diff --git a/app/controllers/api/lessons_controller.rb b/app/controllers/api/lessons_controller.rb
index a1071b654..0c1385ccb 100644
--- a/app/controllers/api/lessons_controller.rb
+++ b/app/controllers/api/lessons_controller.rb
@@ -31,7 +31,9 @@ def show
     end
 
     def create
-      result = Lesson::Create.call(lesson_params: create_params)
+      authorize! :show, source_project if source_project
+
+      result = Lesson::Create.call(lesson_params: create_params, source_project:)
       if result.success?
         track_project_event('Project - Created', result[:lesson].project)
         @lesson_with_user = result[:lesson].with_user
@@ -85,7 +87,7 @@ def verify_school_class_belongs_to_school
     end
 
     def verify_can_create_scratch_projects
-      verify_lesson_scratch!(create_params)
+      verify_lesson_scratch!(create_params, source_project:)
     end
 
     def user_remixes(lessons)
@@ -124,5 +126,29 @@ def school_owner?
     def school
       @school ||= @lesson&.school || School.find_by(id: create_params[:school_id]) || SchoolClass.find_by(id: params[:school_class_id])&.school
     end
+
+    def source_project
+      return @source_project if defined?(@source_project)
+
+      @source_project = find_source_project!(source_project_identifier, create_params.dig(:project_attributes, :locale))
+    end
+
+    def source_project_identifier
+      params.dig(:lesson, :source_project_identifier)
+    end
+
+    def find_source_project!(identifier, locale)
+      return nil if identifier.blank?
+
+      project = ProjectLoader.new(identifier, [locale]).load
+      raise ParameterError, "source project '#{identifier}' not found" if project.nil?
+
+      # Only ExCS 'code editor' projects are remixed here; legacy scratch projects keep the stub path.
+      return nil unless project.scratch_project?
+
+      raise ParameterError, 'source project must be an Experience CS project' unless project.origin == Project::Origins::EXPERIENCE_CS
+
+      project
+    end
   end
 end
diff --git a/app/controllers/concerns/lesson_creation.rb b/app/controllers/concerns/lesson_creation.rb
index 80563dd1c..438f461fb 100644
--- a/app/controllers/concerns/lesson_creation.rb
+++ b/app/controllers/concerns/lesson_creation.rb
@@ -32,8 +32,8 @@ def verify_lesson_school_class!(lesson_params)
     raise ParameterError, 'school_class_id does not correspond to school_id'
   end
 
-  def verify_lesson_scratch!(lesson_params)
-    return unless scratch_project?(lesson_params)
+  def verify_lesson_scratch!(lesson_params, source_project: nil)
+    return unless scratch_project?(lesson_params) || source_project&.scratch_project?
 
     school = School.find_by(id: lesson_params[:school_id])
     return if school&.scratch_enabled?
diff --git a/lib/concepts/lesson/operations/create.rb b/lib/concepts/lesson/operations/create.rb
index 77ac1d55d..9c7e32ede 100644
--- a/lib/concepts/lesson/operations/create.rb
+++ b/lib/concepts/lesson/operations/create.rb
@@ -3,9 +3,10 @@
 class Lesson
   class Create
     class << self
-      def call(lesson_params:)
+      # When source_project is given, the lesson's project is built as a remix of it instead of a stub.
+      def call(lesson_params:, source_project: nil)
         response = OperationResponse.new
-        response[:lesson] = build_lesson(lesson_params)
+        response[:lesson] = build_lesson(lesson_params, source_project)
         response[:lesson].save!
         response
       rescue StandardError => e
@@ -21,14 +22,30 @@ def call(lesson_params:)
 
       private
 
-      def build_lesson(lesson_hash)
+      def build_lesson(lesson_hash, source_project)
         new_lesson = Lesson.new(lesson_hash.except(:project_attributes))
-        project_params = lesson_hash[:project_attributes].merge({ user_id: lesson_hash[:user_id],
-                                                                  school_id: lesson_hash[:school_id],
-                                                                  lesson_id: new_lesson.id })
-        new_lesson.project = Project.new(project_params)
+        project_params = (lesson_hash[:project_attributes] || {}).merge({ user_id: lesson_hash[:user_id],
+                                                                          school_id: lesson_hash[:school_id],
+                                                                          lesson_id: new_lesson.id })
+        new_lesson.project = source_project ? build_copy(source_project, project_params) : Project.new(project_params)
         new_lesson
       end
+
+      def build_copy(source_project, project_params)
+        Project::Copying.copy_project(source_project,
+                                      attributes: attributes_for_copy(source_project, project_params),
+                                      media: %i[images videos audio])
+      end
+
+      def attributes_for_copy(source_project, project_params)
+        {
+          locale: nil,
+          name: project_params[:name].presence || source_project.name,
+          user_id: project_params[:user_id],
+          school_id: project_params[:school_id],
+          lesson_id: project_params[:lesson_id]
+        }
+      end
     end
   end
 end
diff --git a/lib/concepts/lesson/operations/create_copy.rb b/lib/concepts/lesson/operations/create_copy.rb
index 72a8f0aad..866ccbff5 100644
--- a/lib/concepts/lesson/operations/create_copy.rb
+++ b/lib/concepts/lesson/operations/create_copy.rb
@@ -27,34 +27,11 @@ def build_copy(lesson, lesson_params)
         lesson_copy.assign_attributes(lesson_params)
 
