After manually update from 9.0.x to 9.1.* Class Varbase\composer\ScriptHandler is not autoloadable

Thanks, for reporting
Do you have the following in the root composer.json file

  "require": {
    "composer/installers": "~2",
    "oomphinc/composer-installers-extender": "~2",
    "cweagans/composer-patches": "~1",
    "drupal/core-composer-scaffold": "~10",
    "drupal/core-project-message": "~10",
    "webflo/drupal-finder": "~1",
    "drupal/core": "~10",
    "vardot/varbase": "~9.1.0",
    "vardot/varbase-updater": "~2"
  },
  "require-dev": {
    "drupal/core-dev": "~10",
    "drush/drush": "~12",
    "phpstan/phpstan": "~1.10.0",
    "phpstan/extension-installer": "~1.3.0",
    "mglaman/phpstan-drupal": "~1.1.0",
    "phpstan/phpstan-deprecation-rules": "~1.1.0"
  },

as in https://github.com/Vardot/varbase-project/blob/9.1.0/composer.json

Important to follow with the steps notes and steps as in

hi
sorry forgot to add my composer.json before update

{
    "name": "vardot/varbase-project",
    "description": "Project template for Varbase distribution.",
    "type": "project",
    "license": "GPL-2.0-or-later",
    "authors": [
        {
            "name": "Vardot",
            "homepage": "https://github.com/vardot",
            "role": "Maintainer"
        }
    ],
    "support": {
        "issues": "http://drupal.org/project/issues/varbase",
        "source": "http://cgit.drupalcode.org/varbase"
    },
    "repositories": {
        "drupal": {
            "type": "composer",
            "url": "https://packages.drupal.org/8"
        },
        "assets": {
            "type": "composer",
            "url": "https://asset-packagist.org"
        }
    },
    "require": {
        "composer/installers": "~2.0",
        "oomphinc/composer-installers-extender": "~2.0",
        "cweagans/composer-patches": "~1.0",
        "drupal/core-composer-scaffold": "~10",
        "drupal/core-project-message": "~10",
        "webflo/drupal-finder": "~1.0",
        "drupal/core": "~10.1.0",
        "vardot/varbase": "~9.0.0",
        "vardot/varbase-updater": "~2.0",
        "drupal/module_filter": "^4.0",
        "drupal/config_split": "^2.0@RC",
        "drupal/default_content_deploy": "2.0.x-dev@dev",
        "bower-asset/jquery": "^1.6",
        "drupal/jquery_ui": "^1.6",
        "drupal/robotstxt": "^1.5",
        "drupal/unused_modules": "^1.5",
        "drupal/varbase_media_demo": "^10.0",
        "drupal/easy_install_d10": "10.x-dev@dev",
        "drupal/config_import_de": "^1.0",
        "drupal/varbase_media_header": "^9.1",
        "drupal/better_normalizers": "^2.0@beta",
        "drupal/recreate_block_content": "^3.0"
    },
    "require-dev": {
        "drupal/core-dev": "~10",
        "drush/drush": "~12.0",
        "phpstan/phpstan": "~1.10.0",
        "phpstan/extension-installer": "~1.3.0",
        "mglaman/phpstan-drupal": "~1.1.0",
        "phpstan/phpstan-deprecation-rules": "~1.1.0"
    },
    "config": {
        "bin-dir": "bin/",
        "secure-http": false,
        "optimize-autoloader": true,
        "preferred-install": {
            "drupal/core": "dist"
        },
        "allow-plugins": {
            "composer/installers": true,
            "cweagans/composer-patches": true,
            "oomphinc/composer-installers-extender": true,
            "drupal/core-composer-scaffold": true,
            "drupal/core-project-message": true,
            "dealerdirect/phpcodesniffer-composer-installer": true,
            "phpstan/extension-installer": true,
            "vardot/varbase-updater": true
        }
    },
    "scripts": {
        "post-install-cmd": [
            "Varbase\\composer\\ScriptHandler::createRequiredFiles",
            "Varbase\\composer\\ScriptHandler::removeGitDirectories"
        ],
        "post-update-cmd": [
            "Varbase\\composer\\ScriptHandler::createRequiredFiles",
            "Varbase\\composer\\ScriptHandler::removeGitDirectories"
        ],
        "post-drupal-scaffold-cmd": ["Varbase\\composer\\ScriptHandler::postDrupalScaffoldProcedure"]
    },
    "minimum-stability": "dev",
    "prefer-stable": true,
    "conflict": {
        "drupal/drupal": "*"
    },
    "extra": {
        "branch-alias": {
            "dev-9.0.x": "9.0.x-dev"
        },
        "drupal-core-project-message": {
            "include-keys": ["homepage", "support"],
            "post-create-project-cmd-message": [
                "<bg=blue;fg=white>                                                           </>",
                "<bg=blue;fg=white>  Congratulations, you have installed the Varbase codebase </>",
                "<bg=blue;fg=white>  from the vardot/varbase-project template!                </>",
                "<bg=blue;fg=white>                                                           </>",
                "",
                "<bg=yellow;fg=black>Next steps</>:",

