.Fielding.

Hello, I'm Fielding Johnston. With over 15 years of experience, I specialize in building scalable AI infrastructure, healthcare platforms, and distributed systems. Currently I'm building a patient communications platform at Freed. I care deeply about AI adoption, not just shipping AI-powered products, but helping the teams around me get better at using AI every day.

See what I’m building after hours, or dig into my experience, publications, and projects below.

Find me on GitHub, Google Scholar, LinkedIn, or grab my Resume. Want to work together, build something cool, or just chat? Reach out at hello@justfielding.com.

.Now.

As of March 2026

Code is no longer the bottleneck. That changes what's worth building. I've been circling around four areas: highlighting human intent so it isn't lost, encoding constraints so they're enforced automatically, empowering agents to build faster, and eliminating the review bottleneck entirely.

human++ is a color scheme and editor extension built around the idea that code is cheap and intent is scarce. sigil is still finding its shape, somewhere between ADRs and a knowledge graph. nit makes what agents do cheaper. sprawl lets them do it together. review-crew has been a really successful experiment in multi-model adversarial code review. And clipside is a project built entirely by a team of agents (using most of the tools above) so I could watch them work.

Recent writing

The Interview Was the Payload

I Put a Prompt Injection on My Resume

all posts →

.Professional Experience.

Senior Software Engineer

Freed | 2025 – Present

Founding member of a 4-person team that built a greenfield patient communications platform; selected as the company's top strategic bet and scaled to a larger team.

Built end-to-end voice and SMS infrastructure including patient identification with dual validation, AI-initiated call transfer, two-way SMS with TCPA-compliant consent, and PHI screening via LLM.

Shipped BigQuery analytics pipeline as source of truth for pilot metrics, integrating sentiment analysis and call evaluation criteria, and fixing duration reporting accuracy from 0% to 100%.

Designed care collaboration workflows with PostgreSQL RLS and role-based access, enabling multi-clinician visit collaboration with realtime patient updates.

Created and shipped '12 Business Days of AI,' a 12-day internal engineering campaign with guest contributors teaching advanced AI patterns, shifting the team from shadow AI usage to documented shared mastery.

Vice President of Engineering

Nesa | 2023 – 2025

Architected a distributed inference framework for 120,000 models across heterogeneous hardware, handling up to 2M inference requests in a single day.

Designed and implemented Nesa's layer 1 blockchain, enabling decentralized compute for AI workloads.

Developed telemetry pipeline using NATS.io and Prometheus to monitor thousands of nodes.

Led secure containerization for user-submitted models.

Contributed to equivariant encryption (EE) for end-to-end private AI inference with zero-latency overhead.

Developed reinforcement learning system for dynamic model assignment.

Contributed to open-source projects including xFusers and nats.py.

Lead Software Engineer & Director of Design and Development

OpesSky | 2022 – 2023

Led Unity-based lunar colony simulation game development.

Designed and implemented 3D environments and shaders.

Built AI systems for dynamic NPCs with procedural behaviors.

Directed art team and coordinated UI/UX integration.

Lead & Senior Frontend Engineer

Vidy | 2019 – 2022

Lead Frontend Engineer (2020–2022)

Refactored codebase to Svelte, improving performance for 14M+ monthly users.

Built components for scalable real-time video and data applications.

Developed custodial wallet system for user transactions.

Implemented NLP for ad placement to boost engagement.

Senior Software Engineer (2019–2020)

Built scalable APIs and web apps for real-time video.

Led adoption of modern JS frameworks.

Engineered fine-grained reactive vanilla JS framework.

Founder and Software Engineer

justFielding | 2009 – 2019

Built and scaled web apps integrating React and Three.js.

Advocated open-source frameworks to reduce tech debt.

Managed technical, design, and business operations.

.Publications.

.Projects.

Thinktax

Cross-provider AI cost tracking that prefers actual spend over vibes.

AI cost tooling

nit

A git wrapper that cuts token waste by making the right output the default.

Agent-first developer tooling

Specter

An adversarial coding harness where one agent writes the contract and another has to prove it can satisfy it.

Verification / agent infrastructure

Bleeping Weather

A profanity-forward weather app with cross-platform widgets and an actual content system behind the jokes.

Consumer product

Apprentice

A voice mentor for AI coding sessions that tries to teach at the right moments instead of narrating every keystroke.

AI learning product