diff --git a/scripts/release.js b/scripts/release.js
index 406f35f..f36aa07 100755
--- a/scripts/release.js
+++ b/scripts/release.js
@@ -55,6 +55,22 @@ function bumpSemver(current, spec) {
     run(`git commit -m "chore(release): v${newVersion} - bump from v${oldVersion}"`);
     committed = true;
 
+    // ensure tag doesn't already exist locally
+    let localTagExists = false;
+    try {
+      runOutput(`git rev-parse --verify refs/tags/v${newVersion}`);
+      localTagExists = true;
+    } catch (_) {
+      localTagExists = false;
+    }
+    if (localTagExists) throw new Error(`Tag v${newVersion} already exists locally — aborting to avoid overwrite.`);
+
+    // ensure tag doesn't exist on remote
+    const remoteTagInfo = (() => {
+      try { return runOutput(`git ls-remote --tags origin v${newVersion}`); } catch (_) { return ""; }
+    })();
+    if (remoteTagInfo) throw new Error(`Tag v${newVersion} already exists on remote — aborting to avoid overwrite.`);
+
     // tag
     run(`git tag -a v${newVersion} -m "Release v${newVersion}"`);
     tagged = true;