[BUG] Windows: Glob returns "No files found" for existing files when path arg contains non-ASCII (Korean) chars and pattern has a directory segment — deterministic per executor process from spawn

Environment

• Claude Desktop 1.26832.0.0 (Windows 10 Pro 10.0.19045)
• claude-code runtime 2.1.222 (%APPDATA%\Claude\claude-code\2.1.222\claude.exe, spawned per session by the desktop app)
• System locale: Korean (legacy ANSI codepage cp949); working directories contain Hangul segments

Summary

The Glob tool silently returns "No files found" for files that exist, whenever both conditions hold:

1. the path argument contains non-ASCII (Hangul) characters, and
2. the pattern contains an explicit directory segment (literal or * — anything except a leading **).

Either condition alone is fine. The failure is indistinguishable from a genuinely empty result (no error), so the agent concludes the files do not exist.

Additionally, the defect is decided at executor-process spawn: some claude-code executor processes exhibit it consistently for their whole lifetime while others (same binary, same machine, same minute) are consistently unaffected.

Reproduction

Real directory layout (all files exist, git-tracked; 업무저장소, 인프라, 사람 are Hangul names):

C:\00\업무저장소\log\
  2021-W01.md ... 2026-W32.md   (292 top-level .md files)
  인프라\   (6 .md files)
  사람\    (2 .md files)

Measured matrix (12 combos, re-run 6 times over 12h in the affected process — fully deterministic):

| path argument | pattern | result |
|---|---|---|
| C:\00\업무저장소\log (Hangul) | 인프라/*.md | ❌ "No files found" |
| C:\00\업무저장소\log (Hangul) | 사람/*.md | ❌ |
| C:\00\업무저장소\log (Hangul) | */*.md (pure-ASCII pattern!) | ❌ |
| C:\00\업무저장소\log (Hangul) | */2026-08-07.md | ❌ |
| C:\00\업무저장소\log (Hangul) | 인프라/2026-08-07.md (literal) | ❌ |
| C:\00\업무저장소\log (Hangul) | 인프라/**/*.md | ❌ |
| C:\00\업무저장소 (Hangul) | log/인프라/*.md | ❌ |
| C:/00/업무저장소/log (forward slashes) | 인프라/*.md | ❌ |
| C:\00\업무저장소\log (Hangul) | * (single segment) | ✅ 292 files |
| C:\00\업무저장소\log (Hangul) | **/*.md (recursive) | ✅ 300 files incl. both subdirs |
| C:\00 (ASCII) | 업무저장소/log/인프라/*.md (Hangul in pattern) | ✅ 6 files |
| C:\Users\<user>\.claude\skills (ASCII) | 조각/*.md (Hangul in pattern) | ✅ 1 file |

Key observations:

• Determinant = non-ASCII in the path argument × explicit directory segment in the pattern. Hangul inside the pattern is harmless; **-recursive traversal is harmless even with a Hangul path.
• Slash direction in path makes no difference.

Per-process determinism (most diagnostic finding)

Same installed binary (2.1.222 is the only version present, unchanged during the whole period), same machine, measurements within the same minute:

• Executor A (fresh session spawn, previous evening): all directory-segment combos fail, first observed +27 min after spawn, consistent across 6 rounds over 12+ hours.
• Executor B (spawned next morning with --resume=<session-id>): all 5 previously-failing combos pass, +25 min after spawn — reported counts (6 / 2 / 8 / 1) exactly match the real directory contents.

So the defect is fixed at process birth and stable for the process lifetime — not correlated with version, machine, or process age. This smells like an encoding/codepage initialization race at spawn (which would explain the non-ASCII specificity, the per-spawn variance, and the lifetime consistency). Sample size caveat: 1 failing spawn (fresh) vs 2 passing spawns (both --resume); the spawn-mode correlation is noted but unconfirmed.

Impact

The failure mode is a silent false negative. In our case the agent Glob-checked a directory for today's append-only log file, got "No files found", concluded it didn't exist, and attempted to create a "new" file over the existing one — only the Write tool's read-before-write guard prevented data loss. Any "create-if-missing" or "verify-absence" branch driven by Glob is unsafe under this bug. Same hazard class as #68343 (silent empty output on CJK paths misjudged as negative confirmation), but in the Glob tool itself rather than shell output.

Workarounds (verified)

1. Root path at the nearest ASCII ancestor and move the non-ASCII segments into the pattern: path=C:\00, pattern=업무저장소/log/인프라/*.md → works.
2. Use **-recursive patterns and filter the results.
3. Treat Glob's "No files found" as non-evidence of absence before any create-if-missing branch; cross-check with ls or an external search tool.