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.
New essays this week
Teach Cursor Result<T> instead of throwing
Thu 21 May · C# patterns
Stop the AI from undoing your Result/ErrorOr error model with throw and null on every new prompt.
Seven words that stop Cursor hallucination loops
Wed 20 May · Cursor rules
The correction spiral — and the circuit-breaker rule that ends it before you type the stop phrase.
The Scoped→Singleton DI bug your AI just suggested (and how to catch it)
Tue 19 May · .NET DI
The .NET lifetime bug that ships to production silently — and the one Cursor rule that catches it before merge.
The Context Tax: Why every Cursor session costs you 15 minutes
Mon 18 May · Architecture
The hidden cost senior engineers pay every morning — and a four-rule architecture for eliminating it.
5 daily senior rules
Rule 11: Rethrow, Don't throw ex
Sun 24 May
throw ex resets the stack trace. throw preserves it. Cursor gets this wrong about 40 percent of the time when generating catch blocks. Rewrite any naked throw ex to throw unless the exception has been explicitly wrapped.
Rule 10: AsNoTracking for Reads
Sat 23 May
Every read-only EF Core query should call AsNoTracking. Add a rule that recognises query methods returning DTOs (not entities) and inserts the call. Cursor never does this by default and your read perf degrades silently across releases.
Rule 9: Scoped Capture in Singleton
Fri 22 May
The 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.
Rule 8: CancellationToken Propagation
Thu 21 May
Every 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.
Rule 2: Persistence Boundaries
Wed 20 May
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.
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 £19.99.
-
Free sample:
arch-core-lite.mdcon GitHub - Full kit (£19.99, one-time): Agentic Architect on Gumroad
- Daily rules feed: https://agenticstandardcontact-byte.github.io/agentic-architect/blog/
Canonical home for everything in this digest: https://agenticstandardcontact-byte.github.io/agentic-architect/blog/.
