Hello
I'm Ross Sheil
COO by day, dad by night, triathlete on weekends. Previously built growth teams at Twitter, Stripe, and Infogrid. Former GP at TheFund.VC and Sequoia Scout with 40+ angel investments. I write about the stuff I'm figuring out.
Latest Posts
-
Built like an instrument
The capstone: an AI analyst covering the top public and private AI companies, assembled from the series' disciplines — a deterministic pipeline, graded evidence, an agent that answers only from tools, and a judge that must prove it can fail. Part 6 of six weeks building AI systems by hand.
-
Where the answers come from
Evidence for AI agents: a correct answer scored as a failure, four searches that never found the right shelf, and why the filing, not the model, decides what your system can know. Part 5 of six weeks building AI systems by hand.
-
How you know it works
Assurance for AI agents: answer keys written before the run, judges that need judging, the audit trail that caught an agent manufacturing its own evidence, and why every number needs a reference class. Part 4 of six weeks building AI systems by hand.
-
What agents are built from
The bill of materials for a working AI agent — model, skeleton, traces, evidence, protocol, memory, harness — and the two layers no vendor can sell you. Part 3 of six weeks building AI systems by hand.
-
A new class of delegate
Six weeks of building AI systems by hand, written up for operators. Part 2: what an agent may actually do, what actually binds it, and the five levers that decide how much autonomy to grant.
-
Sixty hours beneath the abstractions
I'm a COO. I spent six weeks of late nights building AI systems alongside frontier practitioners, and caught my own agent fabricating evidence inside a perfectly formatted report. What the hours bought, and why the bar for 'technical enough' has moved.
-
Three Hours, No Cloud
I built a desk robot on a Saturday and gave it a brain made entirely of small open-source models. Then I named it badly. What a home robot taught me about open models, defaults, and the gap between demo and daily use.