PG::InvalidColumnReference: ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list

You need to add widget_steps.name to list of selected columns:

SELECT  DISTINCT "widgets".*, "widget_steps.name" FROM "widgets" INNER JOIN "widget_steps" ON "widget_steps"."widget_id" = "widgets"."id" INNER JOIN "widget_steps" "active_steps_widgets" ON "active_steps_widgets"."id" = "widgets"."active_widget_step_id" WHERE "widgets"."account_id" = 1 AND "widgets"."completed_at" IS NULL AND (("widgets"."sequential" = 't' AND "widget_steps"."assigned_to" = 5 AND "widget_steps"."id" = "widgets"."active_widget_step_id" AND "widget_steps"."completed_at" IS NULL) OR ("widgets"."sequential" = 'f' AND "widget_steps"."assigned_to" = 5 AND "widget_steps"."completed_at" IS NULL)) ORDER BY sequential DESC, widget_steps.name ASC LIMIT 10 OFFSET 0

This should not change logic of your query and will work fine.

In Rails you may use select method to set list of selected columns:

Widget.select('"widgets".*, "widget_steps.name"')

Hope this would help.