Coding Prompts for ChatGPT, Claude and Copilot: Ten That Ship, and the Rules Behind Them

Counted from the H2 headings of every base prompt in the library at build time on 26 September 2026.

Context: [stack, e.g. Next.js 15 app router, Supabase auth, Tailwind]. The relevant files are [paths].
Build: [one feature in one sentence].
Must: [2 to 4 behaviours, numbered].
Must not: touch [files or behaviours to leave alone].
States: empty, loading, error and success for every new screen.
Output: the diff per file, then one paragraph on what you assumed.
Before writing code, ask me anything you need to know about [the user or the data].

Context: [stack]. Symptom: [exact error or behaviour, copied]. Expected: [what should happen].
Already tried: [list, so you do not repeat them].
Constraints: do not change [policies, schemas, public APIs].
Do this in order: name the most likely cause and the evidence for it; propose the smallest change that tests that cause; only then write the fix.
If you need a file I have not shown, name it instead of guessing its contents.

Refactor [file or module] to [goal: smaller functions, remove duplication, extract a hook].
Behaviour must be identical: same inputs, same outputs, same side effects.
Keep the public interface and every existing test unchanged; if a test must change, stop and tell me why.
Output: the new code, then a list of every behavioural difference you could not avoid (expected: none).

Review this diff as a senior engineer on this codebase: [paste diff].
Report only findings that would change a decision, ordered by severity: correctness, security (secrets, auth, injection), data loss, performance, then style.
For each: file and line, what breaks, a concrete input that triggers it, the fix.
Do not restate what the code does. If you find nothing above style, say so in one line.

Before implementing [feature], write the tests for it in [framework] covering: the happy path, each validation failure, the empty case, and one concurrency or ordering case if any state is shared.
Use the existing test conventions in [path]. Do not mock what you can run.
Then implement until the tests pass. Never edit or delete a test to make it pass; if a test is wrong, tell me and stop.

Explain [file] to an engineer who knows [language] but not this codebase.
In order: what it is for in one sentence; the data it reads and writes; the entry points and who calls them; the two places most likely to break when changed.
Under 300 words. Quote line numbers, not paraphrases, for anything non-obvious.

Write a migration for [change] against this schema: [paste or path].
Every new table enables row-level security in the same migration and gets policies that compare auth.uid() with an owner or membership column. Never "using (true)" on user data.
Then write two verification queries: one as the owner (expects rows) and one as a different user (expects zero).
Output: the migration file, the two queries, and one paragraph on what could go wrong on existing rows.

Integrate [API] for [purpose]. The key lives in an environment variable on the server and never reaches a client bundle.
Handle, in this order, before any happy-path UI: missing key, network timeout, 4xx from the provider, 5xx from the provider, rate limit with retry-after.
Log the provider's request id on every failure. Output: the server handler, the client call, and the error states the UI shows for each case.

We are moving [from X to Y]. Do not write code yet.
List every file that must change, grouped by risk: mechanical (find and replace), behavioural (semantics differ), and unknown (needs a test to find out).
Propose the order that keeps the app deployable after every step. Name the step where a rollback stops being cheap.
Then wait for my go before the first step.

I am about to ask you to [vague task]. Before you do it, rewrite my request as a prompt with: the context you would need, the exact deliverable, what must not change, the states or cases to cover, and the questions you would ask me first.
Show me that prompt. I will answer the questions, then you run it.