The Pragmatic Engineer
The Pragmatic Engineer

Building Claude Code with Boris Cherny

Brought to You By: • Statsig — ⁠ The unified platform for flags, analytics, experiments, and more. • Sonar – The makers of SonarQube, the industry standard for automated code review • WorkOS – Everything you need to make your app enterprise ready. — Boris Cherny is the creator and Head of Claude Cod

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Boris Cherny Guest

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Episode Summary

Executive Summary: Boris Cherny traces his path from practical tinkering and startup life to leading Claude Code at Anthropic, arguing that AI coding agents are transforming software development as radically as the printing press changed writing. He explains how Claude Code evolved from a side project into a fast-growing product, how Anthropic balances safety, verification, and human review, and why engineers must shift toward generalist, hypothesis-driven, highly adaptable workflows.

Main Topics: Early path into coding as practical problem-solving: Boris explains that he learned coding through tinkering: HTML on eBay listings, calculator programming, freelancing, and early startups. He framed engineering as a tool for building useful things rather than an identity or abstract pursuit. Meta/Instagram experience and code quality at scale: He describes seven years at Meta leading code quality across major products, learning that large orgs need migrations, linting, measurement, and centralized prioritization. Clean codebases and completed migrations mattered both for humans and later for models. Claude Code origin story and internal Anthropic debate: Claude Code began as a simple terminal chatbot and tool-use experiment, then quickly became useful enough that Boris’s first hand-written PR was rejected. Anthropic debated whether to release it, ultimately choosing to do so to study safety in the wild. AI-native development workflow and verification: Boris describes shipping 20-30 PRs daily with no handwritten code, using parallel agents, plan mode, worktrees, mobile/desktop apps, automated tests, lint rules, best-of-n passes, and human review. Review now includes Claude reviewing Claude, plus deterministic checks. Safety, permissions, and enterprise constraints: A major focus is layered safety: model alignment, runtime classifiers, permission prompts, allowlists, static analysis, sandboxing, and human-in-the-loop approval. Enterprise privacy means Anthropic cannot freely inspect user logs, increasing the need for privacy-preserving observability. Shift toward generalists and changing engineering skills: Boris argues that code style debates matter less, while curiosity, adaptability, cross-functional thinking, and methodical debugging matter more. He expects more hybrid roles spanning engineering, product, design, data, and business. Printing press analogy for AI transformation: He compares AI coding to the printing press: a scarce elite skill becomes widely accessible, costs collapse, output explodes, and new roles emerge. The old class of scribes didn’t vanish; it transformed into writers and authors.

Key Arguments: Coding is fundamentally a practical means to build useful things, not an end in itself; Boris’s path from eBay HTML to startups to Meta reflects that worldview. At Meta, code quality had measurable productivity impact; clean, completed migrations and fewer framework choices help both engineers and AI systems. Claude Code grew from experimentation with tool use, not from a conventional product roadmap; letting the model use tools was the key insight. Anthropic released Claude Code partly to learn safety behavior in real usage, not just in evals, and that decision improved the system. AI-generated code still requires verification, but the locus of review has shifted: automated checks, agentic code review, and human approval now work together. The best engineers in the AI era are hypothesis-driven generalists who can move across product, design, and infrastructure and adapt quickly as models improve. The impact of AI coding is comparable to the printing press because it expands who can create software and what kinds of roles and products become possible.

Data Points: Years at Meta: 7 years - Boris spent seven years at Meta before joining Anthropic. Promotions at Meta: 4 promotions - He highlighted four promotions over seven years while leading code quality work. Daily pull requests: 20-30 PRs/day - Boris said he can ship roughly 20 to 30 pull requests each day with AI assistance. Handwritten code in recent workflow: 0 lines manually edited - During a coding month/travel period, he said every PR was written by Claude Code/Opus 4.5 with no manual edits. Bugs introduced in a month: ~2 bugs - He estimated Opus 4.5 introduced only a couple bugs across that period of intense shipping. Meta productivity impact from code quality: Double-digit percent - Boris said code quality contributed double-digit percentage gains to engineering productivity. Anthropic internal adoption: ~100% of technical staff - He said essentially every technical employee at Anthropic uses Claude Code daily. Claude-written code at Anthropic: ~80% - He stated Claude Code writes around 80% of Anthropic’s code on average. Code review bug catch rate: ~80% of bugs - He said Anthropic’s Claude-based code review catches about 80% of bugs. Initial build time for Cowork: 10 days - He said Claude Cowork was built in roughly 10 days by a small team using Claude Code. Prototype count for some features: ~20-30+ prototypes - He mentioned making dozens of prototypes for UI/features like condensed file views. Swarm/plugin weekend experiment: ~200 agents and 100 tasks - A weekend swarm run created roughly 200 agents and 100 Asana tasks to build plugins. Historical literacy: <1% literate in Europe - Used in the printing press analogy to illustrate how rare writing was before mass printing. Printing press cost reduction: ~100x cheaper - He said printed material became roughly 100 times cheaper over decades after the printing press. Printed material growth: ~10,000x more output - He said volume of printed material increased by about 10,000 times over 50-100 years.

Pivotal Quotes: "I think we're living through a time as transformative as a printing press." — Boris Cherny: His core analogy for how AI coding agents will reshape software creation and the wider economy. "I wrote my first pull request by hand because I thought that's how you write code." — Boris Cherny: He described the moment his hand-written PR was rejected at Anthropic and he was directed to use Claude instead. "The model is its own thing. You give it tools. You give it programs that it can run. You let it run programs, you let it write programs, but you don't make it a component of this larger system." — Boris Cherny: His explanation of the agentic AI philosophy behind Claude Code’s design.

Implications: Software engineering is moving from hand-coding toward supervising, verifying, and orchestrating AI agents. Engineers who adapt quickly, think across disciplines, and build strong safety/verification systems will be most valuable.

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