diff --git a/.github/workflows/cleanup-cache-postpr.yml b/.github/workflows/cleanup-cache-postpr.yml
index d352d47a..5e9a70cd 100644
--- a/.github/workflows/cleanup-cache-postpr.yml
+++ b/.github/workflows/cleanup-cache-postpr.yml
@@ -8,7 +8,7 @@ on:
 
 jobs:
   CleanUpCcacheCachePostPR:
-    name: Clean Up Ccahe Cache Post PR
+    name: Clean Up Ccache Cache Post PR
     runs-on: ubuntu-latest
     permissions:
       actions: write
@@ -17,21 +17,27 @@ jobs:
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
     steps:
       - uses: actions/checkout@v4
-      - name: Clean up ccahe
+      - name: Clean up ccache
         run: |
           gh extension install actions/gh-actions-cache
 
           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.
           set +e
 
           keys=$(gh actions-cache list -L 100 -R $REPO -B $BRANCH | cut -f 1)
+          # $keys might contain spaces. Thus we set IFS to \n.
+          IFS=$'\n'
           for k in $keys
           do
-            gh actions-cache delete $k -R $REPO -B $BRANCH --confirm
+            gh actions-cache delete "$k" -R $REPO -B $BRANCH --confirm
           done
+          unset IFS
diff --git a/.github/workflows/cleanup-cache.yml b/.github/workflows/cleanup-cache.yml
index 3448d88b..41882334 100644
--- a/.github/workflows/cleanup-cache.yml
+++ b/.github/workflows/cleanup-cache.yml
@@ -8,7 +8,7 @@ on:
 
 jobs:
   CleanUpCcacheCache:
-    name: Clean Up Ccahe Cache for ${{ github.event.workflow_run.name }}
+    name: Clean Up Ccache Cache for ${{ github.event.workflow_run.name }}
     runs-on: ubuntu-latest
     permissions:
       actions: write
@@ -17,7 +17,7 @@ jobs:
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
     steps:
       - uses: actions/checkout@v4
-      - name: Clean up ccahe
+      - name: Clean up ccache
         run: |
           gh extension install actions/gh-actions-cache
 
@@ -27,11 +27,14 @@ jobs:
           EVENT=${{ github.event.workflow_run.event }}
 
           # Triggering workflow run name (e.g., LinuxClang)
-          WORKFLOW_NAME=${{ github.event.workflow_run.name }}
+          WORKFLOW_NAME="${{ 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 }}
@@ -45,16 +48,20 @@ jobs:
           # The goal is to keep the last used key of each job and delete all others.
 
           # something like ccache-LinuxClang-
-          keyprefix=ccache-${WORKFLOW_NAME}-
+          keyprefix="ccache-${WORKFLOW_NAME}-"
 
-          cached_jobs=$(gh actions-cache list -L 100 -R $REPO -B $BRANCH --key $keyprefix | awk -F '-git-' '{print $1}' | sort | uniq)
+          cached_jobs=$(gh actions-cache list -L 100 -R $REPO -B $BRANCH --key "$keyprefix" | awk -F '-git-' '{print $1}' | sort | uniq)
 
           # cached_jobs is something like "ccache-LinuxClang-configure-1d ccache-LinuxClang-configure-2d".
+          # It might also contain spaces. Thus we set IFS to \n.
+          IFS=$'\n'
           for j in $cached_jobs
           do
-            old_keys=$(gh actions-cache list -L 100 -R $REPO -B $BRANCH --key ${j}-git- --sort last-used | cut -f 1 | tail -n +2)
+            # Delete all entries except the last used one
+            old_keys=$(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
-              gh actions-cache delete $k -R $REPO -B $BRANCH --confirm
+              gh actions-cache delete "$k" -R $REPO -B $BRANCH --confirm
             done
           done
+          unset IFS
diff --git a/.github/workflows/cuda.yml b/.github/workflows/cuda.yml
index 8689de02..a4f952c2 100644
--- a/.github/workflows/cuda.yml
+++ b/.github/workflows/cuda.yml
@@ -159,18 +159,3 @@ 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 a2270043..614c615e 100644
--- a/.github/workflows/gcc.yml
+++ b/.github/workflows/gcc.yml
@@ -153,18 +153,3 @@ 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/hip.yml b/.github/workflows/hip.yml
index b59dd8ef..b9a1b04b 100644
--- a/.github/workflows/hip.yml
+++ b/.github/workflows/hip.yml
@@ -92,18 +92,3 @@ 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 2768ef37..5f0b1534 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/sycl.yml b/.github/workflows/sycl.yml
index 00beaa92..14cab3a4 100644
--- a/.github/workflows/sycl.yml
+++ b/.github/workflows/sycl.yml
@@ -87,18 +87,3 @@ 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