Add web hooks for `onDisabled` and `onUninstalled`

[carlosjeurissen]

Intro

As follow up for the from the London 2026-04-07 F2F, where we discussed ability to be notified as extension on disabled/uninstalled scenarios was discussed. A few points were raised:

• Safari considers runtime.setUninstallURL() too invasive
• Chrome is hesitant to give the exact unload reason for runtime.onInvalidated() (see Update runtime.onInvalidated with unload reason and isolated world restriction #975)
• Unlike runtime.setUninstallURL() this should be a fixed URL set in the manifest, preventing passing additional user data
• If passing additional data, a pre-specified payload without replacement variables would be ideal

In addition, I would like to add:

• The web hooks should not be a replacement for runtime.setUninstallURL() as there would be no way for extension developers to invite users to share uninstalled reasons. Many developers collect this information to improve their products and many users elaborate on there reasoning.

Proposal

Considering this should be in the manifest, and we may want to add more web hooks, having a top level web_hooks object seems to keep the manifest file clean and flexible. Something like:

{
  "web_hooks": {
    "on_disabled": "https://example.com/hooks/on-disabled",
    "on_uninstalled": "https://example.com/hooks/on-uninstalled"
  }
}

Discussion points

• GET vs POST method / payload
• on_disabled vs on_disable naming
• do we indeed want a general web_hooks umbrella object?

[carlosjeurissen]

@xeenon feel free to elaborate on some of the bikeshedding you were hinting at when it comes to naming / how this should be declared if it were to be implemented.