OOM Error When Creating Many ShadowRealms with Heap Snapshots in Node.js

Version

24.13.1, 25.8.1

Platform

Linux KContainer 5.10.0-12-amd64 #1 SMP Debian 5.10.103-1 (2022-03-07) x86_64 x86_64 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

The below PoC can reproduce the result

import { writeHeapSnapshot } from 'v8';

// This script simulates creating many ShadowRealms and taking heap snapshots

async function main() {
  if (typeof ShadowRealm === 'undefined') {
    console.error('ShadowRealm is not available in this Node build');
    process.exit(1);
  }

  const realms = [];

  for (let i = 0; i < 20000; i++) {
    const realm = new ShadowRealm();
    // realms.push(realm);

    // Take heap snapshots periodically
    if (i % 500 === 0) {
      writeHeapSnapshot(`heap-${i}.heapsnapshot`);
      console.log('Created ShadowRealm and heap snapshot at iteration', i);
    }
  }

  console.log('Total ShadowRealms created:', realms.length);
}

main();

How often does it reproduce? Is there a required condition?

No special condition

What is the expected behavior? Why is that the expected behavior?

Even though many objects are allocated, the runtime should handle memory pressure gracefully. The interaction between ShadowRealm creation and heap snapshotting appears to prevent effective garbage collection.

What do you see instead?

root@KContainer:~/49572# node --experimental-shadow-realm --max-old-space-size=1024 test-heapdump-shadow-realm.mjs
Created ShadowRealm and heap snapshot at iteration 0
Created ShadowRealm and heap snapshot at iteration 500

<--- Last few GCs --->

[6100:0x7db2000]    40950 ms: Mark-Compact 995.6 (1033.9) -> 987.2 (1052.6) MB, pooled: 0 MB, 438.54 / 0.00 ms  (average mu = 0.552, current mu = 0.272) allocation failure; scavenge might not succeed
[6100:0x7db2000]    41755 ms: Mark-Compact (reduce) 1002.5 (1054.6) -> 996.6 (1028.6) MB, pooled: 0 MB, 109.72 / 0.01 ms  (+ 572.7 ms in 115 steps since start of marking, biggest step 5.1 ms, walltime since start of marking 725 ms) (average mu = 0.398, cu
FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
----- Native stack trace -----

 1: 0x733eec node::OOMErrorHandler(char const*, v8::OOMDetails const&) [node]
 2: 0xbab3f0  [node]
 3: 0xbab4df  [node]
 4: 0xe43fd5  [node]
 5: 0xe5515c  [node]
 6: 0xd8ca98  [node]
 7: 0x12f5f1e  [node]
 8: 0x19ff636  [node]
Aborted

Code throws OOM after heap snapshot at iteration 500. Ideally, it should keep going as in the case of Bun.

Additional information

Related issue:
https://github.com/nodejs/node/issues/49572

Start by running the provided test-heapdump-shadow-realm.mjs reproduction with Node 24.13.1 or 25.8.1 and the shown heap limit, then compare the behavior around heap snapshots and ShadowRealm creation with related issue #49572. Done means the reproduction no longer reaches an out-of-memory failure under the reported conditions.