Project CLAUDE.md at a drive/filesystem root (subst drive / repo at C:\) is silently not loaded

What happened?

Project memory (CLAUDE.md / .claude/CLAUDE.md) is silently not loaded when the project directory is a drive/filesystem root — e.g. a subst drive on Windows (subst U: D:\repo, then launch from U:\), or a repo checked out directly at D:\.

Project settings.json, skills, commands, and hooks under <root>\.claude\ do load correctly (they resolve directly against cwd). Only the CLAUDE.md memory is missing, which makes this easy to miss and confusing to diagnose.

Root cause

Project-memory discovery walks the ancestors of cwd and excludes the filesystem root:

let u = [], p = originalCwd;                 // e.g. "U:\"
while (p !== path.parse(p).root) {           // stops BEFORE pushing the root
  u.push(p);
  p = path.dirname(p);
}
for (const v of u.reverse()) {
  load(path.join(v, "CLAUDE.md"));
  load(path.join(v, ".claude", "CLAUDE.md"));
}

On Windows path.win32.parse("U:\\").root === "U:\\", so when cwd is the drive root the loop body runs zero times — the ancestor set is empty and neither U:\CLAUDE.md nor U:\.claude\CLAUDE.md is ever examined. (POSIX has the same shape for a repo at /.)

Contrast a normal deep cwd:

• U:\ → ancestors = [] ← nothing loaded (bug)
• D:\repo → ancestors = ["D:\repo"] (D:\ root excluded) → D:\repo\.claude\CLAUDE.md loaded ✔

Note: on Windows a subst drive's cwd is kept as-is (U:\) and is not realpath-resolved to the underlying D:\repo, so the deep-path code path is never reached. (The session state dir confirms this: ~/.claude/projects/U--/.)

Steps to reproduce

1. subst U: D:\some\repo (or use any repo located directly at a drive root)
2. Put instructions in U:\.claude\CLAUDE.md (or U:\CLAUDE.md).
3. cd /d U:\ && claude
4. /memory — the project CLAUDE.md is absent. Project skills/commands from U:\.claude\ are present, confirming .claude\ itself is found.

Expected

The CLAUDE.md / .claude/CLAUDE.md located at the drive-root project directory should load, the same way .claude/settings.json, skills, and commands there already do.

Suggested fix

Make the ancestor walk inclusive of the root, e.g.:

let u = [], p = originalCwd;
while (true) { u.push(p); const parent = path.dirname(p); if (parent === p) break; p = parent; }

so the root directory itself is included as a candidate.

Work-arounds (for others hitting this)

• Launch from the real path (D:\some\repo) instead of the subst drive.
• Or remap subst to the parent (subst U: D:\some, work in U:\repo — a non-root path).
• Or set env CLAUDE_CODE_ADDITIONAL_DIRECTORIES_CLAUDE_MD=1 and launch claude --add-dir D:\some\repo (loads that dir's CLAUDE.md through the normal pipeline, so subagents get it too).

Environment

• Claude Code version: 2.1.217
• Platform: Windows 11 (26100); reproduced with a subst drive root. Logic also affects any repo at a bare drive root / POSIX /.