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.
7 daily senior rules
Rule 1: The Result Pattern
Sun 11 Oct
Stop using nulls for flow control. Use a Result object to force Cursor to handle success and failure cases explicitly. This prevents 90% of AI-generated logic errors in Web APIs.
Rule 25: ActivitySource for OpenTelemetry
Sat 10 Oct
Logs alone won't debug a distributed system. Add a static readonly ActivitySource per project and wrap every external call (DB, HTTP, queue) in StartActivity. Cursor never adds OTEL spans on its own — give it a rule that recognises external-call patterns and proposes the trace.
Rule 24: ValueTask Only When Justified
Fri 09 Oct
ValueTask is a perf optimisation for hot paths that often return synchronously. It is not a drop-in for Task. Cursor swaps them around without thinking. Flag ValueTask returns and ask whether the method is actually mostly synchronous. If not, revert to Task.
Rule 23: No Bool Flag Parameters
Thu 08 Oct
SendEmail(string to, bool isHtml) should be SendHtmlEmail and SendPlainEmail. Bool flags hide branching that belongs in the type system. Flag any method signature with two or more bool parameters as a refactor candidate.
Rule 22: BackgroundService Over Task.Run
Wed 07 Oct
Long-running work in ASP.NET Core goes in a BackgroundService, not Task.Run inside a controller. Cursor will happily fire Task.Run and call it "async work" — your request thread will die mid-execution and you'll never know why. Catch Task.Run outside test code and propose a hosted service.
Rule 21: Channels for Producer Consumer
Tue 06 Oct
System.Threading.Channels beats BlockingCollection and beats roll-your-own queue plus SemaphoreSlim. The AI reaches for ConcurrentQueue every time and stitches it together by hand. A rule that detects producer/consumer patterns and proposes Channel will save you a class.
Rule 20: Source-Generated JSON Serialisation
Mon 05 Oct
Reflection-based System.Text.Json is fine for prototypes. For hot paths and AOT, use JsonSerializable source generation. Cursor never thinks of this on its own — add a rule that flags new DTO classes and asks whether they should be source-generated.
Try one rule before you trust the whole kit
The free arch-core-lite.mdc is 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 £9.00.
-
Free sample:
arch-core-lite.mdcon GitHub - Full kit (£9.00, one-time): Agentic Architect Kit
- Daily rules feed: https://agentic-architect.dev/blog/
Canonical home for everything in this digest: https://agentic-architect.dev/blog/.
Top comments (0)