fix: skip filesystem mkdir in cloud mode for project creation

ConfigManager.add_project() and ProjectService.move_project() unconditionally
called mkdir on the project path. In cloud mode (BASIC_MEMORY_PROJECT_ROOT set),
paths resolve under root (/) which is read-only on macOS, crashing local dev.
Production Fly.io containers have writable /, so this was never caught there.

Skip mkdir when project_root is set since cloud mode uses S3 for file storage.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Joe P <joe@basicmemory.com>

Author: jope-bm

src/basic_memory/config.py

@@ -685,9 +685,10 @@ def add_project(self, name: str, path: str) -> ProjectConfig:
         if project_name:  # pragma: no cover
             raise ValueError(f"Project '{name}' already exists")
 
-        # Ensure the path exists
+        # Ensure the path exists on disk (skip in cloud mode where storage is S3)
         project_path = Path(path)
-        project_path.mkdir(parents=True, exist_ok=True)  # pragma: no cover
+        if not self.config.project_root:
+            project_path.mkdir(parents=True, exist_ok=True)  # pragma: no cover
 
         # Load config, modify it, and save it
         config = self.load_config()

src/basic_memory/services/project_service.py

@@ -459,8 +459,9 @@ async def move_project(self, name: str, new_path: str) -> None:
         if name not in self.config_manager.projects:
             raise ValueError(f"Project '{name}' not found in configuration")
 
-        # Create the new directory if it doesn't exist
-        Path(resolved_path).mkdir(parents=True, exist_ok=True)
+        # Create the new directory if it doesn't exist (skip in cloud mode where storage is S3)
+        if not self.config_manager.config.project_root:
+            Path(resolved_path).mkdir(parents=True, exist_ok=True)
 
         # Update in configuration
         config = self.config_manager.load_config()

tests/test_config.py

@@ -580,6 +580,43 @@ def test_add_project_uses_platform_native_separators(self, monkeypatch):
                 assert "/" in saved_path
                 assert saved_path == str(project_path)
 
+    def test_add_project_skips_mkdir_when_project_root_set(self, monkeypatch):
+        """Test that add_project skips mkdir when project_root is set (cloud mode).
+
+        In cloud mode, file storage is S3 — no local directories needed.
+        Without this, add_project crashes on read-only filesystems (e.g. macOS root /).
+        """
+        import basic_memory.config
+
+        with tempfile.TemporaryDirectory() as temp_dir:
+            temp_path = Path(temp_dir)
+
+            # Simulate cloud mode: project_root set, postgres backend
+            monkeypatch.setenv("BASIC_MEMORY_PROJECT_ROOT", "/cloud-root")
+            monkeypatch.setenv("BASIC_MEMORY_DATABASE_BACKEND", "postgres")
+            # Clear module-level cache so env vars are picked up
+            basic_memory.config._CONFIG_CACHE = None
+
+            config_manager = ConfigManager()
+            config_manager.config_dir = temp_path / "basic-memory"
+            config_manager.config_file = config_manager.config_dir / "config.json"
+            config_manager.config_dir.mkdir(parents=True, exist_ok=True)
+
+            initial_config = BasicMemoryConfig(projects={})
+            config_manager.save_config(initial_config)
+
+            # Use a path that would fail mkdir on most systems (read-only root)
+            config_manager.add_project("test-project", "/nonexistent/cloud/path")
+
+            # Verify project was added to config without creating the directory
+            config = config_manager.load_config()
+            assert "test-project" in config.projects
+            assert config.projects["test-project"].path == "/nonexistent/cloud/path"
+            assert not Path("/nonexistent/cloud/path").exists()
+
+            # Clean up cache for subsequent tests
+            basic_memory.config._CONFIG_CACHE = None
+
     def test_model_post_init_uses_platform_native_separators(self, config_home, monkeypatch):
         """Test that model_post_init uses platform-native separators."""
         import platform