diff --git a/includes/specials/SpecialBlock.php b/includes/specials/SpecialBlock.php
index db30aa004a2..ab2c07387a7 100644
--- a/includes/specials/SpecialBlock.php
+++ b/includes/specials/SpecialBlock.php
@@ -152,6 +152,10 @@ class SpecialBlock extends FormSpecialPage {
 
 		if ( $this->useCodex ) {
 			$this->getOutput()->addModules( 'mediawiki.special.block.codex' );
+			$this->codexFormData[ 'blockAlreadyBlocked' ] = $this->alreadyBlocked;
+			$this->codexFormData[ 'blockTargetUser' ] = $this->target instanceof UserIdentity ?
+				$this->target->getName() :
+				$this->target ?? null;
 			$this->getOutput()->addJsConfigVars( $this->codexFormData );
 		}
 	}
diff --git a/languages/i18n/en.json b/languages/i18n/en.json
index e80381565f1..9b49cde9f9a 100644
--- a/languages/i18n/en.json
+++ b/languages/i18n/en.json
@@ -2693,7 +2693,6 @@
 	"block-user-label": "Which user do you want to block?",
 	"block-user-description": "A user can be a username, IP address, or an IP range.",
 	"block-user-placeholder": "Start typing a user...",
-	"block-save": "Save block",
 	"block-target": "Username, IP address, or IP range:",
 	"block-target-placeholder": "UserName, 1.1.1.42, or 1.1.1.42/16",
 	"unblockip": "Unblock user",
diff --git a/languages/i18n/qqq.json b/languages/i18n/qqq.json
index 01ebba4b2e4..4e7a986168e 100644
--- a/languages/i18n/qqq.json
+++ b/languages/i18n/qqq.json
@@ -2956,7 +2956,6 @@
 	"block-user-label": "Label for the input for specifying the user of a block on [[Special:Block]]",
 	"block-user-description": "Description for the input for specifying the user of a block on [[Special:Block]]",
 	"block-user-placeholder": "Placeholder text for the input specifying the user of a block on [[Special:Block]]",
-	"block-save": "Label for submit button on block form [[Special:Block]]",
 	"block-target": "Label for the input for specifying the target of a block on [[Special:Block]]",
 	"block-target-placeholder": "Placeholder text for the input specifying the target of a block on [[Special:Block]]",
 	"unblockip": "Used as title and legend for the form in [[Special:Unblock]].",
diff --git a/resources/Resources.php b/resources/Resources.php
index 06d5281fd0c..468d21efeee 100644
--- a/resources/Resources.php
+++ b/resources/Resources.php
@@ -2279,20 +2279,25 @@ return [
 			'block-options-description',
 			'block-reason',
 			'block-reason-other',
-			'block-save',
 			'block-user-description',
 			'block-user-label',
 			'block-user-placeholder',
 			'blocklist-type-opt-partial',
 			'blocklist-type-opt-sitewide',
 			'colon-separator',
+			'block-user-label',
+			'block-user-description',
+			'block-user-placeholder',
+			'ipbsubmit',
 			'htmlform-optional-flag',
 			'htmlform-selectorother-other',
 			'ipb-action-create',
 			'ipb-action-move',
 			'ipb-action-upload',
+			'ipb-change-block',
 			'ipb-disableusertalk',
 			'ipb-hardblock',
+			'ipb-needreblock',
 			'ipb-partial-help',
 			'ipb-sitewide-help',
 			'ipbcreateaccount',
diff --git a/resources/src/mediawiki.special.block/SpecialBlock.vue b/resources/src/mediawiki.special.block/SpecialBlock.vue
index c01c758bb45..2d7fc453e97 100644
--- a/resources/src/mediawiki.special.block/SpecialBlock.vue
+++ b/resources/src/mediawiki.special.block/SpecialBlock.vue
@@ -1,5 +1,15 @@
 <template>
-	<user-lookup v-model="targetUser"></user-lookup>
+	<cdx-message
+		v-if="targetUser && alreadyBlocked"
+		type="error"
+		inline
+	>
+		{{ $i18n( 'ipb-needreblock', targetUser ).text() }}
+	</cdx-message>
+	<user-lookup
+		v-model="targetUser"
+		@input="alreadyBlocked = false"
+	></user-lookup>
 	<target-active-blocks></target-active-blocks>
 	<target-block-log></target-block-log>
 	<block-type-field
@@ -25,18 +35,18 @@
 	></block-details-field>
 	<hr class="mw-block-hr">
 	<cdx-button
-		action="progressive"
+		action="destructive"
 		weight="primary"
 		@click="handleSubmit"
 		class="mw-block-submit"
 	>
-		{{ $i18n( 'block-save' ).text() }}
+		{{ submitBtnMsg }}
 	</cdx-button>
 </template>
 
