Freeze

#!/usr/bin/env bash
# check-freeze.sh — PreToolUse hook for /freeze skill
# Reads JSON from stdin, checks if file_path is within the freeze boundary.
# Returns {"permissionDecision":"deny","message":"..."} to block, or {} to allow.
set -euo pipefail

# Read stdin
INPUT=$(cat)

# Locate the freeze directory state file
STATE_DIR="${CLAUDE_PLUGIN_DATA:-$HOME/.gstack}"
FREEZE_FILE="$STATE_DIR/freeze-dir.txt"

# If no freeze file exists, allow everything (not yet configured)
if [ ! -f "$FREEZE_FILE" ]; then
  echo '{}'
  exit 0
fi

FREEZE_DIR=$(tr -d '[:space:]' < "$FREEZE_FILE")

# If freeze dir is empty, allow
if [ -z "$FREEZE_DIR" ]; then
  echo '{}'
  exit 0
fi

# Extract file_path from tool_input JSON
# Try grep/sed first, fall back to Python for escaped quotes
FILE_PATH=$(printf '%s' "$INPUT" | grep -o '"file_path"[[:space:]]*:[[:space:]]*"[^"]*"' | head -1 | sed 's/.*:[[:space:]]*"//;s/"$//' || true)

# Python fallback if grep returned empty
if [ -z "$FILE_PATH" ]; then
  FILE_PATH=$(printf '%s' "$INPUT" | python3 -c 'import sys,json; print(json.loads(sys.stdin.read()).get("tool_input",{}).get("file_path",""))' 2>/dev/null || true)
fi

# If we couldn't extract a file path, allow (don't block on parse failure)
if [ -z "$FILE_PATH" ]; then
  echo '{}'
  exit 0
fi

# Resolve file_path to absolute if it isn't already
case "$FILE_PATH" in
  /*) ;; # already absolute
  *)
    FILE_PATH="$(pwd)/$FILE_PATH"
    ;;
esac

# Normalize: remove double slashes and trailing slash
FILE_PATH=$(printf '%s' "$FILE_PATH" | sed 's|/\+|/|g;s|/$||')

# Resolve symlinks and .. sequences (POSIX-portable, works on macOS)
_resolve_path() {
  local _dir _base
  _dir="$(dirname "$1")"
  _base="$(basename "$1")"
  _dir="$(cd "$_dir" 2>/dev/null && pwd -P || printf '%s' "$_dir")"
  printf '%s/%s' "$_dir" "$_base"
}
FILE_PATH=$(_resolve_path "$FILE_PATH")
FREEZE_DIR=$(_resolve_path "$FREEZE_DIR")

# Check: does the file path start with the freeze directory?
case "$FILE_PATH" in
  "${FREEZE_DIR}/"*|"${FREEZE_DIR}")
    # Inside freeze boundary — allow
    echo '{}'
    ;;
  *)
    # Outside freeze boundary — deny
    # Log hook fire event
    mkdir -p ~/.gstack/analytics 2>/dev/null || true
    echo '{"event":"hook_fire","skill":"freeze","pattern":"boundary_deny","ts":"'$(date -u +%Y-%m-%dT%H:%M:%SZ)'","repo":"'$(basename "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null || echo "unknown")'"}' >> ~/.gstack/analytics/skill-usage.jsonl 2>/dev/null || true

    printf '{"permissionDecision":"deny","message":"[freeze] Blocked: %s is outside the freeze boundary (%s). Only edits within the frozen directory are allowed."}\n' "$FILE_PATH" "$FREEZE_DIR"
    ;;
esac

---
name: freeze
version: 0.1.0
description: |
  Restrict file edits to a specific directory for the session. Blocks Edit and
  Write outside the allowed path. Use when debugging to prevent accidentally
  "fixing" unrelated code, or when you want to scope changes to one module.
  Use when asked to "freeze", "restrict edits", "only edit this folder",
  or "lock down edits". (gstack)
triggers:
  - freeze edits to directory
  - lock editing scope
  - restrict file changes
allowed-tools:
  - Bash
  - Read
  - AskUserQuestion
hooks:
  PreToolUse:
    - matcher: "Edit"
      hooks:
        - type: command
          command: "bash $HOME/.claude/skills/gstack/freeze/bin/check-freeze.sh"
          statusMessage: "Checking freeze boundary..."
    - matcher: "Write"
      hooks:
        - type: command
          command: "bash $HOME/.claude/skills/gstack/freeze/bin/check-freeze.sh"
          statusMessage: "Checking freeze boundary..."
sensitive: true
---

# /freeze — Restrict Edits to a Directory

Lock file edits to a specific directory. Any Edit or Write operation targeting
a file outside the allowed path will be **blocked** (not just warned).

```bash
mkdir -p ~/.gstack/analytics
echo '{"skill":"freeze","ts":"'$(date -u +%Y-%m-%dT%H:%M:%SZ)'","repo":"'$(basename "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null || echo "unknown")'"}'  >> ~/.gstack/analytics/skill-usage.jsonl 2>/dev/null || true
```

## Setup

Ask the user which directory to restrict edits to. Use AskUserQuestion:

- Question: "Which directory should I restrict edits to? Files outside this path will be blocked from editing."
- Text input (not multiple choice) — the user types a path.

Once the user provides a directory path:

1. Resolve it to an absolute path:
```bash
FREEZE_DIR=$(cd "<user-provided-path>" 2>/dev/null && pwd)
echo "$FREEZE_DIR"
```

2. Ensure trailing slash and save to the freeze state file:
```bash
FREEZE_DIR="${FREEZE_DIR%/}/"
eval "$(~/.claude/skills/gstack/bin/gstack-paths)"
STATE_DIR="$GSTACK_STATE_ROOT"
mkdir -p "$STATE_DIR"
echo "$FREEZE_DIR" > "$STATE_DIR/freeze-dir.txt"
echo "Freeze boundary set: $FREEZE_DIR"
```

Tell the user: "Edits are now restricted to `<path>/`. Any Edit or Write
outside this directory will be blocked. To change the boundary, run `/freeze`
again. To remove it, run `/unfreeze` or end the session."

## How it works

The hook reads `file_path` from the Edit/Write tool input JSON, then checks
whether the path starts with the freeze directory. If not, it returns
`permissionDecision: "deny"` to block the operation.

The freeze boundary persists for the session via the state file. The hook
script reads it on every Edit/Write invocation.

## Notes

- The trailing `/` on the freeze directory prevents `/src` from matching `/src-old`
- Freeze applies to Edit and Write tools only — Read, Bash, Glob, Grep are unaffected
- This prevents accidental edits, not a security boundary — Bash commands like `sed` can still modify files outside the boundary
- To deactivate, run `/unfreeze` or end the conversation