v151.0 (2026-04-20)

⚠️ Breaking Changes ⚠️

It is now enforced by nimbus-fml that feature variables using gecko-pref must be have type: Option<T>, for T in Boolean, Int, and String.
nimbus-fml commands now all have a --lax-gecko-pref-validation flag to bypass the above restriction, as well as the restriction that gecko-pref and default are mutually exclusive.
The FmlLoaderConfig now has a lax_gecko_pref_validation field to allow FmlClient consumers (i.e., Experimenter) to opt-in to lax validation.

New allow_empty_passwords feature flag to allow storing logins with empty passwords. This feature is intended to be enabled on desktop during the migration.
Add ignore_form_action_origin_validation_errors feature flag that allows logins with non-URL form_action_origin values (e.g. "email", "UserCode") to be imported without error. URL normalization for valid URLs is still applied.
Add perform_additional_origin_fixups feature flag that repairs origin values which fail URL parsing (bare domains, FireFTP quirks, bare https: / https://, etc.) into parseable URLs instead of rejecting them. Scoped to the origin field only; form_action_origin keeps the stricter behavior, but can be disabled via ignore_form_action_origin_validation_errors. Intended to be enabled on desktop during migration to salvage legacy/addon-generated entries.

Added a client for the merino suggest endpoint
Added a suggest subcommand to merino-cli for locally testing the suggest endpoint.

merino-cli now supports subcommands: recommendations for curated recommendations and suggest for the suggest endpoint.