Claude Code: Behind the Scenes

Claude Code is one of the most popular developer tools today. But did you know that initially it was just a side project inside the company?

This and many other interesting details are discussed in an interview with Boris Cherny, the creator and head of Claude Code at Anthropic.

Key insights from the interview:
🔸 Boris built Claude Code as a bash chat-based tool when he was learning public Anthropic APIs and how people use the model. It quickly became popular among other employees, that led to a future public success.
🔸 Claude writes ~80% of the code at Anthropic on average.
🔸 Boris ships 20-30 PRs a day by running 5 parallel Claude instances. He starts with a plan mode, iterates over the plan, then let the agent do the implementation. Since the Opus 4.5 release, Claude writes 100% of his code.
🔸 There is no "right way" to use Claude Code. According to Boris, "The way we build cloud code is to be hackable because we know every engineer's workflow is different. There's no one way to do things. There's no two engineers that have the same workflow."
🔸 The Claude team doesn't write Product Requirement Documents (specs). They just build dozens of working prototypes before shipping a feature.
🔸 Claude Code reviews every pull request at Anthropic and it catches ~80% of bugs. There are 2 rounds of review: the first is performed by AI agent, the second is always done by human who finally approves the changes.
🔸 Claude Cowork is intended to provide Claude capabilities for non-engineers. The tool was built in ~10 days and the main engineering complexity here is about safety: building classifiers, a shipping VM, OS-level protections against accidental file deletion, and rethinking the permission model for non-technical users.
🔸 There are no technical grades inside Anthropic. Everyone has the same title "Member of Technical Staff", that highlights the assumption that everyone can do everything: product, design, infrastructure, research.

During the interview Boris repeated multiple times that it's more important to ship fast and get user feedback early than to wait and deliver a fully featured product. That's why they built their engineering culture around prototyping. I think it's one of the reasons Anthropic products are so successful.

By the way, if you haven't tried Claude Code yet I highly recommend to do so. And as a starting point you can use Claude Code In Action Anthropic course.

#ai #engineering #usecase