diff --git a/app/assets/javascripts/merge_request_tabs.js b/app/assets/javascripts/merge_request_tabs.js
index 705beb92dad35acc6995a3fe5f76c3d2f2533f28..4312c8f8eb2ae7cc3dfad99a9ceb397abdfe8811 100644
--- a/app/assets/javascripts/merge_request_tabs.js
+++ b/app/assets/javascripts/merge_request_tabs.js
@@ -5,7 +5,7 @@ import VueApollo from 'vue-apollo';
 import createDefaultClient from '~/lib/graphql';
 import { createAlert } from '~/alert';
 import { getCookie, isMetaClick, parseBoolean, scrollToElement } from '~/lib/utils/common_utils';
-import { parseUrlPathname, visitUrl } from '~/lib/utils/url_utility';
+import { parseUrlPathname, visitUrl, getParameterByName } from '~/lib/utils/url_utility';
 import createEventHub from '~/helpers/event_hub_factory';
 import { renderGFM } from '~/behaviors/markdown/render_gfm';
 import BlobForkSuggestion from './blob/blob_fork_suggestion';
@@ -221,6 +221,8 @@ export default class MergeRequestTabs {
     this.diffsClass = null;
     this.commitsLoaded = false;
     this.isFixedLayoutPreferred = this.contentWrapper.classList.contains('container-limited');
+    this.isRapidDiffs = getParameterByName('rapid_diffs') === 'true';
+    this.rapidDiffsApp = null;
     this.eventHub = createEventHub();
     this.loadedPages = { [action]: true };
 
@@ -357,7 +359,7 @@ export default class MergeRequestTabs {
             in practice, this only occurs when comparing commits in
             the new merge request form page.
           */
-          this.loadDiff({ endpoint: href, strip: true });
+          this.startDiffs({ endpoint: href, strip: true });
         }
         // this.hideSidebar();
         this.expandViewContainer();
@@ -528,7 +530,22 @@ export default class MergeRequestTabs {
     this.mergeRequestPipelinesTable = mountPipelines();
   }
 
-  // load the diff tab content from the backend
+  // Initialize the Changes tab
+  async startDiffs(options = {}) {
+    if (this.isRapidDiffs) {
+      if (!this.rapidDiffsApp) {
+        const { createRapidDiffsApp } = await import('~/rapid_diffs/app');
+
+        this.rapidDiffsApp = createRapidDiffsApp();
+
+        this.rapidDiffsApp.reloadDiffs();
+        this.rapidDiffsApp.init();
+      }
+    } else {
+      this.loadDiff(options);
+    }
+  }
+  // load the legacy diff tab content from the backend
   loadDiff({ endpoint, strip = true }) {
     if (this.diffsLoaded) {
       document.dispatchEvent(new CustomEvent('scroll'));
diff --git a/app/assets/javascripts/pages/projects/merge_requests/creations/rapid_diffs/index.js b/app/assets/javascripts/pages/projects/merge_requests/creations/rapid_diffs/index.js
new file mode 100644
index 0000000000000000000000000000000000000000..5b2f57449bb2dc2327c927b42f6377e89db4f6d2
--- /dev/null
+++ b/app/assets/javascripts/pages/projects/merge_requests/creations/rapid_diffs/index.js
@@ -0,0 +1,12 @@
+import { initMarkdownEditor } from 'ee_else_ce/pages/projects/merge_requests/init_markdown_editor';
+import initPipelines from '~/commit/pipelines/pipelines_bundle';
+import MergeRequest from '~/merge_request';
+
+const mrNewSubmitNode = document.querySelector('.js-merge-request-new-submit');
+
+// eslint-disable-next-line no-new
+new MergeRequest({
+  action: mrNewSubmitNode.dataset.mrSubmitAction,
+});
+initPipelines();
+initMarkdownEditor();
diff --git a/app/assets/javascripts/rapid_diffs/app/index.js b/app/assets/javascripts/rapid_diffs/app/index.js
index 5a896ef7bc650530fb0561664be9864a780e8095..161fc98d5f68ec0fdcfee54654580de874dedb2e 100644
--- a/app/assets/javascripts/rapid_diffs/app/index.js
+++ b/app/assets/javascripts/rapid_diffs/app/index.js
@@ -44,6 +44,13 @@ class RapidDiffsFacade {
     return useDiffsList(pinia).streamRemainingDiffs(streamContainer.dataset.diffsStreamUrl);
   }
 
