layer-design
🎯Skillfrom front-depiction/claude-setup
|layer-design skill from front-depiction/claude-setup
Installation
npx skills add https://github.com/front-depiction/claude-setup --skill layer-designSkill Details
Overview
# .claude
Pattern-based suggestions and guardrails for Claude Code tool usage via PreToolUse/PostToolUse hooks.
Overview
The pattern-detector system hooks into Claude Code's PreToolUse and PostToolUse events to provide:
- Context-aware suggestions when patterns are detected in tool inputs
- Permission controls (ask/deny) for dangerous operations
- Automatic skill recommendations based on code patterns
Patterns
Patterns are markdown files in .claude/patterns/ with YAML frontmatter that match against tool inputs:
```markdown
---
name: prefer-option-over-null
description: Suggest Option type instead of null/undefined
event: PostToolUse
tool: Edit|Write
glob: "*/.ts"
pattern: "\bnull\b|\bundefined\b"
action: context
level: info
tag: code-smell
---
Use Option from Effect instead of null or undefined:
```typescript
// Avoid
const findUser = (id: string): User | null => ...
// Prefer
const findUser = (id: string): Option.Option
```
```
Pattern Schema
Frontmatter fields (from patterns/schema.ts):
name: Unique identifier for the patterndescription: Human-readable descriptionevent: "PreToolUse" | "PostToolUse" (default: PostToolUse)tool: Regex matching tool names (default: ".*")glob: Optional glob pattern for file paths (e.g., "*/.ts")pattern: Regex matching tool input content (command, new_string, content, etc.)action: "context" | "ask" | "deny" (default: context)level: "critical" | "high" | "medium" | "warning" | "info" (default: info)tag: Optional XML tag for context blocks (default: "pattern-suggestion")
Actions
context: Add suggestion to PostToolUse responseask: Prompt user for permission (PreToolUse only)deny: Block the operation with reason (PreToolUse only)
Content Matching
The pattern detector searches these fields in order:
command(Bash)new_string(Edit)content(Write)pattern(Grep)query(WebSearch)url(WebFetch)prompt(WebFetch)
Falls back to JSON.stringify(tool_input) if none match.
Testing
test/TestClaude.ts provides tool shape constructors for testing patterns:
```typescript
import * as TestClaude from "./.claude/test/TestClaude"
import { runPatternDetector } from "./.claude/hooks/pattern-detector"
// Create pre/post hook inputs
const bashHook = TestClaude.Bash({ command: "rm -rf /" })
const editHook = TestClaude.Edit({
file_path: "/foo.ts",
old_string: "old",
new_string: "null"
})
// Test against patterns
const output = await runPatternDetector(bashHook.pre)
// or
const output = await runPatternDetector(editHook.post)
```
Each tool constructor returns { pre, post } shapes with correct tool_name and hook_event_name.
Files
hooks/pattern-detector.ts: Main hook implementation (PreToolUse/PostToolUse)patterns/schema.ts: Pattern frontmatter Schema definitionspatterns/TEMPLATE.md: Template for new patternspatterns/dangerous-commands/: PreToolUse ask/deny patternspatterns/code-smells/: PostToolUse context suggestionstest/TestClaude.ts: Tool shape constructors for testingCLAUDE.md: Project guidelines referencing pattern system
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