Cloudflare Guardian Skill

Audit wrangler configurations for security vulnerabilities, performance issues, cost traps, resilience gaps, and proactively enforce budget/privacy constraints. Acts as a senior SRE and FinOps engineer reviewing infrastructure-as-code.

Cost Watchlist Reference

IMPORTANT: For detailed cost trap documentation, reference ${CLAUDE_PLUGIN_ROOT}/COST_SENSITIVE_RESOURCES.md.

When issuing cost warnings, use provenance tags:

• [STATIC:COST_WATCHLIST] - Pattern detected via code analysis
• [LIVE-VALIDATED:COST_WATCHLIST] - Confirmed by observability data
• [REFUTED:COST_WATCHLIST] - Pattern exists but not hitting thresholds

Budget Whisperer Behavior

CRITICAL: When Claude suggests ANY code change involving the following, the guardian skill MUST trigger proactive checks:

D1 Write Operations

If suggesting code that includes .run(), .first(), or database writes:

1. Search for .batch() - If missing, warn about per-row insert costs
2. Search for CREATE INDEX - If querying unindexed columns, warn about scan costs
3. Cite: TRAP-D1-001 or TRAP-D1-002 from COST_SENSITIVE_RESOURCES.md

Budget Whisperer Check:
- Detected: D1 write operation in proposed code
- Searched for: db.batch() usage
- Found: ❌ Missing batch operations
- Warning: [STATIC:COST_WATCHLIST] TRAP-D1-001
  Per-row INSERT detected. At 10K rows, this costs $0.01 vs $0.00001 batched.
  Recommendation: Wrap in db.batch() with max 1000 statements per batch.

R2 Write Operations

If suggesting code that includes .put():

1. Check loop context - Is .put() inside a loop or frequently called handler?
2. Search for buffering - Any aggregation before write?
3. Cite: TRAP-R2-001 from COST_SENSITIVE_RESOURCES.md

Durable Objects Usage

If suggesting DO architecture:

1. Check use case - Is coordination/locking actually needed?
2. Suggest alternatives - KV for simple storage, D1 for relational
3. Cite: TRAP-DO-001 from COST_SENSITIVE_RESOURCES.md

Vibecoder Proactive Safeguards

IMPORTANT: This skill should proactively warn users about cost and privacy impacts BEFORE they deploy or even ask about costs. When reviewing ANY architecture that includes the following, immediately surface budget/privacy alerts:

Budget Enforcement Triggers

Service/Pattern	Threshold	Proactive Warning
Durable Objects	Any usage	"DO charges ~$0.15/GB-month storage + $0.50/M requests. Consider KV for simple key-value."
R2 Class A ops	>1M/month	"R2 writes cost $4.50/M. Buffer writes or use presigned URLs for client uploads."
D1 Writes	>10M/month	"D1 writes cost $1/M. Detected pattern suggests >$10/mo. Batch to ≤1,000 rows."
Workers AI (>8B)	Any usage	"Large models (Llama 11B+) cost $0.68/M tokens. Use 8B or smaller for bulk."
Vectorize	>1M vectors	"Approaching 5M vector limit. Plan sharding strategy."
KV Writes	>5M/month	"KV writes cost $5/M (10× reads). Consider D1 or R2 for write-heavy."

Privacy Enforcement Triggers

Pattern	Severity	Proactive Warning
PII in logs	CRITICAL	"Detected potential PII logging. Use structured logging with redaction."
User data in KV keys	HIGH	"KV keys with user IDs may leak via Workers dashboard. Hash or encrypt."
AI prompts with PII	HIGH	"AI Gateway logs may contain user data. Enable prompt redaction."
R2 public buckets	HIGH	"R2 bucket appears public. Verify intentional or add authentication."
Analytics with user IDs	MEDIUM	"User IDs in Analytics Engine may persist. Use anonymized identifiers."

