diff --git a/packages/forest_admin_agent/lib/forest_admin_agent/utils/action_result.rb b/packages/forest_admin_agent/lib/forest_admin_agent/utils/action_result.rb
index 053d0037c..a4dae3d74 100644
--- a/packages/forest_admin_agent/lib/forest_admin_agent/utils/action_result.rb
+++ b/packages/forest_admin_agent/lib/forest_admin_agent/utils/action_result.rb
@@ -27,9 +27,10 @@ def self.parse(result)
           }
         when 'File'
           keys = {
+            type: 'File',
             name: result[:name],
             mime_type: result[:mime_type],
-            stream: result[:content]
+            stream: result[:stream]
           }
         when 'Redirect'
           keys = {
diff --git a/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/action_result_spec.rb b/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/action_result_spec.rb
new file mode 100644
index 000000000..7f7339199
--- /dev/null
+++ b/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/action_result_spec.rb
@@ -0,0 +1,114 @@
+require 'spec_helper'
+
+module ForestAdminAgent
+  module Utils
+    describe ActionResult do
+      describe '.parse' do
+        context 'when the result type is Success' do
+          let(:result) do
+            {
+              type: 'Success',
+              message: 'Done',
+              invalidated: %w[books authors],
+              html: '<p>ok</p>',
+              response_headers: { 'x-foo' => 'bar' }
+            }
+          end
+
+          it 'maps Success keys and forwards response_headers' do
+            expect(described_class.parse(result)).to eq(
+              success: 'Done',
+              refresh: { relationships: %w[books authors] },
+              html: '<p>ok</p>',
+              headers: { 'x-foo' => 'bar' }
+            )
+          end
+        end
+
+        context 'when the result type is Error' do
+          let(:result) { { type: 'Error', message: 'Boom', html: nil } }
+
+          it 'maps Error keys with status 400' do
+            expect(described_class.parse(result)).to eq(
+              status: 400,
+              error: 'Boom',
+              html: nil,
+              headers: nil
+            )
+          end
+        end
+
+        context 'when the result type is Webhook' do
+          let(:result) do
+            {
+              type: 'Webhook',
+              body: { foo: 'bar' },
+              headers: { 'x-h' => '1' },
+              method: 'POST',
+              url: 'https://example.test/hook'
+            }
+          end
+
+          it 'maps Webhook keys' do
+            expect(described_class.parse(result)).to eq(
+              webhook: {
+                body: { foo: 'bar' },
+                headers: { 'x-h' => '1' },
+                method: 'POST',
+                url: 'https://example.test/hook'
+              },
+              headers: nil
+            )
+          end
+        end
+
+        context 'when the result type is File' do
+          let(:content) { 'binary-payload' }
+          let(:result) do
+            {
+              type: 'File',
+              name: 'report.pdf',
+              mime_type: 'application/pdf',
+              stream: content,
+              response_headers: { 'set-cookie' => 'token=xyz' }
+            }
+          end
+
+          it 'maps File keys including :type so the controller can detect a file response' do
+            parsed = described_class.parse(result)
+
+            expect(parsed[:type]).to eq('File')
+            expect(parsed[:name]).to eq('report.pdf')
+            expect(parsed[:mime_type]).to eq('application/pdf')
+            expect(parsed[:stream]).to eq(content)
+            expect(parsed[:headers]).to eq({ 'set-cookie' => 'token=xyz' })
+          end
+
+          it 'reads the payload from :stream (the key ResultBuilder.file writes)' do
+            parsed = described_class.parse(result)
+            expect(parsed[:stream]).to eq(content)
+          end
+        end
+
+        context 'when the result type is Redirect' do
+          let(:result) { { type: 'Redirect', path: '/anywhere' } }
+
+          it 'maps Redirect keys' do
+            expect(described_class.parse(result)).to eq(
+              redirect_to: '/anywhere',
+              headers: nil
+            )
+          end
+        end
+
+        context 'when the result type is unknown' do
+          let(:result) { { type: 'Mystery' } }
+
+          it 'returns only the merged response_headers' do
+            expect(described_class.parse(result)).to eq(headers: nil)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/packages/forest_admin_rails/app/controllers/forest_admin_rails/forest_controller.rb b/packages/forest_admin_rails/app/controllers/forest_admin_rails/forest_controller.rb
index 26682d75d..765e76aba 100644
--- a/packages/forest_admin_rails/app/controllers/forest_admin_rails/forest_controller.rb
+++ b/packages/forest_admin_rails/app/controllers/forest_admin_rails/forest_controller.rb
@@ -26,6 +26,7 @@ def forest_response(data = {})
         return handle_streaming_response(data) if data.dig(:content, :type) == 'Stream'
 
         if data.dig(:content, :type) == 'File'
+          response.headers['Access-Control-Expose-Headers'] = 'Content-Disposition'
           return send_data data[:content][:stream], filename: data[:content][:name], type: data[:content][:mime_type],
                                                     disposition: 'attachment'
         end
diff --git a/packages/forest_admin_rails/spec/controllers/forest_admin_rails/forest_controller_spec.rb b/packages/forest_admin_rails/spec/controllers/forest_admin_rails/forest_controller_spec.rb
index fdb2acb28..0be7ac4ec 100644
--- a/packages/forest_admin_rails/spec/controllers/forest_admin_rails/forest_controller_spec.rb
+++ b/packages/forest_admin_rails/spec/controllers/forest_admin_rails/forest_controller_spec.rb
@@ -281,5 +281,41 @@ module ForestAdminRails
         end
       end
     end
+
+    describe '#forest_response' do
+      context 'when the content is a File action result' do
+        let(:file_data) do
+          {
+            content: {
+              type: 'File',
+              name: 'report.pdf',
+              mime_type: 'application/pdf',
+              stream: 'binary-payload'
+            }
+          }
+        end
+
+        before do
+          allow(controller).to receive(:send_data)
+        end
+
+        it 'sends the file via send_data with the filename and mime type' do
+          controller.send(:forest_response, file_data)
+
+          expect(controller).to have_received(:send_data).with(
+            'binary-payload',
+            filename: 'report.pdf',
+            type: 'application/pdf',
+            disposition: 'attachment'
+          )
+        end
+
+        it 'exposes Content-Disposition via CORS so cross-origin clients can read it' do
+          controller.send(:forest_response, file_data)
+
+          expect(response_mock.headers['Access-Control-Expose-Headers']).to eq('Content-Disposition')
+        end
+      end
+    end
   end
 end