+  // eslint-disable-next-line class-methods-use-this
+  reloadDiffs() {
+    const { reloadStreamUrl } = document.querySelector('[data-rapid-diffs]').dataset;
+
+    return useDiffsList(pinia).reloadDiffs(reloadStreamUrl);
+  }
+
   #registerCustomElements() {
     customElements.define('diff-file', this.DiffFileImplementation);
     customElements.define('diff-file-mounted', DiffFileMounted);
diff --git a/app/assets/stylesheets/page_bundles/merge_request_rapid_diffs.scss b/app/assets/stylesheets/page_bundles/merge_request_rapid_diffs.scss
index 65707eeb4a9b9cf0010ea1553deb672b6e760e3a..f961b2ec4ed625047418a89c75be1e94b7edbcf7 100644
--- a/app/assets/stylesheets/page_bundles/merge_request_rapid_diffs.scss
+++ b/app/assets/stylesheets/page_bundles/merge_request_rapid_diffs.scss
@@ -4,3 +4,15 @@
 .rd-app {
   --rd-diff-file-sticky-top-padding: calc(#{$calc-application-header-height} + #{$mr-sticky-header-height});
 }
+
+.js-merge-request-new-submit .merge-request-tabs-holder{
+  /*
+    If the settings menu displays upward on the create new/submit page,
+      it needs to be in front of the tab bar.
+    It's not clear that the previously-set z-index (250) has any effect
+      as of today (2025-03-12), but for now it feels safest to isolate
+      this change to just Rapid Diffs.
+  */
+  z-index: unset;
+}
+
diff --git a/app/controllers/projects/merge_requests/creations_controller.rb b/app/controllers/projects/merge_requests/creations_controller.rb
index e8e409f8917eee1081fc72b3ad6f444c5f2caa8e..8ee9a7e6f03bcaa8b5ae605a9c366bec0f1cf3e7 100644
--- a/app/controllers/projects/merge_requests/creations_controller.rb
+++ b/app/controllers/projects/merge_requests/creations_controller.rb
@@ -9,7 +9,7 @@ class Projects::MergeRequests::CreationsController < Projects::MergeRequests::Ap
 
   skip_before_action :merge_request
   before_action :authorize_create_merge_request_from!
-  before_action :apply_diff_view_cookie!, only: [:diffs, :diff_for_path]
+  before_action :apply_diff_view_cookie!, only: [:diffs, :diff_for_path, :rapid_diffs]
   before_action :build_merge_request, except: [:create]
 
   urgency :low, [
@@ -17,6 +17,7 @@ class Projects::MergeRequests::CreationsController < Projects::MergeRequests::Ap
     :create,
     :pipelines,
     :diffs,
+    :rapid_diffs,
     :branch_from,
     :branch_to
   ]
@@ -61,6 +62,14 @@ def pipelines
     }
   end
 
+  def rapid_diffs
+    return render_404 unless ::Feature.enabled?(:rapid_diffs, current_user, type: :wip)
+
+    @show_whitespace_default = current_user.nil? || current_user.show_whitespace_in_diffs
+
+    define_new_vars
+  end
+
   def diffs
     @diffs = @merge_request.diffs(diff_options) if @merge_request.can_be_created
 
