HMHamza Mostafa

Technical writer & builder

Field notes / 2026

Hamza
Mostafa

I write about agents, systems, and how intelligence becomes useful in the real world.

Read the writing About me

01

Featured essay

Agent Systems

The Model Is the Wrong Thing to Own

Own the knowledge. Let the models compete.

July 24, 2026

5 min read

Selected writing

The archive

02EvaluationSalesBench: The Long-Horizon Agent-to-Agent EvalA long-horizon RL environment where a small model learns to manage an insurance sales pipeline against an LLM buyer, scored by revenue closed instead of by an LLM judge. The trained model vastly outperforms the untrained base, and the gap widens as the eval gets harder.May 14, 202612 min read

03Agent SystemsThe Agent Research LoopWhat Karpathy's autoresearch really means, where agent systems are headed, and an open-source harness that ran 550 experiments over a weekend.March 16, 20268 min read

04Personal AgentsI Run a Personal AI Agent 24/7 on a Mac Mini. Here's How It Actually Works.A Mac Mini, some markdown files, and seven communication channels. Inside the setup that gives me a 24/7 AI assistant that monitors my email, iMessage, WhatsApp, and Twitter - and actually does useful things.March 7, 202612 min read

05Model TrainingI Let AI Agents Train Their Own Models. Here's What Actually Happened.Two frontier agents, a pile of bugs, and a reality check on the future of autonomous AI research.February 8, 20267 min read

About / Now

Building, studying, and writing in public.

Background

I'm a builder and tinkerer. Previously on the Agent team at OpenAI. On leave from CS at the University of Waterloo, KP fellow.

Current questions

Right now I'm exploring multi-agent systems, long-horizon agents, and continual learning.

The common thread is simple: how do capable systems become useful, dependable, and better with experience?

Contact

Say
hello.

The fastest way to reach me is a DM on X or a note on LinkedIn. Interesting questions are always welcome.

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