How to stop Cursor AI forgetting your .NET architecture (the $9 fix)

agentic.standard.contact Posted on May 30 • Originally published at agenticstandardcontact-byte.github.io How to stop Cursor AI forgetting your .NET architecture (the $9 fix) # csharp # dotnet # ai # cursor **How to stop Cursor AI forgetting your .NET architecture (the $9 fix) ``** Your Cursor session starts. You type your first prompt. The AI confidently suggests instantiating HttpClient inside your repository — the exact anti-pattern you banned six months ago. You sigh, type 'actually we use typed HttpClients registered via DI,' and burn 15 minutes re-teaching an AI that was supposed to help you. This is the Context Tax. Every .NET developer using Cursor pays it. Here's how to stop. The Context Tax: what it costs you every morning The Context Tax is the fifteen minutes you spend re-explaining your codebase to Cursor at the start of every session. You describe your DI conventions, your Clean Architecture layers, your EF Core patterns, your Result pipeline. Cursor nods along. You build a feature. Session ends. Next morning? Back to square one. Multiply that by 250 working days and you're losing 62 hours a year — nearly two full working weeks — just re-establishing context. At a senior contractor rate of £75/hr, that's £4,650 of lost time. Per developer. Why Cursor's built-in rules aren't enough plaintext Cursor supports a .cursor/rules/ directory. You can drop .mdc files in there and the AI reads them. So why doesn't that solve the problem? Monolithic rules dump tokens, not context ``** Most public Cursor rules repos give you a single rules.mdc file that gets loaded on every prompt. Every. Single. Prompt. That's 2,000+ tokens of preamble before your actual instruction. Your fast-request budget evaporates on rules that aren't even relevant to the file you're editing. Rules describe — they don't persist ** A rule that says "use Result not exceptions" tells Cursor what to do. But it doesn't tell Cursor why you chose that pattern, what you tried before it, or what