Maintain Custom Add-ons In Dev Watch

Use this skill for local add-on authoring workflows where you continuously compile and sync package output into a target app.

Setup

npx @tanstack/cli add-on init
npx @tanstack/cli add-on compile

Core Patterns

Run add-on dev loop while editing source

npx @tanstack/cli add-on dev

Sync watched framework directory into a sandbox target app

# --dev-watch is a flag on `create`, not on `dev`
npx @tanstack/cli create my-sandbox --dev-watch ../path/to/framework-dir

Re-run compile before apply when changing metadata

npx @tanstack/cli add-on compile
npx @tanstack/cli add my-custom-addon

Common Mistakes

HIGH Use --dev-watch with --no-install

Wrong:

npx @tanstack/cli create my-sandbox --dev-watch ../my-addon-package --no-install

Correct:

npx @tanstack/cli create my-sandbox --dev-watch ../my-addon-package

Dev-watch rejects --no-install, so automated loops fail before any sync work starts.

Source: packages/cli/src/dev-watch.ts:112

HIGH Start dev-watch without valid framework directory

Wrong:

npx @tanstack/cli create my-sandbox --dev-watch ../missing-or-invalid-dir

Correct:

npx @tanstack/cli create my-sandbox --dev-watch ../valid-framework-dir

Watch setup validates that the path exists, is a directory, and contains at least one of add-ons/, assets/, or framework.json. Invalid targets fail before file syncing begins.

Source: packages/cli/src/command-line.ts:599

CRITICAL Author add-on from code-router project

Wrong:

npx @tanstack/cli add-on init

Correct:

# Run add-on init from a file-router project
npx @tanstack/cli add-on init

Custom add-on authoring expects file-router mode and exits when run from incompatible project modes.

Source: packages/create/src/custom-add-ons/add-on.ts

HIGH Run add-on workflows without scaffold metadata

Wrong:

npx @tanstack/cli add-on dev

Correct:

# Run in a project scaffolded by TanStack CLI (contains .cta.json), then:
npx @tanstack/cli add-on dev

Custom add-on flows rely on persisted scaffold options, so missing metadata blocks initialization and update paths.

Source: packages/create/src/custom-add-ons/shared.ts:158

HIGH Tension: Backwards support vs deterministic automation

This domain's patterns conflict with add-addons-existing-app. Tooling assumes reusable automation, but hidden metadata preconditions from legacy support make add-on loops non-portable across repositories.

See also: add-addons-existing-app/SKILL.md § Common Mistakes