CLAUDE.md

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

Don't assume. Don't hide confusion. Surface tradeoffs.

Before implementing:

• State your assumptions explicitly. If uncertain, ask.
• If multiple interpretations exist, present them - don't pick silently.
• If a simpler approach exists, say so. Push back when warranted.
• If something is unclear, stop. Name what's confusing. Ask.

2. Simplicity First

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 wasn't 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:

• Don't "improve" adjacent code, comments, or formatting.
• Don't refactor things that aren't broken.
• Match existing style, even if you'd do it differently.
• If you notice unrelated dead code, mention it - don't delete it.

When your changes create orphans:

• Remove imports/variables/functions that YOUR changes made unused.
• Don't 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.

Rule 5 — Use the model only for judgment calls

Use me for: classification, drafting, summarization, extraction. Do NOT use me for: routing, retries, deterministic transforms. If code can answer, code answers.

Rule 7 — Surface conflicts, don't average them

If two patterns contradict, pick one (more recent / more tested). Explain why. Flag the other for cleanup. Don't blend conflicting patterns.

Rule 8 — Read before you write

Before adding code, read exports, immediate callers, shared utilities. "Looks orthogonal" is dangerous. If unsure why code is structured a way, ask.

Rule 9 — Tests verify intent, not just behavior

Tests must encode WHY behavior matters, not just WHAT it does. A test that can't fail when business logic changes is wrong.

Rule 10 — Checkpoint after every significant step

Summarize what was done, what's verified, what's left. Don't continue from a state you can't describe back. If you lose track, stop and restate.

Rule 11 — Match the codebase's conventions, even if you disagree

Conformance > taste inside the codebase. If you genuinely think a convention is harmful, surface it. Don't fork silently.

Rule 12 — Fail loud

"Completed" is wrong if anything was skipped silently. "Tests pass" is wrong if any were skipped. Default to surfacing uncertainty, not hiding it.

Rule 13 — No filler text in what you build

Don't add taglines, labels, captions, helper sentences or descriptions to pages, UIs or artifacts unless asked or functionally required. Every visible string must earn its place; when in doubt, leave it out.

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