[BUG] $CLAUDE_PROJECT_DIR is empty/unset in hook and Bash tool execution (v2.1.74)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

$CLAUDE_PROJECT_DIR is completely empty/unset in both PreToolUse hook execution and Bash tool calls. This causes any hook that references $CLAUDE_PROJECT_DIR to silently fail (script not found → non-zero exit → Claude Code reports a non-blocking hook error and continues).

This is distinct from #27343 (wrong value in worktrees) — in our case the variable is entirely absent from the environment.

What Should Happen?

$CLAUDE_PROJECT_DIR should be set to the project root directory, as documented in the hooks reference.

Error Messages/Logs

PreToolUse:Bash hook error: [python3 "$CLAUDE_PROJECT_DIR"/.claude/hooks/git-safety.py]: No stderr output

Diagnostic evidence

# In a Bash tool call during the session:
$ env | grep -i claude
CLAUDE_CODE_ENTRYPOINT=cli
CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1
CLAUDECODE=1
# Note: no CLAUDE_PROJECT_DIR

$ echo "CLAUDE_PROJECT_DIR=$CLAUDE_PROJECT_DIR"
CLAUDE_PROJECT_DIR=

Other Claude-set env vars (CLAUDECODE, CLAUDE_CODE_ENTRYPOINT) are present — only CLAUDE_PROJECT_DIR is missing.

Steps to Reproduce

1. Create .claude/settings.json with a PreToolUse hook using $CLAUDE_PROJECT_DIR:

``json
{
"hooks": {
"PreToolUse": [
{
"matcher": "Bash",
"hooks": [
{
"type": "command",
"command": "python3 \"$CLAUDE_PROJECT_DIR\"/.claude/hooks/my-hook.py"
}
]
}
]
}
}
``

1. Start Claude Code in the project directory
2. Run any Bash command
3. Observe hook error — $CLAUDE_PROJECT_DIR is empty, so the script path resolves to /.claude/hooks/my-hook.py (nonexistent)

Workaround

Fall back to git rev-parse --show-toplevel:

"command": "bash -c 'root=\"${CLAUDE_PROJECT_DIR:-$(git rev-parse --show-toplevel 2>/dev/null)}\" && python3 \"$root/.claude/hooks/my-hook.py\"'"

Claude Model

Opus

Is this a regression?

Uncertain — $CLAUDE_PROJECT_DIR was added in v1.0.58. It may never have worked in our environment, or it may be a regression in 2.x.

Claude Code Version

2.1.74

Platform

macOS (Darwin 25.3.0)