Code Discipline

1. Extract pure functions

Pull deterministic, side-effect-free logic out of components and handlers into standalone functions - even with only one caller today.

2. Test with the file, not after

Write each new file's test in the same step as the file. Never defer tests to a later pass across several files.

Exception: skip a test with no real failure mode to guard (a trivial one-liner, no branch, no edge case) - state why in one line.

3. Reuse before you add

Search for an existing convention, utility, or shared helper first. Reuse it instead of writing a parallel version - covers patterns (error shapes, service structure), not just literal functions.

4. No local constants for shared concepts

Check for an existing shared type, enum, or constants module before adding a hardcoded list or value to a file. Use the shared one.

Exception: a literal may stay inline only if it has no meaning outside that one function or component.

5. Verify in small steps

Split implementation into pieces small enough to verify individually (build, test, or a quick check) before moving to the next. Never implement several files in one unverified pass.