a16z Podcast

How OpenAI Built Its Coding Agent

401 snips
Sep 16, 2025
Alexander Embiricos, who leads product development for Codex at OpenAI, dives into the groundbreaking world of AI coding agents. He discusses Codex's impressive record of merging pull requests and the critical safety challenges it faces. The conversation touches on the future of software development, where AI transforms coding workflows. Embiricos also addresses career anxieties for tech students and advocates for educational reforms to better integrate AI. This insightful exchange reveals how automated tools are reshaping programming for the better.
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INSIGHT

Agents Are Models Plus Tools

  • Agents pair reasoning models with tools and an environment to perform software tasks autonomously.
  • OpenAI built Codex as a cloud agent that runs on its own compute to act like a teammate.
INSIGHT

Form Factor Drives Merge Success

  • Codex's high PR merge rate reflects its cloud-agent form factor and staged draft-PR workflow.
  • Running work in a protected environment before opening a PR boosts safety and trust in merges.
ADVICE

Defend Agents At Multiple Layers

  • Deploy agents with layered defenses: protect prompts, monitor intermediates, and block exfiltration at outcomes.
  • Treat prompt injection as multi-layer risk and defend at every stage, especially network egress.
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