diff --git a/app/views/projects/merge_requests/creations/_new_submit.html.haml b/app/views/projects/merge_requests/creations/_new_submit.html.haml
index d0e44258987590d0c8962058b9f9bdc3c32512fa..40338fec6901796f4c7a6fb9bd41c297744c40da 100644
--- a/app/views/projects/merge_requests/creations/_new_submit.html.haml
+++ b/app/views/projects/merge_requests/creations/_new_submit.html.haml
@@ -57,6 +57,7 @@
         = render "projects/merge_requests/commits"
       #diffs.diffs.tab-pane{ class: "!gl-m-0" }
         -# This tab is always loaded via AJAX
+        = yield
       - if @pipelines.any?
         #pipelines.pipelines.tab-pane
           = render 'projects/merge_requests/pipelines', endpoint: url_for(safe_params.merge(action: 'pipelines', format: :json)), disable_initialization: true
diff --git a/app/views/projects/merge_requests/creations/_page.html.haml b/app/views/projects/merge_requests/creations/_page.html.haml
new file mode 100644
index 0000000000000000000000000000000000000000..3754eecda67c1752217ec7c5a9a405410c29d0fe
--- /dev/null
+++ b/app/views/projects/merge_requests/creations/_page.html.haml
@@ -0,0 +1,18 @@
+- add_to_breadcrumbs _("Merge requests"), project_merge_requests_path(@project)
+- breadcrumb_title _("New merge request")
+- page_title _("New merge request")
+- add_page_specific_style 'page_bundles/pipelines'
+- add_page_specific_style 'page_bundles/ci_status'
+- add_page_specific_style 'page_bundles/merge_request'
+
+- conflicting_mr = @merge_request.existing_mrs_targeting_same_branch.first
+
+- if @merge_request.can_be_created && !params[:change_branches] && !conflicting_mr
+  = render 'new_submit' do
+    = yield
+- else
+  - if conflicting_mr
+    - link_to_mr = link_to(conflicting_mr.to_reference, project_merge_request_path(conflicting_mr.target_project, conflicting_mr))
+    - flash.now[:alert] = safe_format(s_("These branches already have an open merge request: %{link_to_mr}. Select a different source or target branch."), link_to_mr: link_to_mr)
+
+  = render 'new_compare'
diff --git a/app/views/projects/merge_requests/creations/new.html.haml b/app/views/projects/merge_requests/creations/new.html.haml
index facb6727946e08403a3ebb7349cb08f48724499c..b810c8659bdbab683239a70dbba513d11005774a 100644
--- a/app/views/projects/merge_requests/creations/new.html.haml
+++ b/app/views/projects/merge_requests/creations/new.html.haml
@@ -1,17 +1 @@
-- add_to_breadcrumbs _("Merge requests"), project_merge_requests_path(@project)
-- breadcrumb_title _("New merge request")
-- page_title _("New merge request")
-- add_page_specific_style 'page_bundles/pipelines'
-- add_page_specific_style 'page_bundles/ci_status'
-- add_page_specific_style 'page_bundles/merge_request'
-
-- conflicting_mr = @merge_request.existing_mrs_targeting_same_branch.first
-
-- if @merge_request.can_be_created && !params[:change_branches] && !conflicting_mr
-  = render 'new_submit'
-- else
-  - if conflicting_mr
-    - link_to_mr = link_to(conflicting_mr.to_reference, project_merge_request_path(conflicting_mr.target_project, conflicting_mr))
-    - flash.now[:alert] = safe_format(s_("These branches already have an open merge request: %{link_to_mr}. Select a different source or target branch."), link_to_mr: link_to_mr)
-
-  = render 'new_compare'
+= render "page"
diff --git a/app/views/projects/merge_requests/creations/rapid_diffs.html.haml b/app/views/projects/merge_requests/creations/rapid_diffs.html.haml
new file mode 100644
index 0000000000000000000000000000000000000000..21c3b1feb933d3c5b94c0b23e013d2272984a87c
--- /dev/null
+++ b/app/views/projects/merge_requests/creations/rapid_diffs.html.haml
@@ -0,0 +1,5 @@
+- add_page_specific_style 'page_bundles/merge_request_rapid_diffs'
+
+= render "page" do
+  - args = { diffs_slice: nil, reload_stream_url: project_new_merge_request_diffs_stream_path(@project, merge_request: { source_branch: @merge_request.source_branch, target_branch: @merge_request.target_branch }), stream_url: project_new_merge_request_diffs_stream_path(@project, merge_request: { source_branch: @merge_request.source_branch, target_branch: @merge_request.target_branch }), show_whitespace: @show_whitespace_default, diff_view: diff_view, update_user_endpoint: expose_path(api_v4_user_preferences_path), metadata_endpoint: nil, preload: false }
+  = render ::RapidDiffs::AppComponent.new(**args)
diff --git a/config/routes/merge_requests.rb b/config/routes/merge_requests.rb
index ee4e2e5d529e274b5ad34a3353c2b2cbbed1fa13..7b28a748f3598e6ef9006c8f50d8eabf4d314d99 100644
--- a/config/routes/merge_requests.rb
+++ b/config/routes/merge_requests.rb
@@ -79,6 +79,8 @@
   post '', action: :create, as: nil
 
