[Windows] Background session cwd loses one leading backslash on UNC paths -> "working directory no longer exists or is not accessible"

Environment

• Claude Code 2.1.220 (CLI)
• Windows 11 Pro 10.0.26200
• Node v24.14.0
• Working directory reached through a UNC path (\\RaiDrive-USER\Synology\dev\repo-a). Same share is also mapped to S:, so the identical folder is reachable under two spellings.

Summary

When a session's working directory is a UNC path, Claude Code stores it with one leading backslash instead of two and then rejects it as missing:

working directory no longer exists or is not accessible: \RaiDrive-USER\Synology\dev\repo-a

The path it was given is valid; the path it saved is not. \\server\share\... is a UNC path, \server\share\... is a drive-relative path, so the check can never succeed.

Evidence: the persisted value

~/.claude/jobs/<id>/state.json, verbatim (JSON \\ = one literal backslash):

{
  "state": "failed",
  "detail": "working directory no longer exists or is not accessible: \\RaiDrive-USER\\Synology\\dev\\repo-a",
  "intent": "raidrive test",
  "cwd": "\\RaiDrive-USER\\Synology\\dev\\repo-a",
  "originCwd": "\\RaiDrive-USER\\Synology\\dev\\repo-a",
  "template": "claude",
  "backend": "daemon"
}

Both cwd and originCwd hold the single-backslash form, so the value is already mangled by the time it is recorded.

Evidence: Claude Code receives the correct path

A child process launched from that same directory inherits the correct two-backslash cwd, so nothing upstream is dropping it:

# terminal cwd = \\RaiDrive-USER\Synology\dev\repo-a
> node -e "console.log(process.cwd())"
\\RaiDrive-USER\Synology\dev\repo-a          # correct, two backslashes

# terminal cwd = S:\dev\repo-a  (same folder, drive-letter spelling)
> node -e "console.log(process.cwd())"
S:\dev\repo-a

And the mangled form genuinely does not exist:

\\RaiDrive-USER\Synology\dev\repo-a   ->  exists
\RaiDrive-USER\Synology\dev\repo-a    ->  does not exist

Evidence: same folder, two spellings, opposite outcomes

Every background session I ran today, from ~/.claude/jobs/*/state.json. Note rows 2 and 5 — the same directory, differing only in spelling:

| time | intent | state | stored cwd |
|---|---|---|---|
| 20:51 | TEST | failed | \RaiDrive-USER\Synology\dev\repo-a |
| 21:53 | test | done | S:\dev\repo-b |
| 21:54 | | done | S:\dev\repo-b |
| 21:58 | test | failed | \RaiDrive-USER\Synology\dev\repo-a |
| 22:09 | test4 | failed | \RaiDrive-USER\Synology\dev\repo-b |
| 22:11 | | running | S:\dev\repo-c |
| 21:06 | git pull | running | D:\dev\repo-d |

7 sessions started from a UNC cwd → all failed, all stored with one backslash.
4 sessions started from a drive-letter cwd (S: network drive or D: local) → all fine.

The network share itself is not the problem: S:\dev\repo-b works while \\RaiDrive-USER\Synology\dev\repo-b fails, and those are the same directory on the same share.

Likely cause

Node's path helpers preserve the UNC prefix; a separator-dedupe step does not:

const unc = '\\\\RaiDrive-USER\\Synology\\dev\\repo-a'   // \\RaiDrive-USER\Synology\dev\repo-a

path.win32.normalize(unc)   // \\RaiDrive-USER\Synology\dev\repo-a   ok
path.posix.normalize(unc)   // \\RaiDrive-USER\Synology\dev\repo-a   ok
path.normalize(unc)         // \\RaiDrive-USER\Synology\dev\repo-a   ok

unc.replace(/\\+/g, '\\')   // \RaiDrive-USER\Synology\dev\repo-a    <-- matches the stored value

So this looks like a custom "collapse repeated separators" / path-join step rather than a stdlib call. Whatever normalizes the cwd before it reaches state.json needs to leave a leading \\ (or //) intact.

Steps to reproduce

1. On Windows, have a directory reachable via UNC (\\server\share\project) — a mapped network drive or any SMB share.
2. Open a shell whose cwd is the UNC form (cd \\server\share\project; node -e "console.log(process.cwd())" should print two leading backslashes).
3. Start a background session there.
4. It fails with working directory no longer exists or is not accessible: \server\share\project, and ~/.claude/jobs/<id>/state.json shows cwd with a single leading backslash.
5. Repeat from X:\project (the same folder via a mapped drive letter) — works.

Suggested fix

Preserve the UNC prefix when normalizing a working directory. A guard on the dedupe step is enough:

// keep exactly two leading separators for UNC paths
const isUnc = /^[\\/]{2}[^\\/]/.test(p)

Alternatively, use path.win32.normalize on Windows, which already handles this.

Related

• #76205 documents a different symptom on the same class of drives (empty /resume history from a project-slug mismatch, caused by native realpath resolving mapped drives to UNC). I checked that mechanism here — fs.realpathSync.native('S:\\dev\\repo-a') does return \\RaiDrive-USER\Synology\dev\repo-a on this machine — but it is not what drives this bug: sessions started from S:\... store S:\... and work fine, so the stored cwd is the raw inherited cwd, not a realpath of it. The two issues are independent.
• #69902 asks for graceful recovery when the working directory is gone; here the directory is present and the recorded path is simply wrong.

Happy to provide more state.json samples or test a patch.