fix(studio): custom folder scan fails to find GGUF variants when pointing directly at a model directory (#4860)

Fix custom folder scanning when pointing directly at a model directory.

When a user adds a custom scan folder that points directly at a model
directory (e.g. /path/to/gemma-4-e2b-it-gguf/ containing config.json
and gemma-4-E2B-it-BF16.gguf), the model list previously showed
individual .gguf files as separate entries instead of recognizing the
directory as a single model. Clicking any entry showed "No GGUF
variants found" because list_local_gguf_variants received a file path
and immediately returned empty.

Changes:
- Add _is_model_directory() helper that detects directories with both
  config metadata and actual model weight files (excludes mmproj GGUFs
  and non-weight .bin files like tokenizer.bin)
- _scan_models_dir: detect self-model and return single directory entry
- _scan_lmstudio_dir: surface model directories directly instead of
  descending into them as publisher folders; handle both root and child
  model directories
- Add _resolve_gguf_dir() helper for GGUF path resolution that only
  falls back to parent directory when parent has model metadata
- list_local_gguf_variants / _find_local_gguf_by_variant: use resolver
  so .gguf file paths inside model directories work correctly

studio/backend/routes/models.py

@@ -138,6 +138,47 @@ def _resolve_hf_cache_dir() -> Path:
         return Path.home() / ".cache" / "huggingface" / "hub"
 
 
+def _is_model_directory(d: Path) -> bool:
+    """Return ``True`` when *d* looks like a model directory.
+
+    A model directory must have **both** a config file (``config.json`` or
+    ``adapter_config.json``) **and** actual model weight files.  Both
+    conditions are required: a bare directory with only loose ``.gguf``
+    files (no config) might be a mixed collection, and a ``config.json``
+    alone (no weights) is not a model directory.
+
+    Excludes ``mmproj`` GGUF files (vision projectors) and non-weight
+    ``.bin`` files (``tokenizer.bin``, ``vocab.bin``, etc.) from the
+    weight check to avoid false positives.
+    """
+
+    def _is_weight_file(f: Path) -> bool:
+        suffix = f.suffix.lower()
+        if suffix == ".safetensors":
+            return True
+        if suffix == ".gguf":
+            return "mmproj" not in f.name.lower()
+        if suffix == ".bin":
+            name = f.name.lower()
+            return (
+                name.startswith("pytorch_model")
+                or name.startswith("model")
+                or name.startswith("adapter_model")
+                or name.startswith("consolidated")
+            )
+        return False
+
+    try:
+        has_config = (d / "config.json").exists() or (
+            d / "adapter_config.json"
+        ).exists()
+        if not has_config:
+            return False
+        return any(_is_weight_file(f) for f in d.iterdir() if f.is_file())
+    except OSError:
+        return False
+
+
 def _scan_models_dir(
     models_dir: Path,
     *,
@@ -146,6 +187,23 @@ def _scan_models_dir(
     if not models_dir.exists() or not models_dir.is_dir():
         return []
 
+    _is_self_model = _is_model_directory(models_dir)
+
+    if _is_self_model:
+        try:
+            updated_at = models_dir.stat().st_mtime
+        except OSError:
+            updated_at = None
+        return [
+            LocalModelInfo(
+                id = str(models_dir),
+                display_name = models_dir.name,
+                path = str(models_dir),
+                source = "models_dir",
+                updated_at = updated_at,
+            ),
+        ]
+
     found: List[LocalModelInfo] = []
     for child in models_dir.iterdir():
         if limit is not None and len(found) >= limit:
@@ -243,6 +301,25 @@ def _scan_lmstudio_dir(lm_dir: Path) -> List[LocalModelInfo]:
     if not lm_dir.exists() or not lm_dir.is_dir():
         return []
 
+    # If the directory itself is a model directory (has config AND weight
+    # files), it is not an LM Studio publisher structure -- return it as a
+    # single model entry.  We cannot skip it silently because this function
+    # is the only scanner called for default LM Studio roots.
+    if _is_model_directory(lm_dir):
+        try:
+            updated_at = lm_dir.stat().st_mtime
+        except OSError:
+            updated_at = None
+        return [
+            LocalModelInfo(
+                id = str(lm_dir),
+                display_name = lm_dir.name,
+                path = str(lm_dir),
+                source = "lmstudio",
+                updated_at = updated_at,
+            ),
+        ]
+
     found: List[LocalModelInfo] = []
     for child in lm_dir.iterdir():
         try:
@@ -263,6 +340,25 @@ def _scan_lmstudio_dir(lm_dir: Path) -> List[LocalModelInfo]:
                     )
                 continue
 
+            # If the child directory itself looks like a model directory
+            # (has config AND weight files), surface it directly instead
+            # of descending into it as a publisher.
+            if _is_model_directory(child):
+                try:
+                    updated_at = child.stat().st_mtime
+                except OSError:
+                    updated_at = None
+                found.append(
+                    LocalModelInfo(
+                        id = str(child),
+                        display_name = child.name,
+                        path = str(child),
+                        source = "lmstudio",
+                        updated_at = updated_at,
+                    ),
+                )
+                continue
+
             # child is a publisher directory -- scan its sub-directories
             for model_dir in child.iterdir():
                 try:

studio/backend/utils/models/model_config.py

@@ -1130,6 +1130,26 @@ def list_gguf_variants(
     return variants, has_vision
 
 
+def _resolve_gguf_dir(p: Path) -> Optional[Path]:
+    """Resolve a path to the directory containing GGUF variants.
+
+    If *p* is already a directory, returns it directly.  If *p* is a ``.gguf``
+    file whose parent directory has model metadata (``config.json`` or
+    ``adapter_config.json``), returns the parent -- all GGUFs in that
+    directory belong to the same model.  Returns ``None`` for loose standalone
+    GGUFs (no config) to avoid cross-wiring unrelated models.
+    """
+    if p.is_dir():
+        return p
+    if p.is_file() and p.suffix.lower() == ".gguf":
+        parent = p.parent
+        if (parent / "config.json").exists() or (
+            parent / "adapter_config.json"
+        ).exists():
+            return parent
+    return None
+
+
 def list_local_gguf_variants(
     directory: str,
 ) -> tuple[list[GgufVariantInfo], bool]:
@@ -1142,8 +1162,8 @@ def list_local_gguf_variants(
     Returns:
         (variants, has_vision): list of non-mmproj GGUF variants + vision flag.
     """
-    p = Path(directory)
-    if not p.is_dir():
+    p = _resolve_gguf_dir(Path(directory))
+    if p is None:
         return [], False
 
     quant_totals: dict[str, int] = {}
@@ -1183,8 +1203,8 @@ def _find_local_gguf_by_variant(directory: str, variant: str) -> Optional[str]:
 
     Returns the resolved absolute path, or ``None`` if no match.
     """
-    p = Path(directory)
-    if not p.is_dir():
+    p = _resolve_gguf_dir(Path(directory))
+    if p is None:
         return None
 
     matches = sorted(