developer-detective

What this skill does

# Developer Detective Skill

This skill uses claudemem's callers/callees analysis for implementation investigation.

## Why Claudemem Works Better for Development

| Task | claudemem | Native Tools |
|------|-----------|--------------|
| Find usages | `callers` shows all call sites | Grep (text match) |
| Trace dependencies | `callees` shows called functions | Manual reading |
| Understand context | `context` gives full picture | Multiple reads |
| Impact analysis | Caller chain reveals risk | Unknown |

**Primary commands:**
- `claudemem --agent callers <name>` - What calls this code
- `claudemem --agent callees <name>` - What this code calls
- `claudemem --agent context <name>` - Full understanding

# Developer Detective Skill

**Version:** 3.3.0
**Role:** Software Developer
**Purpose:** Implementation investigation using AST callers/callees and impact analysis

## Role Context

You are investigating this codebase as a **Software Developer**. Your focus is on:
- **Implementation details** - How code actually works
- **Data flow** - How data moves through the system (via callees)
- **Usage patterns** - How code is used (via callers)
- **Dependencies** - What a function needs to work
- **Impact analysis** - What breaks if you change something

## Why callers/callees is Perfect for Development

The `callers` and `callees` commands show you:
- **callers** = Every place that calls this code (impact of changes)
- **callees** = Every function this code calls (its dependencies)
- **Exact file:line** = Precise locations for reading/editing
- **Call kinds** = call, import, extends, implements

## Developer-Focused Commands (v0.3.0)

### Find Implementation

```bash
# Find where a function is defined
claudemem --agent symbol processPayment
# Get full context with callers and callees
claudemem --agent context processPayment```

### Trace Data Flow

```bash
# What does this function call? (data flows OUT)
claudemem --agent callees processPayment
# Follow the chain
claudemem --agent callees validateCardclaudemem --agent callees chargeStripe```

### Find All Usages

```bash
# Who calls this function? (usage patterns)
claudemem --agent callers processPayment
# This shows EVERY place that uses this code
```

### Impact Analysis (v0.4.0+ Required)

```bash
# Before modifying ANY code, check full impact
claudemem --agent impact functionToChange
# Output shows ALL transitive callers:
# direct_callers:
#   - LoginController.authenticate:34
#   - SessionMiddleware.validate:12
# transitive_callers (depth 2):
#   - AppRouter.handleRequest:45
#   - TestSuite.runAuth:89
```

**Why impact matters**:
- `callers` shows only direct callers (1 level)
- `impact` shows ALL transitive callers (full tree)
- Critical for refactoring decisions

**Handling Empty Results:**
```bash
IMPACT=$(claudemem --agent impact functionToChange)
if echo "$IMPACT" | grep -q "No callers"; then
  echo "No callers found. This is either:"
  echo "  1. An entry point (API handler, main function) - expected"
  echo "  2. Dead code - verify with: claudemem dead-code"
  echo "  3. Dynamically called - check for import(), reflection"
fi
```

### Impact Analysis (BEFORE Modifying)

```bash
# Quick check - direct callers only (v0.3.0)
claudemem --agent callers functionToChange
# Deep check - ALL transitive callers (v0.4.0+ Required)
IMPACT=$(claudemem --agent impact functionToChange)

# Handle results
if [ -z "$IMPACT" ] || echo "$IMPACT" | grep -q "No callers"; then
  echo "No static callers found - verify dynamic usage patterns"
else
  echo "$IMPACT"
  echo ""
  echo "This tells you:"
  echo "- Direct callers (immediate impact)"
  echo "- Transitive callers (ripple effects)"
  echo "- Grouped by file (for systematic updates)"
fi
```

### Understanding Complex Code

```bash
# Get full picture: definition + callers + callees
claudemem --agent context complexFunction```

## PHASE 0: MANDATORY SETUP

### Step 1: Verify claudemem v0.3.0

```bash
which claudemem && claudemem --version
# Must be 0.3.0+
```

### Step 2: If Not Installed → STOP

Use AskUserQuestion (see ultrathink-detective for template)

### Step 3: Check Index Status

