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 Cart Items should be added/updated/…

Hey @ceri_waters , thank you for flagging this! Could I get some verbose logs from you? I’ll send you a DM so you can send it that way.

This might be the same as these two threads: Cart API - Error 422 - #4 by Donal-Shopify Issue with ajax cart API async_shipping_rates.json

Also experiencing this. Since it’s a 401, it may be worth mentioning that we are using SHOPIFY_CLI_THEME_TOKEN env var in development.

I am having the same problem. I updated yesterday to the 3.89.0 version and now when I try add to cart in my local with Shopify theme dev, I ve POST 401 /cart/add :melting_face:

same here - updated to 3.89.0 and i’m getting 401 on POST cart/add, but with previous versions (including 3.89.0) i’m also randomly getting 429 with GET /cart, even if there is a single call on the endpoint. at current state it’s impossible to work on the local environment which means it’s blocking…

Thanks for the context folks - I can reproduce this on 3.89.0. The 401 on cart AJAX endpoints (/cart/add.js, etc.) when running shopify theme dev. I’ve raised this with the CLI team internally. In the meantime, rolling back to 3.88.0 should get you unblocked: npm install -g @shopify/cli@3.88.0 I…

I’ve been experiencing this as well. Interestingly, the issue occurred after updating the 3.89.0, but even when downgrading several versions, the issue isn’t resolved for me. This seems to be affecting all endpoints. My store, by default set to GBP, is currently defaulting to US currency. In the s…

Also seeing the 401 response on any calls to cart based endpoints. Also on 3.89.0 CLI. Can also replicate @ConduciveMammal ‘s comments about the localisation issue.

It seems to kind of work when using the --verbose flag. I can now add to cart again but it’s still stuck in the US market. Now if I try to change the market, it directs to this URL: http://127.0.0.1:9292/localization?language_code=en&shpxid=e6a7d728-dae8-4786-a4df-1f3742d06941 and crashes with a 30…

CLI > Theme Dev > cart ajax 401

Shopify CLI and Libraries

Gray-Shopify January 27, 2026, 5:31pm 3

This might be the same as these two threads:

Cart API - Error 422 - #4 by Donal-Shopify
Issue with ajax cart API async_shipping_rates.json

Topic		Replies	Views
429 Too many requests Shopify CLI and Libraries theme-commands , app-dev-on-localhost	51	1591	July 7, 2026
Aggressive bot detection with 429 errors AJAX Cart API Online Store and Theme Development ajax-api	98	2996	August 7, 2026
Limit AJAX Cart API Online Store and Theme Development ajax-api , cli-themes	3	121	December 9, 2025
Your connection needs to be verified before you can proceed Shopify CLI and Libraries theme-commands	35	1564	July 27, 2026
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CLI > Theme Dev > cart ajax 401

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