slopus--happy/docs/plans/pnpm-migration [draft].md

pnpm Migration [Draft]

Status: No-op for now

The expo doctor duplicate dependency warnings are a Yarn 1 monorepo hoisting issue, not a correctness bug. Quick fixes (expanding nohoist, adding resolutions) can silence the dangerous duplicates without a package manager migration.

Why pnpm eventually

• Expo team is leaning pnpm (byCedric's official expo-monorepo-example uses it)
• Faster installs, especially in worktree flows (no re-downloading, content-addressable store)
• Dominant choice for new JS/TS monorepos (~20% market share, fastest growing)
• pnpm.overrides cleaner than Yarn resolutions for pinning singletons

Why not now

• React Native requires node-linker=hoisted, which negates pnpm's strict isolation — you end up with a similar flat layout anyway
• pnpm symlinks + git worktrees (.dev/worktree/) need testing — symlinks may resolve to wrong store location
• pnpm v11 beta just dropped (March 2026) with breaking config changes — migrating now means potentially migrating again
• Half-day of work + risk for moderate gain

When to reconsider

• If quick Yarn 1 fixes don't stick
• When pnpm v11 stabilizes
• When Expo SDK improves isolated dependency support enough to drop node-linker=hoisted

Quick fixes (current plan)

1. Remove @expo/config-plugins from happy-app/package.json
2. Run npx expo install --check for version mismatches
3. Expand nohoist in root package.json for duplicating expo packages
4. Add resolutions to pin react and react-native to single versions