```bash
# Check claudemem installation and index
claudemem --version && ls -la .claudemem/index.db 2>/dev/null
```

### Step 3.5: Check Index Freshness

Before proceeding with investigation, verify the index is current:

```bash
# First check if index exists
if [ ! -d ".claudemem" ] || [ ! -f ".claudemem/index.db" ]; then
  # Use AskUserQuestion to prompt for index creation
  # Options: [1] Create index now (Recommended), [2] Cancel investigation
  exit 1
fi

# Count files modified since last index
STALE_COUNT=$(find . -type f \( -name "*.ts" -o -name "*.tsx" -o -name "*.js" -o -name "*.jsx" -o -name "*.py" -o -name "*.go" -o -name "*.rs" \) \
  -newer .claudemem/index.db 2>/dev/null | grep -v "node_modules" | grep -v ".git" | grep -v "dist" | grep -v "build" | wc -l)
STALE_COUNT=$((STALE_COUNT + 0))  # Normalize to integer

if [ "$STALE_COUNT" -gt 0 ]; then
  # Get index time with explicit platform detection
  if [[ "$OSTYPE" == "darwin"* ]]; then
    INDEX_TIME=$(stat -f "%Sm" -t "%Y-%m-%d %H:%M" .claudemem/index.db 2>/dev/null)
  else
    INDEX_TIME=$(stat -c "%y" .claudemem/index.db 2>/dev/null | cut -d'.' -f1)
  fi
  INDEX_TIME=${INDEX_TIME:-"unknown time"}

  # Get sample of stale files
  STALE_SAMPLE=$(find . -type f \( -name "*.ts" -o -name "*.tsx" \) \
    -newer .claudemem/index.db 2>/dev/null | grep -v "node_modules" | grep -v ".git" | head -5)

  # Use AskUserQuestion (see template in ultrathink-detective)
fi
```

### Step 4: Index if Needed

```bash
claudemem index
```

---

## Workflow: Implementation Investigation (v0.3.0)

### Phase 1: Map the Area

```bash
# Get overview of the feature area
claudemem --agent map "payment processing"```

### Phase 2: Find the Entry Point

```bash
# Locate the main function (highest PageRank in area)
claudemem --agent symbol PaymentService```

### Phase 3: Trace the Flow

```bash
# What does PaymentService call?
claudemem --agent callees PaymentService
# For each major callee, trace further
claudemem --agent callees validatePaymentclaudemem --agent callees processChargeclaudemem --agent callees saveTransaction```

### Phase 4: Understand Usage

```bash
# Who uses PaymentService?
claudemem --agent callers PaymentService
# This shows the entry points
```

### Phase 5: Read Specific Code

```bash
# Now read ONLY the relevant file:line ranges from results
# DON'T read whole files
```

## Output Format: Implementation Report

### 1. Symbol Overview

```
┌─────────────────────────────────────────────────────────┐
│              IMPLEMENTATION ANALYSIS                     │
├─────────────────────────────────────────────────────────┤
│  Symbol: processPayment                                  │
│  Location: src/services/payment.ts:45-89                │
│  Kind: function                                          │
│  PageRank: 0.034                                         │
│  Search Method: claudemem v0.3.0 (AST analysis)         │
└─────────────────────────────────────────────────────────┘
```

### 2. Data Flow (Callees)

```
processPayment
  ├── validateCard (src/validators/card.ts:12)
  ├── getCustomer (src/services/customer.ts:34)
  ├── chargeStripe (src/integrations/stripe.ts:56)
  │     └── stripe.charges.create (external)
  └── saveTransaction (src/repositories/transaction.ts:78)
        └── database.insert (src/db/index.ts:23)
```

### 3. Usage (Callers)

```
processPayment is called by:
  ├── CheckoutController.submit (src/controllers/checkout.ts:45)
  ├── SubscriptionService.renew (src/services/subscription.ts:89)
  └── RetryQueue.processPayment (src/workers/retry.ts:23)
```

### 4. Impact Analysis

```
⚠️ IMPACT: Changing processPayment will affect:
  - 3 direct callers (shown above)
  - Checkout flow (user-facing)
  - Subscription renewals (automated)
  - Payment retry logic (background)
```

## Scenarios

### Scenario: "How does X