# Maintain Custom Addons Dev Watch

> Build and iterate custom add-ons/templates with tanstack add-on init, add-on compile, add-on dev, and tanstack create --dev-watch, including sync loop preconditions, watch-path validation, and project metadata constraints.

- Skill: `tanstack/maintain-custom-addons-dev-watch` (Agent Skill)
- Install (CLI): `npx skillmds@latest add tanstack/maintain-custom-addons-dev-watch`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tanstack/maintain-custom-addons-dev-watch/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: TanStack (https://skillmd.com/u/tanstack)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tanstack/maintain-custom-addons-dev-watch

---


# 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

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

## Core Patterns

### Run add-on dev loop while editing source

```bash
npx @tanstack/cli add-on dev
```

### Sync watched framework directory into a sandbox target app

```bash
# --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

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

## Common Mistakes

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

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

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

Correct:
```bash
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:
```bash
npx @tanstack/cli add-on init
```

Correct:
```bash
# 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:
```bash
npx @tanstack/cli add-on dev
```

Correct:
```bash
# 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