Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/tanstack/cli/add-addons-existing-appnpx skills add TanStack/cli --skill add-addons-existing-appgit clone --depth 1 https://github.com/TanStack/cliWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00037 | $0.00628 |
| Opus 5 | $0.00018 | $0.00314 |
| Sonnet 5 | $0.00007 | $0.00126 |
| Haiku 4.5 | $0.00004 | $0.00063 |
Grade A, and why
add-addons-existing-app scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.
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
npx @tanstack/cli add clerk drizzle
Core Patterns
Add multiple integrations in one pass
npx @tanstack/cli add tanstack-query drizzle
Resolve candidate ids before applying
npx @tanstack/cli create --list-add-ons --json
Validate optionized add-ons before install
npx @tanstack/cli create --addon-details prisma --json
Common Mistakes
CRITICAL Run tanstack add without .cta.json
Wrong:
npx @tanstack/cli add clerk
Correct:
# 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:
npx @tanstack/cli add drizle
Correct:
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:
npx @tanstack/cli add custom-addon-with-missing-deps
Correct:
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:
# Avoid tanstack add on Windows and patch manually
Correct:
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.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 115 lines · 37 tokens per session scan A 62bab4e0d208
add-addons-existing-app is a skill published in the GitHub repository TanStack/cli (1,295 stars, last pushed 25d ago), licensed MIT. It adds 37 tokens to every session and 628 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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