It started as one page and now it's a real app. Claude Code keeps re-implementing helpers that already exist (formatDate, useUser) because it doesn't see them, so I have three versions of everything.
Reading the whole repo doesn't scale. What works for me:
CLAUDE.md: "Before writing a helper, grep lib/ for an existing one." Claude Code actually runs the grep.lib/index.ts that re-exports everything. One file to read, and it's the map of what exists.The root cause is that it starts each session blind. Give it a map, not the territory.
Also worth it: npx knip finds unused and duplicate exports. Paste the output into the chat and ask it to fix exactly that list.
Complementary trick: make the duplicates fail loudly instead of hoping the model remembers. A lint rule that bans imports from anywhere except lib/ for the helpers you care about:
// eslint.config.js
rules: {
'no-restricted-syntax': ['error', {
selector: 'FunctionDeclaration[id.name=/^(formatDate|useUser)$/]',
message: 'Use the existing helper from lib/.'
}]
}Claude Code runs the linter, sees the error, and fixes it itself. A rule it can hit beats a rule it has to remember.
formatDatein lib/ on its own instead of writing a fourth one. rosa_m