[Bug] Memory usage increases linearly when adding/removing monaco embedded in same-origin iframes in Chrome

Reproducible in vscode.dev or in VS Code Desktop?

• Not reproducible in vscode.dev or VS Code Desktop

Reproducible in the monaco editor playground?

• Not reproducible in the monaco editor playground

Monaco Editor Playground Link

No response

Monaco Editor Playground Code

External repro here: https://github.com/awphi/monaco-chrome-iframe-issue/

Reproduction Steps

• Clone this repo
• pnpm install && pnpm dev (or whatever package manager)
• Open the app in Chrome
• Open the Performance Monitor in DevTools
• Repeatedly press the add/remove iframe button
• Observe memory usage and retained document/document frame count increase

https://github.com/user-attachments/assets/befeae8d-a62f-4e99-8627-c7f184ae8c23

Actual (Problematic) Behavior

Memory usage increases linearly with number of total iframes created in the page's lifespan.

Expected Behavior

Documents using monaco are not retained after its containing iframe is removed, preventing significant memory retention.

Additional Context

Browser Versions: Version 133.0.6943.142 (Official Build) (arm64), Version 135.0.7039.1 (Official Build) canary-dcheck (arm64)
OS: MacOS 15.3.1 (24D70)

Interestingly, reducing the text length in the model (e.g. change the dummy HTML in the above repro to abc) seems to circumvent this issue.

Also doesn't seem to affect FF 135.0.1 afaict

Clone the linked external reproduction, run pnpm install && pnpm dev, and reproduce the issue in Chrome with Performance Monitor open while repeatedly adding and removing iframes. Trace the retained documents and document frames; done means Monaco documents are no longer retained after their containing iframe is removed, without reproducing the reported memory increase.