diff --git a/lib/ash_phoenix/form/auto.ex b/lib/ash_phoenix/form/auto.ex
index 9c6bf3f..f87b866 100644
--- a/lib/ash_phoenix/form/auto.ex
+++ b/lib/ash_phoenix/form/auto.ex
@@ -69,7 +69,8 @@ defmodule AshPhoenix.Form.Auto do
     ],
     sparse_lists?: [
       type: :boolean,
-      doc: "Sets all list type forms to `sparse?: true` by default.",
+      doc:
+        "Sets all list type forms to `sparse?: true` by default. Has no effect on forms derived for embedded resources.",
       default: false
     ]
   ]
@@ -451,9 +452,9 @@ defmodule AshPhoenix.Form.Auto do
        [
          type: type,
          resource: embed,
-         sparse?: auto_opts[:sparse_lists?],
          create_action: create_action.name,
          update_action: update_action.name,
+         embed?: true,
          data: data,
          forms: [],
          updater: fn opts ->
diff --git a/lib/ash_phoenix/form/form.ex b/lib/ash_phoenix/form/form.ex
index 6e26093..93ff53a 100644
--- a/lib/ash_phoenix/form/form.ex
+++ b/lib/ash_phoenix/form/form.ex
@@ -1260,8 +1260,12 @@ defmodule AshPhoenix.Form do
   """
   @spec params(t()) :: map
   def params(form, opts \\ []) do
+    # These options aren't documented because they are still experimental
     hidden? = opts[:hidden?] || false
-    indexed_lists? = opts[:indexed_lists?] || false
+    indexer = opts[:indexer]
+    indexed_lists? = opts[:indexed_lists?] || not is_nil(indexer) || false
+    transform = opts[:transform]
+    only_touched? = Keyword.get(opts, :only_touched?, true)
 
     form_keys =
       form.form_keys
@@ -1279,57 +1283,79 @@ defmodule AshPhoenix.Form do
         params
       end
 
-    form.form_keys
-    |> Enum.filter(fn {key, _} ->
+    untransformed_params =
+      form.form_keys
+      |> only_touched(form, only_touched?)
+      |> Enum.reduce(params, fn {key, config}, params ->
+        case config[:type] || :single do
+          :single ->
+            if form.forms[key] do
+              nested_params =
+                if form.forms[key] do
+                  params(form.forms[key], opts)
+                else
+                  nil
+                end
+
+              if form.form_keys[key][:merge?] do
+                Map.merge(nested_params || %{}, params)
+              else
+                Map.put(params, to_string(config[:for] || key), nested_params)
+              end
+            else
+              Map.put(params, to_string(config[:for] || key), nil)
+            end
+
+          :list ->
+            for_name = to_string(config[:for] || key)
+
+            if indexed_lists? do
+              params
+              |> Map.put_new(for_name, %{})
+              |> Map.update!(for_name, fn current ->
+                if indexer do
+                  Enum.reduce(form.forms[key], current, fn form, current ->
+                    Map.put(current, indexer.(form), params(form, opts))
+                  end)
+                else
+                  max =
+                    current
+                    |> Map.keys()
+                    |> Enum.map(&String.to_integer/1)
+                    |> Enum.max(fn -> -1 end)
+
+                  form.forms[key]
+                  |> Enum.reduce({current, max + 1}, fn form, {current, i} ->
+                    {Map.put(current, to_string(i), params(form, opts)), i + 1}
+                  end)
+                  |> elem(0)
+                end
+              end)
+            else
+              params
+              |> Map.put_new(for_name, [])
+              |> Map.update!(for_name, fn current ->
+                current ++ Enum.map(form.forms[key] || [], &params(&1, opts))
+              end)
+            end
+        end
+      end)
+
+    if transform do
+      Map.new(untransformed_params, transform)
+    else
+      untransformed_params
+    end
+  end
+
+  defp only_touched(form_keys, true, form) do
+    Enum.filter(form_keys, fn {key, _} ->
       MapSet.member?(form.touched_forms, to_string(key))
     end)
-    |> Enum.reduce(params, fn {key, config}, params ->
-      case config[:type] || :single do
-        :single ->
-          if form.forms[key] do
-            nested_params =
-              if form.forms[key] do
-                params(form.forms[key], opts)
-              else
-                nil
-              end
-
-            if form.form_keys[key][:merge?] do
-              Map.merge(nested_params || %{}, params)
-            else
-              Map.put(params, to_string(config[:for] || key), nested_params)
-            end
-          else
-            Map.put(params, to_string(config[:for] || key), nil)
-          end
-
-        :list ->
-          for_name = to_string(config[:for] || key)
-
-          if indexed_lists? do
-            params
-            |> Map.put_new(for_name, %{})
-            |> Map.update!(for_name, fn current ->
-              max =
-                current |> Map.keys() |> Enum.map(&String.to_integer/1) |> Enum.max(fn -> -1 end)
-
-              form.forms[key]
-              |> Enum.reduce({current, max + 1}, fn form, {current, i} ->
-                {Map.put(current, to_string(i), params(form, opts)), i + 1}
-              end)
-              |> elem(0)
-            end)
-          else
-            params
-            |> Map.put_new(for_name, [])
-            |> Map.update!(for_name, fn current ->
-              current ++ Enum.map(form.forms[key] || [], &params(&1, opts))
-            end)
-          end
-      end
-    end)
   end
 
+  defp only_touched(form_keys, _, _), do: form_keys
+
   @add_form_opts [
     prepend: [
       type: :boolean,
@@ -2851,6 +2877,9 @@ defmodule AshPhoenix.Form do
     |> Enum.sort_by(fn {params, key} ->
       params["_index"] || key
     end)
+
+    # rescue
+    #   _ ->
   end
 
   defp indexed_list(other) do