diff --git a/.github/workflows/regenerate-all.yml b/.github/workflows/regenerate-all.yml
index 1cc79a531cbc..3cc5e49bbb70 100644
--- a/.github/workflows/regenerate-all.yml
+++ b/.github/workflows/regenerate-all.yml
@@ -1,7 +1,7 @@
 name: Regenerate all packages after merging to main
 
 on:
-  push:
+  pull_request:
     branches:
       - main
 
@@ -14,6 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       PANDOC_VERSION: 3.8.2
+      CACHE_VERSION: v2
 
     steps:
       - name: Checkout
@@ -27,7 +28,7 @@ jobs:
       - name: Install protoc
         uses: arduino/setup-protoc@v3
         with:
-          version: "25.3"
+          version: "33.2"
 
       - name: Install pandoc
         run: |
@@ -39,13 +40,42 @@ jobs:
       - name: Install Python packages for Librarian
         run: |
           version=$(sed -n 's/^version: *//p' librarian.yaml)
-          go run "github.com/googleapis/librarian/cmd/librarian@${version}" install
+          go run "github.com/googleapis/librarian/cmd/librarian@v0.13.0" install
+
+      - name: Debug Git State
+        run: |
+          echo "Current directory: $(pwd)"
+          echo "Git status:"
+          git status
+          echo "Git branch output:"
+          git branch
+          echo "HEAD reference:"
+          git rev-parse HEAD
+          echo "Current branch:"
+          git branch --show-current
+          echo "Is this a shallow clone?"
+          [ -f .git/shallow ] && echo "Yes, it is shallow" || echo "No, it is not shallow"
+
+      - name: Force Git Environment
+        run: |
+          # The runner image likely updated and is now stricter about git state.
+          # We force a valid git state so that synthtool doesn't panic.
+          git config --global user.email "ci@example.com"
+          git config --global user.name "CI Bot"
+          git config --global init.defaultBranch main
+          # Ensure current directory is a safe directory for git
+          git config --global --add safe.directory /home/runner/work/google-cloud-python/google-cloud-python
+          # Ensure a local branch exists
+          git checkout -B main
 
       - name: Regenerate
         run: |
+          # 1. Clean the cache that synthtool uses
+          rm -rf $HOME/.cache/synthtool
+
           version=$(sed -n 's/^version: *//p' librarian.yaml)
           PATH=$PATH:/tmp/pandoc/bin
-          go run "github.com/googleapis/librarian/cmd/librarian@${version}" generate -all -v
+          go run "github.com/googleapis/librarian/cmd/librarian@v0.13.0" generate -all -v
 
       - name: Create issue on diff
         env: