution rather than relying on human comparison labels for every preference. The technique remains the technical foundation of every Claude release since, and is the most widely-cited piece of Anthropic research outside of the earlier “Scaling Laws” paper.

The funding story

After the 2021 Series A, Anthropic raised a Series B and C in 2022 with participation from Sam Bankman-Fried's FTX and Alameda Research (reportedly around $500M). The FTX collapse in November 2022 left the FTX bankruptcy estate as Anthropic's largest single shareholder; the estate later sold the stake in 2024.

In 2023 Google invested an initial $300M, later expanded to a multibillion-dollar commitment. Amazon committed an initial $4 billion in September 2023, increased the commitment through 2024 to a reported $8 billion total, and on April 20, 2026 expanded again with $5 billion now plus up to $20 billion more, alongside a $100B+ ten-year AWS-services commitment from Anthropic for up to 5 GW of training and inference capacity. The two-cloud financial structure (Google + Amazon) is a recurring background fact in coverage of the company.

Venture rounds since then have moved fast: Series E in March 2025 (~$3.5B at $61.5B post-money, Lightspeed lead), Series F in September 2025 (~$13B at $183B post-money, Iconiq / Fidelity / Lightspeed co-leading), and Series G on February 12, 2026 (~$30B at $380B post-money, Coatue and GIC co-leading), with a follow-on round at a reported $850B–$900B in talks as of April 2026.

For the round-by-round timeline with valuations, lead investors, and primary-source links, see the funding rows on the dedicated Anthropic Leadership page.

The Claude 1 / Claude 2 era (2023)

Claude 1 launched March 14, 2023 in limited access via Anthropic's API, Slack, and Quora's Poe — the same week GPT-4 became publicly available. Claude 2 launched July 11, 2023 as the first broadly available Claude, with the Claude.ai consumer chat product as its delivery surface. The headline differentiator was a 100,000-token context window, an order of magnitude beyond the GPT-4 8k / 32k offerings of the time.

Claude 2.1 in November 2023 doubled that to 200k and added tool-use in beta. The pre-tier era was also the period during which Anthropic's role in the AI-safety conversation crystallized publicly — Dario Amodei's Senate testimony, the “responsible scaling policy,” and the early model-card publishing convention.

The tier system (March 2024)

Claude 3 in March 2024 introduced the Opus / Sonnet / Haiku naming — three models released together for the first time, sharing a generation number and differentiated by capability and price. The convention has held through every release since, and is the one piece of product naming Anthropic has kept stable while everything around it (mid-version numbers, snapshot dates, “new” suffixes) has shifted. Claude 3 Opus was also Anthropic's first model widely considered competitive with the contemporary GPT-4 line on hard benchmarks — the moment the “serious challenger” framing became standard.

The 3.5 / 3.7 mid-version era (2024 – early 2025)

Claude 3.5 Sonnet shipped Artifacts in June 2024 — a side-panel rendering surface for code, documents, and diagrams that became the template for similar features across the chat-product industry. Sonnet 3.5 (new) in October 2024 shipped Computer Use, the first frontier-model capability where the model could take screenshots of a virtual desktop, click, type, and navigate UIs the way a human does. The Model Context Protocol (MCP) was announced alongside this period in November 2024 and has since become the de-facto standard for tool integration across the industry.

Sonnet 3.7 in February 2025 introduced extended thinking — an exposed reasoning mode toggleable per request. Claude Code launched the same week as the CLI agent for developers. Together those two changes set the shape of Anthropic's 2025: a sustained push into “agent” products on top of frontier models, with a deliberate distance from competitor strategies that emphasized consumer chat features.

The Claude 4 line (May 2025 onward)

Claude Opus 4 and Sonnet 4 launched together on May 22, 2025 as the public debut of the Claude 4 line. Opus 4 was the first new Opus-tier model in fourteen months — the longest gap between flagships in the line's history. The mid-version cadence accelerated noticeably afterward: Opus 4.1 in August, the 4.5 generation across all three tiers in September / October / November 2025, Opus 4.6 in February 2026 alongside Sonnet 4.6, Opus 4.7 in April 2026, and Opus 4.8 on May 28, 2026 — the latter shipping the Dynamic Workflows orchestration feature and the effort-control dial alongside the model itself.

The Claude 4 era has also been when Claude Code went from a developer side-project to a cornerstone product, and when the “agentic” framing of the platform — Opus 4.x for long-horizon coding, Sonnet 4.x for routed everyday work, Haiku 4.5 for high-volume cheap calls — became the canonical recommendation.

On June 9, 2026, Anthropic pushed past the Opus tier entirely with Claude Fable 5 (claude-fable-5), the first generally-available model in the new Mythos class — a tier it positions above Opus in capability, and the model the Opus 4.8 release notes above described as the “bridge” to. Fable 5 is the public, safety-gated counterpart to Claude Mythos 5 (claude-mythos-5), an unrestricted variant released only to a small group of cyberdefenders and infrastructure providers; on some sensitive topics Fable 5 routes the answer to Opus 4.8 instead, tuned to trigger in under 5% of sessions. It is priced at $10 / $50 per million input / output tokens.

