Coreframe Labs

The Field Guide

Where AI coding assistants get it wrong.

Codex, Copilot, Claude Code and Cursor genuinely changed how software gets built. But productivity and correctness are different problems — and AI-assisted codebases fail in the same places, again and again. This is a map of where, why, and what a reviewer needs to look for.

Not a criticism of the tools. We use them. Every pattern below is one we have found in a real review, with the code that causes it and a test you can run today — whether or not you ever talk to us.

4
guides
25
documented patterns
4
disciplines

Why the gaps are predictable

  • SecurityControls that work under expected conditions and fail under adversarial ones — auth error paths, tenant isolation, timing side-channels.
  • Backend & DataCorrectness under concurrency, load, and partial failure: transactions, retries, N+1 queries, and migrations that lock the table.
  • FrontendInterfaces that pass the demo and fall over on real data volume — render cost, stale closures, race conditions, accessibility.
  • AI / MLLLM features built without an evaluation harness, a cost ceiling, or a plan for what happens when the model is confidently wrong.

Assistants are trained on code that is predominantly correct at the functional level — it does what it was asked to do. But most defects that matter are not visible in the happy path. They live in error paths, in concurrent requests, at the boundary between layers, and in the assumptions baked into an implementation choice nobody stated.

So a model asked to “add authentication” or “paginate this endpoint” produces something that passes a reasonable functional test — and rarely considers what happens on the second concurrent request, the millionth row, or the request that bypasses the route entirely.

We call the result implementation gaps: controls and code paths that work under expected conditions and fail under adversarial ones. They are the hardest kind to find, because they do not produce obvious bugs. The tests pass. The demo works. The code looks reasonable.

Guides by discipline

A guide tells you what to look for. A review tells you what you have.

Everything here is checkable by your own team, and we would rather you checked it than didn't. When you want an independent pass — because the system is about to see real user data, because an investor is asking, or because nobody internally has the distance to review it — that is the Technical Audit: five business days, a written report with findings ranked by severity and evidence attached, a live findings call, and a remediation proposal you can execute with or without us.

£1,500–£2,500 solo · £3,000–£5,000 funded startup · £3,000–£6,000 SME

Written up in more depth elsewhere: Blog & TechTalks carries the published benchmarks, and the audit guides cover stack-specific failure modes.