diff --git a/src/companion/config.py b/src/companion/config.py
index 7ba76a8..2495024 100644
--- a/src/companion/config.py
+++ b/src/companion/config.py
@@ -1,6 +1,5 @@
 import json
 import os
-from pathlib import Path
 from typing import Any, Dict, List
 
 from pydantic import BaseModel, Field
diff --git a/tests/test_config.py b/tests/test_config.py
index 7df4a53..73a0130 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -140,5 +140,187 @@ def test_load_config_reads_json_and_expands_tilde():
         assert config.rag.vector_store.path == os.path.expanduser(
             "~/.companion/vectors.lance"
         )
+        assert config.companion.memory.persistent_store == os.path.expanduser(
+            "~/mem.db"
+        )
+    finally:
+        os.unlink(path)
+
+
+def test_tilde_expansion_in_list_values():
+    """Test that tilde expansion works for list values."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".json", delete=False) as f:
+        json.dump(
+            {
+                "companion": {
+                    "name": "SAN",
+                    "persona": {
+                        "role": "companion",
+                        "tone": "reflective",
+                        "style": "questioning",
+                        "boundaries": [],
+                    },
+                    "memory": {
+                        "session_turns": 20,
+                        "persistent_store": "~/mem.db",
+                        "summarize_after": 10,
+                    },
+                    "chat": {
+                        "streaming": True,
+                        "max_response_tokens": 2048,
+                        "default_temperature": 0.7,
+                        "allow_temperature_override": True,
+                    },
+                },
+                "vault": {
+                    "path": "~/test-vault",
+                    "indexing": {
+                        "auto_sync": False,
+                        "auto_sync_interval_minutes": 1440,
+                        "watch_fs_events": False,
+                        "file_patterns": ["*.md"],
+                        "deny_dirs": ["~/secret", ".git"],
+                        "deny_patterns": [".*"],
+                    },
+                    "chunking_rules": {},
+                },
+                "rag": {
+                    "embedding": {
+                        "provider": "ollama",
+                        "model": "dummy",
+                        "base_url": "http://localhost:11434",
+                        "dimensions": 4,
+                        "batch_size": 2,
+                    },
+                    "vector_store": {
+                        "type": "lancedb",
+                        "path": "~/.companion/vectors.lance",
+                    },
+                    "search": {
+                        "default_top_k": 8,
+                        "max_top_k": 20,
+                        "similarity_threshold": 0.75,
+                        "hybrid_search": {
+                            "enabled": False,
+                            "keyword_weight": 0.3,
+                            "semantic_weight": 0.7,
+                        },
+                        "filters": {
+                            "date_range_enabled": True,
+                            "tag_filter_enabled": True,
+                            "directory_filter_enabled": True,
+                        },
+                    },
+                },
+                "model": {
+                    "inference": {
+                        "backend": "llama.cpp",
+                        "model_path": "",
+                        "context_length": 8192,
+                        "gpu_layers": 35,
+                        "batch_size": 512,
+                        "threads": 8,
+                    },
+                    "fine_tuning": {
+                        "base_model": "",
+                        "output_dir": "",
+                        "lora_rank": 16,
+                        "lora_alpha": 32,
+                        "learning_rate": 0.0002,
+                        "batch_size": 4,
+                        "gradient_accumulation_steps": 4,
+                        "num_epochs": 3,
+                        "warmup_steps": 100,
+                        "save_steps": 500,
+                        "eval_steps": 250,
+                        "training_data_path": "",
+                        "validation_split": 0.1,
+                    },
+                    "retrain_schedule": {
+                        "auto_reminder": True,
+                        "default_interval_days": 90,
+                        "reminder_channels": [],
+                    },
+                },
+                "api": {
+                    "host": "127.0.0.1",
+                    "port": 7373,
+                    "cors_origins": [],
+                    "auth": {"enabled": False},
+                },
+                "ui": {
+                    "web": {
+                        "enabled": True,
+                        "theme": "obsidian",
+                        "features": {
+                            "streaming": True,
+                            "citations": True,
+                            "source_preview": True,
+                        },
+                    },
+                    "cli": {"enabled": True, "rich_output": True},
+                },
+                "logging": {
+                    "level": "INFO",
+                    "file": "",
+                    "max_size_mb": 100,
+                    "backup_count": 5,
+                },
+                "security": {
+                    "local_only": True,
+                    "vault_path_traversal_check": True,
+                    "sensitive_content_detection": True,
+                    "sensitive_patterns": [],
+                    "require_confirmation_for_external_apis": True,
+                },
+            },
+            f,
+        )
+        path = f.name
+    try:
+        config = load_config(path)
+        # Check tilde expansion in list values
+        assert config.vault.indexing.deny_dirs[0] == os.path.expanduser("~/secret")
+    finally:
+        os.unlink(path)
+
+
+def test_load_config_missing_file():
+    """Test that loading a missing file raises FileNotFoundError."""
+    with tempfile.TemporaryDirectory() as tmp:
+        missing_path = os.path.join(tmp, "nonexistent.json")
+        try:
+            load_config(missing_path)
+            assert False, "Should have raised an exception"
+        except FileNotFoundError:
+            pass  # Expected
+
+
+def test_load_config_malformed_json():
+    """Test that malformed JSON raises JSONDecodeError."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".json", delete=False) as f:
+        f.write("{invalid json")
+        path = f.name
+    try:
+        load_config(path)
+        assert False, "Should have raised an exception"
+    except json.JSONDecodeError:
+        pass  # Expected
+    finally:
+        os.unlink(path)
+
+
+def test_load_config_missing_required_field():
+    """Test that missing required field raises ValidationError."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".json", delete=False) as f:
+        # Missing required fields like "companion"
+        json.dump({"vault": {"path": "~/test"}}, f)
+        path = f.name
+    try:
+        load_config(path)
+        assert False, "Should have raised an exception"
+    except Exception as e:
+        # Should be a Pydantic validation error
+        assert "companion" in str(e).lower() or "validation" in str(e).lower()
     finally:
         os.unlink(path)