diff --git a/.github/scripts/audit-check.mjs b/.github/scripts/audit-check.mjs
new file mode 100644
index 0000000..c0a92d9
--- /dev/null
+++ b/.github/scripts/audit-check.mjs
@@ -0,0 +1,51 @@
+// Weekly dependency audit (Dependabot alerts are off). Reads `npm audit --json` and the lockfile and
+// prints, as Markdown for an issue, the high and critical findings a production install can reach.
+// Findings reachable only through a package named in IGNORE (comma-separated) are left out: @x402/paywall
+// bundles browser wallet libraries (WalletConnect, Reown) that the server never runs.
+// Usage: node audit-check.mjs audit.json package-lock.json > report.md (empty output = nothing to report)
+import { readFileSync } from "node:fs";
+
+const [auditPath, lockPath] = process.argv.slice(2);
+const audit = JSON.parse(readFileSync(auditPath, "utf8"));
+if (audit.error) throw new Error(`npm audit failed: ${audit.error.summary || JSON.stringify(audit.error)}`);
+const pkgs = JSON.parse(readFileSync(lockPath, "utf8")).packages || {};
+const ignore = new Set((process.env.IGNORE || "").split(",").map((s) => s.trim()).filter(Boolean));
+
+// Where Node finds `name` when `from` requires it: the nearest node_modules on the way up to the root.
+const resolve = (from, name) => {
+  for (let dir = from; ; ) {
+    const path = (dir ? `${dir}/` : "") + `node_modules/${name}`;
+    if (pkgs[path]) return path;
+    if (!dir) return null;
+    const i = dir.lastIndexOf("/node_modules/");
+    dir = i === -1 ? "" : dir.slice(0, i);
+  }
+};
+
+// Every installed path a production install reaches from the root, skipping ignored packages.
+const reached = new Set();
+const root = pkgs[""] || {};
+const queue = Object.keys({ ...root.dependencies, ...root.optionalDependencies }).map((n) => [n, ""]);
+while (queue.length) {
+  const [name, from] = queue.pop();
+  if (ignore.has(name)) continue;
+  const path = resolve(from, name);
+  if (!path || reached.has(path)) continue;
+  reached.add(path);
+  const e = pkgs[path];
+  for (const dep of Object.keys({ ...e.dependencies, ...e.optionalDependencies, ...e.peerDependencies })) queue.push([dep, path]);
+}
+
+const rank = { critical: 0, high: 1 };
+const found = Object.values(audit.vulnerabilities || {})
+  .filter((v) => v.severity in rank && (v.nodes || []).some((n) => reached.has(n)))
+  .sort((a, b) => rank[a.severity] - rank[b.severity] || a.name.localeCompare(b.name));
+if (found.length) {
+  const fix = (f) => (f === true ? "update available" : f && f.name ? `fix needs ${f.name}@${f.version}${f.isSemVerMajor ? " (major)" : ""}` : "no fix yet");
+  const lines = found.map((v) => {
+    const advisories = [...new Map(v.via.filter((x) => typeof x === "object").map((x) => [x.url, `[${x.title}](${x.url})`])).values()];
+    const through = v.via.filter((x) => typeof x === "string");
+    return `- **${v.name}** ${v.severity}, ${v.range}: ${advisories.join("; ") || `through ${through.join(", ")}`}. ${fix(v.fixAvailable)}.`;
+  });
+  console.log(`The weekly \`npm audit\` found ${found.length} high or critical finding(s) in production dependencies${ignore.size ? ` (not counting what only ${[...ignore].join(", ")} pulls in)` : ""}:\n\n${lines.join("\n")}\n\nFix with \`npm install <package>@<fixed version>\` or \`npm audit fix --omit=dev\`, run the tests, and open a PR. This issue closes itself after a clean weekly run.`);
+}
diff --git a/.github/workflows/audit.yml b/.github/workflows/audit.yml
new file mode 100644
index 0000000..bba1f3b
--- /dev/null
+++ b/.github/workflows/audit.yml
@@ -0,0 +1,43 @@
+name: Dependency audit
+# Every Monday: npm audit on PlainText's production dependencies (Dependabot alerts are off on this repo).
+# A high or critical finding the server can reach opens one issue labelled dependency-audit (GitHub
+# emails the owner), or adds the new list to the open one; the next clean run closes it.
+on:
+  schedule:
+    - cron: "17 5 * * 1"
+  workflow_dispatch: {}
+  push:
+    branches: ['claude/**']
+    paths: ['.github/scripts/audit-check.mjs', '.github/workflows/audit.yml']
+permissions:
+  contents: read
+  issues: write
+jobs:
+  audit:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v5
+      - uses: actions/setup-node@v5
+        with:
+          node-version: 22
+      # npm audit exits non-zero whenever it finds anything; the next step decides what counts.
+      - run: npm audit --omit=dev --package-lock-only --json > "$RUNNER_TEMP/audit.json" || true
+      - name: High and critical findings the server can reach
+        run: node "$GITHUB_WORKSPACE/.github/scripts/audit-check.mjs" "$RUNNER_TEMP/audit.json" package-lock.json > "$RUNNER_TEMP/report.md"
+      - name: Keep one issue open while findings remain
+        env:
+          GH_TOKEN: ${{ github.token }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          report="$RUNNER_TEMP/report.md"
+          num=$(gh issue list --label dependency-audit --state open --json number --jq '.[0].number // empty')
+          if [ -s "$report" ]; then
+            cat "$report" >> "$GITHUB_STEP_SUMMARY"
+            if [ -n "$num" ]; then gh issue comment "$num" --body-file "$report"; exit 0; fi
+            gh label create dependency-audit --color B60205 --description "Weekly npm audit found a high or critical advisory" 2>/dev/null || true
+            gh issue create --title "Dependency audit: high or critical advisory" --label dependency-audit --body-file "$report"
+          else
+            echo "No high or critical findings the server can reach." >> "$GITHUB_STEP_SUMMARY"
+            if [ -n "$num" ]; then gh issue close "$num" --comment "The weekly audit is clean again."; fi
+          fi