Firefox AI chatbot sidebar

[o7ux]

CanvasBlocker breaks Firefox AI chatbot sidebar

CanvasBlocker causes Firefox's AI chatbot sidebar to become partially rendered and non-interactive: text cannot be selected, controls cannot be focused or clicked, and some interface elements appears to be missing.

Normal Install

CanvasBlocker

Behavior

OAuth initially failed both when launched from ChatGPT and when returning from the identity-provider callback.
Authentication succeeded after restarting Firefox in Troubleshoot Mode.

After returning to live browser state interactive elements inside the AI chatbot sidebar stopped functioning:

• text cannot be selected
• input fields cannot be focused
• buttons do not respond
• some controls remain disabled
• some interface elements are absent

All five listed providers work outside the sidebar in ordinary Firefox tabs under the same browser configuration, with CanvasBlocker enabled.

Provider	Authentication	Rendering	Interaction	Chat submission
ChatGPT	❌	❌	❌	❌
Gemini	❌	❌	❌	❌
Claude	❌	✅	✅	Not tested
Mistral Le Chat	❌	❌	❌	❌
Microsoft Copilot	✅	✅	✅	❌

All built-in providers should remain fully functional inside Firefox's AI chatbot sidebar , as they do when opened in ordinary Firefox tabs or with CanvasBlocker disabled.

Workaround

Setting CanvasBlocker's site-specific blocking mode to allow everything for ChatGPT restores interaction
while CanvasBlocker remains enabled.

ChatGPT was the only provider tested with CanvasBlocker disabled and
with site-specific allow everything rules.

chatgpt.com allow everything *.chatgpt.com allow everything *.oaiusercontent.com allow everything *.openai.com allow everything *.oaistatsig.com allow everything

Triage

All extension were disabled, then reintroduced one-by-one while I was troubleshooting.

1. Disabling Chrome Mask restored some missing UI elements, did not fix interactions.
   • Chrome Mask could later be re-enabled after applying the CanvasBlocker exception while all UI elements remained.
2. Re-enabling NoScript restored intended functionality for Firefox's "Summarize page" feature, but removing it did not restore provider interaction.
3. Re-enabling CanvasBlocker reproduced the non-interactive page, and also caused ChatGPT to lose its OAuth authentication.
   • May be related to Plugin being enabled is causing chatgpt to force login #746
4. No other extensions that were toggled during triage were conclusive of the non-interactive state.

Current State:

Test	Working?
ChatGPT Firefox tab, CanvasBlocker enabled	✅
ChatGPT AI sidebar, CanvasBlocker enabled	❌
ChatGPT AI sidebar, CanvasBlocker disabled	✅
ChatGPT AI sidebar, site-specific allow everything	✅

Environment

• Operating system: Windows 10 22H2
• Firefox version: 153.0
• Firefox channel: release
• Firefox build ID: 20260715202819
• CanvasBlocker version: 1.12
• CanvasBlocker blocking mode: fake

Relevant Logs

CanvasBlocker 1.10 added unconditional protection for about:blank.
This may be relevant to the failure, but I have not confirmed that it is the responsible code path.

One captured console line directly identified CanvasBlocker during sidebar teardown. The affected sidebar also
created about:blank and about:srcdoc child contexts that inherited the provider origin:

sendRemoveListener on closed conduit
CanvasBlocker@kkapsner.de.1924145348621
ConduitsChild.sys.mjs:122:13

url: "about:blank"
origin: "https://chatgpt.com"

url: "about:srcdoc"
origin: "https://chatgpt.com"

Firefox's built-in AI sidebar appears to host provider pages in a browsing context that differs from an ordinary tab.

NoScript independently fails while in the same tabless AI Chatbot state, included here as contextual evidence that extension
messaging behaves differently in the sidebar.

Could not dispatch message

Object {
   url:
     "https://chatgpt.com/cdn-cgi/challenge-platform/scripts/jsd/main.js",
   type: "script",
   isReport: true
}
Object {
   envType: "content_child",
   url: "about:srcdoc",
   documentId: "<>",
   origin: "https://chatgpt.com"
}```