One Way Door

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write",
        "hooks": [
          {
            "type": "command",
            "command": "/path/to/one-way-door-check.sh"
          }
        ]
      }
    ],
    "PostToolUse": [
      {
        "matcher": "AskUserQuestion",
        "hooks": [
          {
            "type": "command",
            "command": "/path/to/one-way-door-approve.sh"
          }
        ]
      }
    ]
  }
}

#!/bin/sh
# One-way door check hook (PreToolUse:Write)
# Flags architectural decisions that are hard to reverse.
# The most expensive mistakes aren't bugs, they're irreversible decisions.

INPUT=$(cat)
[ -z "$INPUT" ] && exit 0

# Extract the file path from tool_input
FILE_PATH=$(echo "$INPUT" | grep -oP '"file_path"\s*:\s*"[^"]*"' | head -1 | sed 's/.*"file_path"\s*:\s*"//;s/"//')
[ -z "$FILE_PATH" ] && exit 0

# Session-scoped approval ledger. Once the user approves a one-way-door file
# via the required AskUserQuestion, the PostToolUse:AskUserQuestion hook
# promotes it to approved, and subsequent writes to that same file proceed.
SESSION_ID=$(echo "$INPUT" | grep -oP '"session_id"\s*:\s*"[^"]*"' | head -1 | sed 's/.*"session_id"\s*:\s*"//;s/"//')
[ -z "$SESSION_ID" ] && SESSION_ID="default"

STATE_DIR="$HOME/.claude/hooks/state/one-way-door"
mkdir -p "$STATE_DIR"
APPROVED_FILE="$STATE_DIR/$SESSION_ID.approved"
PENDING_FILE="$STATE_DIR/$SESSION_ID.pending"

# Already approved this session: allow without re-blocking.
if [ -f "$APPROVED_FILE" ] && grep -Fxq "$FILE_PATH" "$APPROVED_FILE"; then
    echo "one-way-door: proceeding with previously-approved $(basename "$FILE_PATH")" >&2
    exit 0
fi

FILENAME=$(basename "$FILE_PATH")
FILENAME_LOWER=$(echo "$FILENAME" | tr "[:upper:]" "[:lower:]")
FILE_PATH_LOWER=$(echo "$FILE_PATH" | tr "[:upper:]" "[:lower:]")
DIR=$(dirname "$FILE_PATH")

# ---------------------------------------------------------------------------
# Early-exit safelist: clearly-additive, reversible file classes that should
# never trip a one-way-door check even if the filename contains a keyword like
# "auth" or "security". Tests and docs are the common false-positives.
# ---------------------------------------------------------------------------

# Test files (pytest, jest, vitest, go test conventions)
if echo "$FILENAME_LOWER" | grep -qE "^test_.*\.py$|_test\.py$|\.test\.(ts|tsx|js|jsx)$|\.spec\.(ts|tsx|js|jsx)$"; then
    exit 0
fi

# Test / fixture / mock directories anywhere in the path
if echo "$FILE_PATH_LOWER" | grep -qE "/tests?/|/__tests__/|/fixtures?/|/mocks?/|/__mocks__/"; then
    exit 0
fi

# Markdown is always reversible (broader than the later docs-only check, which
# required a docs/ parent dir and missed ad-hoc notes).
if echo "$FILENAME_LOWER" | grep -qE "\.md$"; then
    exit 0
fi

ONE_WAY=0
REASON=""

# Documentation and plan files are always reversible - skip all checks
if echo "$FILENAME_LOWER" | grep -qE "\.txt$|\.rst$"; then
    if echo "$DIR" | grep -qE "plans?|docs?|notes?|superpowers"; then
        exit 0
    fi
fi

# Database schemas and migrations
if echo "$FILENAME_LOWER" | grep -qE "schema\.(prisma|graphql|sql)|migration|\.sql$|models?\.(py|ts|js)$|entities?\.(py|ts|js)$"; then
    ONE_WAY=1
    REASON="data model / database schema"
fi

# Infrastructure and deployment configs
if echo "$FILENAME_LOWER" | grep -qE "^(docker-compose|dockerfile|terraform|pulumi|cdk)|\.tf$|cloudformation|k8s|kubernetes|helm"; then
    ONE_WAY=1
    REASON="infrastructure / deployment config"
fi

# Authentication and authorization (code/config files only - not docs)
if echo "$FILENAME_LOWER" | grep -qE "auth\.(ts|js|py)|firestore\.rules|storage\.rules|security\.(ts|js|py|json|rules|yaml|yml)|\.rules$|rbac\.(ts|js|py|json)|permissions\.(ts|js|py|json)"; then
    ONE_WAY=1
    REASON="auth / security rules"
fi

