{"slug": "this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026", "title": "This week in Cursor + .NET — 3 rules + 4 essays (week ending May 22, 2026)", "summary": "This article summarizes a week of daily rules for senior C#/.NET engineers using the Cursor AI coding assistant, covering topics such as preventing AI from corrupting error models, catching silent DI lifetime bugs, and enforcing async CancellationToken usage. It also promotes a free Cursor rule file called \"arch-core-lite.mdc\" designed to stop the AI from forgetting architectural constraints, with a full kit available for £19.99. The canonical versions of these posts are hosted on the Agentic Architect blog.", "body_md": "Every weekday a single, opinionated rule for senior C#/.NET engineers using Cursor. Here's the full week in one read — canonical posts live on the Agentic Architect blog.\nThu 21 May · C# patterns\nStop the AI from undoing your Result/ErrorOr error model with throw and null on every new prompt.\nWed 20 May · Cursor rules\nThe correction spiral — and the circuit-breaker rule that ends it before you type the stop phrase.\nTue 19 May · .NET DI\nThe .NET lifetime bug that ships to production silently — and the one Cursor rule that catches it before merge.\nMon 18 May · Architecture\nThe hidden cost senior engineers pay every morning — and a four-rule architecture for eliminating it.\nFri 22 May\nThe single most expensive .NET runtime bug: a Singleton holding a Scoped service. Cursor cheerfully writes this without warning. Audit constructor parameters of any class registered as Singleton — if any are typically Scoped (DbContext, repositories, MediatR sender), flag it before merge.\nThu 21 May\nEvery async method in your codebase should accept and forward a CancellationToken. Make it a rule that any new async signature without one is flagged. Stops the AI from quietly losing cancellation half-way down a call chain.\nWed 20 May\nNever let the AI write database logic in your Controllers. Enforce a strict boundary where all IQueryable access stays in the Infrastructure layer. This keeps your business logic \"pure\" and readable for the LLM.\nThe free arch-core-lite.mdc\nis one drop-in Cursor rule that ends the morning re-explanation ritual. Install in 60 seconds, see whether Cursor actually remembers your DI lifetimes, and decide for yourself whether the full kit is worth £19.99.\narch-core-lite.mdc\non GitHub\nCanonical home for everything in this digest: https://agenticstandardcontact-byte.github.io/agentic-architect/blog/.", "url": "https://wpnews.pro/news/this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026", "canonical_source": "https://dev.to/agentic_standard/this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026-29i5", "published_at": "2026-05-22 21:32:35+00:00", "updated_at": "2026-05-22 22:03:27.645395+00:00", "lang": "en", "topics": ["developer-tools", "artificial-intelligence", "large-language-models", "enterprise-software"], "entities": ["Cursor", ".NET", "MediatR", "DbContext", "Agentic Architect"], "alternates": {"html": "https://wpnews.pro/news/this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026", "markdown": "https://wpnews.pro/news/this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026.md", "text": "https://wpnews.pro/news/this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026.txt", "jsonld": "https://wpnews.pro/news/this-week-in-cursor-net-3-rules-4-essays-week-ending-may-22-2026.jsonld"}}