Bug: React Dev Playground | Shows Application error: a client-side exception has occurred while loading playground.react.dev

[Akshit6828]

Bug Report

React version:
React 19.0.0 (playground.react.dev - latest build as of October 2025)

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Steps To Reproduce

1. Open React Playground.
2. Observe that the page crashes with a client-side exception. (Screenshot attached)

Note: I have disabled all the chrome extensions so that any other client side extension are not interfering still the issue persists. (Attaching screenshots).

Chrome version: Version 128.0.6613.85 (Official Build) (64-bit)

Link to code example

Not required — this issue occurs even with an empty playground or default example (no user code modification).

Console error:
2718.2ef44c120f1f0fb2.js:1 Uncaught TypeError: Cannot read properties of undefined (reading 'code') at R (2718.2ef44c120f1f0fb2.js:1:2240553) at 2718.2ef44c120f1f0fb2.js:1:2242468 at V (2718.2ef44c120f1f0fb2.js:1:2242518) at aO (f5e865f6-c532ae16ddb2f8e0.js:1:54636) at il (f5e865f6-c532ae16ddb2f8e0.js:1:75762) at iS (f5e865f6-c532ae16ddb2f8e0.js:1:87054) at sI (f5e865f6-c532ae16ddb2f8e0.js:1:128665) at f5e865f6-c532ae16ddb2f8e0.js:1:124455 at sE (f5e865f6-c532ae16ddb2f8e0.js:1:124556) at ca (f5e865f6-c532ae16ddb2f8e0.js:1:157236) at MessagePort.S (2970-8a45648598c363f4.js:1:128748)

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The current behavior

• The playground fails to render and shows:
  “Application error: a client-side exception has occurred while loading playground.react.dev”
• Console logs show repeated errors:

Additional Info

• The website works fine in incognito tab.
• Feel free to drop a comment if any additional info is required.

Screenshots:

Console error

Network

Exact Line Causing Error (JS File - Minified)

Possible Cause & Fix Suggestion

It seems the compiled bundle (2718.e2f4dc12affbf02.js) attempts to read a.code from an undefined variable — likely during the compilation or rendering of code snippets in the playground.

Possible cause:

• The result object (possibly from a code transformer or Babel worker) is undefined for some edge case, but its code property is accessed without a null check.

Suggested fix:

• Add a safe check before accessing properties:

if (a && a.code) {
  // use a.code
} else {
  console.error("Unexpected undefined compiler result:", a);
}