The lawsuits

Four significant cases have shaped the legal context around Claude. The case-name links below jump to the per-case rows on the dedicated Anthropic Lawsuits page, which carries plaintiffs, procedural milestones, ruling summaries, and primary-source links per case.

• Bartz v. Anthropic (N.D. Cal., filed 2024). Class action by authors Andrea Bartz, Charles Graeber, and Kirk Wallace Johnson over training-data sourcing including pirated copies from sites like LibGen. In June 2025, Judge William Alsup ruled on summary judgment that training on lawfully-acquired books is fair use, but that the acquisition of pirated copies is not — setting the trial up around piracy liability for over seven million books Anthropic had downloaded. Anthropic settled in August 2025 for $1.5 billion, the largest copyright settlement in U.S. history. The four-installment payment schedule runs October 2025 / April 2026 / September 2026 / September 2027 at roughly $3,000 per eligible work; the claim deadline was March 30, 2026 (91.3% of 482,460 eligible works claimed). The final fairness hearing was held May 14, 2026 before Judge Martínez-Olguín, who heard class counsel and objectors (publisher-favoritism, inadequate-compensation, and transparency objections from ~120,000 authors) and took the matter under submission — final-approval order pending as of late May 2026. The fair-use ruling on training data is now the most-cited piece of LLM-copyright law.
• Concord Music Group, et al. v. Anthropic (N.D. Cal., transferred from M.D. Tenn., filed October 2023). Music publishers (Concord, UMG, ABKCO) sued over Claude's training on copyrighted song lyrics and over the model's lyric outputs. In March 2025, Judge Eumi K. Lee denied the motion for a preliminary injunction and granted Anthropic's motion to dismiss the contributory and vicarious infringement counts (with leave to amend), narrowing the case substantially; the direct-infringement claim on the training side survived and the case continues in active discovery.
• Concord Music Group v. Anthropic (II) (N.D. Cal., filed January 28, 2026). The same publisher coalition's second Anthropic suit, applying the Bartz piracy template to music. The complaint alleges mass torrenting of 20,000+ copyrighted songs from LibGen and PiLiMi, names CEO Dario Amodei and cofounder Benjamin Mann individually, and seeks roughly $3 billion. The first major LLM piracy-acquisition case filed after the Bartz settlement.
• Reddit v. Anthropic (San Francisco Superior Court, filed June 2025). Reddit alleged that Anthropic continued scraping Reddit user posts after access was revoked, with claims for breach of contract, unjust enrichment, trespass to chattels, tortious interference, and unfair competition. After Anthropic removed to N.D. Cal., Judge Trina L. Thompson remanded the case to state court on March 30, 2026, holding that none of Reddit's claims is preempted by the Copyright Act — a first-of-its-kind ruling making contract / TOS theories durable against AI-lab preemption defenses. The case is the highest-profile of the “platform-data-licensing” suits to date.

The OpenAI superalignment exodus (2024)

In May 2024, several senior members of OpenAI's superalignment team left and the team was dissolved within days. Jan Leike, who had co-led that work with Ilya Sutskever, joined Anthropic publicly the same week, citing concerns about OpenAI's safety culture. John Schulman, an OpenAI cofounder and the original lead on RLHF and on ChatGPT itself, joined Anthropic in August 2024 (and later moved on to other ventures). The pattern echoed the original 2021 founding exodus: several of the most-influential alignment-focused OpenAI researchers ending up at Anthropic.

People who shaped Claude

Founders: Dario Amodei (CEO; Research VP at OpenAI before), Daniela Amodei (President), Tom Brown (lead author of the GPT-3 paper), Sam McCandlish, Jared Kaplan (Chief Science Officer; “Scaling Laws” paper), Jack Clark (Policy), Chris Olah (interpretability lead), Tom Henighan, Andy Jones, Nick Joseph.

Post-founding leadership: Mike Krieger joined as Chief Product Officer in 2024 (cofounder of Instagram). Jan Leike joined from OpenAI's superalignment team in 2024. The interpretability team that Chris Olah leads has produced much of the published research that defines Anthropic's public technical voice (mechanistic interpretability, sparse autoencoders, the “Towards Monosemanticity” line of work).

Public face: Dario Amodei has been the company's primary public voice through Senate testimony, the “Machines of Loving Grace” essay (October 2024), and the major podcast appearances. Jack Clark writes the long-running “Import AI” newsletter and handles much of the policy-side communication.

For per-cofounder bios, the Long-Term Benefit Trust, the funding arc, and the senior team additions in chronological-timeline form, see the dedicated Anthropic Leadership page.

The competitive landscape

Claude is one of three frontier-model families that meaningfully compete in 2026, alongside OpenAI's GPT and o-series and Google's Gemini. Meta's Llama family is the largest open-weights line; xAI's Grok is the fourth notable closed-weights contender. The positioning between Claude and its closed-weights peers has shifted over time — Claude is widely associated with coding and agentic workflows in 2026, GPT with the broadest consumer surface, Gemini with multimodal and long-context strength — but the rankings move release-to-release and the page does not attempt to capture them.