Turborepo Pipeline Builder

A Turborepo pipeline defines tasks and their relationships in turbo.json. When you run `turbo run build`, Turborepo reads the pipeline to determine the order to execute tasks across all packages in your monorepo. Tasks with `dependsOn: ["^build"]` wait for the upstream package's build to finish first. Tasks without dependencies run in parallel. Turborepo caches task outputs and replays them on cache hits, dramatically speeding up CI and local development.

The ^ prefix in dependsOn means 'wait for all upstream packages in the dependency graph to complete this task first'. For example, `dependsOn: ["^build"]` means: before building package A, build all packages that A depends on. Without the caret, `dependsOn: ["test"]` means the task must run after the `test` task in the same package completes. Use ^ for cross-package dependencies and plain names for same-package ordering.

Turborepo computes a hash of the task's inputs (source files, env vars, turbo.json config) and checks a local or remote cache. On a cache hit, it replays the cached outputs and logs without re-running the task. Configure what files to hash with `inputs[]` and what to cache with `outputs[]`. Set `cache: false` for tasks like `dev` that should always run. Remote caching (Vercel Remote Cache or self-hosted) shares the cache across CI runs and team members.

Set `persistent: true` for long-running tasks that don't exit, like `dev`, `start`, or `storybook`. This tells Turborepo not to wait for the task to finish before starting downstream tasks. Without persistent, Turborepo would block waiting for a server process that never exits. Persistent tasks are excluded from remote caching since they produce continuous output, not discrete artifacts.

inputs[] are the files that affect the task's output — changes to these files invalidate the cache. Typical inputs: source files (`src/**`), config files (`tsconfig.json`, `.eslintrc.js`), and env var names. outputs[] are the files produced by the task that should be cached. Typical outputs: `dist/**`, `.next/**`, `coverage/**`. If outputs[] is empty, the task result is still cached (exit code + logs) but no files are restored on cache hit.

Use `--filter` flag: `turbo run build --filter=[HEAD^1]` runs build only for packages changed since the last commit. `turbo run build --filter=./apps/web...` runs build for the web app and all its local dependencies. You can combine filters: `turbo run test --filter=./packages/... --filter=[origin/main...HEAD]`. In CI, combine with `--affected` (Turborepo v2+) or git diff to run only what changed.