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| author | sillylaird <sillyfanboy@gmail.com> | 2026-09-03 00:33:59 +0000 |
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| committer | sillylaird <sillyfanboy@gmail.com> | 2026-09-03 00:33:59 +0000 |
| commit | 898b52edcb47bcb3e9d6106e74ca73e74ea01e70 (patch) | |
| tree | 85c6ee5ad58b860144551184d4cf86b560c62b91 /.agents/skills/hook-development/references/patterns.md | |
| download | www-898b52edcb47bcb3e9d6106e74ca73e74ea01e70.tar.gz www-898b52edcb47bcb3e9d6106e74ca73e74ea01e70.zip | |
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diff --git a/.agents/skills/hook-development/references/patterns.md b/.agents/skills/hook-development/references/patterns.md new file mode 100644 index 0000000..4475386 --- /dev/null +++ b/.agents/skills/hook-development/references/patterns.md @@ -0,0 +1,346 @@ +# Common Hook Patterns + +This reference provides common, proven patterns for implementing Claude Code hooks. Use these patterns as starting points for typical hook use cases. + +## Pattern 1: Security Validation + +Block dangerous file writes using prompt-based hooks: + +```json +{ + "PreToolUse": [ + { + "matcher": "Write|Edit", + "hooks": [ + { + "type": "prompt", + "prompt": "File path: $TOOL_INPUT.file_path. Verify: 1) Not in /etc or system directories 2) Not .env or credentials 3) Path doesn't contain '..' traversal. Return 'approve' or 'deny'." + } + ] + } + ] +} +``` + +**Use for:** Preventing writes to sensitive files or system directories. + +## Pattern 2: Test Enforcement + +Ensure tests run before stopping: + +```json +{ + "Stop": [ + { + "matcher": "*", + "hooks": [ + { + "type": "prompt", + "prompt": "Review transcript. If code was modified (Write/Edit tools used), verify tests were executed. If no tests were run, block with reason 'Tests must be run after code changes'." + } + ] + } + ] +} +``` + +**Use for:** Enforcing quality standards and preventing incomplete work. + +## Pattern 3: Context Loading + +Load project-specific context at session start: + +```json +{ + "SessionStart": [ + { + "matcher": "*", + "hooks": [ + { + "type": "command", + "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/load-context.sh" + } + ] + } + ] +} +``` + +**Example script (load-context.sh):** +```bash +#!/bin/bash +cd "$CLAUDE_PROJECT_DIR" || exit 1 + +# Detect project type +if [ -f "package.json" ]; then + echo "📦 Node.js project detected" + echo "export PROJECT_TYPE=nodejs" >> "$CLAUDE_ENV_FILE" +elif [ -f "Cargo.toml" ]; then + echo "🦀 Rust project detected" + echo "export PROJECT_TYPE=rust" >> "$CLAUDE_ENV_FILE" +fi +``` + +**Use for:** Automatically detecting and configuring project-specific settings. + +## Pattern 4: Notification Logging + +Log all notifications for audit or analysis: + +```json +{ + "Notification": [ + { + "matcher": "*", + "hooks": [ + { + "type": "command", + "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/log-notification.sh" + } + ] + } + ] +} +``` + +**Use for:** Tracking user notifications or integration with external logging systems. + +## Pattern 5: MCP Tool Monitoring + +Monitor and validate MCP tool usage: + +```json +{ + "PreToolUse": [ + { + "matcher": "mcp__.*__delete.*", + "hooks": [ + { + "type": "prompt", + "prompt": "Deletion operation detected. Verify: Is this deletion intentional? Can it be undone? Are there backups? Return 'approve' only if safe." + } + ] + } + ] +} +``` + +**Use for:** Protecting against destructive MCP operations. + +## Pattern 6: Build Verification + +Ensure project builds after code changes: + +```json +{ + "Stop": [ + { + "matcher": "*", + "hooks": [ + { + "type": "prompt", + "prompt": "Check if code was modified. If Write/Edit tools were used, verify the project was built (npm run build, cargo build, etc). If not built, block and request