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 6: TimeProvider Injection
Sun 02 Aug
Never let Cursor hardcode DateTime.Now or DateTime.UtcNow in business logic. Inject TimeProvider (or your own IClock) instead. This makes time deterministic for tests and stops the AI reaching for static APIs whenever it generates time-aware code.
Rule 5: Minimal API Groups
Sat 01 Aug
Use MapGroup and EndPoints for .NET 9 services. It keeps the context window lean and focused, helping the AI provide more accurate code suggestions than it can with massive, bloated Controllers.
Rule 4: Validator Enforcement
Fri 31 Jul
Every MediatR Request must have a FluentValidation rule. Force the AI to check the validator before writing handler logic. This prevents "context rot" where the AI forgets your business constraints.
Rule 3: Structured Logging
Thu 30 Jul
Enforce ILogger with structured templates. Never use string interpolation in logs. This ensures that when you feed logs back into Cursor for debugging, the AI recognizes the patterns immediately.
Rule 2: Persistence Boundaries
Wed 29 Jul
Never 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.
Rule 1: The Result Pattern
Tue 28 Jul
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
Mon 27 Jul
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.
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.
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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/.
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