diff --git a/.github/workflows/lock.yml b/.github/workflows/lock.yml
@@ -1,29 +1,91 @@
-name: 'Lock Threads'
+name: Close old issues and pull requests
 
 on:
   schedule:
     - cron: '0 6 * * *'
+  workflow_dispatch:
 
 permissions:
-  contents: read
+  issues: write
+  pull-requests: write
 
 jobs:
-  lock:
-    permissions:
-      issues: write
-      pull-requests: write
+  close-old-threads:
     runs-on: ubuntu-latest
+
     steps:
-      - uses: dessant/lock-threads@v2.0.1
+      - uses: actions/github-script@v9
         with:
-          github-token: ${{ github.token }}
-          issue-lock-inactive-days: '30'
-          issue-lock-comment: >
-            This issue has been automatically locked. To avoid confusion
-            with reports that have already been resolved, closed issues
-            are automatically locked 30 days after the last comment.
-            Please open a new issue for related bugs.
-          pr-lock-comment: >
-            This pull request has been automatically locked.
-            Pull requests that have been closed are automatically
-            locked 30 days after the last comment.
+          script: |
+            const cutoffDays = 30;
+            const exemptLabels = ['keep-open'];
+
+            const cutoff = new Date();
+            cutoff.setDate(cutoff.getDate() - cutoffDays);
+
+            const closeIssueMessage = `This issue has been automatically closed and locked.
+
+            Processing 3.x is no longer actively developed. Since January 2020, development moved to the Processing 4 repository.
+
+            If this issue is still relevant to Processing 4, we'd love to hear from you. Please open a new issue at:
+            https://github.com/processing/processing4/issues/new/choose
+
+            Thank you for helping improve Processing.`;
+
+            const closePrMessage = `This pull request has been automatically closed and locked.
+
+            Processing 3.x is no longer actively developed. Since January 2020, development moved to the Processing 4 repository.
+
+            If you'd still like to contribute this work, please open an issue in the Processing 4 repository to discuss it first:
+            https://github.com/processing/processing4/issues/new/choose
+
+            Thank you for your contribution.`;
+
+            const threads = await github.paginate(github.rest.issues.listForRepo, {
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              state: 'open',
+              per_page: 100,
+              sort: 'updated',
+              direction: 'asc'
+            });
+
+            for (const thread of threads) {
+              const updatedAt = new Date(thread.updated_at);
+
+              if (updatedAt > cutoff) {
+                continue;
+              }
+
+              const labels = thread.labels.map(label => label.name);
+              const isExempt = labels.some(label => exemptLabels.includes(label));
+
+              if (isExempt) {
+                continue;
+              }
+
+              const isPr = Boolean(thread.pull_request);
+              const body = isPr ? closePrMessage : closeIssueMessage;
+
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: thread.number,
+                body
+              });
+
+              await github.rest.issues.update({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: thread.number,
+                state: 'closed',
+                state_reason: 'not_planned'
+              });
+
+              await github.rest.issues.lock({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: thread.number,
+                lock_reason: 'resolved'
+              });
+            }