I'm a solo founder, and Claude is on both sides of my company. I build with Claude Code — it's written a real share of FetchSandbox, from the sandbox engine to the deploy scripts — and Claude runs inside the product: it distills real API failures into runnable bug patterns, writes the docs for 60+ API specs, and powers the loop that reproduces a bug and reasons about the fix.
What stands out after months of daily use is that the reasoning holds up on hard, multi-step problems where other models hand-wave. Opus for the deep work, Haiku for the fast paths. And because it speaks MCP, my users' agents call my tools through Claude directly — no glue code. As a one-person team, it's the closest thing I have to a second engineer.
Codex 3.0 by OpenAI
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