         project_params = { name: lesson_copy.name, user_id: lesson_params[:user_id], lesson_id: lesson_copy.id }
-        lesson_copy.project = build_project_copy(lesson.project, project_params)
+        lesson_copy.project = Project::Copying.copy_project(lesson.project, attributes: project_params)
 
         lesson_copy
       end
 
-      def build_project_copy(project, project_params)
-        project_attributes = project.attributes.except('id', 'identifier', 'created_at', 'updated_at').merge(project_params)
-        project_copy = Project.new(project_attributes)
-
-        project.images.each do |image|
-          project_copy.images.attach(image.blob)
-        end
-
-        project.components.each do |component|
-          project_copy.components.build({ name: component.name, extension: component.extension, content: component.content })
-        end
-
-        copy_scratch_component(project, project_copy)
-
-        project_copy
-      end
-
-      def copy_scratch_component(project, project_copy)
-        return unless project.scratch_project? && project.scratch_component
-
-        project_copy.build_scratch_component(content: project.scratch_component.content.deep_dup)
-      end
-
       def copy_scratch_assets(project, project_copy)
         return unless project.scratch_project?
 
diff --git a/lib/concepts/project/copying.rb b/lib/concepts/project/copying.rb
new file mode 100644
index 000000000..408719cf5
--- /dev/null
+++ b/lib/concepts/project/copying.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+class Project
+  class Copying
+    class << self
+      def copy_project(source_project, attributes: {}, media: %i[images])
+        source_project.dup.tap do |project_copy|
+          project_copy.identifier = nil
+          project_copy.assign_attributes(attributes)
+
+          copy_components(source_project, project_copy)
+          copy_scratch_component(source_project, project_copy)
+          copy_media(source_project, project_copy, media)
+        end
+      end
+
+      def copy_media(source_project, project_copy, media)
+        media.each do |collection|
+          source_project.public_send(collection).each do |attachment|
+            project_copy.public_send(collection).attach(attachment.blob)
+          end
+        end
+      end
+
+      private
+
+      def copy_components(source_project, project_copy)
+        source_project.components.each do |component|
+          project_copy.components.build(component.attributes.slice('name', 'extension', 'content'))
+        end
+      end
+
+      def copy_scratch_component(source_project, project_copy)
+        return unless source_project.scratch_project? && source_project.scratch_component
+
+        project_copy.build_scratch_component(content: source_project.scratch_component.content.deep_dup)
+      end
+    end
+  end
+end
diff --git a/lib/concepts/project/operations/create_remix.rb b/lib/concepts/project/operations/create_remix.rb
index 81f70714b..a306576dd 100644
--- a/lib/concepts/project/operations/create_remix.rb
+++ b/lib/concepts/project/operations/create_remix.rb
@@ -35,17 +35,7 @@ def remix_project(response, params, user_id, original_project, remix_origin)
       def create_remix(original_project, params, user_id, remix_origin)
         remix = format_project(original_project, params, user_id, remix_origin)
 
-        original_project.images.each do |image|
-          remix.images.attach(image.blob)
-        end
-
-        original_project.videos.each do |video|
-          remix.videos.attach(video.blob)
-        end
-
-        original_project.audio.each do |audio_file|
-          remix.audio.attach(audio_file.blob)
-        end
+        Project::Copying.copy_media(original_project, remix, %i[images videos audio])
 
