Shantanu Jain
Author of OpenAI's tiktoken tokenizer; mypy and typeshed maintainer and CPython core developer
- Works on language models, including training data and training infrastructure (since 2020), OpenAI12
- Member of the mypy core team and typeshed maintainer, mypy61
Shantanu Jain, who publishes open-source work under the username hauntsaninja, has worked on language models at OpenAI since 2020, studying training data and building training infrastructure. Jain is the listed author of tiktoken, OpenAI's open-source BPE tokeniser for use with its models, and is a maintainer of mypy and typeshed and a CPython core developer.12356
Career
Open-source work
Jain is the listed author of tiktoken, a fast BPE tokeniser for use with OpenAI's models, whose README directs OpenAI staff with questions to Jain. The Python package first appeared on PyPI in December 2022 and has continued to receive releases, including version 0.14.0 in August 2026.345
Outside OpenAI, Jain works in the Python static typing ecosystem: the mypy CREDITS file lists Jain among the non-Dropbox core team members, and Jain also maintains typeshed and is a CPython core developer. Jain wrote pyp, a tool for running Python one-liners at the shell.6127
Work
tiktokenOpen-source code
Listed as the author of the tiktoken package in its pyproject.toml and on PyPI, where the first release (0.1.1) was published in December 2022.354
pyp (external site: github.com)Open-source code
Author of pyp, a command-line tool for running Python at the shell, published on PyPI as pypyp since April 2020.781
Career timeline
2020
Began working on language models at OpenAI.1
Apr 14, 2020
Published the first release of pyp on PyPI under the package name pypyp.8
Dec 15, 2022
Published the first release of tiktoken (0.1.1) on PyPI as its listed author.5
Aug 17, 2026
Version 0.14.0 of tiktoken was published on PyPI, still listing Jain as author.5
Other documented roles
Roles the sources document but that are not confirmed as current.
- Previous employer before OpenAI, Quora1
Related people
More sourced profiles at the same organization, in the same field, or from the same school.
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- Greg BrockmanAlso at OpenAI
- Binyuan HuiLanguage models
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