diff --git a/.github/workflows/deploy-site.yml b/.github/workflows/deploy-site.yml
index d2927d53..22c6dd54 100644
--- a/.github/workflows/deploy-site.yml
+++ b/.github/workflows/deploy-site.yml
@@ -95,7 +95,9 @@ jobs:
 
       # mkdocs-material >= 9.7.5 caps mkdocs < 2, and the upper bound keeps a major
       # theme release from changing the site without a deliberate bump here.
-      - run: pip install pyyaml "jsonschema[format-nongpl]==4.26.0" "mkdocs-material>=9.7.5,<10" "pymdown-extensions>=10.14"
+      # mkdocs is pinned below 2 on its own too: MkDocs 2 drops plugins, and the
+      # theme, in maintenance mode since 9.7.0, will not follow it.
+      - run: pip install pyyaml "jsonschema[format-nongpl]==4.26.0" "mkdocs>=1.6,<2" "mkdocs-material>=9.7.5,<10" "pymdown-extensions>=10.14"
 
       - name: Validate data contracts
         run: python scripts/validate_schemas.py
diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
index 2787400f..915696b7 100644
--- a/.github/workflows/validate.yml
+++ b/.github/workflows/validate.yml
@@ -216,7 +216,7 @@ jobs:
       # heading guard's premise, and skipped on every run without it. The docs
       # group builds the site as deploy-site.yml does, with the same bounds.
       - name: Install dependencies
-        run: pip install pyyaml "jsonschema[format-nongpl]==4.26.0" "markdown==3.10.2" "mkdocs-material>=9.7.5,<10" "pymdown-extensions>=10.14"
+        run: pip install pyyaml "jsonschema[format-nongpl]==4.26.0" "markdown==3.10.2" "mkdocs>=1.6,<2" "mkdocs-material>=9.7.5,<10" "pymdown-extensions>=10.14"
 
       # The exporter fidelity cases compare what we hand back against the
       # file each platform publishes, so they need those files. They skip