When defining local tasks (= tabs) in your Drupal 8 modules, you can specify a title for the tab via the 'title' property in your [MODULENAME].links.task.yml file.

However, in some cases you might want to make the task title dynamic, e.g. depending on the context of the entity where the tab is displayed.
This can be achieved by overriding the \Drupal\Core\Menu\LocalTaskDefault class with your own class for that tab.

Here is an example that uses a callback function to dynamically set the title, both for the route and the local task:

1. Add the dynamic logic to your controller

   File: my_module/src/Controller/DynamicTabController.php

   t('Dynamic tab for @type', ['@type' => $node->bundle()]);
     }
   
   }
   

2. Use the dynamic title callback for your route

   File: my_module/my_module.routing.yml

   entity.node.dynamic_tab:
     path: '/node/{node}/dynamic_tab'
     defaults:
       _entity_form: 'node.dynamic_tab'
       _title_callback: '\Drupal\my_module\Controller\DynamicTabController::getDynamicTabTitle'
     requirements:
       _entity_access: 'node.view'

3. Add your custom LocalTask plugin

   File: my_module/src/Plugin/Menu/LocalTask/DynamicTabLocalTask.php

   attributes->get('node');
       if ($node instanceof NodeInterface) {
         $controller = new DynamicTabController();
         return $controller->getDynamicTabTitle($node);
       }
       return $this->t('Default');
     }
   
   }
   

4. Set your custom class for your local task

   File: my_module/my_module.links.task.yml

   entity.node.dynamic_tab:
     route_name: entity.node.dynamic_tab
     base_route: entity.company.canonical
     title: 'Default'
     class: '\Drupal\my_module\Plugin\Menu\LocalTask\DynamicTabLocalTask'

Now the dynamic title will be used to render your tab name, and the tab page title.