From 690a18258c617d832960f320a11d7eed5d48341d Mon Sep 17 00:00:00 2001
From: Emily KL <4672118+emilykl@users.noreply.github.com>
Date: Wed, 9 Sep 2026 12:59:51 -0400
Subject: [PATCH 1/4] add CI workflow to make sure changelog gets updated with
 every PR

---
 .github/workflows/check-changelog.yml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 .github/workflows/check-changelog.yml

diff --git a/.github/workflows/check-changelog.yml b/.github/workflows/check-changelog.yml
new file mode 100644
index 00000000000..340f39e8531
--- /dev/null
+++ b/.github/workflows/check-changelog.yml
@@ -0,0 +1,18 @@
+name: Check changelog
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize, labeled, unlabeled]
+
+jobs:
+  check-changelog:
+    name: Check if CHANGELOG.md was updated
+    if: ${{ !contains(github.event.pull_request.labels.*.name, 'no-changelog') }}
+    runs-on: ubuntu-latest
+    steps:
+      - env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh api "repos/${{ github.repository }}/pulls/${{ github.event.number }}/files" --paginate --jq '.[].filename' \
+            | grep -qx CHANGELOG.md \
+            || { echo "::error::CHANGELOG.md was not updated. Either add a changelog entry, or add the 'no-changelog' label to this PR if a changelog entry is not needed."; exit 1; }

From 6c49d1162fce6dccda447b92c71555830d8211e9 Mon Sep 17 00:00:00 2001
From: Emily KL <4672118+emilykl@users.noreply.github.com>
Date: Wed, 9 Sep 2026 13:47:49 -0400
Subject: [PATCH 2/4] add dummy changelog entry

---
 CHANGELOG.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf2816487b4..bc0dfe046bd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+Adding a line here for demonstration purposes
+
 ### Added
 - Support `marginal_x`/`marginal_y="heatmap"` in `density_heatmap`, drawing a single-row/column heatmap strip in the margin colored by the same `z`/`histfunc` aggregate as the main plot and sharing its color scale [[#5706](https://github.com/plotly/plotly.py/issues/5706)], with thanks to @lucasjamar for the contribution!
 - Add support for custom tick values in `mpl_to_plotly` when the matplotlib tick positions don't follow an arithmetic progression, including custom tick labels and tick values on date axes [[#5262](https://github.com/plotly/plotly.py/pull/5262)], with thanks to @robertoffmoura for the contribution!

From f2110c37b9069399f8f50843315a8402bfdc4758 Mon Sep 17 00:00:00 2001
From: Emily KL <4672118+emilykl@users.noreply.github.com>
Date: Wed, 9 Sep 2026 13:50:56 -0400
Subject: [PATCH 3/4] Revert "add dummy changelog entry"

This reverts commit 6c49d1162fce6dccda447b92c71555830d8211e9.
---
 CHANGELOG.md | 2 --
 1 file changed, 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bc0dfe046bd..cf2816487b4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,8 +4,6 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
-Adding a line here for demonstration purposes
-
 ### Added
 - Support `marginal_x`/`marginal_y="heatmap"` in `density_heatmap`, drawing a single-row/column heatmap strip in the margin colored by the same `z`/`histfunc` aggregate as the main plot and sharing its color scale [[#5706](https://github.com/plotly/plotly.py/issues/5706)], with thanks to @lucasjamar for the contribution!
 - Add support for custom tick values in `mpl_to_plotly` when the matplotlib tick positions don't follow an arithmetic progression, including custom tick labels and tick values on date axes [[#5262](https://github.com/plotly/plotly.py/pull/5262)], with thanks to @robertoffmoura for the contribution!

From e5a6ebfe7134afe2ea5b8f30a3f499f3f7cf01c4 Mon Sep 17 00:00:00 2001
From: Emily KL <4672118+emilykl@users.noreply.github.com>
Date: Wed, 9 Sep 2026 13:54:11 -0400
Subject: [PATCH 4/4] update changelog instructions in CONTRIBUTING.md

---
 CONTRIBUTING.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e1e5f211bc9..2a32b8d34c9 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -181,7 +181,8 @@ When creating your pull request, please follow the guidelines below.
 - If your PR modifies code of `plotly.graph_objects`, the modifications should be made to the code generator, *not* the generated files.
 - You have added tests or modified existing tests, as needed.
 - For a new feature, you have added documentation examples (please see the doc checklist as well).
-- You have added a CHANGELOG entry if changing anything substantial.
+- You have added a changelog entry to `CHANGELOG.md` if changing anything substantial.
+  - The CI job "Check changelog" will fail if the PR does not update `CHANGELOG.md`. To bypass this check for PRs which don't require a changelog entry (e.g. docs updates), add the `no-changelog` label to the PR.
 - For a new feature or a change in behavior, you have updated the relevant docstrings in the code.
 
 ### Documentation pull request