# API contracts and service interfaces
if echo "$FILENAME_LOWER" | grep -qE "openapi|swagger|\.proto$|\.graphql$|api-schema|routes\.(ts|js|py)$"; then
    ONE_WAY=1
    REASON="API contract / service interface"
fi

# Event systems and message queues
if echo "$FILENAME_LOWER" | grep -qE "event(s|bus|emitter|handler)\.(ts|js|py)$|pubsub|queue|kafka|rabbit"; then
    ONE_WAY=1
    REASON="event system / message bus"
fi

# Package manager configs (dependency choices)
if echo "$FILENAME_LOWER" | grep -qE "^(package\.json|cargo\.toml|go\.mod|requirements\.txt|pyproject\.toml|gemfile)$"; then
    ONE_WAY=1
    REASON="dependency / package config"
fi

# Firebase and cloud service configs
if echo "$FILENAME_LOWER" | grep -qE "^firebase\.json$|^\.firebaserc$|firestore\.indexes"; then
    ONE_WAY=1
    REASON="cloud service config (Firebase)"
fi

# CI/CD pipelines
if echo "$DIR" | grep -qE "\.(github|gitlab|circleci)" || echo "$FILENAME_LOWER" | grep -qE "^(jenkinsfile|\.travis\.yml|cloudbuild)"; then
    ONE_WAY=1
    REASON="CI/CD pipeline"
fi

if [ "$ONE_WAY" = "1" ]; then
    # Record this file as pending approval for the session (deduped).
    if [ ! -f "$PENDING_FILE" ] || ! grep -Fxq "$FILE_PATH" "$PENDING_FILE"; then
        printf '%s\n' "$FILE_PATH" >> "$PENDING_FILE"
    fi
    cat >&2 <<HOOK_MSG
ONE_WAY_DOOR: You tried to create $FILENAME ($REASON). This write has been blocked because it is a one-way door -- a decision that becomes hard to reverse once other code, data, or users depend on it.

REQUIRED ACTION: You MUST use the AskUserQuestion tool before retrying this write. Present the user with:
1. What this file does and why it is a one-way door
2. At least 2 alternative approaches (if any exist) with their trade-offs
3. An option to proceed as planned

Frame the question around the specific architectural decision, not just "should I create this file?" The user needs to understand what they are committing to.

After the user answers the AskUserQuestion, retry the same write -- it will proceed automatically, because answering the question promotes this file to approved for the rest of the session. (Other unapproved one-way-door files still block.)
HOOK_MSG
    exit 2
fi

exit 0

#!/bin/sh
# One-way door approval promoter (PostToolUse:AskUserQuestion)
# When the user answers any AskUserQuestion, promote every one-way-door file
# that the PreToolUse:Write hook recorded as pending into the approved ledger
# for this session. The retried Write then passes instead of re-blocking.
# Never blocks: PostToolUse hooks must not interrupt the flow.

INPUT=$(cat)
[ -z "$INPUT" ] && exit 0

SESSION_ID=$(echo "$INPUT" | grep -oP '"session_id"\s*:\s*"[^"]*"' | head -1 | sed 's/.*"session_id"\s*:\s*"//;s/"//')
[ -z "$SESSION_ID" ] && SESSION_ID="default"

STATE_DIR="$HOME/.claude/hooks/state/one-way-door"
mkdir -p "$STATE_DIR"
APPROVED_FILE="$STATE_DIR/$SESSION_ID.approved"
PENDING_FILE="$STATE_DIR/$SESSION_ID.pending"

# Nothing pending: nothing to promote.
[ -s "$PENDING_FILE" ] || exit 0

# Promote each pending path into approved, deduped.
while IFS= read -r path; do
    [ -z "$path" ] && continue
    if [ ! -f "$APPROVED_FILE" ] || ! grep -Fxq "$path" "$APPROVED_FILE"; then
        printf '%s\n' "$path" >> "$APPROVED_FILE"
    fi
done < "$PENDING_FILE"

# Empty the pending list now that everything is approved.
: > "$PENDING_FILE"

exit 0

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Write",
        "hooks": [
          {
            "type": "command",
            "command": "powershell -ExecutionPolicy Bypass -File C:/Users/<you>/.claude/hooks/one-way-door-check.ps1"
          }
        ]
      }
    ],
    "PostToolUse": [
      {
        "matcher": "AskUserQuestion",
        "hooks": [
          {
            "type": "command",
            "command": "powershell -ExecutionPolicy Bypass -File C:/Users/<you>/.claude/hooks/one-way-door-approve.ps1"
          }
        ]
      }
    ]
  }
}