diff --git a/src/tinker/lib/public_interfaces/rest_client.py b/src/tinker/lib/public_interfaces/rest_client.py
index eed3402..7df81eb 100644
--- a/src/tinker/lib/public_interfaces/rest_client.py
+++ b/src/tinker/lib/public_interfaces/rest_client.py
@@ -456,9 +456,13 @@ class RestClient(TelemetryProvider):
         types.ParsedCheckpointTinkerPath.from_tinker_path(tinker_path)
 
         def _safe_extract(tar: tarfile.TarFile, path: Path) -> None:
+            base = path.resolve()
             for member in tar.getmembers():
-                member_path = path / member.name
-                if not str(member_path.resolve()).startswith(str(path.resolve())):
+                # Reject symlinks/hardlinks to avoid traversal via link targets
+                if member.issym() or member.islnk():
+                    raise ValueError("Unsafe symlink or hardlink in tar archive")
+                member_path = (path / member.name).resolve()
+                if not str(member_path).startswith(str(base)):
                     raise ValueError("Unsafe path in tar archive")
             tar.extractall(path=path)
 
@@ -502,11 +506,17 @@ class RestClient(TelemetryProvider):
             adapter_config = extract_dir / "adapter_config.json"
             adapter_safetensors = extract_dir / "adapter_model.safetensors"
             adapter_bin = extract_dir / "adapter_model.bin"
+            checkpoint_complete = extract_dir / "checkpoint_complete"
             if not adapter_config.exists() or not (adapter_safetensors.exists() or adapter_bin.exists()):
                 raise ValueError(
                     "Checkpoint archive does not contain a PEFT adapter. "
                     "Expected adapter_config.json and adapter_model.safetensors (or adapter_model.bin)."
                 )
+            if not checkpoint_complete.exists():
+                raise ValueError(
+                    "Checkpoint archive is missing 'checkpoint_complete'. "
+                    "The adapter files may be incomplete."
+                )
 
             base_model = "unknown"
             lora_rank = None