   scope path: 'new', as: :new_merge_request do
+    get '', action: :new, to: 'merge_requests/creations#rapid_diffs', defaults: { tab: 'commits' },
+      constraints: ->(params) { params[:rapid_diffs] == 'true' }
     get '', action: :new
 
     scope constraints: ->(req) { req.format == :json }, as: :json do
@@ -88,7 +90,11 @@
     end
 
     scope action: :new do
+      get :diffs, to: 'merge_requests/creations#rapid_diffs', defaults: { tab: 'diffs' },
+        constraints: ->(params) { params[:rapid_diffs] == 'true' }
       get :diffs, defaults: { tab: 'diffs' }
+      get :pipelines, to: 'merge_requests/creations#rapid_diffs', defaults: { tab: 'pipelines' },
+        constraints: ->(params) { params[:rapid_diffs] == 'true' }
       get :pipelines, defaults: { tab: 'pipelines' }
     end
 
diff --git a/spec/frontend/merge_request_tabs_spec.js b/spec/frontend/merge_request_tabs_spec.js
index 97c51f7a21b396feb7d80ee2ee69a7be1a1e3331..e0ce216f0d87881963bb838101e7ac7048952545 100644
--- a/spec/frontend/merge_request_tabs_spec.js
+++ b/spec/frontend/merge_request_tabs_spec.js
@@ -4,6 +4,8 @@ import htmlMergeRequestsWithTaskList from 'test_fixtures/merge_requests/merge_re
 import { setHTMLFixture, resetHTMLFixture } from 'helpers/fixtures';
 import initMrPage from 'helpers/init_vue_mr_page_helper';
 import { stubPerformanceWebAPI } from 'helpers/performance';
+import setWindowLocation from 'helpers/set_window_location_helper';
+import waitForPromises from 'helpers/wait_for_promises';
 import axios from '~/lib/utils/axios_utils';
 import MergeRequestTabs, { getActionFromHref } from '~/merge_request_tabs';
 import Diff from '~/diff';
@@ -14,6 +16,13 @@ jest.mock('~/lib/utils/webpack', () => ({
   resetServiceWorkersPublicPath: jest.fn(),
 }));
 
+const mockCreateRapidDiffsApp = jest
+  .fn()
+  .mockReturnValue({ reloadDiffs: jest.fn(), init: jest.fn() });
+jest.mock('~/rapid_diffs/app', () => ({
+  createRapidDiffsApp: mockCreateRapidDiffsApp,
+}));
+
 jest.mock('~/lib/utils/url_utility', () => ({
   ...jest.requireActual('~/lib/utils/url_utility'),
   visitUrl: jest.fn(),
@@ -50,6 +59,15 @@ describe('MergeRequestTabs', () => {
     document.body.innerHTML = '';
   });
 
+  describe('constructor', () => {
+    it('infers "Rapid Diffs" mode from the URL parameter', () => {
+      setWindowLocation('https://example.com?rapid_diffs=true');
+      const tabs = new MergeRequestTabs();
+
+      expect(tabs.isRapidDiffs).toBe(true);
+    });
+  });
+
   describe('clickTab', () => {
     let params;
 
