Fix Windows local GGUF model loading crash (#4730)

* Fix Windows "Non-relative patterns are unsupported" when loading local GGUF models

When a user loads a GGUF model from a local Windows path (e.g.
C:\Users\danie\.lmstudio\models\unsloth\functiongemma-270m-it-GGUF),
the model identifier contains backslashes and a drive letter. Both
load_model_defaults() and _has_specific_yaml() constructed a YAML
filename from the full absolute path and passed it to Path.rglob(),
which rejects non-relative patterns on Windows.

Fixed by detecting Windows-style paths (drive letters, UNC paths,
backslashes) in addition to Unix-style paths, and using only the
directory basename for the YAML filename lookup when the identifier
is a local filesystem path.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Refactor: reuse is_local_path helper, fix case-sensitive suffix lookup

- Replace inline local-path detection in model_config.py and
  inference_config.py with the existing is_local_path() from utils.paths,
  which already handles Unix, Windows drive-letter, UNC, and backslash paths
- Fix case-sensitive suffix lookup in load_model_defaults(): the
  _REVERSE_MODEL_MAPPING is lowercase-keyed, so suffix comparisons must use
  .lower() to match paths like /path/to/Spark-TTS-0.5B/LLM

* Fix WSL path parsing and _has_specific_yaml suffix lookup

- Use normalize_path() before Path() operations so backslash Windows
  paths (e.g. C:\Users\...\model) are correctly split on POSIX/WSL hosts
  where pathlib treats backslashes as literal characters
- Add suffix-based (2-component and 1-component) lookup to
  _has_specific_yaml() so it matches the same resolution rules as
  load_model_defaults(), fixing wrong inference params for local
  suffix-mapped models like Spark-TTS-0.5B/LLM

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

studio/backend/utils/inference/inference_config.py

@@ -17,6 +17,7 @@ import structlog
 from loggers import get_logger
 
 from utils.models.model_config import load_model_defaults
+from utils.paths import is_local_path, normalize_path
 
 logger = get_logger(__name__)
 
@@ -93,8 +94,28 @@ def _has_specific_yaml(model_identifier: str) -> bool:
     if model_identifier.lower() in _REVERSE_MODEL_MAPPING:
         return True
 
-    # Check for exact filename match
-    model_filename = model_identifier.replace("/", "_") + ".yaml"
+    # For local filesystem paths (e.g. C:\Users\...\model on Windows),
+    # normalize backslashes so Path().parts splits correctly on POSIX/WSL,
+    # then try matching the last 1-2 path components against the registry
+    # (mirrors the logic in load_model_defaults).
+    _is_local = is_local_path(model_identifier)
+    _normalized = normalize_path(model_identifier) if _is_local else model_identifier
+
+    if _is_local:
+        parts = Path(_normalized).parts
+        for depth in (2, 1):
+            if len(parts) >= depth:
+                suffix = "/".join(parts[-depth:])
+                if suffix.lower() in _REVERSE_MODEL_MAPPING:
+                    return True
+        _lookup = Path(_normalized).name
+    else:
+        _lookup = model_identifier
+
+    # Check for exact filename match (basename for local paths to avoid
+    # passing absolute paths into rglob which raises
+    # "Non-relative patterns are unsupported" on Windows).
+    model_filename = _lookup.replace("/", "_") + ".yaml"
     for config_path in defaults_dir.rglob(model_filename):
         if config_path.is_file():
             return True

studio/backend/utils/models/model_config.py

@@ -1420,17 +1420,20 @@ def load_model_defaults(model_name: str) -> Dict[str, Any]:
                         return config
 
         # If model_name is a local path (e.g. /home/.../Spark-TTS-0.5B/LLM from
-        # adapter_config.json), try matching the last 1-2 path components against
-        # the registry (e.g. "Spark-TTS-0.5B/LLM").
-        if model_name not in _REVERSE_MODEL_MAPPING and (
-            model_name.startswith("/") or model_name.startswith(".")
-        ):
-            parts = Path(model_name).parts
+        # adapter_config.json, or C:\Users\...\model on Windows), try matching
+        # the last 1-2 path components against the registry
+        # (e.g. "Spark-TTS-0.5B/LLM").
+        _is_local_path = is_local_path(model_name)
+        # Normalize Windows backslash paths so Path().parts splits correctly
+        # on POSIX/WSL hosts (pathlib treats backslashes as literals on Linux).
+        _normalized = normalize_path(model_name) if _is_local_path else model_name
+        if model_name.lower() not in _REVERSE_MODEL_MAPPING and _is_local_path:
+            parts = Path(_normalized).parts
             for depth in [2, 1]:
                 if len(parts) >= depth:
                     suffix = "/".join(parts[-depth:])
-                    if suffix in _REVERSE_MODEL_MAPPING:
-                        canonical_file = _REVERSE_MODEL_MAPPING[suffix]
+                    if suffix.lower() in _REVERSE_MODEL_MAPPING:
+                        canonical_file = _REVERSE_MODEL_MAPPING[suffix.lower()]
                         for config_path in defaults_dir.rglob(canonical_file):
                             if config_path.is_file():
                                 with open(config_path, "r", encoding = "utf-8") as f:
@@ -1440,8 +1443,12 @@ def load_model_defaults(model_name: str) -> Dict[str, Any]:
                                     )
                                     return config
 
-        # Try exact model name match (for backward compatibility)
-        model_filename = model_name.replace("/", "_") + ".yaml"
+        # Try exact model name match (for backward compatibility).
+        # For local filesystem paths, use only the directory basename to
+        # avoid passing absolute paths (e.g. C:\...) into rglob which
+        # raises "Non-relative patterns are unsupported" on Windows.
+        _lookup_name = Path(_normalized).name if _is_local_path else model_name
+        model_filename = _lookup_name.replace("/", "_") + ".yaml"
         # Search in subfolders and root
         for config_path in defaults_dir.rglob(model_filename):
             if config_path.is_file():