add-addons-existing-app

# Add Add-ons To Existing App Use this skill when the project already exists and you need to layer add-ons safely without breaking dependency or metadata assumptions. ## Setup ```bash npx @tanstack/cli add clerk drizzle ``` ## Core Patterns ### Add multiple integrations in one pass ```bash npx @tanstack/cli add tanstack-query drizzle ``` ### Resolve candidate ids before applying ```bash npx @tanstack/cli create --list-add-ons --json ``` ### Validate optionized add-ons before install ```bash npx @tanstack/cli create --addon-details prisma --json ``` ## Common Mistakes ### CRITICAL Run tanstack add without .cta.json Wrong: ```bash npx @tanstack/cli add clerk ``` Correct: ```bash # Run in a project scaffolded by TanStack CLI (contains .cta.json), then: npx @tanstack/cli add clerk ``` Add flows depend on persisted scaffold metadata, so commands can fail or apply incomplete config when `.cta.json` is missing. Source: packages/create/src/custom-add-ons/shared.ts:158 ### HIGH Use invalid add-on id Wrong: ```bash npx @tanstack/cli add drizle ``` Correct: ```bash npx @tanstack/cli add drizzle ``` Unknown ids stop resolution and force manual correction before any add-on work proceeds. Source: packages/create/src/add-ons.ts:44 ### HIGH Ignore add-on dependency requirements Wrong: ```bash npx @tanstack/cli add custom-addon-with-missing-deps ``` Correct: ```bash npx @tanstack/cli add required-dependency custom-addon-with-missing-deps ``` Add-ons with `dependsOn` can fail during finalization if required dependencies are not present. Source: packages/create/src/add-ons.ts:48 ### MEDIUM Assume old Windows path bug still present Wrong: ```bash # Avoid tanstack add on Windows and patch manually ``` Correct: ```bash npx @tanstack/cli add clerk ``` Avoiding supported workflows based on historical bug reports causes unnecessary manual drift. Fixed in newer versions, but agents trained on older threads may still avoid this path. Source: https://github.com/TanStack/cli/issues/329 ### HIGH Tension: Backwards support vs deterministic automation This domain's patterns conflict with maintain-custom-addons-dev-watch. Automation that assumes universal add flows tends to fail because legacy compatibility still relies on hidden scaffold metadata. See also: maintain-custom-addons-dev-watch/SKILL.md § Common Mistakes