         params[:components].each do |x|
           remix.components.build(x.slice(:name, :extension, :content))
diff --git a/spec/concepts/lesson/create_spec.rb b/spec/concepts/lesson/create_spec.rb
index 253aff556..d8dc75470 100644
--- a/spec/concepts/lesson/create_spec.rb
+++ b/spec/concepts/lesson/create_spec.rb
@@ -159,4 +159,179 @@
       expect(Sentry).to have_received(:capture_exception).with(kind_of(StandardError))
     end
   end
+
+  # Lesson::Create builds the lesson's project as a remix of
+  # an Experience CS project instead of a stub.
+  context 'when a source project is given' do
+    let(:english_content) { { 'targets' => [{ 'name' => 'Stage' }], 'monitors' => [], 'extensions' => [], 'meta' => {} } }
+    let(:french_content) { { 'targets' => [{ 'name' => 'Scène' }], 'monitors' => [], 'extensions' => [], 'meta' => {} } }
+
+    let(:source_project_en) do
+      create(:scratch_project, identifier: 'my-digital-canvas', locale: 'en', user_id: nil,
+                               name: 'My digital canvas', origin: Project::Origins::EXPERIENCE_CS,
+                               instructions: 'English instructions')
+        .tap { |project| project.scratch_component.update!(content: english_content) }
+    end
+
+    let(:source_project_fr) do
+      create(:scratch_project, identifier: source_project_en.identifier, locale: 'fr-FR', user_id: nil,
+                               name: 'Ma toile numérique', origin: Project::Origins::EXPERIENCE_CS,
+                               instructions: 'Instructions en français')
+        .tap { |project| project.scratch_component.update!(content: french_content) }
+    end
+
+    # Eager, so the count matchers below only see what the operation itself creates.
+    let!(:source_project) { source_project_fr }
+
+    let(:lesson_params) do
+      {
+        name: 'Test Lesson',
+        user_id: teacher.id,
+        school_id: school.id,
+        project_attributes: { name: 'My digital canvas' }
+      }
+    end
+
+    let(:response) { described_class.call(lesson_params:, source_project:) }
+
+    let(:lesson_project) { response[:lesson].project }
+
+    before do
+      allow(User).to receive(:from_userinfo).with(ids: teacher.id).and_return([teacher])
+    end
+
+    it 'returns a successful operation response' do
+      expect(response.success?).to be(true)
+    end
+
+    it 'creates a lesson' do
+      expect { described_class.call(lesson_params:, source_project:) }.to change(Lesson, :count).by(1)
+    end
+
+    it 'creates one project for the lesson' do
+      expect { response }.to change(Project, :count).by(1)
+    end
+
+    it 'generates a new identifier rather than reusing the source identifier' do
+      expect(lesson_project.identifier).not_to eq(source_project.identifier)
+    end
+
+    it 'copies the scratch component content from the source project' do
+      expect(lesson_project.scratch_component.content).to eq(french_content)
+    end
+
+    it 'copies the project_type from the source project' do
+      expect(lesson_project.project_type).to eq(Project::Types::CODE_EDITOR_SCRATCH)
+    end
+
+    it 'copies the instructions from the source project' do
+      expect(lesson_project.instructions).to eq('Instructions en français')
+    end
+
+    # remix of the requested locale row, but locale is null
+    it 'copies content from the requested locale, not the en locale' do
+      expect(lesson_project.scratch_component.content).not_to eq(english_content)
+    end
+
+    it 'does not copy the instructions from the en locale' do
+      expect(lesson_project.instructions).not_to eq(source_project_en.instructions)
+    end
+
+    it 'sets the lesson project locale to nil' do
+      expect(lesson_project.locale).to be_nil
+    end
+
+    it 'inherits origin from the source project' do
+      expect(lesson_project.origin).to eq(source_project.origin)
+    end
+
+    it 'assigns the lesson id to the project' do
+      expect(lesson_project.lesson_id).to eq(response[:lesson].id)
+    end
+
+    it 'assigns the teacher user id to the project' do
+      expect(lesson_project.user_id).to eq(teacher.id)
+    end
+
+    it 'assigns the school id to the project' do
+      expect(lesson_project.school_id).to eq(school.id)
+    end
+
+    it 'builds a school project for the school' do
+      expect(lesson_project.school_project.school_id).to eq(school.id)
+    end
+
+    it 'uses the name from project_attributes when one is given' do
+      expect(lesson_project.name).to eq('My digital canvas')
+    end
+
+    it 'does not change the source project' do
+      expect { response }.not_to(change { source_project.reload.attributes })
+    end
+
+    it 'does not copy scratch assets (global assets resolve through the lineage)' do
+      create(:scratch_asset, :with_file, project: nil, uploaded_user_id: nil)
+      expect { response }.not_to change(ScratchAsset, :count)
+    end
+
+    context 'when the source project has no origin' do
+      let(:source_project) do
+        create(:scratch_project, identifier: 'not-backfilled-yet', locale: 'en', user_id: nil, origin: nil)
+      end
+
+      it 'leaves the origin nil on the lesson project' do
