Grep tool (ripgrep) silently returns no matches for strings that exist

Bug Description

The built-in Grep tool (ripgrep-based) silently returns "No matches found" for patterns that definitely exist in the codebase. Bash grep finds the same patterns immediately.

Reproduction

Search for the string va_return which exists in src/data/common/utils.py (in docstrings and f-strings):

Grep tool (fails):

Grep(pattern="va_return", output_mode="content")
→ "No matches found"

Bash grep (succeeds):

grep -rn "va_return" src/data/common/utils.py
→ 309:    1. Vol-adjusted forward return (va_return): Float32
→ 320:    va_return uses symmetric ATR% for vol-adjustment.
→ 386:            .alias(f"va_return_{s}")

Behavior

• The Grep tool returns no results — no error, no warning, just "No matches found"
• The pattern is a simple literal string, no regex complexity
• Bash grep -rn finds it immediately in the same file
• Tested with and without -i (case insensitive) flag — same result
• Reproducible across multiple sessions

Environment

• Claude Code version: 2.1.74
• OS: Windows 11 Pro (10.0.26200)
• Shell: Git Bash
• GNU grep version: 3.0

Additional Context

• Started occurring after updating to the latest Claude Code version
• Reproduced in at least 2 separate sessions
• The file being searched is a normal .py file, not gitignored, not binary
• This causes Claude to waste many turns trying different search strategies before falling back to bash grep or direct file reads