# 14 review comments. 11 were conventions.

> Copilot guessed. Nothing told it otherwise.

- **Format:** short video, 9 steps, ~51 seconds
- **Topic:** What GitHub Copilot custom instructions are and why a project needs one — a first Flutter task without .github/copilot-instructions.md ends in 14 review comments, 11 of them about conventions Copilot could not know, and the same request with the file is approved first time.
- **Author:** Suthahar Jegatheesan (MSDEVBUILD)
- **Category:** GitHub Copilot · copilot
- **Published:** 2026-01-05
- **Tags:** githubcopilot, flutter, bloc, cleanarchitecture, aicoding, codereview, developerproductivity, msdevbuild
- **Canonical URL:** https://blog.msdevbuild.com/shorts/copilot-instructions-eleven-of-fourteen/

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## What you'll learn

- Why Copilot picks the most common pattern, not yours
- How to count convention mistakes in a pull request
- Which lines in copilot-instructions.md carry the weight

## Understand it one step at a time

### 1. Same Copilot, same Monday

Two new developers, one task. One clone has no instructions file.

### 2. setState, by Monday

The first screen it scaffolds is a StatefulWidget. The app runs on BLoC.

### 3. Wrong layer, twice

A try/catch inside CartBloc. A feature importing from lib/data.

### 4. 14 review comments

The pull request goes up Wednesday. Merged Thursday, third round.

### 5. Count them with git diff

Added lines that break the three rules the app lives by.

### 6. One file, read first

.github/copilot-instructions.md is added to every chat request.

### 7. Three lines do the work

Name what you do not use, the error contract, and what nobody can infer.

### 8. Same request, approved

A CartEvent, a Result, points priced on the Cart entity.

### 9. Write it once, read every time

Stack, structure, conventions, testing, and what is off-limits.

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## The takeaway

**Write it down once.**

Copilot reads .github/copilot-instructions.md before every suggestion in your repo.