diff --git a/packages/bbob-preset/src/preset.ts b/packages/bbob-preset/src/preset.ts
index 7e9d3dbe..13f7f883 100644
--- a/packages/bbob-preset/src/preset.ts
+++ b/packages/bbob-preset/src/preset.ts
@@ -1,87 +1,64 @@
 import type {
   BBobCoreTagNodeTree,
-  BbobPluginOptions,
-  BBobPluginFunction,
+  BBobPluginOptions,
 } from "@bbob/core";
 import { isTagNode } from "@bbob/plugin-helper";
 import type {
+  PresetFactory,
   PresetExtendCallback,
-  PresetFactoryOptions,
   PresetOptions,
   PresetTagsDefinition,
+  ProcessorFunction,
 } from "./types";
 
-function process<Name extends string = string>(
-  tags: PresetTagsDefinition<Name>,
+export function process<Tags extends PresetTagsDefinition = PresetTagsDefinition, Options extends PresetOptions = PresetOptions>(
+  tags: Tags,
   tree: BBobCoreTagNodeTree,
-  core: BbobPluginOptions,
-  options: PresetFactoryOptions = {}
+  core: BBobPluginOptions,
+  options: Options
 ) {
   return tree.walk((node) => {
-    if (isTagNode(node) && typeof tags[node.tag] === "function") {
+    if (isTagNode(node)) {
       const tag = node.tag;
       const tagCallback = tags[tag];
 
-      return tagCallback(node, core, options);
+      if (typeof tagCallback === "function") {
+        return tagCallback(node, core, options);
+      }
     }
 
     return node;
   });
 }
 
-export type ProcessorFunction = typeof process;
-
-export type ProcessorReturnType = ReturnType<ProcessorFunction>;
-
-export interface PresetExecutor<
-  TagName extends string = string,
-  AttrValue = unknown
-> extends BBobPluginFunction {
-  (tree: BBobCoreTagNodeTree, core?: BbobPluginOptions): ProcessorReturnType;
-  options: PresetOptions;
-}
-
-export interface PresetFactory<
-  TagName extends string = string,
-  AttrValue = unknown,
-  Names extends string = string
-> {
-  (opts?: PresetOptions): PresetExecutor;
-  options?: PresetOptions;
-  extend: (
-    cb: PresetExtendCallback<Names>
-  ) => PresetFactory<TagName, AttrValue, Names>;
-}
-
 /**
  * Create a preset plugin for @bbob/core
  */
-function createPreset<Names extends string = string>(
-  defTags: PresetTagsDefinition<Names>,
-  processor: ProcessorFunction = process
+function createPreset<Tags extends PresetTagsDefinition = PresetTagsDefinition, RootOptions extends PresetOptions = PresetOptions,>(
+  defTags: Tags,
+  processor: ProcessorFunction<Tags> = process
 ) {
-  const presetFactory: PresetFactory = (opts: PresetOptions = {}) => {
+  const presetFactory: PresetFactory<typeof defTags, RootOptions> = <Options extends RootOptions>(opts: Options) => {
     presetFactory.options = Object.assign(presetFactory.options || {}, opts);
 
     function presetExecutor(
       tree: BBobCoreTagNodeTree,
-      core: BbobPluginOptions
+      core: BBobPluginOptions
     ) {
-      return processor(defTags, tree, core, presetFactory.options);
+      return processor(defTags, tree, core, presetFactory.options || {});
     }
 
-    presetExecutor.options = presetFactory.options;
+    presetExecutor.options = presetFactory.options as Options;
 
     return presetExecutor;
   };
 
-  presetFactory.extend = function presetExtend<ExtendNames extends string>(
-    callback: PresetExtendCallback<Names & ExtendNames>
+  presetFactory.extend = function presetExtend<NewTags extends PresetTagsDefinition = PresetTagsDefinition>(
+    callback: PresetExtendCallback<Tags, NewTags, RootOptions>
   ) {
-    return createPreset(
-      callback(defTags, presetFactory.options || {}),
-      processor
-    );
+    const newTags = callback(defTags, presetFactory.options)
+
+    return createPreset<typeof newTags, RootOptions>(newTags, processor as unknown as ProcessorFunction<NewTags>);
   };
 
   return presetFactory;
diff --git a/packages/bbob-preset/src/types.ts b/packages/bbob-preset/src/types.ts
index 50e93a3b..ee123723 100644
--- a/packages/bbob-preset/src/types.ts
+++ b/packages/bbob-preset/src/types.ts
@@ -1,15 +1,41 @@
 import type { TagNodeObject } from "@bbob/plugin-helper";
-import type { BbobPluginOptions } from "@bbob/core";
+import type { BBobCoreTagNodeTree, BBobPluginFunction, BBobPluginOptions } from "@bbob/core";
+import type { process } from "./preset";
 
