diff --git a/.changeset/four-apricots-relate.md b/.changeset/four-apricots-relate.md
new file mode 100644
index 0000000000..ac75e6c5b1
--- /dev/null
+++ b/.changeset/four-apricots-relate.md
@@ -0,0 +1,5 @@
+---
+'@openproject/primer-view-components': patch
+---
+
+Add I18n locale strings for demo app (en only)
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/aria-snapshot--after-interaction.yml b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/aria-snapshot--after-interaction.yml
index fb45feb90d..57a8b347d0 100644
--- a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/aria-snapshot--after-interaction.yml
+++ b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/aria-snapshot--after-interaction.yml
@@ -4,5 +4,5 @@
   - button "Close"
   - heading "Delete this item?" [level=2]
   - paragraph: Do you want to continue?
-  - 'button "Translation missing: en.button_cancel"'
-  - 'button "Translation missing: en.button_delete"'
\ No newline at end of file
+  - button "Cancel"
+  - button "Delete"
\ No newline at end of file
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark.png
index c63d5915b8..244aaa4af9 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_colorblind.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_colorblind.png
index 99010f69be..a732e5e930 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_colorblind.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_colorblind.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_dimmed.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_dimmed.png
index febb853e33..a449bff3f5 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_dimmed.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_dimmed.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_high_contrast.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_high_contrast.png
index 30546be4e3..225f63a124 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_high_contrast.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/dark_high_contrast.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light.png
index 36a31323fd..cd74f7c096 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_colorblind.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_colorblind.png
index 2eb5e55619..16d1a098ad 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_colorblind.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_colorblind.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_high_contrast.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_high_contrast.png
index b06c5aefcd..f4abf975b1 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_high_contrast.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/default/light_high_contrast.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/aria-snapshot--after-interaction.yml b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/aria-snapshot--after-interaction.yml
index cb55869a97..44e48edb90 100644
--- a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/aria-snapshot--after-interaction.yml
+++ b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/aria-snapshot--after-interaction.yml
@@ -6,5 +6,5 @@
   - paragraph: This action is not reversible. Please proceed with caution.
   - checkbox "I understand that this deletion cannot be reversed": "1"
   - text: I understand that this deletion cannot be reversed
-  - 'button "Translation missing: en.button_cancel"'
-  - 'button "Translation missing: en.button_delete_permanently" [disabled]'
\ No newline at end of file
+  - button "Cancel"
+  - button "Delete permanently" [disabled]
\ No newline at end of file
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark.png
index 90f1b9eb4a..265a28286c 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_colorblind.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_colorblind.png
index d4fd6b8e81..8d16981bc2 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_colorblind.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_colorblind.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_dimmed.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_dimmed.png
index b1eee96e61..ffe8455b99 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_dimmed.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_dimmed.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_high_contrast.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_high_contrast.png
index 9570987ad1..d390175965 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_high_contrast.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/dark_high_contrast.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light.png
index 70dd1b9e68..9cdcfaa28f 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_colorblind.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_colorblind.png
index 4bd0ad55e8..999c6eb661 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_colorblind.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_colorblind.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_high_contrast.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_high_contrast.png
index 56d4ea1b22..50ee9c83a9 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_high_contrast.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/danger_dialog/with_confirmation_check_box/light_high_contrast.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/aria-snapshot--after-interaction.yml b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/aria-snapshot--after-interaction.yml
index d04c2ed339..c8092f7de3 100644
--- a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/aria-snapshot--after-interaction.yml
+++ b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/aria-snapshot--after-interaction.yml
@@ -4,4 +4,4 @@
   - button "Close"
   - heading "Success" [level=2]
   - paragraph: Great! Everything worked well.
-  - 'button "Translation missing: en.button_close"'
\ No newline at end of file
+  - button "Close"
\ No newline at end of file
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark.png
index a10643546e..586b9b3e8d 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_colorblind.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_colorblind.png
index 43b7ec7756..f5e80fe272 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_colorblind.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_colorblind.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_dimmed.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_dimmed.png
index a2811342e3..007c098405 100644
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diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_high_contrast.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/dark_high_contrast.png
index a53348dd57..eefb500037 100644
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diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light.png
index 21d8ff21a4..88262f6580 100644
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diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_colorblind.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_colorblind.png
index e533238d9e..d5c7094c30 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_colorblind.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_colorblind.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_high_contrast.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_high_contrast.png
index cac62c617b..cf5657a2b6 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_high_contrast.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/feedback_dialog/default/light_high_contrast.png differ
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/aria-snapshot.yml b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/aria-snapshot.yml
index cf0e0cc41b..287f8d2bf7 100644
--- a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/aria-snapshot.yml
+++ b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/aria-snapshot.yml
@@ -1 +1 @@
-- 'button "Translation missing: en.label_zen_mode"'
\ No newline at end of file
+- button "Zen mode"
\ No newline at end of file
diff --git a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/focused.png b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/focused.png
index a481d4b485..78bd57dc27 100644
Binary files a/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/focused.png and b/.playwright/screenshots/snapshots.test.ts-snapshots/primer/open_project/zen_mode_button/default/focused.png differ
diff --git a/demo/config/locales/en.yml b/demo/config/locales/en.yml
new file mode 100644
index 0000000000..18289dbc39
--- /dev/null
+++ b/demo/config/locales/en.yml
@@ -0,0 +1,11 @@
+en:
+  button_cancel: "Cancel"
+  button_close: "Close"
+  button_delete: "Delete"
+  button_delete_permanently: "Delete permanently"
+  button_filter: "Filter"
+  button_save: "Save"
+  label_more: "More"
+  label_loading: "Loading"
+  label_title: "Title"
+  label_zen_mode: "Zen mode"
diff --git a/test/components/primer/open_project/danger_dialog_test.rb b/test/components/primer/open_project/danger_dialog_test.rb
index 8538325ee0..440e53c28f 100644
--- a/test/components/primer/open_project/danger_dialog_test.rb
+++ b/test/components/primer/open_project/danger_dialog_test.rb
@@ -50,8 +50,8 @@ def test_renders_default_button_text
     end
 
     assert_selector("dialog.DangerDialog") do
-      assert_selector(".Overlay-footer .Button", text: "en.button_cancel")
-      assert_selector(".Overlay-footer .Button", text: "en.button_delete")
+      assert_selector(".Overlay-footer .Button", text: "Cancel")
+      assert_selector(".Overlay-footer .Button", text: "Delete")
     end
   end
 
@@ -97,8 +97,8 @@ def test_renders_with_confirmation_check_box_button_text
     end
 
     assert_selector("dialog.DangerDialog") do
-      assert_selector(".Overlay-footer .Button", text: "en.button_cancel")
-      assert_selector(".Overlay-footer .Button", text: "en.button_delete_permanently")
+      assert_selector(".Overlay-footer .Button", text: "Cancel")
+      assert_selector(".Overlay-footer .Button", text: "Delete permanently")
     end
   end