 <script>
 const { defineComponent, ref } = require( 'vue' );
-const { CdxButton } = require( '@wikimedia/codex' );
+const { CdxButton, CdxMessage } = require( '@wikimedia/codex' );
 const UserLookup = require( './components/UserLookup.vue' );
 const TargetActiveBlocks = require( './components/TargetActiveBlocks.vue' );
 const TargetBlockLog = require( './components/TargetBlockLog.vue' );
@@ -56,10 +66,11 @@ module.exports = exports = defineComponent( {
 		ExpiryField,
 		ReasonField,
 		BlockDetailsField,
-		CdxButton
+		CdxButton,
+		CdxMessage
 	},
 	setup() {
-		const targetUser = ref( '' );
+		const targetUser = ref( mw.config.get( 'blockTargetUser' ) );
 		const expiry = ref( {} );
 
 		const blockPartialOptions = mw.config.get( 'partialBlockActionOptions' ) ?
@@ -206,9 +217,13 @@ module.exports = exports = defineComponent( {
 				} );
 		}
 
+		const alreadyBlocked = mw.config.get( 'blockAlreadyBlocked' );
+
 		return {
 			targetUser,
 			expiry,
+			alreadyBlocked,
+			submitBtnMsg: mw.message( alreadyBlocked ? 'ipb-change-block' : 'ipbsubmit' ).text(),
 			handleSubmit,
 			blockDetailsOptions,
 			blockDetailsSelected,
diff --git a/resources/src/mediawiki.special.block/components/UserLookup.vue b/resources/src/mediawiki.special.block/components/UserLookup.vue
index a9f4e2474dd..e980cf6e2e6 100644
--- a/resources/src/mediawiki.special.block/components/UserLookup.vue
+++ b/resources/src/mediawiki.special.block/components/UserLookup.vue
@@ -2,6 +2,7 @@
 	<cdx-field :is-fieldset="true">
 		<cdx-lookup
 			v-model:selected="wrappedModel"
+			v-model:input-value="wrappedModel"
 			name="wpTarget"
 			:menu-items="menuItems"
 			:start-icon="cdxIconSearch"
@@ -36,7 +37,7 @@ module.exports = exports = defineComponent( {
 	],
 	setup( props, { emit } ) {
 		const menuItems = ref( [] );
-		const currentSearchTerm = ref( '' );
+		const currentSearchTerm = ref( props.modelValue || '' );
 		const wrappedModel = useModelWrapper(
 			toRef( props, 'modelValue' ),
 			emit
@@ -54,7 +55,6 @@ module.exports = exports = defineComponent( {
 			const api = new mw.Api();
 
 			const params = {
-				origin: '*',
 				action: 'query',
 				format: 'json',
 				formatversion: 2,
@@ -96,13 +96,10 @@ module.exports = exports = defineComponent( {
 					}
 
 					// Build an array of menu items.
-					const results = data.allusers.map( ( result ) => ( {
+					menuItems.value = data.allusers.map( ( result ) => ( {
 						label: result.name,
 						value: result.name
 					} ) );
-
-					// Update menuItems.
-					menuItems.value = results;
 				} )
 				.catch( () => {
 					// On error, set results to empty.
diff --git a/tests/jest/jest.setup.js b/tests/jest/jest.setup.js
index 5aa5690e309..d55cd1c9a90 100644
--- a/tests/jest/jest.setup.js
+++ b/tests/jest/jest.setup.js
@@ -31,6 +31,12 @@ config.global.directives = {
 	}
 };
 
