Not Able to save changes in Checkout Editor

Extensions
1

I am not able to save any changes in the checkout editor when adding a custom app block on checkout, and I am continuously getting this error. Can somebody tell me a way to debug the issue

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2

I’m getting the same thing. I try to add my account extension to a production store and it will not save.

Everytime I press the save button in the editor, I get the message in the console:

A router only supports one blocker at a time

Here are my extension details.

Extension Type: Customer Account UI Extension

  • Extension Target: customer-account.page.render

  • Shopify CLI Version: Latest

  • API Version: 2025-10

  • Browser: Chrome (also tested in Incognito mode - same result)

  • Date Issue Started: Around January 26-29, 2026

Steps to Reproduce

  1. Deploy a customer-account.page.render extension using shopify app deploy

  2. Open Shopify Admin → Settings → Checkout → Customize

  3. Select “Profile” from the page dropdown to enter Customer accounts section

  4. Click “Apps” button in the sidebar

  5. Click the + button next to the extension (e.g., “Warranty Claims”)

  6. Click the Save button in the checkout editor

Expected Result: Configuration saves successfully, extension is added to customer accounts

Actual Result: Nothing happens. Save button does not respond. No success message. No error toast. If attempting to exit, editor warns “You have unsaved changes.”

Console Output

The following warning appears exactly when clicking the Save button (multiple times):

A router only supports one blocker at a time

at Ke @ common-c53c10817b23.js:74

at Vp @ common-c53c10817b23.js:74

at Mn @ common-c53c10817b23.js:74

at (anonymous) @ common-c53c10817b23.js:77

at (anonymous) @ useRouteForm-e9d7ab58499f.js:1

at (anonymous) @ CheckoutEditor-7d0b3d9dabba.js:5

at (anonymous) @ CheckoutEditor-7d0b3d9dabba.js:4

at KA @ render-common-1021283fdcc0.js:25

at batchUpdates @ CheckoutEditor-7d0b3d9dabba.js:4

at recoilCallback @ CheckoutEditor-7d0b3d9dabba.js:4

The error originates from Shopify’s internal checkout editor code (CheckoutEditor-7d0b3d9dabba.js, useRouteForm-e9d7ab58499f.js), not from the extension.

Extensive Debugging Performed

We performed comprehensive debugging to rule out extension code issues:

1. Static Extension Test

Replaced the entire extension with a completely static component (no React hooks, no state, no side effects):

export default async () => {

  const isInEditor = Boolean(shopify.extension?.editor);

  

  if (isInEditor) {

    render(<EditorPreview />, document.body);  // Completely static

    return;

  }

  render(<WarrantyClaimsPage />, document.body);

};

// EditorPreview has NO hooks, NO state, NO network requests

function EditorPreview() {

  return (

    <s-page heading="Warranty Claims">

      <s-text>Preview Mode</s-text>

    </s-page>

  );

}

Result: Same error. Save still fails.

2. Removed All Capabilities

Tested with all capabilities removed from shopify.extension.toml:

  • Removed api_access = true

  • Removed network_access = true

  • Removed allow_direct_linking = true

Result: Same error. Save still fails.

3. Incognito Mode Test

Tested in Chrome Incognito to rule out browser extensions.

Result: Same error. Save still fails.

Possible Cause

On the 26th of January, Shopify’s Checkout UI extensions now default to non-blocking behaviour. To enable blocking, merchants must explicitly activate the ‘Allow app to block checkout’ setting in the checkout and accounts editor.

I wonder if it has something to do with this.

Any help would be greatly appreciated.

3

Not sure what has changed in the checkout but its now working. I made no changes to my source code.