build." + } + ] + } + ] +} +``` + +**Use for:** Catching build errors before committing or stopping work. + +## Pattern 7: Permission Confirmation + +Ask user before dangerous operations: + +```json +{ + "PreToolUse": [ + { + "matcher": "Bash", + "hooks": [ + { + "type": "prompt", + "prompt": "Command: $TOOL_INPUT.command. If command contains 'rm', 'delete', 'drop', or other destructive operations, return 'ask' to confirm with user. Otherwise 'approve'." + } + ] + } + ] +} +``` + +**Use for:** User confirmation on potentially destructive commands. + +## Pattern 8: Code Quality Checks + +Run linters or formatters on file edits: + +```json +{ + "PostToolUse": [ + { + "matcher": "Write|Edit", + "hooks": [ + { + "type": "command", + "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/check-quality.sh" + } + ] + } + ] +} +``` + +**Example script (check-quality.sh):** +```bash +#!/bin/bash +input=$(cat) +file_path=$(echo "$input" | jq -r '.tool_input.file_path') + +# Run linter if applicable +if [[ "$file_path" == *.js ]] || [[ "$file_path" == *.ts ]]; then + npx eslint "$file_path" 2>&1 || true +fi +``` + +**Use for:** Automatic code quality enforcement. + +## Pattern Combinations + +Combine multiple patterns for comprehensive protection: + +```json +{ + "PreToolUse": [ + { + "matcher": "Write|Edit", + "hooks": [ + { + "type": "prompt", + "prompt": "Validate file write safety" + } + ] + }, + { + "matcher": "Bash", + "hooks": [ + { + "type": "prompt", + "prompt": "Validate bash command safety" + } + ] + } + ], + "Stop": [ + { + "matcher": "*", + "hooks": [ + { + "type": "prompt", + "prompt": "Verify tests run and build succeeded" + } + ] + } + ], + "SessionStart": [ + { + "matcher": "*", + "hooks": [ + { + "type": "command", + "command": "bash ${CLAUDE_PLUGIN_ROOT}/scripts/load-context.sh" + } + ] + } + ] +} +``` + +This provides multi-layered protection and automation. + +## Pattern 9: Temporarily Active Hooks + +Create hooks that only run when explicitly enabled via flag files: + +```bash +#!/bin/bash +# Hook only active when flag file exists +FLAG_FILE="$CLAUDE_PROJECT_DIR/.enable-security-scan" + +if [ ! -f "$FLAG_FILE" ]; then + # Quick exit when disabled + exit 0 +fi + +# Flag present, run validation +input=$(cat) +file_path=$(echo "$input" | jq -r '.tool_input.file_path') + +# Run security scan +security-scanner "$file_path" +``` + +**Activation:** +```bash +# Enable the hook +touch .enable-security-scan + +# Disable the hook +rm .enable-security-scan +``` + +**Use for:** +- Temporary debugging hooks +- Feature flags for development +- Project-specific validation that's opt-in +- Performance-intensive checks only when needed + +**Note:** Must restart Claude Code after creating/removing flag files for hooks to recognize changes. + +## Pattern 10: Configuration-Driven Hooks + +Use JSON configuration to control hook behavior: + +```bash +#!/bin/bash +CONFIG_FILE="$CLAUDE_PROJECT_DIR/.claude/my-plugin.local.json" + +# Read configuration +if [ -f "$CONFIG_FILE" ]; then + strict_mode=$(jq -r '.strictMode // false' "$CONFIG_FILE") + max_file_size=$(jq -r '.maxFileSize // 1000000' "$CONFIG_FILE") +else + # Defaults + strict_mode=false + max_file_size=1000000 +fi + +# Skip if not in strict mode +if [ "$strict_mode" != "true" ]; then + exit 0 +fi + +# Apply configured limits +input=$(cat) +file_size=$(echo "$input" | jq -r '.tool_input.content | length') + +if [ "$file_size" -gt "$max_file_size" ]; then + echo '{"decision": "deny", "reason": "File exceeds configured size limit"}' >&2 + exit 2 +fi +``` + +**Configuration file (.claude/my-plugin.local.json):** +```json +{ + "strictMode": true, + "maxFileSize": 500000, + "allowedPaths": ["/tmp", "/home/user/projects"] +} +``` + +**Use for:** +- User-configurable hook behavior +- Per-project settings +- Team-specific rules +- Dynamic validation criteria |
