9 files declare their use of ContextInterface in Drupal 9

BlockComponentRenderArrayTest.php in core/modules/layout_builder/tests/src/Unit/BlockComponentRenderArrayTest.php

ConditionPluginCollection.php in core/lib/Drupal/Core/Condition/ConditionPluginCollection.php

ContextAwarePluginBase.php in core/lib/Drupal/Component/Plugin/ContextAwarePluginBase.php

ContextAwarePluginInterface.php in core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php

ContextAwarePluginTrait.php in core/lib/Drupal/Core/Plugin/ContextAwarePluginTrait.php

ContextAwarePluginTraitTest.php in core/tests/Drupal/KernelTests/Core/Plugin/Context/ContextAwarePluginTraitTest.php

ContextInterface.php in core/lib/Drupal/Core/Plugin/Context/ContextInterface.php

DefaultsSectionStorage.php in core/modules/layout_builder/src/Plugin/SectionStorage/DefaultsSectionStorage.php

SectionStorageManagerTest.php in core/modules/layout_builder/tests/src/Unit/SectionStorageManagerTest.php