Jeffery Vincent  /  Virginia Beach, VA

I build AI agents that don't get the last word.

Staff mobile engineer, ten years in. React Native, TypeScript, Python, LLMs. Lately I build trading agents that reason on local hardware — and answer to deterministic code they can't argue with.

Decisions worth writing down

The trading agent that doesn't get the last word

The easy path
Let the model decide. Prompt it to be careful and hope the prompt holds.
What shipped
An LLM committee debates a trade and a judge model returns a verdict — then that verdict hits a deterministic rules gate that can overrule it and can't be argued with. The autonomous mode is real, but it acts inside a fence of portfolio circuit breakers and a daily-loss kill switch that latches until cleared by hand. Exits are never blocked. Every place a model touches money, non-probabilistic code gets the final say.

Read the writeup  ·  Python · FastAPI · Ollama · Alpaca

One entitlement model, three billing systems

The easy path
Handle StoreKit, Play Billing, and Stripe where each one shows up in the app.
What shipped
A single source of truth for what a user is entitled to, with the three billing systems reduced to adapters feeding it. Restore, refund, and cross-platform purchase stopped being three separate bug surfaces.

React Native · StoreKit · Play Billing · Stripe

Knowing when to turn it off

The easy path
Keep shipping features into the silence and tell yourself the users are coming.
What shipped
TradeScans — post-trade AI analysis for options traders, built solo end to end: React Native client, a pluggable multi-provider LLM backend, credit-based pricing live across all three storefronts. Then I checked the subscriber count, found zero, and sunset it. The infrastructure got reused. The sunk cost didn't get honored.

React Native · FastAPI · Railway · LLM providers

Now

Mobile engineering at Upward Sports, on Upward Run Club. Building trading agents on the side, and writing about what closed trades reveal that open ones can't.

Open to Staff and Principal mobile roles.