Guides
Practical guides for building with money.
Not a blog. A small set of pages that answer a specific question properly and stay correct, written for the engineer who has to make money move without losing any of it.
- Featured guide
Moving from a balances column to a double-entry ledger
Read guideHow to get off a stored balance without downtime, without a big-bang migration, and without asking anyone to trust a number twice.
For the team that already has money in production · 9 min read
- Engineering guide
How idempotency actually works in financial transactions
Read guideRetries are not the hard part. Deciding what a replayed write means, and for how long, is. The failure modes and how to design against them.
For backend engineers moving money · 8 min read
- Engineering guide
How to give an AI agent a spending limit it cannot raise
Read guideProvider caps do not sum, in-process checks ship inside the thing they constrain, and sub-agents inherit the whole ceiling. What a real limit needs.
For teams running agents in production · 7 min read
Each one states where it stops being true. If a guide does not tell you when the advice fails, it is marketing.
Reading is cheaper than a bad migration.
Test mode is free, takes no card, and runs the same engine as live. Try the thing the guide describes rather than taking our word for it.