@@ -429,6 +447,45 @@ describe('MergeRequestTabs', () => {
         expect(window.scrollTo).not.toHaveBeenCalled();
       });
     });
+
+    describe('switching to the diffs tab', () => {
+      beforeEach(() => {
+        setWindowLocation('https://example.com');
+        mockCreateRapidDiffsApp.mockClear();
+      });
+
+      it.each`
+        rdEnabled | rdExists | isConstructed
+        ${true}   | ${false} | ${true}
+        ${true}   | ${true}  | ${false}
+        ${false}  | ${false} | ${false}
+      `(
+        'creates the Rapid Diffs app only when on the diffs page that does not already have the app initialized ($rdExists), and where the feature is enabled in the search parameters ($rdEnabled)',
+        async ({ rdEnabled, rdExists, isConstructed }) => {
+          if (rdEnabled) {
+            setWindowLocation('https://example.com?rapid_diffs=true');
+          }
+
+          testContext.class = new MergeRequestTabs({ stubLocation });
+
+          if (rdExists) {
+            testContext.class.rapidDiffsApp = 'non-falsey';
+          }
+
+          testContext.class.tabShown('diffs', 'not-a-vue-page');
+
+          await waitForPromises();
+
+          if (isConstructed) {
+            expect(mockCreateRapidDiffsApp).toHaveBeenCalledTimes(1);
+            expect(testContext.class.rapidDiffsApp).toEqual(expect.any(Object));
+          } else {
+            expect(mockCreateRapidDiffsApp).not.toHaveBeenCalled();
+            expect(testContext.class.rapidDiffsApp).toBe(rdExists ? 'non-falsey' : null);
+          }
+        },
+      );
+    });
   });
 
   describe('tabs <-> diff interactions', () => {
diff --git a/spec/frontend/rapid_diffs/app/app_spec.js b/spec/frontend/rapid_diffs/app/app_spec.js
index 75b65fe2a68c556d9dabb395ce947023ebde6aed..5109e2ada8fe581120eacb05339924dbabb26bc1 100644
--- a/spec/frontend/rapid_diffs/app/app_spec.js
+++ b/spec/frontend/rapid_diffs/app/app_spec.js
@@ -60,4 +60,10 @@ describe('Rapid Diffs App', () => {
     app.streamRemainingDiffs();
     expect(useDiffsList().streamRemainingDiffs).toHaveBeenCalledWith('/stream');
   });
+
+  it('reloads diff files', () => {
+    createApp();
+    app.reloadDiffs();
+    expect(useDiffsList().reloadDiffs).toHaveBeenCalledWith('/reload');
+  });
 });
diff --git a/spec/requests/projects/merge_requests/creations_controller_spec.rb b/spec/requests/projects/merge_requests/creations_controller_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0aa9e745ccb282b800fa806df1d0d69ff40318df
--- /dev/null
+++ b/spec/requests/projects/merge_requests/creations_controller_spec.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Merge Request Creation', feature_category: :code_review_workflow do
+  let_it_be(:project) { create(:project, :public, :repository) }
+  let_it_be(:user) { create(:user, maintainer_of: project) }
+  let_it_be(:source_branch) { 'fix' }
+  let_it_be(:target_branch) { 'master' }
+
+  before do
+    sign_in(user)
+  end
+
+  describe 'GET rapid_diffs' do
+    def get_diffs(**extra_params)
+      params = {
+        namespace_id: project.namespace,
+        project_id: project,
+        merge_request: {
+          source_branch: source_branch,
+          target_branch: target_branch
+        }
+      }
+
+      get namespace_project_new_merge_request_diffs_path(params.merge(extra_params))
+    end
+
+    context 'when the feature flag rapid_diffs is disabled' do
+      before do
+        stub_feature_flags(rapid_diffs: false)
+      end
+
+      it 'returns 404' do
+        get_diffs(rapid_diffs: 'true')
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+
+    it 'does not use rapid diffs action when rapid_diffs flag is false' do
+      get_diffs(rapid_diffs: 'false')
+
+      expect(response).to have_gitlab_http_status(:ok)
+      expect(response.body).to include('data-page="projects:merge_requests:creations:new"')
+    end
+
+    it 'uses rapid diffs action when rapid_diffs flag is true' do
+      get_diffs(rapid_diffs: 'true')
+
+      expect(response).to have_gitlab_http_status(:ok)
+      expect(response.body).to include('data-page="projects:merge_requests:creations:rapid_diffs"')
+    end
+
+    it 'sets flash alert when there is an existing MR targeting same branch' do
+      create(:merge_request, source_project: project, source_branch: source_branch, target_branch: target_branch)
+      get_diffs(rapid_diffs: 'true')
+
+      expect(flash[:alert]).to be_present
+    end
+
+    it 'assigns show_whitespace_default' do
+      get_diffs(rapid_diffs: 'true')
+
+      expect(assigns(:show_whitespace_default)).to be(true)
+    end
+  end
+end