Audit Categories

Security Audit Rules

ID	Name	Severity	Check
SEC001	Secrets in plaintext	CRITICAL	vars.* contains API_KEY, SECRET, PASSWORD, TOKEN patterns
SEC002	Missing route auth	HIGH	Routes without cf.access or auth middleware
SEC003	CORS wildcard	MEDIUM	cors.origins includes *
SEC004	Exposed admin routes	HIGH	/admin/* routes without auth
SEC005	Missing rate limiting	MEDIUM	No rate limit bindings for public APIs
SEC006	Debug mode enabled	LOW	ENVIRONMENT or DEBUG set to development/true

Performance Audit Rules

ID	Name	Severity	Check
PERF001	Missing Smart Placement	LOW	placement.mode not set
PERF002	D1 without indexes	MEDIUM	D1 bindings but no CREATE INDEX in migrations
PERF003	Large bundled dependencies	MEDIUM	Bundle >10MB (check main entry)
PERF004	Missing observability	LOW	No observability config block
PERF005	Frequent cron	LOW	Cron more often than every 5 minutes

Cost Audit Rules

ID	Name	Severity	Check
COST001	Queue retries high	MEDIUM	max_retries > 1 for potentially idempotent consumers
COST002	No cron batching	LOW	Multiple crons that could be combined
COST003	AI without caching	MEDIUM	AI bindings but no AI Gateway
COST004	Large model usage	LOW	Workers AI with >8B parameter models
COST005	Missing Analytics Engine	INFO	Using D1/KV for metrics instead of free AE

Resilience Audit Rules

ID	Name	Severity	Check
RES001	Missing DLQ	HIGH	Queues without dead_letter_queue binding
RES002	No concurrency limit	MEDIUM	max_concurrency not set for queue consumers
RES003	Single region	LOW	No cf.smart_placement for latency-sensitive
RES004	Missing retry config	MEDIUM	Queue consumer without explicit retry config
RES005	No circuit breaker	LOW	External API calls without timeout/fallback

Budget Audit Rules (Proactive)

ID	Name	Severity	Check
BUDGET001	Durable Objects usage	INFO	Any DO binding - proactively explain cost model
BUDGET002	R2 write-heavy pattern	MEDIUM	Frequent R2 Class A ops without buffering
BUDGET003	D1 per-row inserts	HIGH	Loop-based INSERTs instead of batch
BUDGET004	Large AI model	MEDIUM	Workers AI with >8B parameter model
BUDGET005	KV write-heavy	MEDIUM	>5M KV writes/month pattern
BUDGET006	Vectorize scaling	INFO	>1M vectors - warn about 5M limit

Privacy Audit Rules

ID	Name	Severity	Check
PRIV001	PII in logs	CRITICAL	console.log with user data patterns
PRIV002	User IDs in KV keys	HIGH	KV key patterns containing user/email/phone
PRIV003	AI prompts PII	HIGH	AI bindings without redaction middleware
PRIV004	R2 public access	HIGH	R2 bucket without authentication
PRIV005	Analytics PII	MEDIUM	User identifiers in Analytics Engine writes

Audit Workflow

Step 1: Parse Wrangler Config

Support both TOML and JSONC formats:

1. Read wrangler.toml or wrangler.jsonc
2. Parse into structured format
3. Extract: name, bindings, routes, triggers, vars

Step 2: Run Security Checks

For each security rule:
1. Check if pattern exists in config
2. If violation found:
   - Record rule ID, severity, location
   - Generate specific recommendation
   - Include docs URL if available

Step 3: Run Performance Checks

For each performance rule:
1. Check config for anti-patterns
2. Cross-reference with migrations (for D1 index checks)
3. Record findings with optimization recommendations

Step 4: Run Cost Checks

For each cost rule:
1. Identify cost-amplifying patterns
2. Estimate impact if possible
3. Provide specific fixes

Step 5: Run Resilience Checks

For each resilience rule:
1. Check for missing failure handling
2. Identify single points of failure
3. Recommend redundancy patterns

Step 5b: Run Budget Enforcement Checks (Proactive)

For bindings that trigger budget warnings:
1. Detect Durable Objects → Explain cost model proactively
2. Detect R2 writes → Check for buffering patterns
3. Detect D1 writes → Check for batch vs per-row
4. Detect Workers AI → Check model size selection
5. Detect high-volume KV → Suggest alternatives

Key principle: Surface budget impacts BEFORE the user asks about costs.

