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Writing
Notes on payment systems, device software, transaction uncertainty, platform design, and the emerging role of AI in commerce. I write from the questions that appear in real operating conditions.
A host can approve a payment while the terminal still shows UNKNOWN. That third state is not a bug — it's the whole point.
Retry-safe means idempotency-key aware. Reversal-safe means preserving the original approval alongside the reversal. Neither is the default.
A short field guide to the structure that carries every EMV response — tags, lengths, primitives, constructed nesting — with a live parser.
How an agent can pay on your behalf and audibly prove why. A short taxonomy of the guardrails, and where each is easy to get wrong.
Multiple industry proposals for how AI agents should initiate payments have emerged in 2025-2026. Where they agree and where they don't.
Payment Services Directive 3 and the Payment Services Regulation land in staggered dates through 2027. Here's what merchant integrators need to prepare for now.
Terminal key rotation is the operation most fleets avoid until they can't. A design for making it routine rather than dramatic.
Stablecoin payment corridors have real cost advantages and specific operational trade-offs. A comparison against traditional rails.
The contactless-with-CVM threshold quietly moved in most European markets during 2024. What the practical implications look like.
On-call for a team spread across three or more time zones needs different shapes than a co-located team. The patterns that work.