diff --git a/openspace/host_detection/resolver.py b/openspace/host_detection/resolver.py
index ee43408..ec6e41c 100644
--- a/openspace/host_detection/resolver.py
+++ b/openspace/host_detection/resolver.py
@@ -36,6 +36,10 @@
 _env_loaded = False
 
 
+def _get_env_stripped(name: str) -> str:
+    return os.environ.get(name, "").strip()
+
+
 def _load_env_once() -> None:
     """Load .env files once per process.
 
@@ -141,8 +145,8 @@ def build_llm_kwargs(model: str) -> tuple[str, Dict[str, Any]]:
     source = "inherited env"
 
     has_explicit_llm_override = bool(
-        os.environ.get("OPENSPACE_LLM_API_BASE")
-        or os.environ.get("OPENSPACE_LLM_API_KEY")
+        _get_env_stripped("OPENSPACE_LLM_API_BASE")
+        or _get_env_stripped("OPENSPACE_LLM_API_KEY")
     )
     provider_native_env_used = _has_provider_native_env(
         resolved_model or _DEFAULT_MODEL
@@ -185,16 +189,16 @@ def build_llm_kwargs(model: str) -> tuple[str, Dict[str, Any]]:
         source = host_source or "host config"
 
     # --- Tier 1: explicit env vars override everything ---
-    api_key = os.environ.get("OPENSPACE_LLM_API_KEY")
+    api_key = _get_env_stripped("OPENSPACE_LLM_API_KEY")
     if api_key:
         kwargs["api_key"] = api_key
         source = "OPENSPACE_LLM_* env"
 
-    api_base = os.environ.get("OPENSPACE_LLM_API_BASE")
+    api_base = _get_env_stripped("OPENSPACE_LLM_API_BASE")
     if api_base:
         kwargs["api_base"] = api_base
 
-    extra_headers_raw = os.environ.get("OPENSPACE_LLM_EXTRA_HEADERS")
+    extra_headers_raw = _get_env_stripped("OPENSPACE_LLM_EXTRA_HEADERS")
     if extra_headers_raw:
         try:
             headers = json.loads(extra_headers_raw)
@@ -203,7 +207,7 @@ def build_llm_kwargs(model: str) -> tuple[str, Dict[str, Any]]:
         except json.JSONDecodeError:
             logger.warning("Invalid JSON in OPENSPACE_LLM_EXTRA_HEADERS: %r", extra_headers_raw)
 
-    llm_config_raw = os.environ.get("OPENSPACE_LLM_CONFIG")
+    llm_config_raw = _get_env_stripped("OPENSPACE_LLM_CONFIG")
     if llm_config_raw:
         try:
             llm_config = json.loads(llm_config_raw)
@@ -322,4 +326,5 @@ def build_grounding_config_path() -> Optional[str]:
         except Exception as e:
             logger.warning("Failed to write config overrides: %s", e)
 
-    return os.environ.get("OPENSPACE_CONFIG_PATH")
+    config_path = _get_env_stripped("OPENSPACE_CONFIG_PATH")
+    return config_path or None
diff --git a/tests/test_host_detection_resolver.py b/tests/test_host_detection_resolver.py
new file mode 100644
index 0000000..89c95ec
--- /dev/null
+++ b/tests/test_host_detection_resolver.py
@@ -0,0 +1,36 @@
+import os
+import unittest
+from unittest.mock import patch
+
+from openspace.host_detection.resolver import build_llm_kwargs, build_grounding_config_path
+
+
+class ResolverWhitespaceEnvTests(unittest.TestCase):
+    @patch("openspace.host_detection.nanobot.try_read_nanobot_config")
+    @patch("openspace.host_detection.openclaw.try_read_openclaw_config")
+    def test_whitespace_explicit_llm_env_does_not_disable_host_fallback(self, mock_openclaw, mock_nanobot):
+        mock_nanobot.return_value = {"api_key": "host-key", "api_base": "https://host.example/v1"}
+        mock_openclaw.return_value = None
+
+        with patch.dict(
+            os.environ,
+            {
+                "OPENSPACE_LLM_API_KEY": "   ",
+                "OPENSPACE_LLM_API_BASE": "\t",
+                "OPENROUTER_API_KEY": "",
+            },
+            clear=False,
+        ):
+            model, kwargs = build_llm_kwargs("openrouter/anthropic/claude-sonnet-4.5")
+
+        self.assertEqual(model, "openrouter/anthropic/claude-sonnet-4.5")
+        self.assertEqual(kwargs.get("api_key"), "host-key")
+        self.assertEqual(kwargs.get("api_base"), "https://host.example/v1")
+
+    def test_whitespace_config_path_returns_none(self):
+        with patch.dict(os.environ, {"OPENSPACE_CONFIG_PATH": "   "}, clear=False):
+            self.assertIsNone(build_grounding_config_path())
+
+
+if __name__ == "__main__":
+    unittest.main()