Repopulate GGUF dropdown via gr.update in Gradio 6

Returning a bare list of (label, value) tuples no longer re-renders a
Dropdown under Gradio 6 SSR. Use gr.update(choices=..., value=...) so
the file picker populates and auto-selects the first GGUF.

Co-Authored-By: Claude <noreply@anthropic.com>

app.py

@@ -32,23 +32,31 @@ COMPUTE_DTYPES = ["f16", "bf16", "f32"]
 
 
 def list_gguf_files(repo_id: str, hf_token: str):
-    """List *.gguf files in a repo and auto-detect their quant names."""
+    """List *.gguf files in a repo and auto-detect their quant names.
+
+    Returns gr.update objects (not bare lists) so Gradio 6 reliably re-renders
+    the dropdown and pre-selects the first file. A plain list return no longer
+    repopulates a Dropdown under SSR in Gradio 6.
+    """
     if not repo_id or not repo_id.strip():
-        return [], "Enter a Hugging Face repo id."
+        return gr.update(choices=[], value=None), "Enter a Hugging Face repo id."
     try:
         api = HfApi(token=hf_token or None)
         files = api.list_repo_files(repo_id=repo_id.strip())
     except Exception as e:  # noqa: BLE001
-        return [], f"Error listing repo: {e}"
+        return gr.update(choices=[], value=None), f"Error listing repo: {e}"
     ggufs = sorted(f for f in files if f.lower().endswith(".gguf"))
     if not ggufs:
-        return [], f"No .gguf files found in {repo_id!r}."
+        return gr.update(choices=[], value=None), f"No .gguf files found in {repo_id!r}."
     choices = []
     for f in ggufs:
         q = quant_from_filename(f)
         label = f"{f}" + (f"  [{q}]" if q else "")
         choices.append((label, f))
-    return choices, f"Found {len(ggufs)} GGUF file(s)."
+    return (
+        gr.update(choices=choices, value=ggufs[0]),
+        f"Found {len(ggufs)} GGUF file(s).",
+    )
 
 
 def fetch_arch(repo_id: str, filename: str, hf_token: str):