                "  * Install the site: https://www.drupal.org/docs/installing-drupal",
                "  * Read the user guide: https://docs.varbase.vardot.com",
                "  * Get support: https://www.vardot.com/en/form/get-support-varbase",
                "  * Join Our Slack Team for Feedback and Support:",
                "      http://slack.varbase.vardot.com",
                "  * Remove the plugin that prints this message:",
                "      composer remove drupal/core-project-message"
            ]
        },
        "drupal-scaffold": {
            "allowed-packages": [
                "drupal/core",
                "vardot/varbase"
            ],
            "gitignore": true,
            "locations": {
                "web-root": "./docroot"
            },
            "file-mapping": {
                "[web-root]/sites/default/default.services.yml": {
                    "mode": "replace",
                    "overwrite": false,
                    "path": "docroot/core/assets/scaffold/files/default.services.yml"
                },
                "[web-root]/sites/default/default.settings.php": {
                    "mode": "replace",
                    "overwrite": false,
                    "path": "docroot/core/assets/scaffold/files/default.settings.php"
                }
            }
        },
        "installer-paths": {
            "docroot/core": ["type:drupal-core"],
            "docroot/profiles/{$name}": ["type:drupal-profile"],
            "docroot/modules/contrib/{$name}": ["type:drupal-module"],
            "docroot/themes/contrib/{$name}": ["type:drupal-theme"],
            "docroot/libraries/slick": ["npm-asset/slick-carousel"],
            "docroot/libraries/ace": ["npm-asset/ace-builds"],
            "docroot/libraries/jquery-ui-touch-punch": ["bower-asset/jqueryui-touch-punch"],
            "docroot/libraries/swagger-ui/dist": ["npm-asset/swagger-ui-dist"],
            "docroot/libraries/{$name}": [
                "type:drupal-library",
                "type:bower-asset",
                "type:npm-asset"
            ],
            "docroot/modules/custom/{$name}": ["type:drupal-custom-module"],
            "docroot/themes/custom/{$name}": ["type:drupal-custom-theme"],
            "drush/contrib/{$name}": ["type:drupal-drush"]
        },
        "installer-types": [
            "bower-asset",
            "npm-asset"
        ],
        "drupal-libraries": {
            "library-directory": "docroot/libraries",
            "libraries": [
                {"name": "objectfitpolyfill", "package": "bower-asset/objectfitpolyfill"},
                {"name": "chartjs", "package": "bower-asset/chartjs"},
                {"name": "c3","package": "bower-asset/c3"},
                {"name": "d3", "package": "bower-asset/d3"},
                {"name": "dropzone","package": "npm-asset/dropzone"},
                {"name": "blazy", "package": "npm-asset/blazy"},
                {"name": "slick", "package": "npm-asset/slick-carousel"},
                {"name": "ace", "package": "npm-asset/ace-builds"},
                {"name": "jquery-ui-touch-punch", "package": "bower-asset/jqueryui-touch-punch"},
                {"name": "imagesloaded", "package": "npm-asset/imagesloaded"},
                {"name": "swagger-ui", "package": "npm-asset/swagger-ui-dist"}
            ]
        },
        "enable-patching": true,
        "composer-exit-on-patch-failure": true,
        "patchLevel": {
            "drupal/core": "-p2"
        },
        "patches": {
            "drupal/core":{
                "(Serge for DCD)[PP-1] Expose Layout Builder data to REST and JSON:API": "https://www.drupal.org/files/issues/2023-12-11/2942975-252_revised_239.patch"
            },
            "drupal/hal": {
                "(Serge for DCD) Translated field denormalization creates duplicate values":"https://www.drupal.org/files/issues/2023-04-05/2904423-90.patch"
            },
            "drupal/easy_install": {
                "PHP warning on": "https://www.drupal.org/files/issues/2020-07-25/Solution.patch"
            },
            "drupal/default_content": {
                "2 - Don't add translation, if exist - https://www.drupal.org/project/default_content/issues/3176839#comment-13859359": "https://www.drupal.org/files/issues/2020-10-14/default_content-3176839-2.patch",
                "3 - Add a Normalizer and Denormalizer to support Layout Builder - https://www.drupal.org/project/default_content/issues/3160146#comment-14814050": "https://www.drupal.org/files/issues/2022-12-06/default_content-3160146-53.patch",
                "4 - Update inline block usage on import - https://www.drupal.org/project/default_content/issues/3359137#comment-15042582": "https://www.drupal.org/files/issues/2023-05-09/default_content-3359137-3.patch"
            }
        },
        "patches-ignore": {
            "drupal/varbase_core": {
                "drupal/default_content": {
                    "Issue #3160146: Add Layout Builder Normalizer and Denormalize": "https://www.drupal.org/files/issues/2021-04-07/3160146-37.patch"
                }
            }
        }
    }
}

hi

i just notice line are missing ..
let me retry and get back to you please

Change "vardot/varbase": "~9.0.0", to "vardot/varbase": "~9.1.0", in the root composer.json

Thanks for reporting issues while updating.
Adding the highlights for that in the documentation.

✅ Released Varbase 9.0.17 → ( Drupal ~9 old way )
✅ Released Varbase 9.1.0 → ( Drupal ~10 old way ) for upgrades
✅ Released Varbase 10.0.0-rc1 → ( Drupal ~10 new way )

→

Planed to drop support for Drupal 9

Drupal 10 has 3 years LTS

Updated the documentaiotn for

hi
ok thanks .. Update run successfully now