Storybook notifications addon: does the filter function apply in CI mode?

Goal

Teams want to use Storybook's notifications addon to surface critical alerts (e.g., errors, warnings) while silencing informational toasts during local development and in CI pipelines.

Constraints and uncertainty

The addon accepts a filter function to exclude notifications by type or message, but when CI=true the built-in suppression hides all toasts regardless of configuration. The public API does not expose a way to disable or customize this CI behavior, and the documentation does not state whether a custom filter is still evaluated in CI mode. Additionally, CI detection relies on the CI environment variable, whose interpretation can differ across services (GitHub Actions, GitLab CI, etc.), adding further variability.

Questions

1. Does the filter function continue to run when Storybook detects a CI environment, or is it bypassed entirely?
2. Can the built-in CI suppression be opted out of or configured without forking the addon?
3. Which CI providers reliably set the CI variable in a way that triggers the current suppression logic?