diff --git a/src/depnav/config.py b/src/depnav/config.py
index 90d9496..3a54dc3 100644
--- a/src/depnav/config.py
+++ b/src/depnav/config.py
@@ -1 +1,161 @@
-/app/depnav/src/depnav/config.py
\ No newline at end of file
+from pathlib import Path
+from typing import Any, Optional
+
+import yaml
+
+
+class Config:
+    """Configuration management for depnav."""
+
+    DEFAULT_CONFIG_FILE = ".depnav.yaml"
+    DEFAULT_THEME = "default"
+    DEFAULT_EXCLUDE_PATTERNS = [
+        "__pycache__",
+        ".git",
+        "node_modules",
+        "*.egg-info",
+        ".venv",
+        "venv",
+        ".tox",
+        "build",
+        "dist",
+        "*.pyc",
+        ".pytest_cache",
+        ".mypy_cache",
+        ".ruff_cache",
+        ".hypothesis",
+    ]
+    DEFAULT_INCLUDE_EXTENSIONS = [".py", ".js", ".ts", ".go"]
+
+    def __init__(
+        self,
+        config_file: Optional[Path] = None,
+        theme: str = DEFAULT_THEME,
+        exclude_patterns: Optional[list[str]] = None,
+        include_extensions: Optional[list[str]] = None,
+        max_nodes: int = 50,
+        layout: str = "tree",
+    ):
+        self.config_file = config_file
+        self.theme = theme
+        self.exclude_patterns = (
+            exclude_patterns if exclude_patterns is not None else self.DEFAULT_EXCLUDE_PATTERNS.copy()
+        )
+        self.include_extensions = (
+            include_extensions if include_extensions is not None else self.DEFAULT_INCLUDE_EXTENSIONS.copy()
+        )
+        self.max_nodes = max_nodes
+        self.layout = layout
+
+        self._config: dict[str, Any] = {}
+        self._load_config()
+
+    def _load_config(self) -> None:
+        """Load configuration from file if it exists."""
+        if self.config_file and self.config_file.exists():
+            try:
+                content = self.config_file.read_text()
+
+                if self.config_file.suffix == ".toml":
+                    import tomli
+
+                    data = tomli.loads(content)
+                    data = data.get("tool", {}).get("depnav", {})
+                else:
+                    data = yaml.safe_load(content) or {}
+
+                if isinstance(data, dict):
+                    self._config.update(data)
+            except (yaml.YAMLError, OSError):
+                pass
+
+    def _apply_env_overrides(self) -> None:
+        """Apply environment variable overrides."""
+        env_map = {
+            "DEPNAV_CONFIG": ("config_file", None),
+            "DEPNAV_THEME": ("theme", "default"),
+            "DEPNAV_PAGER": ("pager", "auto"),
+        }
+
+        for env_var, (attr, default) in env_map.items():
+            value = Path.environ.get(env_var)
+            if value is not None:
+                if attr == "config_file":
+                    setattr(self, attr, Path(value))
+                else:
+                    setattr(self, attr, value)
+
+    def get(self, key: str, default: Any = None) -> Any:
+        """Get a configuration value."""
+        return self._config.get(key, default)
+
+    def set(self, key: str, value: Any) -> None:
+        """Set a configuration value."""
+        self._config[key] = value
+
+    def merge_config(self, config_dict: dict[str, Any]) -> None:
+        """Merge additional configuration."""
+        if isinstance(config_dict, dict):
+            self._config.update(config_dict)
+
+    def load_from_yaml(self, path: Path) -> None:
+        """Load configuration from a YAML file."""
+        content = path.read_text()
+        data = yaml.safe_load(content) or {}
+        self.merge_config(data)
+
+    def load_from_pyproject(self, path: Path) -> None:
+        """Load configuration from a pyproject.toml file."""
+        if path.name == "pyproject.toml":
+            import tomli
+
+            content = path.read_text()
+            data = tomli.loads(content)
+            data = data.get("tool", {}).get("depnav", {})
+            self.merge_config(data)
+
+    def get_theme(self) -> str:
+        """Get the current theme."""
+        return self.theme or self.DEFAULT_THEME
+
+    def default_theme(self) -> str:
+        """Get the default theme name."""
+        return self.DEFAULT_THEME
+
+    def get_exclude_patterns(self) -> list[str]:
+        """Get the exclude patterns."""
+        return self.exclude_patterns or self.DEFAULT_EXCLUDE_PATTERNS
+
+    def get_include_extensions(self) -> list[str]:
+        """Get the include extensions."""
+        return self.include_extensions or self.DEFAULT_INCLUDE_EXTENSIONS
+
+    def save_config(self, path: Path) -> None:
+        """Save configuration to a file."""
+        config_data = {
+            "theme": self.theme,
+            "exclude_patterns": self.exclude_patterns,
+            "include_extensions": self.include_extensions,
+            "max_nodes": self.max_nodes,
+            "layout": self.layout,
+        }
+        path.write_text(yaml.dump(config_data))
+
+    def __repr__(self) -> str:
+        return (
+            f"Config(theme={self.theme!r}, "
+            f"exclude_patterns={self.exclude_patterns!r}, "
+            f"include_extensions={self.include_extensions!r})"
+        )
+
+
+def load_config(config_path: Optional[Path] = None) -> Config:
+    """Load configuration with environment variable overrides."""
+    if config_path is None:
+        env_config = Path.environ.get("DEPNAV_CONFIG", "")
+        if env_config:
+            config_path = Path(env_config)
+        else:
+            config_path = Path.cwd() / Config.DEFAULT_CONFIG_FILE
+
+    return Config(config_file=config_path)