Why humans are AI’s biggest bottleneck (and what’s coming in 2026) | Alexander Embiricos (OpenAI Codex Product Lead)

Alexander Embiricos leads product on Codex, OpenAI’s powerful coding agent, which has grown 20x since August and now serves trillions of tokens weekly. Before joining OpenAI, Alexander spent five years building a pair programming product for engineers. He now works at the frontier of AI-led software development, building what he describes as a software engineering teammate—an AI agent designed to participate across the entire development lifecycle.

We discuss:

1. Why Codex has grown 20x since launch and what product decisions unlocked this growth

2. How OpenAI built the Sora Android app in just 18 days using Codex

3. Why the real bottleneck to AGI-level productivity isn’t model capability—it’s human typing speed

4. The vision of AI as a proactive teammate, not just a tool you prompt

5. The bottleneck shifting from building to reviewing AI-generated work

6. Why coding will be a core competency for every AI agent—because writing code is how agents use computers best

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Transcript: https://www.lennysnewsletter.com/p/why-humans-are-ais-biggest-bottleneck

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My biggest takeaways (for paid newsletter subscribers): https://www.lennysnewsletter.com/i/180365355/my-biggest-takeaways-from-this-conversation

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Where to find Alexander Embiricos:

• X: https://x.com/embirico

• LinkedIn: https://www.linkedin.com/in/embirico

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Where to find Lenny:

• Newsletter: https://www.lennysnewsletter.com

• X: https://twitter.com/lennysan

• LinkedIn: https://www.linkedin.com/in/lennyrachitsky/

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In this episode, we cover:

(00:00) Introduction to Alexander Embiricos 

(05:13) The speed and ambition at OpenAI

(11:34) Codex: OpenAI’s coding agent

(15:43) Codex’s explosive growth

(24:59) The future of AI and coding agents

(33:11) The impact of AI on engineering

(44:08) How Codex has impacted the way PMs operate

(45:40) Throwaway code and ubiquitous coding

(47:10) Shipping the Sora Android app

(49:01) Building the Atlas browser

(53:34) Codex’s impact on productivity

(55:35) Measuring progress on Codex

(58:09) Why they are building a web browser

(01:01:58) Non-engineering use cases for Codex

(01:02:53) Codex’s capabilities

(01:04:49) Tips for getting started with Codex

(01:05:37) Skills to lean into in the AI age

(01:10:36) How far are we from a human version of AI?

(01:13:31) Hiring and team growth at Codex

(01:15:47) Lightning round and final thoughts

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Referenced:

• OpenAI: https://openai.com

• Codex: https://openai.com/codex

• Inside ChatGPT: The fastest-growing product in history | Nick Turley (Head of ChatGPT at OpenAI): https://www.lennysnewsletter.com/p/inside-chatgpt-nick-turley

• Dropbox: http://dropbox.com

• Datadog: https://www.datadoghq.com

• Andrej Karpathy on X: https://x.com/karpathy

• The ris