🎯

context-witness

🎯Skill

from front-depiction/claude-setup

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What it does

context-witness skill from front-depiction/claude-setup

context-witness

Installation

Install skill:

npx skills add https://github.com/front-depiction/claude-setup --skill context-witness

4

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Last UpdatedJan 19, 2026

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Skill Details

SKILL.md

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:

const findUser = (id: string): User | null => ...

const findUser = (id: string): Option.Option => ...

Pattern Schema

Frontmatter fields (from patterns/schema.ts):

name: Unique identifier for the pattern
description: Human-readable description
event: "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 response
ask: 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:

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)

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 definitions
patterns/TEMPLATE.md: Template for new patterns
patterns/dangerous-commands/: PreToolUse ask/deny patterns
patterns/code-smells/: PostToolUse context suggestions
test/TestClaude.ts: Tool shape constructors for testing
CLAUDE.md: Project guidelines referencing pattern system

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