Problem

When Cursor, Windsurf, or VS Code launch codedb mcp as an MCP server they do not set cwd to the open project directory — they inherit their own application process cwd, which is typically /Applications, /usr/local, ~, or whatever the OS assigns at app launch.

codedb mcp resolves its scan root from cwd at startup (src/main.zig L97: root = ".", then resolveRoot calls cwd().realpath(".", ...)). This means codedb silently indexes the wrong directory — one the user never asked for — and the user gets no results or, worse, results from an unrelated path.

The existing root_policy.isIndexableRoot guard only blocks /, /tmp, and the literal home directory. Paths like /Applications, /usr/local, /opt, and /opt/homebrew all pass the guard today and will trigger a full scan.

The MCP protocol has a roots handshake (roots/list) that codedb already implements, but it races: scanBg fires unconditionally on startup (main.zig L636–638) before the first JSON-RPC message arrives, so the roots response always comes too late.

Failing Test

test "issue-332: root_policy rejects dangerous ambient cwd roots" {
    const root_policy = @import("root_policy.zig");
    try testing.expect(!root_policy.isIndexableRoot("/"));
    try testing.expect(!root_policy.isIndexableRoot("/Applications"));
    try testing.expect(!root_policy.isIndexableRoot("/usr"));
    try testing.expect(!root_policy.isIndexableRoot("/usr/local"));
    try testing.expect(!root_policy.isIndexableRoot("/usr/local/bin"));
    try testing.expect(!root_policy.isIndexableRoot("/opt"));
    try testing.expect(!root_policy.isIndexableRoot("/opt/homebrew"));
}

Verified failing on current main:

error: 'tests.test.issue-332: root_policy rejects dangerous ambient cwd roots' failed
src/tests.zig:7604: try testing.expect(!root_policy.isIndexableRoot("/Applications"));
409/410 tests passed (1 failed)

Expected

codedb mcp launched without an explicit path arg should either:

1. Block startup until a valid root is confirmed (MCP roots handshake or CLI positional arg), or
2. Exit immediately with a clear error rather than scanning the ambient cwd

isIndexableRoot must also reject shallow system paths (/Applications, /usr, /opt, etc.).

Fix

See RFC: docs/rfc-mcp-root-resolution.md (filed alongside this issue).

Short-term: expand isIndexableRoot to deny all paths shallower than a real project dir.
Long-term: defer the initial scan until a confirmed root is available. See RFC for full design.