+function ApiMock() {}
+ApiMock.prototype.get = jest.fn();
+ApiMock.prototype.post = jest.fn();
+ApiMock.prototype.postWithEditToken = jest.fn();
+ApiMock.prototype.postWithToken = jest.fn();
+
 function RestMock() {}
 RestMock.prototype.get = jest.fn();
 
@@ -41,6 +47,7 @@ TitleMock.prototype.getUrl = jest.fn();
 
 // Mock the mw global object.
 const mw = {
+	Api: ApiMock,
 	log: {
 		error: jest.fn(),
 		warn: jest.fn()
diff --git a/tests/jest/mediawiki.special.block/SpecialBlock.setup.js b/tests/jest/mediawiki.special.block/SpecialBlock.setup.js
new file mode 100644
index 00000000000..012a5434cc5
--- /dev/null
+++ b/tests/jest/mediawiki.special.block/SpecialBlock.setup.js
@@ -0,0 +1,30 @@
+/**
+ * Mock calls to mw.config.get().
+ * The default implementation correlates to the SpecialBlock::codexFormData property in PHP.
+ *
+ * @param {Object} [config]
+ */
+function mockMwConfigGet( config = {} ) {
+	const mockConfig = Object.assign( {
+		blockAlreadyBlocked: false,
+		blockTargetUser: null,
+		blockAllowsEmailBan: true,
+		blockAllowsUTEdit: true,
+		blockAutoblockExpiry: '1 day',
+		blockDefaultExpiry: 'infinite',
+		blockHideUser: true,
+		blockExpiryOptions: {
+			infinite: 'infinite',
+			'Other time:': 'other'
+		},
+		blockReasonOptions: [
+			{ label: 'block-reason-1', value: 'block-reason-1' },
+			{ label: 'block-reason-2', value: 'block-reason-2' }
+		]
+	}, config );
+	mw.config.get.mockImplementation( ( key ) => mockConfig[ key ] );
+}
+
+module.exports = {
+	mockMwConfigGet
+};
diff --git a/tests/jest/mediawiki.special.block/SpecialBlock.test.js b/tests/jest/mediawiki.special.block/SpecialBlock.test.js
index 2bcc7551451..599e0c7b608 100644
--- a/tests/jest/mediawiki.special.block/SpecialBlock.test.js
+++ b/tests/jest/mediawiki.special.block/SpecialBlock.test.js
@@ -1,31 +1,21 @@
 'use strict';
 
 const { mount } = require( '@vue/test-utils' );
-
-// Mock calls to mw.config.get.
-// This correlates to the SpecialBlock::codexFormData property in PHP.
-const mockConfig = {
-	blockAllowsEmailBan: true,
-	blockAllowsUTEdit: true,
-	blockAutoblockExpiry: '1 day',
-	blockDefaultExpiry: 'infinite',
-	blockHideUser: true,
-	blockExpiryOptions: {
-		infinite: 'infinite',
-		'Other time:': 'other'
-	},
-	blockReasonOptions: [
-		{ label: 'block-reason-1', value: 'block-reason-1' },
-		{ label: 'block-reason-2', value: 'block-reason-2' }
-	]
-};
-mw.config.get.mockImplementation( ( key ) => mockConfig[ key ] );
-
+const { mockMwConfigGet } = require( './SpecialBlock.setup.js' );
 const SpecialBlock = require( '../../../resources/src/mediawiki.special.block/SpecialBlock.vue' );
 
