diff --git a/.dagger/src/hephaestus_ci/main.py b/.dagger/src/hephaestus_ci/main.py
index 0c89604..3d923bc 100644
--- a/.dagger/src/hephaestus_ci/main.py
+++ b/.dagger/src/hephaestus_ci/main.py
@@ -57,6 +57,10 @@ class HephaestusCi:
                     "git",
                     "clone",
                     "--depth=1",
+                    # Pin to last v4 release. v5.0.0 restructured config
+                    # layout (.quartz/plugins, ../quartz imports) and breaks
+                    # our quartz.config.ts/quartz.layout.ts. See changelog.
+                    "--branch=v4.5.2",
                     "https://github.com/jackyzha0/quartz.git",
                     "/tmp/quartz",
                 ]
diff --git a/docs/changelog.d/+pin-quartz-v4.bugfix.md b/docs/changelog.d/+pin-quartz-v4.bugfix.md
new file mode 100644
index 0000000..e073bbb
--- /dev/null
+++ b/docs/changelog.d/+pin-quartz-v4.bugfix.md
@@ -0,0 +1 @@
+Pin the Quartz docs build to v4.5.2. The Dagger `build_docs` pipeline cloned Quartz from the default branch unpinned; Quartz v5.0.0 restructured its config layout (`.quartz/plugins`, `../quartz` imports) and broke the docs build against our existing `quartz.config.ts`/`quartz.layout.ts`.