stop-gate.sh

#!/bin/bash
# Stop gate: prevents accidental session termination.
# Generates a nonce, asks Claude to confirm it wants to stop.
# If Claude hasn't seen the nonce, blocks and shows reminders.

NONCE_FILE="/tmp/claude-stop-nonce"
INPUT=$(cat)

# Check if Claude included the nonce in its last message
LAST_MSG=$(echo "$INPUT" | jq -r '.assistant_message // .content // .transcript // empty' 2>/dev/null)
if [ -z "$LAST_MSG" ]; then
    LAST_MSG=$(echo "$INPUT")
fi

# If nonce file exists, check if Claude confirmed it
if [ -f "$NONCE_FILE" ]; then
    EXPECTED=$(cat "$NONCE_FILE")
    if echo "$LAST_MSG" | grep -q "STOP_CONFIRMED_$EXPECTED" 2>/dev/null; then
        rm -f "$NONCE_FILE"
        exit 0
    fi
fi

# Generate new nonce
NONCE=$(head -c 6 /dev/urandom | xxd -p)
echo "$NONCE" > "$NONCE_FILE"

# Build reason message
REASON="STOP GATE: Before stopping, please:"
REASON="$REASON [1] Review your task list -- any incomplete tasks?"
REASON="$REASON [2] Review user messages -- did you miss anything?"
REASON="$REASON [3] If you have overnight work queued, make a tool call to ensure the loop continues."
REASON="$REASON [4] Terminate any background commands that are stuck, legacy, or unused -- clean up after yourself."
REASON="$REASON [5] Consider stretch goals: if the main work is done, try bonus improvements on an experimental branch or separate folder -- the criteria is that the main work and the homelab must not be jeopardized. If the stretch succeeds, switch back to main before signing off. If it fails, keep the artifact and explain what went wrong in your final sign-off alongside the nonce."
REASON="$REASON [6] To confirm stop, include this nonce: STOP_CONFIRMED_${NONCE}"
REASON="$REASON -- You may also send the nonce even with pending work IF a background command will complete it in bounded time. Spawn one via Bash run_in_background if you just need to wait N minutes instead of hot-grinding."

jq -n --arg reason "$REASON" '{"decision":"block","reason":$reason}'