-export type PresetFactoryOptions = Record<string, unknown>
+type PartialRecord<K extends keyof any, T> =  Partial<Record<K, T>>
 
-export type PresetTagFunction<Node extends object = TagNodeObject> = (
-    node: Node,
-    core: BbobPluginOptions,
-    options: PresetFactoryOptions
-) => Node
-
-export type PresetTagsDefinition<Name extends string = string> = Record<Name | string, PresetTagFunction>
+export type PresetTagsDefinition<Key extends string = string> = PartialRecord<Key, PresetTagFunction>
 
 export type PresetOptions = Record<string, unknown>
-export type PresetExtendCallback<Names extends string> = (defTags: PresetTagsDefinition<Names>, options: PresetOptions) => PresetTagsDefinition<Names>
+
+export type ProcessorFunction<Tags extends PresetTagsDefinition = PresetTagsDefinition> = typeof process<Tags>;
+
+export type ProcessorReturnType<Tags extends PresetTagsDefinition = PresetTagsDefinition> = ReturnType<ProcessorFunction<Tags>>;
+
+export interface PresetTagFunction<Node extends TagNodeObject = TagNodeObject, Options extends PresetOptions = PresetOptions> {
+  (
+      node: Node,
+      data: BBobPluginOptions,
+      options: Options
+  ): Node
+}
+
+export interface PresetExtendCallback<Tags, NewTags = Tags, Options extends PresetOptions = PresetOptions> {
+  (defTags: Tags, options?: Options): NewTags
+}
+
+export interface PresetExecutor<Tags extends PresetTagsDefinition = PresetTagsDefinition, Options extends PresetOptions = PresetOptions> extends BBobPluginFunction {
+  (tree: BBobCoreTagNodeTree, core?: BBobPluginOptions): ProcessorReturnType<Tags>;
+  options: Options;
+}
+
+export interface PresetFactory<
+    Tags extends PresetTagsDefinition = PresetTagsDefinition,
+    RootOptions extends PresetOptions = PresetOptions,
+> {
+  <Options extends RootOptions>(opts: Options): PresetExecutor<Tags, Options>;
+  options?: RootOptions;
+  extend: <NewTags extends PresetTagsDefinition = PresetTagsDefinition>(
+      cb: PresetExtendCallback<Tags, NewTags, RootOptions>
+  ) => PresetFactory<NewTags, RootOptions>;
+}
diff --git a/packages/bbob-preset/test/index.test.ts b/packages/bbob-preset/test/index.test.ts
index 6c724086..da00718e 100644
--- a/packages/bbob-preset/test/index.test.ts
+++ b/packages/bbob-preset/test/index.test.ts
@@ -2,21 +2,22 @@ import { createPreset, PresetTagsDefinition } from '../src';
 import { BBobCoreOptions, createTree } from '@bbob/core'
 
 describe('@bbob/preset', () => {
-  const presetFactory = (defTags: PresetTagsDefinition) => {
+  const presetFactory = <Tags extends PresetTagsDefinition = PresetTagsDefinition>(defTags: Tags) => {
     const processor = jest.fn((tags, tree, core, options) => tags)
+    const preset = createPreset<Tags>(defTags, processor)
 
     return {
-      preset: createPreset(defTags, processor),
+      preset,
       processor,
       core: {} as BBobCoreOptions
     }
   }
 
   test('create', () => {
-    const defTags = { test: () => 'test' }
+    const defTags = { test: () => ({ tag: 'test' }) }
     const options = { foo: 'bar' }
     const tree = createTree([], {})
-    const { preset, processor, core } = presetFactory(defTags);
+    const { preset, processor } = presetFactory(defTags);
 
     expect(preset.extend)
       .toBeDefined();