diff --git a/bin/multiagent-safety.js b/bin/multiagent-safety.js
index fc98160..a6e4b7b 100755
--- a/bin/multiagent-safety.js
+++ b/bin/multiagent-safety.js
@@ -1769,6 +1769,12 @@ function isInteractiveTerminal() {
   return Boolean(process.stdin.isTTY && process.stdout.isTTY);
 }
 
+const stdinWaitArray = new Int32Array(new SharedArrayBuffer(4));
+
+function sleepSyncMs(milliseconds) {
+  Atomics.wait(stdinWaitArray, 0, 0, milliseconds);
+}
+
 function readSingleLineFromStdin() {
   let input = '';
   const buffer = Buffer.alloc(1);
@@ -1777,11 +1783,19 @@ function readSingleLineFromStdin() {
     let bytesRead = 0;
     try {
       bytesRead = fs.readSync(process.stdin.fd, buffer, 0, 1);
-    } catch {
+    } catch (error) {
+      if (error && ['EAGAIN', 'EWOULDBLOCK', 'EINTR'].includes(error.code)) {
+        sleepSyncMs(15);
+        continue;
+      }
       return input;
     }
 
     if (bytesRead === 0) {
+      if (process.stdin.isTTY) {
+        sleepSyncMs(15);
+        continue;
+      }
       return input;
     }
 
@@ -1921,9 +1935,8 @@ function maybeSelfUpdateBeforeStatus() {
   }
 
   const shouldUpdate = interactive
-    ? promptYesNo(
+    ? promptYesNoStrict(
       `Update now? (${NPM_BIN} i -g ${packageJson.name}@latest)`,
-      false,
     )
     : autoApproval;
 
diff --git a/test/install.test.js b/test/install.test.js
index 018ccfa..d630a51 100644
--- a/test/install.test.js
+++ b/test/install.test.js
@@ -763,11 +763,11 @@ exit 1
   assert.equal(fs.existsSync(markerPath), true, 'expected self-update command to run');
 });
 
-test('self-update prompt defaults to no when approval is not preconfigured', () => {
+test('self-update prompt requires explicit y/n when approval is not preconfigured', () => {
   const source = fs.readFileSync(cliPath, 'utf8');
   assert.match(
     source,
-    /const shouldUpdate = interactive\s*\?\s*promptYesNo\(\s*`Update now\?\s*\(\$\{NPM_BIN\} i -g \$\{packageJson\.name\}@latest\)`\s*,\s*false,\s*\)\s*:\s*autoApproval;/s,
+    /const shouldUpdate = interactive\s*\?\s*promptYesNoStrict\(\s*`Update now\?\s*\(\$\{NPM_BIN\} i -g \$\{packageJson\.name\}@latest\)`\s*,?\s*\)\s*:\s*autoApproval;/s,
   );
 });