diff --git a/.github/workflows/apps.yml b/.github/workflows/apps.yml
index 7de78c964a..e909193601 100644
--- a/.github/workflows/apps.yml
+++ b/.github/workflows/apps.yml
@@ -152,18 +152,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/bittree.yml b/.github/workflows/bittree.yml
index 4532000872..299fb025d8 100644
--- a/.github/workflows/bittree.yml
+++ b/.github/workflows/bittree.yml
@@ -110,18 +110,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/clang.yml b/.github/workflows/clang.yml
index d02342899b..c84d19850a 100644
--- a/.github/workflows/clang.yml
+++ b/.github/workflows/clang.yml
@@ -212,18 +212,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/cleanup-cache-postpr.yml b/.github/workflows/cleanup-cache-postpr.yml
index 9a2ffb0f61..5e9a70cd5a 100644
--- a/.github/workflows/cleanup-cache-postpr.yml
+++ b/.github/workflows/cleanup-cache-postpr.yml
@@ -23,8 +23,11 @@ jobs:
 
           REPO=${{ github.repository }}
 
-          gh run download ${{ github.event.workflow_run.id }} -n pr_number
-          pr_number=`cat pr_number.txt`
+          # For debugging cat ${GITHUB_EVENT_PATH} to see the payload.
+
+          pr_head_sha=${{ github.event.workflow_run.head_sha }}
+          pr_number=$(gh pr list --state all --search $pr_head_sha --json number --jq '.[0].number')
+          echo "Post-PR cache cleanup for PR ${pr_number}"
           BRANCH=refs/pull/${pr_number}/merge
 
           # Setting this to not fail the workflow while deleting cache keys.
diff --git a/.github/workflows/cleanup-cache.yml b/.github/workflows/cleanup-cache.yml
index d18acbaa78..75bd8453aa 100644
--- a/.github/workflows/cleanup-cache.yml
+++ b/.github/workflows/cleanup-cache.yml
@@ -29,9 +29,12 @@ jobs:
           # Triggering workflow run name (e.g., LinuxClang)
           WORKFLOW_NAME="${{ github.event.workflow_run.name }}"
 
+          # For debugging, cat ${GITHUB_EVENT_PATH} to see the payload.
+
           if [[ $EVENT == "pull_request" ]]; then
-            gh run download ${{ github.event.workflow_run.id }} -n pr_number
-            pr_number=`cat pr_number.txt`
+            pr_head_sha=${{ github.event.workflow_run.head_sha }}
+            pr_number=$(gh pr list --search $pr_head_sha --json number --jq '.[0].number')
+            echo "Clean up cache for PR ${pr_number}"
             BRANCH=refs/pull/${pr_number}/merge
           else
             BRANCH=refs/heads/${{ github.event.workflow_run.head_branch }}
@@ -54,6 +57,7 @@ jobs:
           IFS=$'\n'
           for j in $cached_jobs
           do
+            # Delete all entries except the last used one
             old_keys=$(gh actions-cache list -L 100 -R $REPO -B $BRANCH --key "${j}-git-" --sort last-used | cut -f 1 | tail -n +2)
             for k in $old_keys
             do
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index c7340ee449..c9c34bf34f 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -92,18 +92,3 @@ jobs:
         uses: github/codeql-action/analyze@v3
         with:
           category: "/language:${{ matrix.language }}"
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/cuda.yml b/.github/workflows/cuda.yml
index 1ceed52ba6..50d45846f0 100644
--- a/.github/workflows/cuda.yml
+++ b/.github/workflows/cuda.yml
@@ -205,18 +205,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/gcc.yml b/.github/workflows/gcc.yml
index 5d8c9ad9c3..26ad6eaf52 100644
--- a/.github/workflows/gcc.yml
+++ b/.github/workflows/gcc.yml
@@ -664,18 +664,3 @@ jobs:
         mpirun -np 2 ./main3d.gnu.TPROF.MPI.ex ./inputs
         h5dump -d "level_0/data:offsets=0"  -s "1" -c "1" ./plt00000.h5
         h5dump -d "level_0/data:datatype=1" -s "1" -c "1" ./plt00000/particle0/particle0.h5
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/hip.yml b/.github/workflows/hip.yml
index 3e11dda151..a38c1f6547 100644
--- a/.github/workflows/hip.yml
+++ b/.github/workflows/hip.yml
@@ -181,18 +181,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/hypre.yml b/.github/workflows/hypre.yml
index b147423273..c6f2ee20ed 100644
--- a/.github/workflows/hypre.yml
+++ b/.github/workflows/hypre.yml
@@ -154,18 +154,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/intel.yml b/.github/workflows/intel.yml
index 4d1612d0ec..36fc674ecd 100644
--- a/.github/workflows/intel.yml
+++ b/.github/workflows/intel.yml
@@ -249,18 +249,3 @@ jobs:
         set -e
         cd build
         ctest --output-on-failure
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index d1e217380e..76aba4cef6 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -91,18 +91,3 @@ jobs:
 
         du -hs ~/Library/Caches/ccache
         ccache -s
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/petsc.yml b/.github/workflows/petsc.yml
index 7ca42f0141..efde21b89a 100644
--- a/.github/workflows/petsc.yml
+++ b/.github/workflows/petsc.yml
@@ -56,18 +56,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/post-pr.yml b/.github/workflows/post-pr.yml
index 2768ef376c..5f0b153497 100644
--- a/.github/workflows/post-pr.yml
+++ b/.github/workflows/post-pr.yml
@@ -4,17 +4,13 @@ on:
     types:
       - closed
 
+# This workflow does not have the permission to clean up cache for PRs
+# originated from a fork. The purpose here is to trigger a workflow_run
+# cleanup-cache-postpr.yml that has the right permission.
+
 jobs:
-  cleanup:
+  noop:
     runs-on: ubuntu-latest
     steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
+      - name: No OP
+        run: echo "This workflow is going to trigger CleanUpCachePostPR."
diff --git a/.github/workflows/smoke.yml b/.github/workflows/smoke.yml
index 84e67d9aae..650ef144e8 100644
--- a/.github/workflows/smoke.yml
+++ b/.github/workflows/smoke.yml
@@ -63,18 +63,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/sundials.yml b/.github/workflows/sundials.yml
index a44b21b8d0..e17234ba28 100644
--- a/.github/workflows/sundials.yml
+++ b/.github/workflows/sundials.yml
@@ -133,18 +133,3 @@ jobs:
 
         ccache -s
         du -hs ~/.cache/ccache
-
-  save_pr_number:
-    if: github.event_name == 'pull_request'
-    runs-on: ubuntu-latest
-    steps:
-      - name: Save PR number
-        env:
-          PR_NUMBER: ${{ github.event.number }}
-        run: |
-          echo $PR_NUMBER > pr_number.txt
-      - uses: actions/upload-artifact@v4
-        with:
-          name: pr_number
-          path: pr_number.txt
-          retention-days: 1
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index e0e7bf6911..4dd9a3f391 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -136,17 +136,3 @@ jobs:
         cmake --build build --config Release --target test_install
 
   # If we add ccache back, don't forget to update cleanup-cache.yml
-  #save_pr_number:
-  #  if: github.event_name == 'pull_request'
-  #  runs-on: ubuntu-latest
-  #  steps:
-  #    - name: Save PR number
-  #      env:
-  #        PR_NUMBER: ${{ github.event.number }}
-  #      run: |
-  #        echo $PR_NUMBER > pr_number.txt
-  #    - uses: actions/upload-artifact@v3
-  #      with:
-  #        name: pr_number
-  #        path: pr_number.txt
-  #        retention-days: 1