diff --git a/.github/workflows/techapi-pr-validation-comment.yml b/.github/workflows/techapi-pr-validation-comment.yml
index 0a784c6..340b79e 100644
--- a/.github/workflows/techapi-pr-validation-comment.yml
+++ b/.github/workflows/techapi-pr-validation-comment.yml
@@ -63,6 +63,9 @@ jobs:
         with:
           python-version: "3.12"
           cache: pip
+          # Avoid the default whole-workspace manifest search after the large
+          # TechAPI PR and main worktrees have been checked out.
+          cache-dependency-path: pyproject.toml
 
       - name: Detect TechAPI homepage changes
         id: site_changes