The session from init/1 is NOT automatically merged into socket assigns for render/1. It's only passed directly to menu_link/2 and to mount/3 if implemented. You must implement mount/3 to explicitly assign the session values to the socket:

@impl true
def init(opts) do
  oban_name = Keyword.fetch!(opts, :oban)
  title = Keyword.get(opts, :title, "Default Title")
  {:ok, %{oban_name: oban_name, title: title}}
end

@impl true
def mount(_params, session, socket) do
  # Session contains the return value from init/1
  # Must explicitly assign it to socket for render/1 to access
  {:ok, Phoenix.Component.assign(socket, session)}
end

@impl true
def menu_link(%{oban_name: oban_name, title: title}, _capabilities) do
  # menu_link receives session directly - this works without mount/3
  {:ok, title}
end

@impl true
def render(assigns) do
  # Now assigns.oban_name and assigns.title are available
  # because mount/3 assigned them
end

The flow is: init/1 → session stored → menu_link/2 receives session directly → mount/3 receives session as 2nd arg → you must assign to socket → render/1 receives socket.assigns