+        expect(lesson_project.origin).to be_nil
+      end
+    end
+
+    context 'when project_attributes has no name' do
+      let(:lesson_params) do
+        {
+          name: 'Test Lesson',
+          user_id: teacher.id,
+          school_id: school.id,
+          project_attributes: {}
+        }
+      end
+
+      it 'falls back to the source project name' do
+        expect(lesson_project.name).to eq('Ma toile numérique')
+      end
+    end
+
+    context 'when the lesson project is not a school project' do
+      let(:lesson_params) do
+        {
+          name: 'Test Lesson',
+          user_id: teacher.id,
+          project_attributes: { name: 'My digital canvas' }
+        }
+      end
+
+      before do
+        allow(Sentry).to receive(:capture_exception)
+      end
+
+      it 'returns a failed operation response' do
+        expect(response.failure?).to be(true)
+      end
+
+      it 'returns the error message in the operation response' do
+        expect(response[:error]).to include('Error creating lesson')
+      end
+
+      it 'does not create a lesson' do
+        expect { response }.not_to change(Lesson, :count)
+      end
+
+      it 'does not create a project' do
+        expect { response }.not_to change(Project, :count)
+      end
+
+      it 'sent the exception to Sentry' do
+        response
+        expect(Sentry).to have_received(:capture_exception).with(kind_of(StandardError))
+      end
+    end
+  end
 end
diff --git a/spec/features/lesson/creating_a_lesson_spec.rb b/spec/features/lesson/creating_a_lesson_spec.rb
index 93827bd78..4757f1d8a 100644
--- a/spec/features/lesson/creating_a_lesson_spec.rb
+++ b/spec/features/lesson/creating_a_lesson_spec.rb
@@ -246,4 +246,98 @@
       expect(response).to have_http_status(:forbidden)
     end
   end
+
+  # #create resolves `lesson[:source_project_identifier]` through
+  # ProjectLoader, authorizes it, and hands the Project to Lesson::Create
+  # so the lesson project is built as a remix instead of a stub.
+  describe 'creating a lesson from a source project' do
+    let(:source_content) { { 'targets' => [{ 'name' => 'Stage' }], 'monitors' => [], 'extensions' => [], 'meta' => {} } }
+
+    let!(:source_project) do
+      create(:scratch_project, identifier: 'my-digital-canvas', locale: 'en', user_id: nil, school_id: nil,
+                               name: 'My digital canvas', origin: Project::Origins::EXPERIENCE_CS,
+                               instructions: 'English instructions')
+        .tap { |project| project.scratch_component.update!(content: source_content) }
+    end
+
+    let(:params) do
+      {
+        lesson: {
+          name: 'Test Lesson',
+          school_id: school.id,
+          source_project_identifier: source_project.identifier,
+          project_attributes: {
+            name: 'My digital canvas',
+            locale: 'en'
+          }
+        }
+      }
+    end
+
+    let(:lesson_project) { Lesson.find(JSON.parse(response.body, symbolize_names: true)[:id]).project }
+
+    context 'when the source project is a shared Experience CS project' do
+      before do
+        school.update!(scratch_enabled: true)
+        post('/api/lessons', headers:, params:)
+      end
+
+      it 'responds 201 Created' do
+        expect(response).to have_http_status(:created)
+      end
+
+      it 'responds with the lesson JSON' do
+        data = JSON.parse(response.body, symbolize_names: true)
+
+        expect(data[:name]).to eq('Test Lesson')
+      end
+
+      it 'copies the scratch component content from the source project' do
+        expect(lesson_project.scratch_component.content).to eq(source_content)
+      end
+
+      it 'gives the lesson project a new identifier' do
+        expect(lesson_project.identifier).not_to eq(source_project.identifier)
+      end
+
+      it 'sets the lesson project locale to nil' do
+        expect(lesson_project.locale).to be_nil
+      end
+
+      it 'inherits project_type from the source project' do
+        expect(lesson_project.project_type).to eq(source_project.project_type)
+      end
+
+      it 'inherits origin from the source project' do
+        expect(lesson_project.origin).to eq(source_project.origin)
+      end
+    end
+
+    context 'when the school does not have Scratch enabled' do
+      # The request carries no project_attributes[:project_type], so the scratch gate has to
+      # look at the source project to see that a Scratch project is about to be created.
+      let(:params) do
+        {
+          lesson: {
+            name: 'Test Lesson',
+            school_id: school.id,
+            source_project_identifier: source_project.identifier,
+            project_attributes: {
+              name: 'My digital canvas',
+              locale: 'en'
+            }
+          }
+        }
+      end
+
+      before do
+        school.update!(scratch_enabled: false)
+      end
+
+      it 'responds 403 Forbidden when only source_project_identifier points at a scratch project' do
+        post('/api/lessons', headers:, params:)
+        expect(response).to have_http_status(:forbidden)
+      end
+    end
+  end
 end