Monorepo Navigator

Tier: POWERFUL
Category: Engineering
Domain: Monorepo Architecture / Build Systems

Overview

Navigate, manage, and optimize monorepos. Covers Turborepo, Nx, pnpm workspaces, and Lerna. Enables cross-package impact analysis, selective builds/tests on affected packages only, remote caching, dependency graph visualization, and structured migrations from multi-repo to monorepo. Includes Claude Code configuration for workspace-aware development.

Core Capabilities

Cross-package impact analysis — determine which apps break when a shared package changes
Selective commands — run tests/builds only for affected packages (not everything)
Dependency graph — visualize package relationships as Mermaid diagrams
Build optimization — remote caching, incremental builds, parallel execution
Migration — step-by-step multi-repo → monorepo with zero history loss
Publishing — changesets for versioning, pre-release channels, npm publish workflows
Claude Code config — workspace-aware CLAUDE.md with per-package instructions

When to Use

Use when:

Multiple packages/apps share code (UI components, utils, types, API clients)
Build times are slow because everything rebuilds when anything changes
Migrating from multiple repos to a single repo
Need to publish packages to npm with coordinated versioning
Teams work across multiple packages and need unified tooling

Skip when:

Single-app project with no shared packages
Team/project boundaries are completely isolated (polyrepo is fine)
Shared code is minimal and copy-paste overhead is acceptable

Tool Selection

| Tool | Best For | Key Feature | |---|---|---| | Turborepo | JS/TS monorepos, simple pipeline config | Best-in-class remote caching, minimal config | | Nx | Large enterprises, plugin ecosystem | Project graph, code generation, affected commands | | pnpm workspaces | Workspace protocol, disk efficiency | workspace:* for local package refs | | Lerna | npm publishing, versioning | Batch publishing, conventional commits | | Changesets | Modern versioning (preferred over Lerna) | Changelog generation, pre-release channels |

Most modern setups: pnpm workspaces + Turborepo + Changesets

Turborepo

→ See references/monorepo-tooling-reference.md for details

Common Pitfalls

| Pitfall | Fix | |---|---| | Running turbo run build without --filter on every PR | Always use --filter=...[origin/main] in CI | | workspace:* refs cause publish failures | Use pnpm changeset publish — it replaces workspace:* with real versions automatically | | All packages rebuild when unrelated file changes | Tune inputs in turbo.json to exclude docs, config files from cache keys | | Shared tsconfig causes one package to break all type-checks | Use extends properly — each package extends root but overrides rootDir / outDir | | git history lost during migration | Use git filter-repo --to-subdirectory-filter before merging — never move files manually | | Remote cache not working in CI | Check TURBO_TOKEN and TURBO_TEAM env vars; verify with turbo run build --summarize | | CLAUDE.md too generic — Claude modifies wrong package | Add explicit "When working on X, only touch files in apps/X" rules per package CLAUDE.md |

Best Practices

Root CLAUDE.md defines the map — document every package, its purpose, and dependency rules
Per-package CLAUDE.md defines the rules — what's allowed, what's forbidden, testing commands
Always scope commands with --filter — running everything on every change defeats the purpose
Remote cache is not optional — without it, monorepo CI is slower than multi-repo CI
Changesets over manual versioning — never hand-edit package.json versions in a monorepo
Shared configs in root, extended in packages — tsconfig.base.json, .eslintrc.base.js, jest.base.config.js
Impact analysis before merging shared package changes — run affected check, communicate blast radius
Keep packages/types as pure TypeScript — no runtime code, no dependencies, fast to build and type-check