diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 4bd0ee0c8e..063bef8184 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -1,6 +1,12 @@
 name: continuous-integration
 
-on: [push, pull_request]
+# This prevents workflows from being run twice on PRs
+# ref: https://github.community/t/how-to-trigger-an-action-on-push-or-pull-request-but-not-both/16662
+on:
+  push:
+    branches:
+      - main
+  pull_request:
 
 env:
   COVERAGE_THRESHOLD: 60
diff --git a/docs/conf.py b/docs/conf.py
index e3ffb30321..d6c6008ebf 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -16,6 +16,7 @@
     "jupyter_sphinx",
     "matplotlib.sphinxext.plot_directive",
     "myst_nb",
+    # "nbsphinx",  # Uncomment and comment-out MyST-NB for local testing purposes.
     "numpydoc",
     "sphinx.ext.autodoc",
     "sphinx.ext.autosummary",
@@ -126,7 +127,6 @@
 
 html_sidebars = {
     "contribute/index": [
-        "search-field",
         "sidebar-nav-bs",
         "custom-template",
     ],  # This ensures we test for custom sidebars
diff --git a/docs/demo/index.rst b/docs/demo/index.rst
index 0c64a810d6..04863f9e27 100644
--- a/docs/demo/index.rst
+++ b/docs/demo/index.rst
@@ -23,10 +23,12 @@ See the sections to the left and below to explore.
     api
 
 
+.. Note: the caption below is intentionally long in order to test out what long captions look like.
+
 .. toctree::
     :maxdepth: 3
     :numbered:
-    :caption: Reference and test section. This section has headers and examples that are meant for theme developers to test functionality, like this long caption header to test its behavior.
+    :caption: Reference and test section. Mostly meant for developers to check that things look OK.
 
     no-sidebar
     mult_headers
diff --git a/docs/demo/pydata.md b/docs/demo/pydata.md
index a11d977762..6a90576d73 100644
--- a/docs/demo/pydata.md
+++ b/docs/demo/pydata.md
@@ -2,8 +2,16 @@
 file_format: mystnb
 kernelspec:
   name: python3
+  display_name: Python 3
 ---
 
+% To test this file with nbsphinx we need to convert to ipynb. To do this:
+% - Run this command: jupytext docs/demo/pydata.md --to ipynb
+% - _Temporarily_ delete the pydata.md file
+% - Uncomment `nbsphinx` and comment `myst_nb` in "extensions" in our conf.py file
+% - Build the docs and test that the results look OK
+% - Undo everything in this list to make sure we revert back to the old structure
+
 # PyData Library Styles
 
 This theme has built-in support and special styling for several major visualization libraries in the PyData ecosystem.
diff --git a/pyproject.toml b/pyproject.toml
index 1d0f3d6c0c..c53f8741cf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,7 +55,10 @@ doc = [
   "matplotlib",
   "numpy",
   "xarray",
-  "sphinx-design"
+  "sphinx-design",
+  # Install nbsphinx in case we want to test it locally even though we can't load
+  # it at the same time as MyST-NB.
+  "nbsphinx"
 ]
 test = [
   "pytest",
diff --git a/src/pydata_sphinx_theme/assets/styles/extensions/_execution.scss b/src/pydata_sphinx_theme/assets/styles/extensions/_execution.scss
index 14e39569f8..19f5226969 100644
--- a/src/pydata_sphinx_theme/assets/styles/extensions/_execution.scss
+++ b/src/pydata_sphinx_theme/assets/styles/extensions/_execution.scss
@@ -6,36 +6,50 @@
  * In the future, we might add dark theme support for specific packages.
  */
 
+// Set background of some cell outputs to white-ish to make sure colors work
+// This is because many libraries make output that only looks good on white
+@mixin cell-output-background {
+  color: var(--pst-color-on-background);
+  background-color: var(--pst-color-text-base);
+  border-radius: 0.25rem;
+  padding: 0.5rem;
+}
+
 // Dark theme special-cases
-html[data-theme="dark"] {
-  // MyST-NB outputs should have a white background so content behaves the same
-  .bd-content div.cell_output {
+html[data-theme="dark"] .bd-content {
+  // MyST-NB
+  div.cell_output {
     img,
-    div.text_html {
-      color: var(--pst-color-on-background);
-      background-color: var(--pst-color-text-base);
-      border-radius: 0.25rem;
-      padding: 0.5rem;
+    .text_html {
+      @include cell-output-background;
+    }
+  }
+
+  // NBSphinx
+  .nboutput {
+    .output_area.rendered_html {
+      @include cell-output-background;
+    }
+
+    .output_area.stderr {
+      background: var(--pst-color-danger);
     }
   }
 
   // Jupyter Sphinx
   div.jupyter_container {
+    // Background has slightly more custom background behavior because of hard-coded color
     border: 1px solid var(--pst-color-border);
-    background-color: var(--pst-color-on-background);
+    background-color: var(--pst-color-surface);
+    border-radius: 0.25rem;
 
+    div.output,
     div.highlight {
-      background-color: var(--pst-color-on-background);
+      border-radius: 0.25rem;
     }
-  }
-}
 
-// Jupyter Sphinx
-div.jupyter_container {
-  border-radius: 0.25rem;
-
-  div.output,
-  div.highlight {
-    border-radius: 0.25rem;
+    div.highlight {
+      background-color: var(--pst-color-surface);
+    }
   }
 }
diff --git a/src/pydata_sphinx_theme/assets/styles/sections/_announcement.scss b/src/pydata_sphinx_theme/assets/styles/sections/_announcement.scss
index 970acf51ed..071824c0e4 100644
--- a/src/pydata_sphinx_theme/assets/styles/sections/_announcement.scss
+++ b/src/pydata_sphinx_theme/assets/styles/sections/_announcement.scss
@@ -1,11 +1,11 @@
-$announcement-height: 3rem;
 .bd-header-announcement {
-  height: $announcement-height;
+  min-height: 3rem;
   width: 100%;
   display: flex;
   position: relative;
   align-items: center;
   justify-content: center;
+  text-align: center;
   padding: 0.5rem 12.5%; // Horizontal padding so the width is 75%
   @include media-breakpoint-down(md) {
     // Announcements can take a bit more width on mobile