feat(core): add XDG_CONFIG_HOME support (#844)

Signed-off-by: Rafael Madriz <rafa@rafaelmadriz.com>

src/basic_memory/config.py

@@ -21,7 +21,7 @@ from basic_memory.utils import setup_logging, generate_permalink
 
 DATABASE_NAME = "memory.db"
 APP_DATABASE_NAME = "memory.db"  # Using the same name but in the app directory
-DATA_DIR_NAME = ".basic-memory"
+DATA_DIR_NAME = "basic-memory"
 CONFIG_FILE_NAME = "config.json"
 WATCH_STATUS_JSON = "watch-status.json"
 CONFIG_DIR_MODE = 0o700
@@ -69,15 +69,18 @@ def resolve_data_dir() -> Path:
 
     Single source of truth for the per-user state directory. Honors
     ``BASIC_MEMORY_CONFIG_DIR`` so each process/worktree can isolate config
-    and database state; otherwise falls back to ``<user home>/.basic-memory``.
+    and database state; otherwise falls back to ``<user home>/.basic-memory``,
+    and then to ``XDG_CONFIG_HOME``.
 
     Cross-platform: ``Path.home()`` reads ``$HOME`` on POSIX and
     ``%USERPROFILE%`` on Windows, so there's no need to check ``$HOME``
     explicitly here.
     """
-    if config_dir := os.getenv("BASIC_MEMORY_CONFIG_DIR"):
-        return Path(config_dir)
-    return Path.home() / DATA_DIR_NAME
+    if basic_memory_dir := os.getenv("BASIC_MEMORY_CONFIG_DIR"):
+        return Path(basic_memory_dir)
+    if xdg_config := os.getenv("XDG_CONFIG_HOME"):
+        return Path(xdg_config) / DATA_DIR_NAME
+    return Path.home() / ("." + DATA_DIR_NAME)
 
 
 def default_fastembed_cache_dir() -> str:

tests/test_config.py

@@ -308,8 +308,9 @@ class TestDataDirHelpers:
     """Module-level helpers that resolve the Basic Memory data directory."""
 
     def test_resolve_data_dir_defaults_to_home_dot_basic_memory(self, config_home, monkeypatch):
-        """Without BASIC_MEMORY_CONFIG_DIR, resolver returns ~/.basic-memory."""
+        """Without BASIC_MEMORY_CONFIG_DIR and XDG_CONFIG_HOME, resolver returns ~/.basic-memory."""
         monkeypatch.delenv("BASIC_MEMORY_CONFIG_DIR", raising=False)
+        monkeypatch.delenv("XDG_CONFIG_HOME", raising=False)
 
         assert resolve_data_dir() == config_home / ".basic-memory"
 
@@ -320,6 +321,23 @@ class TestDataDirHelpers:
 
         assert resolve_data_dir() == custom
 
+    def test_resolve_data_dir_honors_xdg_config_home(self, tmp_path, monkeypatch):
+        """XDG_CONFIG_HOME is honored when BASIC_MEMORY_CONFIG_DIR is not set."""
+        monkeypatch.delenv("BASIC_MEMORY_CONFIG_DIR", raising=False)
+        xdg_config = tmp_path / "xdg-config"
+        monkeypatch.setenv("XDG_CONFIG_HOME", str(xdg_config))
+
+        assert resolve_data_dir() == xdg_config / "basic-memory"
+
+    def test_basic_memory_config_dir_takes_precedence_over_xdg(self, tmp_path, monkeypatch):
+        """BASIC_MEMORY_CONFIG_DIR takes precedence over XDG_CONFIG_HOME."""
+        xdg_config = tmp_path / "xdg-config"
+        custom = tmp_path / "custom-config"
+        monkeypatch.setenv("XDG_CONFIG_HOME", str(xdg_config))
+        monkeypatch.setenv("BASIC_MEMORY_CONFIG_DIR", str(custom))
+
+        assert resolve_data_dir() == custom
+
     def test_default_fastembed_cache_dir_uses_data_dir(self, config_home, monkeypatch):
         """Default cache path is a subdir of the Basic Memory data dir."""
         monkeypatch.delenv("BASIC_MEMORY_CONFIG_DIR", raising=False)