diff --git a/RELEASE.md b/RELEASE.md
index 6c33a21a..6a761bf0 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -1,6 +1,7 @@
 # Orbit Release Process
 
 ## Full Release
+
 1. Create a **doc-refresh** branch. Add the logs of changes under
    [changelog](https://github.com/uber/orbit/blob/dev/docs/changelog.rst).
    The logs can be reused later for drafting release notes.
@@ -8,13 +9,13 @@
 2. Submit a PR to dev branch for any changes of any documentation.
 3. After the approval and merge from previous PR, create a release branch from `dev`
     - e.g. `release-v1.0.15`
-4. Update the version number in `orbit/__init__.py`. This version number will be propagated to `docs/conf.py`, `setup.cfg`, and `setup.py`.
+4. Update the version number in `pyproject.toml`. This version number will be propagated to `docs/conf.py`, `setup.cfg`, and `setup.py`.
 5. Commit changes
 6. Test PyPI deployment locally by running [Optional]
     - `python3 -m build`
     - `python3 -m twine check dist/*`
     - `python3 -m twine upload --repository testpypi dist/*`
-    - Verify the package on https://test.pypi.org/project/orbit-ml/
+    - Verify the package on <https://test.pypi.org/project/orbit-ml/>
 
     > **Legacy (deprecated):** `python3 setup.py sdist bdist_wheel`
 7. If necessary, additional PRs may be merged to the release branch directly, but this should be for bug fixes only.
@@ -29,35 +30,35 @@
     - `git push origin dev`
 
     here option `--no-ff` is important to have same commit ids between `master` and `dev`; `git rebase` instead of `git merge` is to avoid the additional merge commit.
-10. Draft a new release: https://github.com/uber/orbit/releases/new
+10. Draft a new release: <https://github.com/uber/orbit/releases/new>
     - Select the `master` as the target branch
     - Use version number for both the tag and title e.g. `v1.0.15`
     - Add a bulleted list of changes in the description; this can be similar to change logs from step 1.
 11. Click `Publish Release` once all changes are finalized and description is updated
-12. All the documentation should be refreshed and can be found in https://orbit-ml.readthedocs.io/en/stable/
-
+12. All the documentation should be refreshed and can be found in <https://orbit-ml.readthedocs.io/en/stable/>
 
 ## Quick Release
+
 Sometimes we just want to release a patch, and no subsequent commits are needed on the release branch.
 In this case, we can avoid creating the branch and create a release directly from dev.
 
 1. From `dev`, update the version number in `orbit/__init__.py`.
 2. Commit changes
 3. Merge to `master`
-4. Draft a new release: https://github.com/uber/orbit/releases/new
+4. Draft a new release: <https://github.com/uber/orbit/releases/new>
     - Select the master branch as the target branch
     - Use version number for both the tag and title
     - Add a bulleted list of changes in the description as well as
       [changelog](https://github.com/uber/orbit/blob/dev/docs/changelog.rst).
 
-
 ## Hotfix
+
 Sometimes we may need to address a bug fix directly from master after a release, but `dev` may have moved on with new commits.
 
 1. Create a hotfix branch from master and update the version number
 2. Make fix
 3. Merge changes into `master`
-4. Draft a new release: https://github.com/uber/orbit/releases/new
+4. Draft a new release: <https://github.com/uber/orbit/releases/new>
     - Select the master branch as the target branch
     - Use version number for both the tag and title
     - Add a bulleted list of changes in the description as well as
diff --git a/docs/changelog.rst b/docs/changelog.rst
index f7a442b9..315c283f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -3,6 +3,26 @@
 Changelog
 =========
 
+1.1.5.1 (2026-05-20) (`release notes <https://github.com/uber/orbit/releases/tag/v1.1.5.1>`__)
+-------------------------------------------------------------------------------------------------
+:Python Version Support:
+  - Drop Python 3.9–3.11; require Python ≥ 3.12
+  - Add support for Python 3.13 (#894)
+  - Update Trove classifiers for Python 3.12 and 3.13
+
+:Core Changes:
+  - Bump minimum dependency versions (numpy≥2.1.0, pandas≥2.2.3, matplotlib≥3.9.2, etc.) for Python 3.13 wheel availability
+  - Replace deprecated ``np.in1d`` with ``np.isin`` (removed in NumPy 2.x)
+  - Fix deprecated pandas frequency aliases (``M`` → ``ME``) in tests
+  - Fix chained assignment for pandas Copy-on-Write compatibility
+  - Fix invalid escape sequence in ``rmsse`` docstring
+
+:CI/CD:
+  - Update GitHub Actions (``checkout`` to v4, ``setup-python`` to v5)
+  - Update test matrix to [3.12, 3.13]
+  - Update ``tox`` envlist to ``py312, py313``
+  - Update ``black`` target-version to ``py312, py313``
+
 1.1.5.0 (2026-03-02) (`release notes <https://github.com/uber/orbit/releases/tag/v1.1.5.0>`__)
 -------------------------------------------------------------------------------------------------
 :Core Changes:
diff --git a/pyproject.toml b/pyproject.toml
index 672d3a6c..fa8076d8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -28,7 +28,7 @@ authors = [
 maintainers = [
   {name = "Edwin Ng", email = "edwinnglabs@gmail.com"},
 ]
-version = "1.1.5.0"
+version = "1.1.5.1"
 description = "Orbit is a package for Bayesian time series modeling and inference."
 readme = "README.md"
 requires-python = ">=3.12"