diff --git a/.github/workflows/pytest.yaml b/.github/workflows/pytest.yaml
index ad355f70b..ccaf669f5 100644
--- a/.github/workflows/pytest.yaml
+++ b/.github/workflows/pytest.yaml
@@ -193,6 +193,15 @@ jobs:
         working-directory: examples/brownian/shinymediapipe
         run: |
           npm ci
+      - name: Checkout py-shiny-templates repository
+        uses: actions/checkout@v4
+        with:
+          repository: posit-dev/py-shiny-templates
+          path: py-shiny-templates
+
+      - name: Install py-shiny-templates dependencies
+        run: |
+          make install-py-shiny-templates-deps
 
       - name: Run example app tests
         timeout-minutes: 60
diff --git a/Makefile b/Makefile
index 215ef4cb4..1a8c9338e 100644
--- a/Makefile
+++ b/Makefile
@@ -220,13 +220,15 @@ ci-install-wheel: dist FORCE
 	uv pip install dist/shiny*.whl
 
 install-deps: FORCE ## install dependencies
-	pip install -e ".[dev,test]" --upgrade
+	uv pip install -e ".[dev,test]" --upgrade
 ci-install-deps: FORCE
 	uv pip install -e ".[dev,test]"
+install-py-shiny-templates-deps: FORCE
+	uv pip install -r py-shiny-templates/requirements.txt
 
 install-docs: FORCE
-	pip install -e ".[dev,test,doc]"
-	pip install https://github.com/posit-dev/py-shinylive/tarball/main
+	uv pip install -e ".[dev,test,doc]"
+	uv pip install https://github.com/posit-dev/py-shinylive/tarball/main
 ci-install-docs: FORCE
 	uv pip install -e ".[dev,test,doc]" \
 		"shinylive @ git+https://github.com/posit-dev/py-shinylive.git"
diff --git a/pyproject.toml b/pyproject.toml
index 0a5ef7e76..f69807faa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -91,6 +91,7 @@ test = [
     "dask[dataframe]",
     "pyarrow",
     "pyarrow-stubs",
+
 ]
 dev = [
     "black>=24.0",
diff --git a/tests/playwright/examples/example_apps.py b/tests/playwright/examples/example_apps.py
index a3bf05c1a..2dce2eab2 100644
--- a/tests/playwright/examples/example_apps.py
+++ b/tests/playwright/examples/example_apps.py
@@ -4,7 +4,7 @@
 from pathlib import PurePath
 from typing import Literal
 
-from playwright.sync_api import ConsoleMessage, Page
+from playwright.sync_api import ConsoleMessage, Page, expect
 
 from shiny.run import ShinyAppProc, run_shiny_app
 
@@ -15,6 +15,9 @@
 reruns = 1 if is_interactive else 3
 reruns_delay = 0
 
+SHINY_INIT_TIMEOUT = 30_000
+ERROR_ELEMENT_TIMEOUT = 1_000
+
 
 def get_apps(path: str) -> typing.List[str]:
     full_path = pyshiny_root / path
@@ -95,6 +98,13 @@ def get_apps(path: str) -> typing.List[str]:
     "examples/brownian": ["Failed to acquire camera feed:"],
 }
 
+# Check for Shiny output errors, except for known exception cases
+app_allow_output_error = [
+    "shiny/api-examples/SafeException/app-express.py",
+    "shiny/api-examples/SafeException/app-core.py",
+    "examples/global_pyplot/app.py",
+]
+
 
 # Altered from `shinytest2:::app_wait_for_idle()`
 # https://github.com/rstudio/shinytest2/blob/b8fdce681597e9610fc078aa6e376134c404f3bd/R/app-driver-wait.R
@@ -250,3 +260,8 @@ def on_console_msg(msg: ConsoleMessage) -> None:
             + " had JavaScript console errors!\n"
             + "* ".join(console_errors)
         )
+
+        if ex_app_path not in app_allow_output_error:
+            # Ensure there are no output errors present
+            error_locator = page.locator(".shiny-output-error")
+            expect(error_locator).to_have_count(0, timeout=ERROR_ELEMENT_TIMEOUT)
diff --git a/tests/playwright/examples/test_external_templates.py b/tests/playwright/examples/test_external_templates.py
new file mode 100644
index 000000000..ae158b8ab
--- /dev/null
+++ b/tests/playwright/examples/test_external_templates.py
@@ -0,0 +1,20 @@
+from pathlib import Path
+
+import pytest
+from conftest import here_root
+from example_apps import get_apps, reruns, reruns_delay, validate_example
+from playwright.sync_api import Page
+
+if not Path(here_root / "py-shiny-templates").exists():
+    pytest.skip(
+        "./py-shiny-templates dir is not available. Skipping test.",
+        allow_module_level=True,
+    )
+
+
+@pytest.mark.only_browser("chromium")
+@pytest.mark.flaky(reruns=reruns, reruns_delay=reruns_delay)
+@pytest.mark.parametrize("ex_app_path", get_apps("py-shiny-templates"))
+def test_external_templates(page: Page, ex_app_path: str) -> None:
+
+    validate_example(page, ex_app_path)
diff --git a/tests/playwright/shiny/components/data_frame/edit/app.py b/tests/playwright/shiny/components/data_frame/edit/app.py
index 2f8707e39..ed7c580b1 100644
--- a/tests/playwright/shiny/components/data_frame/edit/app.py
+++ b/tests/playwright/shiny/components/data_frame/edit/app.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import pkgutil
+from typing import Any
 
 # pyright: reportUnknownMemberType = false
 # pyright: reportMissingTypeStubs = false
@@ -264,7 +265,7 @@ def df_styles_fn(data: pd.DataFrame) -> list[StyleInfo]:
     # from shiny import reactive
 
     @render_widget
-    def country_detail_pop():
+    def country_detail_pop() -> Any:
         import plotly.express as px
 
         return px.line(