mempalace/hooks/mempal_precompact_hook.sh

#!/bin/bash
# MEMPALACE PRE-COMPACT HOOK — Emergency save before compaction
#
# Claude Code "PreCompact" hook. Fires RIGHT BEFORE the conversation
# gets compressed to free up context window space.
#
# This is the safety net. When compaction happens, the AI loses detailed
# context about what was discussed. This hook forces one final save of
# EVERYTHING before that happens.
#
# Unlike the save hook (which triggers every N exchanges), this ALWAYS
# blocks — because compaction is always worth saving before.
#
# === INSTALL ===
# Add to .claude/settings.local.json:
#
#   "hooks": {
#     "PreCompact": [{
#       "hooks": [{
#         "type": "command",
#         "command": "/absolute/path/to/mempal_precompact_hook.sh",
#         "timeout": 30
#       }]
#     }]
#   }
#
# For Codex CLI, add to .codex/hooks.json:
#
#   "PreCompact": [{
#     "type": "command",
#     "command": "/absolute/path/to/mempal_precompact_hook.sh",
#     "timeout": 30
#   }]
#
# === HOW IT WORKS ===
#
# Claude Code sends JSON on stdin with:
#   session_id — unique session identifier
#
# We always return decision: "block" with a reason telling the AI
# to save everything. After the AI saves, compaction proceeds normally.
#
# === MEMPALACE CLI ===
# The hook ALWAYS mines the active conversation transcript synchronously
# before compaction (via `mempalace mine <transcript-dir> --mode convos`).
# MEMPAL_DIR is an *additional*, optional target for project files — it
# does not replace the conversation mine.

STATE_DIR="$HOME/.mempalace/hook_state"
mkdir -p "$STATE_DIR"

# Optional: project directory (code / notes / docs) to also mine before
# compaction. Mined with `--mode projects`. The conversation transcript
# is always mined regardless — this is purely additive.
# Example: MEMPAL_DIR="$HOME/projects/my_app"
MEMPAL_DIR=""

# Resolve the Python interpreter. Same contract as mempal_save_hook.sh:
# MEMPAL_PYTHON (explicit override) → $(command -v python3) → bare python3.
MEMPAL_PYTHON_BIN="${MEMPAL_PYTHON:-}"
if [ -z "$MEMPAL_PYTHON_BIN" ] || [ ! -x "$MEMPAL_PYTHON_BIN" ]; then
    MEMPAL_PYTHON_BIN="$(command -v python3 2>/dev/null || echo python3)"
fi

# Read JSON input from stdin
INPUT=$(cat)

# Parse session_id and transcript_path in one call. Sanitize both before
# interpolating into shell — same contract as mempal_save_hook.sh.
eval $(echo "$INPUT" | "$MEMPAL_PYTHON_BIN" -c "
import sys, json, re
data = json.load(sys.stdin)
sid = data.get('session_id', 'unknown')
tp = data.get('transcript_path', '')
safe = lambda s: re.sub(r'[^a-zA-Z0-9_/.\-~]', '', str(s))
print(f'SESSION_ID=\"{safe(sid)}\"')
print(f'TRANSCRIPT_PATH=\"{safe(tp)}\"')
" 2>/dev/null)

# Expand ~ in path
TRANSCRIPT_PATH="${TRANSCRIPT_PATH/#\~/$HOME}"

echo "[$(date '+%H:%M:%S')] PRE-COMPACT triggered for session $SESSION_ID" >> "$STATE_DIR/hook.log"

# Run ingest synchronously so memories land before compaction. Two
# independent targets — both run if both are set:
#   1. TRANSCRIPT_PATH (from Claude Code) → parent dir, --mode convos
#   2. MEMPAL_DIR → --mode projects
if [ -n "$TRANSCRIPT_PATH" ] && [ -f "$TRANSCRIPT_PATH" ]; then
    mempalace mine "$(dirname "$TRANSCRIPT_PATH")" --mode convos \
        >> "$STATE_DIR/hook.log" 2>&1
fi
if [ -n "$MEMPAL_DIR" ] && [ -d "$MEMPAL_DIR" ]; then
    mempalace mine "$MEMPAL_DIR" --mode projects \
        >> "$STATE_DIR/hook.log" 2>&1
fi

# Silent: return empty JSON to not block. "decision": "allow" is invalid —
# only "block" or {} are recognized.
echo '{}'