diff --git a/install_npuir.sh b/install_npuir.sh
index 2daa606dc..1258df5b1 100755
--- a/install_npuir.sh
+++ b/install_npuir.sh
@@ -37,7 +37,10 @@ normalize_cann_version() {
             echo "9.0.0.beta2"
             ;;
         *)
-            return 1
+            if [ -n "$raw" ]; then
+                echo "Warning: Unsupported CANN version '$raw'; defaulting to 8.5.0." >&2
+            fi
+            echo "8.5.0"
             ;;
     esac
 }
@@ -45,11 +48,9 @@ normalize_cann_version() {
 infer_cann_version_from_env() {
     local current_home="${ASCEND_HOME_PATH}"
     if [ -z "$current_home" ]; then
-        echo "Error: neither --cann-version nor ASCEND_HOME_PATH is set." >&2
-        echo "Please choose one of the following before re-running:" >&2
-        echo "  1. Pass --cann-version=<${SUPPORTED_CANN_VERSIONS[*]}>" >&2
-        echo "  2. Export ASCEND_HOME_PATH to a supported CANN install, then re-run" >&2
-        return 1
+        echo "Warning: neither --cann-version nor ASCEND_HOME_PATH is set; defaulting to 8.5.0." >&2
+        echo "8.5.0"
+        return 0
     fi
     normalize_cann_version "$current_home"
 }
@@ -119,11 +120,7 @@ while [[ $# -gt 0 ]]; do
 done
 
 if [ -n "$CANN_VERSION" ]; then
-    CANN_VERSION="$(normalize_cann_version "$CANN_VERSION")" || {
-        echo "Error: Unsupported CANN version '$CANN_VERSION'." >&2
-        print_usage
-        exit 1
-    }
+    CANN_VERSION="$(normalize_cann_version "$CANN_VERSION")"
 else
     CANN_VERSION="$(infer_cann_version_from_env)" || {
         print_usage
diff --git a/tilelang/utils/npu_utils.py b/tilelang/utils/npu_utils.py
index 7d31eda50..6117eeae2 100644
--- a/tilelang/utils/npu_utils.py
+++ b/tilelang/utils/npu_utils.py
@@ -121,12 +121,12 @@ def get_device_num(self):
 }
 
 
-def _normalize_cann_version(value: str) -> str:
+def _normalize_cann_version(value: str | None) -> str:
     if not value:
-        raise ValueError(
-            "Unsupported CANN version: "
-            f"{value!r}. Supported versions: {', '.join(_SUPPORTED_CANN_TO_HIVMC)}"
+        logging.warning(
+            "CANN version is not configured; defaulting to 8.5.0."
         )
+        return "8.5.0"
 
     normalized = os.path.basename(value.rstrip("/").strip().lower())
     if normalized.startswith("cann-"):
@@ -137,10 +137,11 @@ def _normalize_cann_version(value: str) -> str:
     if re.fullmatch(r"9\.0\.0(?:[.-]?beta(?:[.-]?2)?)", normalized):
         return "9.0.0.beta2"
 
-    raise ValueError(
-        "Unsupported CANN version: "
-        f"{value!r}. Supported versions: {', '.join(_SUPPORTED_CANN_TO_HIVMC)}"
+    logging.warning(
+        "Unsupported CANN version %r; defaulting to 8.5.0.",
+        value,
     )
+    return "8.5.0"
 
 
 def get_configured_hivmc_version() -> str:
@@ -151,10 +152,6 @@ def get_configured_hivmc_version() -> str:
         ascend_home = os.environ.get("ASCEND_HOME_PATH") or os.environ.get(
             "ASCEND_HOME"
         )
-        if not ascend_home:
-            raise ValueError(
-                "ASCEND_HOME_PATH is not set; unable to infer the target CANN version."
-            )
         cann_version = _normalize_cann_version(ascend_home)
     return _SUPPORTED_CANN_TO_HIVMC[cann_version]