The Pragmatic Engineer — selected conversations
Building Claude Code with Boris Cherny
Eighteen curated conversations on agent workflows, design, harnesses, and software quality
A manually reviewed selection of Pragmatic Engineer conversations with Maggie Appleton, Matt Pocock, Tibo Sottiaux, Martin Fowler, Dex Horthy, Boris Cherny, Mario Zechner and Armin Ronacher, Laura Tacho, Hillel Wayne, Mitchell Hashimoto, Kent Beck, Peter Steinberger, Grady Booch, Steve Yegge, DHH, Dax Raad, Charity Majors, and Addy Osmani. Topics include design prototyping, reusable skills, agent workflows, context and harness design, TDD and verification, architecture, measurement, accountability, and open-source governance. Practitioner observations, product-team claims, and forecasts are not controlled findings.
In this collection Browse 18 summaries 6 of 18
Gergely Orosz interviews Boris Cherny, introduced as Claude Code's creator and engineering lead at Anthropic. Cherny describes Claude Code as an experiment that grew into a widely used development tool, and argues that stronger models are shifting software work from writing code toward planning, verification, rapid prototyping, and coordination across disciplines 00:58–01:48(opens in a new tab), 23:40–30:08(opens in a new tab), 37:11–45:59(opens in a new tab).
Key Points Covered
- Claude Code became agentic through simple tools: Cherny says the original terminal chatbot changed after he gave the model Bash and file-editing tools. His design lesson is to give the model room to act rather than constrain it as one fixed program component 23:40–27:12(opens in a new tab).
- Public release was also a safety experiment: He says Anthropic debated keeping Claude Code internal, then released it partly to study real-world use. The reported near-universal internal adoption and estimate that it writes about 80% of Anthropic's code are internal observations, not independent measurements 27:12–30:08(opens in a new tab).
- High personal throughput remains anecdotal evidence: Cherny reports that with Opus 4.5 he stopped editing code manually and produced roughly 10–20 pull requests per day during one month, with about two bugs by his count 31:11–33:13(opens in a new tab).
- Plan first and isolate parallel attempts: His workflow starts several isolated Claude Code sessions in plan mode, refines each plan, and then lets the model implement. He recommends explanatory mode for unfamiliar codebases and warns that no one workflow fits every engineer 33:13–38:12(opens in a new tab).
- Review combines probabilistic and deterministic layers: Cherny describes model-written tests, end-to-end checks, Claude Code review in CI, types, linting, builds, best-of-N review, and final human approval. His estimated review catch rate is not substantiated with evaluation details in the interview 40:18–45:59(opens in a new tab).
- Security is layered risk reduction: He describes model alignment, runtime classifiers, sub-agent summarization for fetched web content, static analysis, allowlists, sandboxing, and permission prompts without claiming that the stack eliminates prompt injection or unsafe actions 47:02–54:21(opens in a new tab).
- Cheap implementation favors working prototypes: Cherny says the team uses prototypes, dogfooding, and user feedback rather than relying on static mockups or PRDs. The prototype counts and short timelines discussed are team recollections, not comparative studies 59:17–1:04:37(opens in a new tab).
- Fresh contexts may help agent teams: He attributes improved internal results to multiple “uncorrelated” context windows and Opus 4.6, while noting that the research preview uses many tokens and fits complex tasks rather than every task 1:14:24–1:18:20(opens in a new tab).
Full video: https://www.youtube.com/watch?v=julbw1JuAz0(opens in a new tab)