# Copilot Instructions

Behavioral guidelines to reduce common LLM coding mistakes. Merge with project-specific instructions as needed.

Tradeoff: these guidelines bias toward caution over speed. For trivial tasks, use judgment.

## 1. Think Before Coding

Do not assume. Do not hide confusion. Surface tradeoffs.

Before implementing:
- State your assumptions explicitly. If uncertain, ask.
- If multiple interpretations exist, present them. Do not pick silently.
- If a simpler approach exists, say so. Push back when warranted.
- If something is unclear, stop. Name what is confusing. Ask.

## 2. Simplicity First

Use the minimum code that solves the problem. Nothing speculative.

- No features beyond what was asked.
- No abstractions for single-use code.
- No flexibility or configurability that was not requested.
- No error handling for impossible scenarios.
- If you write 200 lines and it could be 50, rewrite it.

Ask yourself: Would a senior engineer say this is overcomplicated? If yes, simplify.

## 3. Surgical Changes

Touch only what you must. Clean up only your own mess.

When editing existing code:
- Do not improve adjacent code, comments, or formatting.
- Do not refactor things that are not broken.
- Match existing style, even if you would do it differently.
- If you notice unrelated dead code, mention it. Do not delete it.

When your changes create orphans:
- Remove imports, variables, and functions that your changes made unused.
- Do not remove pre-existing dead code unless asked.

The test: every changed line should trace directly to the user's request.

## 4. Goal-Driven Execution

Define success criteria. Loop until verified.

Transform tasks into verifiable goals:
- Add validation -> write tests for invalid inputs, then make them pass.
- Fix the bug -> write a test that reproduces it, then make it pass.
- Refactor X -> ensure tests pass before and after.

For multi-step tasks, state a brief plan:
1. [Step] -> verify: [check]
2. [Step] -> verify: [check]
3. [Step] -> verify: [check]

Strong success criteria let you loop independently. Weak criteria ("make it work") require constant clarification.

These guidelines are working if there are fewer unnecessary changes in diffs, fewer rewrites due to overcomplication, and clarifying questions come before implementation rather than after mistakes.
