Agentic coding

Plain English. Letting AI agents write software: the model plans, edits files, runs tests and iterates inside a harness, with a human reviewing outcomes rather than keystrokes. "Vibe coding" — Andrej Karpathy's coinage — is the casual variant: describe what you want, accept what works, don't read the code.

Why it moves money. Coding is AI's first proven market and its largest token sink — by OpenAI's own account, Codex generates 99.8% of its weekly output tokens. It is also where labour substitution has real, auditable numbers: a full JavaScript-runtime port, a million lines in 11 days, for a reported API cost of about US$165,000.

What to watch. Verification cost, not generation cost. The Bun port passed the full test suite and still surfaced 19 regressions post-merge — review and testing are where the economics of agentic coding will be decided.

From the signals. Codex is 99.8% of OpenAI's weekly output tokens. Claude Code ported the Bun runtime from Zig to Rust in 11 days, with costs and regressions both on the record. The vibe-coding skills-decay panic mistakes the artefact for the value.