diff --git a/scripts/test-model-conversion-update.py b/scripts/test-model-conversion-update.py
index cfe5ab7..fed66bd 100644
--- a/scripts/test-model-conversion-update.py
+++ b/scripts/test-model-conversion-update.py
@@ -122,6 +122,17 @@ with tempfile.TemporaryDirectory(prefix='easyai-conversion-update-') as temporar
         assert result.returncode != 0
         assert '应用更新成功' not in result.stdout
         if name == 'bash':
+            log.write_text('')
+            result = run(command, root, {**env, 'UPDATE_SERVICES': 'easyai-server easyai-web', 'UPDATE_RELEASE_VERSION': '3.25.0.20261009.3'})
+            assert result.returncode == 0, result.stdout + result.stderr
+            core_values = dict(line.split('=', 1) for line in (root / '.env').read_text().splitlines() if '=' in line and not line.startswith('#'))
+            assert core_values['VERSION'] == '3.25.0.20261009.3'
+            assert core_values['MODEL_CONVERSION_WORKER_VERSION'] == values['MODEL_CONVERSION_WORKER_VERSION']
+            assert ['compose', 'pull', 'easyai-server', 'easyai-web'] in calls(log)
+            assert ['compose', 'up', '-d', '--no-deps', 'easyai-server', 'easyai-web'] in calls(log)
+            assert not any('model-conversion-worker' in call for call in calls(log) if call[:2] in [['compose', 'pull'], ['compose', 'up']])
+            values = core_values
+            print('bash: core-only release preserves non-target Worker pin passed')
             companion_env = {**env, 'UPDATE_SERVICES': 'ws-gateway easyai-updater',
                              'UPDATE_GATEWAY_VERSION': '3.25.0.20261009',
                              'UPDATE_UPDATER_VERSION': '3.25.0.20261009'}
diff --git a/update.sh b/update.sh
index 70f197a..1736a30 100755
--- a/update.sh
+++ b/update.sh
@@ -202,7 +202,10 @@ bash ./scripts/init-infrastructure-update-env.sh "$SCRIPT_DIR"
 
 if [ -n "${UPDATE_RELEASE_VERSION:-}" ]; then
     write_env_value .env VERSION "$UPDATE_RELEASE_VERSION"
-    write_env_value .env MODEL_CONVERSION_WORKER_VERSION "$UPDATE_RELEASE_VERSION"
+    # 定向发布主服务时保留未参与的 Worker 固定版本。
+    if [ -z "${UPDATE_SERVICES:-}" ] || [[ " ${UPDATE_SERVICES} " == *" model-conversion-worker "* ]]; then
+        write_env_value .env MODEL_CONVERSION_WORKER_VERSION "$UPDATE_RELEASE_VERSION"
+    fi
     echo "📌 已固定本次发布版本: $UPDATE_RELEASE_VERSION"
 fi