Workshops for teachers, superintendents, and faculty. 10,000+ people so far, from Ghana to California.
Ethan
Castro
I like helping people find and use their gifts. Most days that means teaching, building things for schools, and running a small company with friends.
Now
Senior Learning Engineer, Playlab — employee #2.
Building
Offline Base — private AI on a drive you own.
Studied
Baruch College · Brooklyn College — both CUNY.
Based
Brooklyn — Brooklyn Tech, then CUNY.
01 / What I do
Teaching, building, and starting things.
Most of my work sits somewhere between a classroom and a codebase. I want people to learn faster, work with less stress, and have more time for what matters to them.
Apps for classrooms, clinics, and nonprofits. 1,000+ of them, and a hackathon win or two.
Build
Offline Base, with Hussam Ali. Private AI that runs on hardware you own.
Start
02 / Experience
Mostly with educators. Based in New York.
I joined Playlab as employee #2, and it's about 50 people now. Along the way I was also the first intern in a new AI division at BGB, a research fellow at CUNY, and a TA at BEAM.
-
Senior Learning Engineer
Playlab
I work with school districts and nonprofits from the first conversation through rollout, and co-lead our team of learning engineers.
2026 — Now
New York -
AI Learning Engineer
Playlab
Ran AI workshops for educators around the world, including Ghana's national education system, and a multi-week training for faculty across California's community colleges. Privileged to have worked under the great Wyman Khuu.
2024 — 2026
New York -
Founder
Offline Base
Private, offline AI that runs on hardware you own, and only reaches for the cloud when it has to.
2026 — Now
New York -
Innovation & Intelligence AI Intern
BGB Group
The first intern in a new division. Fine-tuned Llama 3.1 8B and deployed it within HIPAA guidelines.
2024 — 2025
New York -
Teaching Assistant
Bridge to Enter Advanced Mathematics
A summer helping teach math at BEAM.
2024
-
SURGE Research Fellow
CUNY Office of Research
An NIH-funded fellowship that prepares students for PhD research. Research in R.
2023 — 2024
Brooklyn -
President & CEO
Gen Z Labs
A nonprofit consulting agency of Gen Z'ers for youth-serving people and institutions, later pivoted to spinning out products for Gen Z to run.
2024 — 2026
-
Model
Fusion Models BK
Modeled for Hanes, NuSkin, and more.
2022 — 2025
Education
-
Statistics & Quantitative Modeling
Baruch College, CUNY
BBA program with a data science concentration. 3.85 GPA.
Manhattan
-
Computer Science & Nutrition Science
Brooklyn College, CUNY
3.96 GPA. Two research fellowships, two full-ride scholarships, and president of the CRU Christian fellowship.
Brooklyn
-
High School
Brooklyn Technical High School
Where it started.
Brooklyn
03 / Now
Offline Base · Founder
AI you can hold. Most questions never leave your machine.
I started Offline Base with Hussam Ali. The idea is simple: run small, open models on your own device, and only hand a question to a bigger model in the cloud when it really needs one.
- Base DrivePrivate, offline AI from a drive. Coming soon.
- Base RouterAn always-on private AI box for your home. Follows Base Drive.
- Tryingopen ↗Try open models in your browser, no account needed. 20,000 people a month.
- Gemma Gemini ↗Gemma on a Jetson, Gemini in the cloud, and a router that picks.
Accepted into NVIDIA Inception · AWS Activate · Google Cloud for Startups
04 / Highlights
A few things I'm proud of.
Winner · Cerebras × Google DeepMind Gemma 4 Hackathon · 2026
Track 1: Best Multi-Agent + Multimodal Use Case.
With Hussam Ali and Hazem Abo-Donia, at the biggest hackathon Cerebras has hosted. We submitted four projects, including the winner.
~900
Hackers
500+
Projects
4
We submitted
Workshop · May 14, 2026 · College of Staten Island
Run AI Models Locally. Wi‑Fi off, models on flash drives.
Co-led with Hussam Ali. 48 people got Google DeepMind's Gemma and other local models running on their own laptops and phones in about 90 minutes.
48
People
90
Minutes
0
Wi-Fi
Training · Playlab
A multi-week AI training for 500+ faculty. Across all 116 California Community Colleges, plus UC Berkeley and CSU.
I designed and led it. The community college system alone serves 2.6 million students.
500+
Faculty
116
Colleges
4.8+
Workshop rating
Writing · The Institute, IEEE Spectrum · 2023
How Artificial Intelligence Can Personalize Education.
Written with Saurabh Sinha and Catherine Moran. We argue for welcoming AI into classrooms, with an approach that keeps teachers and peers in the loop.
05 / ProjectsGitHub ↗
Things I've made, mostly with friends.
-
P-01 · Offline Base
Tryingopen ↗
Try open AI models in your browser. No account, nothing saved, and you can share any chat as a link.
-
P-02 · Offline Base
Gemma Gemini ↗
Gemma running on a Jetson, Gemini in the cloud, and a router that decides which one answers each message.
-
P-03 · With Hussam Ali
CUNY HPCC Docs ↗
Student-facing docs for the College of Staten Island's high-performance computing center and AI tools.
-
P-04 · With Hussam Ali
An agent on a Jetson
An on-device LLM agent on an NVIDIA Jetson Orin Nano, with an E-Ink drawing pad for input.
-
P-05 · With Edward · 2025 — Now
AccommPass ↗
A simple, dignified way to tell businesses and service providers about your accessibility needs.
-
P-06 · Team project · 2025 — 2026
Augmenting Work
If AI is supposed to save time, you shouldn't sit waiting on it. On Cerebras we generated websites and textbook chapters in about two seconds.
-
P-07 · Nonprofit
Gen Z Labs ↗
Youth serving those who serve us. Consulting by Gen Z'ers, for people and institutions that work with young people.
-
P-08 · Consulting
Therapy clinic AI suite
Five apps for three therapy clinics serving 2,000+ patients. Therapists got about half their admin time back.
06 / Contact
Say
hello.
Email is the best way to reach me. Always happy to talk about teaching, building, or local AI.