429 Too many requests

Shopify CLI and Libraries
,
1

I have reproduced the issue on the latest CLI version.

Yes, I am on the latest version

I have searched existing posts and this report is not a duplicate.

Yes, this isn’t a duplicate

In which of these areas are you experiencing a problem?

Theme

Expected behavior

Should have allowed reasonable rate.

Actual behavior

shop_events_listener-3da45d37.js:1 POST http://127.0.0.1:9292/cart/add.js 429 (Too Many Requests)
window2.fetch @ shop_events_listener-3da45d37.js:1
(anonymous) @ b3918e4e0wbf3ac3cepc5707306mb02b36c6m.js:1
(anonymous) @ liquid-ajax-cart.js:1
A @ liquid-ajax-cart.js:1
w @ liquid-ajax-cart.js:1
x @ liquid-ajax-cart.js:1
(anonymous) @ liquid-ajax-cart.js:1Understand this error
installHook.js:1 Liquid Ajax Cart: Error while performing cart Ajax request
overrideMethod @ installHook.js:1
(anonymous) @ liquid-ajax-cart.js:1
Promise.catch
(anonymous) @ liquid-ajax-cart.js:1
A @ liquid-ajax-cart.js:1
w @ liquid-ajax-cart.js:1
x @ liquid-ajax-cart.js:1
(anonymous) @ liquid-ajax-cart.js:1Understand this error
installHook.js:1 SyntaxError: Unexpected token ‘<’, "<!DOCTYPE "... is not valid JSON overrideMethod @ installHook.js:1 (anonymous) @ liquid-ajax-cart.js:1 Promise.catch (anonymous) @ liquid-ajax-cart.js:1 A @ liquid-ajax-cart.js:1 w @ liquid-ajax-cart.js:1 x @ liquid-ajax-cart.js:1 (anonymous) @ liquid-ajax-cart.js:1Understand this error liquid-ajax-cart.js:1 Uncaught TypeError: Cannot read properties of null (reading 'body') at HTMLDocument. (liquid-ajax-cart.js:1:20396)
at L (liquid-ajax-cart.js:1:3503)
at liquid-ajax-cart.js:1:3093
at

Reproduction steps

Just click add to cart a few times.

Verbose output

shop_events_listener-3da45d37.js:1 POST http://127.0.0.1:9292/cart/add.js 429 (Too Many Requests)
window2.fetch @ shop_events_listener-3da45d37.js:1
(anonymous) @ b3918e4e0wbf3ac3cepc5707306mb02b36c6m.js:1
(anonymous) @ liquid-ajax-cart.js:1
A @ liquid-ajax-cart.js:1
w @ liquid-ajax-cart.js:1
x @ liquid-ajax-cart.js:1
(anonymous) @ liquid-ajax-cart.js:1Understand this error
installHook.js:1 Liquid Ajax Cart: Error while performing cart Ajax request
overrideMethod @ installHook.js:1
(anonymous) @ liquid-ajax-cart.js:1
Promise.catch
(anonymous) @ liquid-ajax-cart.js:1
A @ liquid-ajax-cart.js:1
w @ liquid-ajax-cart.js:1
x @ liquid-ajax-cart.js:1
(anonymous) @ liquid-ajax-cart.js:1Understand this error
installHook.js:1 SyntaxError: Unexpected token ‘<’, "<!DOCTYPE "... is not valid JSON overrideMethod @ installHook.js:1 (anonymous) @ liquid-ajax-cart.js:1 Promise.catch (anonymous) @ liquid-ajax-cart.js:1 A @ liquid-ajax-cart.js:1 w @ liquid-ajax-cart.js:1 x @ liquid-ajax-cart.js:1 (anonymous) @ liquid-ajax-cart.js:1Understand this error liquid-ajax-cart.js:1 Uncaught TypeError: Cannot read properties of null (reading 'body') at HTMLDocument. (liquid-ajax-cart.js:1:20396)
at L (liquid-ajax-cart.js:1:3503)
at liquid-ajax-cart.js:1:3093
at

Operating system

Mac OS Tahoe

CLI version

3.88

Nodejs version

22.21.1

What language and version are you using in your application?

Node

2

I’m getting the same. Tried different CLI and Node versions with no success

3

Thanks for reviewing this.

Based on debugging, the issue appears to be local rate‑limiting on the Shopify CLI dev server, not Liquid Ajax Cart itself.

What’s happening

  • Multiple rapid /cart/add.js POST requests are triggered by repeated clicks.

  • The local dev server at http://127.0.0.1:9292 starts returning HTTP 429.

  • When the 429 occurs, the response body is HTML (error page), not JSON.

  • liquid-ajax-cart.js expects JSON and fails with:

    • Unexpected token '<'

    • Followed by Cannot read properties of null (reading 'body')

So the real failure chain is:

429 response (HTML)
→ JSON.parse fails
→ Ajax Cart crashes

Why this is unexpected

On production Shopify storefronts:

  • /cart/add.js tolerates rapid user interaction reasonably well

  • 429 responses are rare and usually return JSON

  • This behavior only reproduces consistently on Shopify CLI local dev

Questions / clarification needed

  1. Is the CLI dev server intentionally rate‑limiting /cart/* endpoints?

  2. Is this rate limit configurable or documented anywhere?

  3. Why does the CLI return HTML instead of JSON for /cart/add.js errors?

  4. Is this behavior expected, or is it a regression in CLI 3.88?

Temporary workarounds (not ideal)

  • Debouncing add to cart clicks in JS

  • Adding manual retry / 429 handling in Ajax Cart

  • Slowing down interaction artificially during development

These workarounds hide the issue but don’t match real storefront behavior.

Suggested fixes

Any of the following would resolve the problem cleanly:

  • Relax rate‑limits for /cart/* routes in CLI dev

  • Return JSON error responses for /cart/add.js consistently

  • Document the rate‑limit so theme/app developers can account for it

Happy to test any proposed fix or provide a minimal reproduction repo if needed.

Thanks.

5

I mentioned this thread to the author of Liquid Ajax Cart, but I don’t think it’s that library that’s the problem. I’ve used it for years without ever experiencing 422. I think rate limits need to be laxed or returned to what they were before.

6

Hi all, thanks for reporting this!

We will be addressing this issue in this post:

Please follow that post for updates.

7

When can we expect to see this resolved? It’s even worse today.

8

@James_Auble, we have relaxed the throttles slightly. Can you confirm if you’re seeing the issue being worse while running app dev or without it?