# John Hallman (slim)

> John Hallman is credited gpt-oss contributor; post-training researcher. gpt-oss-120b and gpt-oss-20b on Anchor Terminal, with grades, an about and public profiles.

- Full: https://www.anchorterminal.com/people/john-hallman/index.md (~1,450 tokens) · this version ~1,230 tokens · JSON https://www.anchorterminal.com/people/john-hallman/index.json · canonical https://www.anchorterminal.com/people/john-hallman/
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-10-28
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)

Credited gpt-oss contributor; post-training researcher.

- LinkedIn: https://www.linkedin.com/in/john-hallman/

## What John builds

- [gpt-oss-120b](https://www.anchorterminal.com/tools/gpt-oss-120b.md), graded BB, 70.2/100, in Open-weight models. gpt-oss-120b is OpenAI's open-weight mixture-of-experts reasoning model, 116.8B parameters with 5.1B active and a 131,072-token context, published on Hugging Face in MXFP4 under Apache 2.0. Credited gpt-oss contributor; post-training researcher, researched 2026-10-26.
- [gpt-oss-20b](https://www.anchorterminal.com/tools/gpt-oss-20b.md), graded B, 69.9/100, in Open-weight models. gpt-oss-20b is OpenAI's open-weight mixture-of-experts reasoning model, 21B parameters with 3.6B active and a 131,072-token context, published on Hugging Face in MXFP4 under Apache 2.0 and trained on the harmony prompt format. Credited gpt-oss contributor; post-training researcher, researched 2026-10-26.

## Works with

- [Andrej Karpathy](https://www.anchorterminal.com/people/andrej-karpathy/), Co-founder, OpenAI
- [Durk Kingma](https://www.anchorterminal.com/people/durk-kingma/), Co-founder, OpenAI
- [Elon Musk](https://www.anchorterminal.com/people/elon-musk/), Co-founder, OpenAI
- [Greg Brockman](https://www.anchorterminal.com/people/greg-brockman/), Co-founder, OpenAI
- [Hannah Koch](https://www.anchorterminal.com/people/hannah-koch/), Product Manager, Codex
- [Ian Kivlichan](https://www.anchorterminal.com/people/ian-kivlichan/), Safety researcher; credited Moderation model contributor
- [Ilya Sutskever](https://www.anchorterminal.com/people/ilya-sutskever/), Co-founder, OpenAI
- [John Schulman](https://www.anchorterminal.com/people/john-schulman/), Co-founder, OpenAI
- [Justin Beckwith](https://www.anchorterminal.com/people/justin-beckwith/), OpenAI engineering leader; Guardrails repository contributor
- [Justin Uberti](https://www.anchorterminal.com/people/justin-uberti/), Head of Realtime AI; Member of Technical Staff
- [Nikunj Handa](https://www.anchorterminal.com/people/nikunj-handa/), Head of Product, OpenAI API
- [Pamela Vagata](https://www.anchorterminal.com/people/pamela-vagata/), Co-founder, OpenAI
- [Rennie Song](https://www.anchorterminal.com/people/rennie-song/), Member of Technical Staff; Dots engineer
- [Sam Altman](https://www.anchorterminal.com/people/sam-altman/), Co-founder, OpenAI
- [Trevor Blackwell](https://www.anchorterminal.com/people/trevor-blackwell/), Co-founder, OpenAI
- [Vicki Cheung](https://www.anchorterminal.com/people/vicki-cheung/), Co-founder, OpenAI
- [Wojciech Zaremba](https://www.anchorterminal.com/people/wojciech-zaremba/), Co-founder, OpenAI

## Backed by

- [SoftBank](https://www.anchorterminal.com/investors/softbank/)
- [Thrive Capital](https://www.anchorterminal.com/investors/thrive-capital/)
- [Microsoft](https://www.anchorterminal.com/investors/microsoft/)
- [NVIDIA](https://www.anchorterminal.com/investors/nvidia/)
- [Altimeter Capital](https://www.anchorterminal.com/investors/altimeter-capital/)
- [Coatue](https://www.anchorterminal.com/investors/coatue/)
- [Khosla Ventures](https://www.anchorterminal.com/investors/khosla-ventures/)
- [Fidelity Investments](https://www.anchorterminal.com/investors/fidelity-investments/)
- [MGX](https://www.anchorterminal.com/investors/mgx/)
- [Tiger Global](https://www.anchorterminal.com/investors/tiger-global/)

## Questions

### Who is John Hallman?

John Hallman is credited gpt-oss contributor; post-training researcher.

### What does OpenAI make?

Anchor Terminal lists gpt-oss-120b and gpt-oss-20b from OpenAI.

### Who has invested in OpenAI?

The sources our research read name SoftBank, Thrive Capital, Microsoft, NVIDIA, Altimeter Capital, Coatue, Khosla Ventures, Fidelity Investments, MGX and Tiger Global.

### How are John's tools graded?

gpt-oss-120b is graded BB, 70.2 out of 100; gpt-oss-20b is graded B, 69.9 out of 100, on Anchor Terminal's benchmark, which scores every listing against the same checklist.

## Sources

- https://openai.com/index/introducing-gpt-oss/
- https://www.linkedin.com/in/john-hallman/
- https://openai.com/index/introducing-openai/
- https://x.com/sama/with_replies?lang=en
- https://x.com/gdb/with_replies
- https://x.com/ilyasut/with_replies
- https://x.com/woj_zaremba/with_replies
- https://openai.com/
- https://help.openai.com/en/articles/6614161-how-can-i-contact-support

These are the people building the tools we list, named for their public role in the company or project behind a listing, from public pages, with the date it was researched.