Step 5c: Run Privacy Checks

For privacy-sensitive patterns:
1. Scan code for console.log with user data patterns
2. Check KV key naming for PII patterns
3. Verify AI prompts have redaction middleware
4. Check R2 bucket access controls
5. Review Analytics Engine write patterns

Step 6: Calculate Score

score = 100 - (critical × 25) - (high × 15) - (medium × 5) - (low × 2)

Grades:

• 90-100: A (Production ready)
• 80-89: B (Minor issues)
• 70-79: C (Address before deployment)
• 60-69: D (Significant issues)
• <60: F (Critical problems)

Output Format

# Cloudflare Configuration Audit

**Score**: XX/100 (Grade: X)
**File**: wrangler.jsonc

## Proactive Budget & Privacy Alerts

> **Budget Impact Detected**: [List any BUDGET* findings with cost estimates]
> **Privacy Concern**: [List any PRIV* findings requiring attention]

## Summary

| Category | Critical | High | Medium | Low | Info |
|----------|----------|------|--------|-----|------|
| Security | X | X | X | X | - |
| Performance | X | X | X | X | - |
| Cost | X | X | X | X | - |
| Resilience | X | X | X | X | - |
| Budget | - | X | X | - | X |
| Privacy | X | X | X | - | - |

## Critical Issues (Must Fix)

### SEC001: Secrets in plaintext
- **Location**: `vars.API_KEY`
- **Issue**: Plaintext API key in configuration
- **Fix**: Use `wrangler secret put API_KEY`
- **Docs**: https://developers.cloudflare.com/workers/configuration/secrets/

## High Priority Issues

### RES001: Missing dead letter queue
- **Location**: `queues[0]` (harvest-queue)
- **Issue**: No DLQ for failed message inspection
- **Fix**: Add `dead_letter_queue = "harvest-dlq"`

## Medium Priority Issues

[List all medium issues]

## Low Priority Issues

[List all low issues]

## Recommendations

1. [ ] Move secrets to wrangler secret
2. [ ] Add DLQ for all production queues
3. [ ] Enable Smart Placement
4. [ ] Consider Analytics Engine for metrics

Migration Checks

When D1 bindings exist, also scan migration files:

-- Good: Has index
CREATE INDEX idx_projects_source ON projects(source);

-- Bad: Missing index for common query pattern
SELECT * FROM projects WHERE source = ? ORDER BY created_at DESC;

Flag missing indexes for:

• Columns in WHERE clauses
• Columns in ORDER BY
• Compound queries (need compound indexes)

Wrangler Config Patterns

Good Patterns to Recognize

{
  // Smart Placement enabled
  "placement": { "mode": "smart" },

  // Observability configured
  "observability": { "logs": { "enabled": true } },

  // Queue with DLQ
  "queues": {
    "consumers": [{
      "queue": "my-queue",
      "dead_letter_queue": "my-dlq",
      "max_retries": 1,
      "max_concurrency": 10
    }]
  }
}

Bad Patterns to Flag

{
  // Secrets in vars
  "vars": { "API_KEY": "sk-xxxxx" },

  // No DLQ
  "queues": { "consumers": [{ "queue": "my-queue" }] },

  // High retries
  "queues": { "consumers": [{ "max_retries": 10 }] }
}

Live Validation with Probes

When MCP tools are available (via --validate mode in /cf-audit), enhance static findings with live data.

Reference @skills/probes/SKILL.md for detailed query patterns.

Security Validation

• Error rate analysis: High errors on specific paths may indicate attacks
• Request patterns: Verify authentication is actually enforced
• Resource exposure: Check KV/R2 for public access settings

Performance Validation

• EXPLAIN QUERY PLAN: Verify D1 index usage
• Latency percentiles: P50/P95/P99 analysis
• CPU time analysis: Identify hotspots

Resilience Validation

• Queue health: Check DLQ depth and retry rates
• Error patterns: Identify cascading failures

Provenance Tagging

Tag findings based on data source:

• [STATIC] - Inferred from code/config analysis only
• [LIVE-VALIDATED] - Confirmed by observability data
• [LIVE-REFUTED] - Code smell not observed in production
• [INCOMPLETE] - MCP tools unavailable for verification

Pattern Recommendations

When issues are found, recommend applicable patterns from @skills/patterns/:

Finding	Recommended Pattern
Per-row D1 inserts	d1-batching
External API issues	circuit-breaker
Monolithic Worker	service-bindings

Tips

• Run before every deployment
• Use --validate for production-ready verification
• Focus on CRITICAL and HIGH first
• Use --fix suggestions to auto-generate patches
• Compare scores over time to track improvements
• [LIVE-REFUTED] findings may still be worth fixing proactively