[BUG] MCP server automatically creates empty folder in home directory

[samuel032khoury]

Bug Description

When launching the MCP server, a visible ~/basic-memory directory is automatically created in the home directory, even if active project directory is set to other path. This results in unwanted visible configuration/data folder in the home directory.

Steps To Reproduce

1. Running uvx basic-memory mcp
2. Update the server with the following configuration:

   {
     "env": "dev",
     "projects":
     {
       "main": "/Users/user_name/.basic-memory/projects/main"
      },
     "default_project": "main",
     "default_project_mode": true,
     "project_root": null,
     "cloud_mode": false
   }

3. Manually delete ~/basic-memory.
4. Relaunch the MCP server.
5. Observe that ~/basic-memory is created automatically.

Expected Behavior

No visible project directory should be created in the user’s home directory if configured. The server should not create default project directories implicitly.

Actual Behavior

Upon launching the MCP server, a visible directory is created at home directory.

Environment

• OS: macOS 26.4 Developer Beta1
• Python version: 3.12.8
• Basic Memory version: v0.18.4
• Installation method: running through uvx

[phernandez]

Fixed in commit da4d369 → 18f00f8 on main.

Root cause: BasicMemoryConfig.default_project had a hardcoded field default of "main". When a config file had projects named something other than "main" and no explicit default_project key, the config resolved to default_project="main" — which didn't match any project. The model_post_init fixup logic existed but was behind # pragma: no cover and only handled the stale-name case, not the missing-key case. This caused the server to fall through to the empty-projects path and create ~/basic-memory.

Fix: Changed the field default from "main" to None and used Pydantic's model_fields_set to distinguish between "config file omitted the key" (auto-resolve to first project) and "user explicitly set null" (preserve for discovery mode). Stale names that don't match any project are also corrected.

10 new tests added covering all edge cases.