Best Claude Prompts for Coding (2026)

You are a senior engineer. Here is a bug: [describe symptom]. Here is the relevant code and the error: [paste]. Walk through the most likely root causes in order of probability, explain your reasoning, and propose the smallest fix that addresses the actual cause, not the symptom.

Refactor the code below for readability and maintainability while preserving behavior exactly. Explain each change and why it helps. Do not introduce new dependencies. Flag anything that looks like a latent bug. Code: [paste]

Review this diff as a skeptical senior reviewer. Find correctness bugs, edge cases, security issues, and performance traps. For each, give severity, the exact line, and a concrete fix. Be direct; assume I want the hard feedback. Diff: [paste]

Write unit tests for the function below using [framework]. Cover the happy path, boundary conditions, and failure modes. List the cases first, then the code. Point out any behavior that's untestable as written. Function: [paste]

Explain what this code does at three levels: one-sentence summary, a short paragraph for a teammate, and a line-by-line walkthrough of the tricky parts. Note any assumptions or side effects. Code: [paste]

I need to implement [feature] in this codebase: [context]. Propose 2 implementation approaches with trade-offs, name the files likely to change, list edge cases to handle, and recommend one. Don't write code yet.

Write a [regex|SQL query] that does the following: [describe precisely]. Show the expression, explain each part, and give 3 example inputs with expected outputs, including one that should NOT match.

Given this diff, write a concise commit message (imperative subject under 60 chars + short body) and a PR description with: what changed, why, and how to test. Diff: [paste]