 describe( 'SpecialBlock', () => {
-	it( 'should show a submit button with the correct text', () => {
-		const wrapper = mount( SpecialBlock );
-		expect( wrapper.find( 'button.cdx-button' ).text() ).toBe( 'block-save' );
+	it( 'should show a banner and a submit button with text based on if user is already blocked', () => {
+		mockMwConfigGet();
+		let wrapper = mount( SpecialBlock );
+		expect( wrapper.find( 'button.cdx-button' ).text() ).toStrictEqual( 'ipbsubmit' );
+		mockMwConfigGet( {
+			blockAlreadyBlocked: true,
+			blockTargetUser: 'ExampleUser'
+		} );
+		wrapper = mount( SpecialBlock );
+		expect( wrapper.find( '.cdx-message__content' ).text() )
+			.toStrictEqual( 'ipb-needreblock:[ExampleUser]' );
+		expect( wrapper.find( 'button.cdx-button' ).text() ).toStrictEqual( 'ipb-change-block' );
 	} );
 } );
diff --git a/tests/jest/mediawiki.special.block/UserLookup.test.js b/tests/jest/mediawiki.special.block/UserLookup.test.js
new file mode 100644
index 00000000000..e85a1df0e42
--- /dev/null
+++ b/tests/jest/mediawiki.special.block/UserLookup.test.js
@@ -0,0 +1,31 @@
+'use strict';
+
+const { nextTick } = require( 'vue' );
+const { mount } = require( '@vue/test-utils' );
+const UserLookup = require( '../../../resources/src/mediawiki.special.block/components/UserLookup.vue' );
+
+describe( 'UserLookup', () => {
+	it( 'should update menu items based on the API response', async () => {
+		mw.Api.prototype.get = jest.fn().mockResolvedValue( {
+			query: {
+				allusers: [
+					{ name: 'UserLookup1' },
+					{ name: 'UserLookup2' }
+				]
+			}
+		} );
+		const wrapper = mount( UserLookup, {
+			props: { modelValue: 'UserLookup' }
+		} );
+		const input = wrapper.find( '.cdx-text-input__input' );
+		expect( input.element.value ).toBe( 'UserLookup' );
+		const listBox = wrapper.find( '.cdx-menu__listbox' );
+		// "No results"
+		expect( listBox.element.children ).toHaveLength( 1 );
+		await input.trigger( 'input' );
+		await nextTick();
+		expect( listBox.element.children ).toHaveLength( 2 );
+		expect( listBox.element.children[ 0 ].textContent ).toBe( 'UserLookup1' );
+		expect( listBox.element.children[ 1 ].textContent ).toBe( 'UserLookup2' );
+	} );
+} );
diff --git a/tests/phpunit/includes/specials/SpecialBlockTest.php b/tests/phpunit/includes/specials/SpecialBlockTest.php
index 563407aa4d0..d9bbc8f73c2 100644
--- a/tests/phpunit/includes/specials/SpecialBlockTest.php
+++ b/tests/phpunit/includes/specials/SpecialBlockTest.php
@@ -57,6 +57,7 @@ class SpecialBlockTest extends SpecialPageTestBase {
 		$this->overrideConfigValues( [
 			MainConfigNames::BlockAllowsUTEdit => true,
 			MainConfigNames::EnablePartialActionBlocks => true,
+			MainConfigNames::UseCodexSpecialBlock => false,
 		] );
 		$page = $this->newSpecialPage();
 		$wrappedPage = TestingAccessWrapper::newFromObject( $page );
@@ -72,11 +73,30 @@ class SpecialBlockTest extends SpecialPageTestBase {
 		$this->assertArrayHasKey( 'PreviousTarget', $fields );
 		$this->assertArrayHasKey( 'Confirm', $fields );
 		$this->assertArrayHasKey( 'EditingRestriction', $fields );
+		$this->assertArrayNotHasKey( 'options-messages', $fields['EditingRestriction'] );
+		$this->assertArrayNotHasKey( 'option-descriptions-messages', $fields['EditingRestriction'] );
 		$this->assertArrayHasKey( 'PageRestrictions', $fields );
 		$this->assertArrayHasKey( 'NamespaceRestrictions', $fields );
 		$this->assertArrayHasKey( 'ActionRestrictions', $fields );
 	}
 
+	/**
+	 * @covers ::getFormFields
+	 */
+	public function testGetFormFieldsCodex(): void {
+		$this->overrideConfigValues( [
+			MainConfigNames::BlockAllowsUTEdit => true,
+			MainConfigNames::EnablePartialActionBlocks => true,
+			MainConfigNames::UseCodexSpecialBlock => true,
+		] );
+		$page = $this->newSpecialPage();
+		$wrappedPage = TestingAccessWrapper::newFromObject( $page );
+		$fields = $wrappedPage->getFormFields();
+		$this->assertIsArray( $fields );
+		$this->assertArrayHasKey( 'options-messages', $fields[ 'EditingRestriction' ] );
+		$this->assertArrayHasKey( 'option-descriptions-messages', $fields[ 'EditingRestriction' ] );
+	}
+
 	/**
 	 * @covers ::getFormFields
 	 */