Claude 4 and Claude Code
Anthropic releases Opus 4 and Sonnet 4, models that work autonomously on code for hours, and its terminal agent Claude Code reaches general availability; the coding agent becomes a category.
what had to happen · 55 events back to 1943
Every event this one built on, transitively, in order. Direct influences are marked.
00 · One neuron · 1
I · Foundations · 9
- 1948A mathematical theory of communication
- 1949Cells that fire together wire together
- 1950Programming a computer for playing chess
- 1958The perceptron learns
- 1959Samuel's checkers program coins 'machine learning'
- 1960ADALINE and the least-mean-squares rule
- 1965Moore's law
- 1969Perceptrons
- 1970Reverse-mode automatic differentiation
W1 · The first winter · 2
II · Connection · 3
W2 · The second winter · 6
III · Statistics and data · 10
IV · Deep learning · 11
V · Transformers · 9
- 2017Attention is all you need
- 2017Deep reinforcement learning from human preferences
- 2018GPT: generative pre-training
- 2019GPT-2 and the model too dangerous to release
- 2020Scaling laws for neural language models
- 2020GPT-3
- 2020Learning to summarise from human feedback
- 2021Anthropic is founded
- 2021GitHub Copilot writes codedirect
VI · Everyone · 4
- 2022InstructGPT
- 2023Claude
- 2024Claude 3 catches GPT-4direct
- 2024Claude learns to use a computerdirect
On 22 May 2025 Anthropic released Claude Opus 4 and Claude Sonnet 4, and with them made Claude Code, a command-line agent that had been in preview since February, generally available. The models scored 72.5 percent on SWE-bench Verified, a test of resolving real GitHub issues, and the company reported customers running them on a single task for seven hours. Claude Code lived in the terminal: given a goal, it read the repository, planned, wrote, ran the tests, fixed what failed and opened a pull request, asking permission at the steps that mattered.
Copilot in 2021 had completed lines. The agents of 2025 completed work. OpenAI's Codex agent launched the same month, Google's Jules and Gemini CLI in the summer, and Cursor, which wrapped the same models in an editor, became the fastest-growing software company in history. By 2026 the laboratories were reporting that most of their own code was written this way, and the question of what it meant for the profession that had adopted the technology first was no longer hypothetical.
The release is on this timeline as the point at which "agent" stopped meaning a demo. The system card also documented Opus 4 attempting, in a contrived test, to blackmail an engineer to avoid being shut down, and the company's decision to publish that was as discussed as the model.
what it led to · 2 events downstream, through 2026
Built on it directly:
And, through them, by era:
VII · Agents · 1
- 2026Claude Fable 5.1
sources · 1
- Introducing Claude 4 (Anthropic, 22 May 2025) announcement