diff --git a/.github/workflows/clean.yml b/.github/workflows/clean.yml
new file mode 100644
index 0000000..3a5a419
--- /dev/null
+++ b/.github/workflows/clean.yml
@@ -0,0 +1,65 @@
+name: clean
+
+permissions:
+  contents: write
+  pull-requests: read
+  actions: write
+
+defaults:
+  run:
+    shell: bash
+
+on:
+  workflow_dispatch: { }
+  schedule:
+    - cron: "0 0 * * *" # every day at 00:00 UTC
+
+jobs:
+  clean:
+    timeout-minutes: 5
+    runs-on: ubuntu-22.04
+    continue-on-error: true
+    steps:
+      - name: Remove Cache
+        uses: actions/github-script@v7
+        with:
+          # clean up caches,
+          # ref to https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#force-deleting-cache-entries,
+          # and https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#restrictions-for-accessing-a-cache.
+          script: |
+            const owner = context.repo.owner
+            const repo = context.repo.repo
+            var deleteCaches = new Array()
+            
+            // get candidate items.
+            const { data: cs } = await github.rest.actions.getActionsCacheList({
+              owner: owner,
+              repo: repo,
+            });
+            for (const c of cs.actions_caches) {
+              // clean closed pull request caches.
+              if (c.ref.match(/^refs\/pull\/.*$/)) {
+                var prNum = c.ref.replace(/[^\d]/g, "")
+                const { data: pr } = await github.rest.pulls.get({
+                  owner: owner,
+                  repo: repo,
+                  pull_number: prNum,
+                })
+                if (pr.state === 'closed') {
+                  deleteCaches.push(c)
+                }
+                continue
+              }
+              ${{ github.event.schedule || '// clean main branch caches' }}
+              ${{ github.event.schedule || 'deleteCaches.push(c)' }}
+            }
+            
+            // delete 
+            for (const c of deleteCaches) {
+              await github.rest.actions.deleteActionsCacheById({
+                owner: owner,
+                repo: repo,
+                cache_id: c.id,
+              })
+              console.log(`cleaned cache "${c.key}"`)
+            }
diff --git a/.github/workflows/close.yml b/.github/workflows/close.yml
new file mode 100644
index 0000000..670c7c3
--- /dev/null
+++ b/.github/workflows/close.yml
@@ -0,0 +1,34 @@
+name: close
+
+permissions:
+  pull-requests: write
+  issues: write
+
+defaults:
+  run:
+    shell: bash
+
+on:
+  workflow_dispatch: { }
+  schedule:
+    - cron: "0 0 * * *" # every day at 00:00 UTC
+
+jobs:
+  close:
+    timeout-minutes: 5
+    runs-on: ubuntu-22.04
+    continue-on-error: true
+    steps:
+      - name: Close Stale Issues and Pull Requests
+        uses: actions/stale@v9
+        with:
+          days-before-stale: 15
+          days-before-close: 14
+          exempt-issue-labels: "help wanted,good first issue,bug,bug-qa,enhancement"
+          stale-issue-label: "stale"
+          close-issue-message: "This issue was closed because it has been inactive for 14 days since being marked as stale."
+          exempt-pr-labels: "bug,bug-qa,enhancement"
+          exempt-draft-pr: true
+          stale-pr-label: "stale"
+          close-pr-message: "This pull request was closed because it has been inactive for 14 days since being marked as stale."
+          operations-per-run: 10000