diff --git a/hermes_cli/main.py b/hermes_cli/main.py
index 2e580bea84..babcad7191 100644
--- a/hermes_cli/main.py
+++ b/hermes_cli/main.py
@@ -2499,8 +2499,11 @@ def _model_flow_api_key_provider(config, provider_id, current_model=""):
         print()
         override = ""
     if override and base_url_env:
-        save_env_value(base_url_env, override)
-        effective_base = override
+        if not override.startswith(("http://", "https://")):
+            print("  Invalid URL — must start with http:// or https://. Keeping current value.")
+        else:
+            save_env_value(base_url_env, override)
+            effective_base = override
 
     # Model selection — resolution order:
     #   1. models.dev registry (cached, filtered for agentic/tool-capable models)
diff --git a/tests/hermes_cli/test_model_provider_persistence.py b/tests/hermes_cli/test_model_provider_persistence.py
index 55f7ac69c7..a06facd300 100644
--- a/tests/hermes_cli/test_model_provider_persistence.py
+++ b/tests/hermes_cli/test_model_provider_persistence.py
@@ -257,3 +257,76 @@ class TestProviderPersistsAfterModelSave:
         assert model.get("provider") == "opencode-go"
         assert model.get("default") == "minimax-m2.5"
         assert model.get("api_mode") == "anthropic_messages"
+
+
+class TestBaseUrlValidation:
+    """Reject non-URL values in the base URL prompt (e.g. shell commands)."""
+
+    def test_invalid_base_url_rejected(self, config_home, monkeypatch, capsys):
+        """Typing a non-URL string should not be saved as the base URL."""
+        from hermes_cli.auth import PROVIDER_REGISTRY
+
+        pconfig = PROVIDER_REGISTRY.get("zai")
+        if not pconfig:
+            pytest.skip("zai not in PROVIDER_REGISTRY")
+
+        monkeypatch.setenv("GLM_API_KEY", "test-key")
+
+        from hermes_cli.main import _model_flow_api_key_provider
+        from hermes_cli.config import load_config, get_env_value
+
+        # User types a shell command instead of a URL at the base URL prompt
+        with patch("hermes_cli.auth._prompt_model_selection", return_value="glm-5"), \
+             patch("hermes_cli.auth.deactivate_provider"), \
+             patch("builtins.input", return_value="nano ~/.hermes/.env"):
+            _model_flow_api_key_provider(load_config(), "zai", "old-model")
+
+        # The garbage value should NOT have been saved
+        saved = get_env_value("GLM_BASE_URL") or ""
+        assert not saved or saved.startswith(("http://", "https://")), \
+            f"Non-URL value was saved as GLM_BASE_URL: {saved}"
+        captured = capsys.readouterr()
+        assert "Invalid URL" in captured.out
+
+    def test_valid_base_url_accepted(self, config_home, monkeypatch):
+        """A proper URL should be saved normally."""
+        from hermes_cli.auth import PROVIDER_REGISTRY
+
+        pconfig = PROVIDER_REGISTRY.get("zai")
+        if not pconfig:
+            pytest.skip("zai not in PROVIDER_REGISTRY")
+
+        monkeypatch.setenv("GLM_API_KEY", "test-key")
+
+        from hermes_cli.main import _model_flow_api_key_provider
+        from hermes_cli.config import load_config, get_env_value
+
+        with patch("hermes_cli.auth._prompt_model_selection", return_value="glm-5"), \
+             patch("hermes_cli.auth.deactivate_provider"), \
+             patch("builtins.input", return_value="https://custom.z.ai/api/paas/v4"):
+            _model_flow_api_key_provider(load_config(), "zai", "old-model")
+
+        saved = get_env_value("GLM_BASE_URL") or ""
+        assert saved == "https://custom.z.ai/api/paas/v4"
+
+    def test_empty_base_url_keeps_default(self, config_home, monkeypatch):
+        """Pressing Enter (empty) should not change the base URL."""
+        from hermes_cli.auth import PROVIDER_REGISTRY
+
+        pconfig = PROVIDER_REGISTRY.get("zai")
+        if not pconfig:
+            pytest.skip("zai not in PROVIDER_REGISTRY")
+
+        monkeypatch.setenv("GLM_API_KEY", "test-key")
+        monkeypatch.delenv("GLM_BASE_URL", raising=False)
+
+        from hermes_cli.main import _model_flow_api_key_provider
+        from hermes_cli.config import load_config, get_env_value
+
+        with patch("hermes_cli.auth._prompt_model_selection", return_value="glm-5"), \
+             patch("hermes_cli.auth.deactivate_provider"), \
+             patch("builtins.input", return_value=""):
+            _model_flow_api_key_provider(load_config(), "zai", "old-model")
+
+        saved = get_env_value("GLM_BASE_URL") or ""
+        assert saved == "", "Empty input should not save a base URL"