Agent Skills: Concurrency Auditor (L3 Worker)

Paths: File paths (shared/, references/, ../ln-*) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root.

Concurrency Auditor (L3 Worker)

Specialized worker auditing concurrency and async patterns.

Purpose & Scope

• Worker in ln-620 coordinator pipeline
• Audit concurrency (Category 11: High Priority)
• Check race conditions, async/await, thread safety
• Calculate compliance score (X/10)

Inputs (from Coordinator)

Receives contextStore with tech stack, language, codebase root, output_dir.

Workflow

1. Parse context + output_dir
2. Check concurrency patterns
3. Collect findings
4. Calculate score
5. Write Report: Build full markdown report in memory per shared/templates/audit_worker_report_template.md, write to {output_dir}/628-concurrency.md in single Write call
6. Return Summary: Return minimal summary to coordinator

Audit Rules

1. Race Conditions

What: Shared state modified without synchronization

Detection Patterns:

| Language | Pattern | Grep | |----------|---------|------| | Python | Global modified in async | global\s+\w+ inside async def | | TypeScript | Module-level let in async | ^let\s+\w+ at file scope + async function modifies it | | Go | Map access without mutex | map\[.*\].*= without sync.Mutex in same file | | All | Shared cache | cache\[.*\]\s*= or cache\.set without lock |

Severity:

• CRITICAL: Race in payment/auth (payment, balance, auth, token in variable name)
• HIGH: Race in user-facing feature
• MEDIUM: Race in background job

Recommendation: Use locks, atomic operations, message queues

Effort: M-L

2. Missing Async/Await

What: Callback hell or unhandled promises

Detection Patterns:

| Issue | Grep | Example | |-------|------|---------| | Callback hell | \.then\(.*\.then\(.*\.then\( | .then().then().then() | | Fire-and-forget | async.*\(\) not preceded by await | saveToDb() without await | | Missing await | return\s+new\s+Promise in async function | Should just return await or return value | | Dangling promise | \.catch\(\s*\) | Empty catch swallows errors |

Severity:

• HIGH: Fire-and-forget async (can cause data loss)
• MEDIUM: Callback hell (hard to maintain)
• LOW: Mixed Promise styles

Recommendation: Convert to async/await, always await or handle promises

Effort: M

3. Resource Contention

What: Multiple processes competing for same resource

Detection Patterns:

| Issue | Grep | Example | |-------|------|---------| | File lock missing | open\(.*["']w["']\) without flock or lockfile | Concurrent file writes | | Connection exhaustion | create_engine\(.*pool_size check if pool_size < 5 | DB pool too small | | Concurrent writes | writeFile or fs\.write without lock check | File corruption risk |

Severity:

• HIGH: File corruption risk, DB exhaustion
• MEDIUM: Performance degradation

Recommendation: Use connection pooling, file locking, asyncio.Lock

Effort: M

4. Thread Safety Violations

What: Shared mutable state without synchronization

Detection Patterns:

| Language | Safe Pattern | Unsafe Pattern | |----------|--------------|----------------| | Go | sync.Mutex with map | map[...] without Mutex in same struct | | Rust | Arc<Mutex<T>> | Rc<RefCell<T>> in multi-threaded context | | Java | synchronized or ConcurrentHashMap | HashMap shared between threads | | Python | threading.Lock | Global dict modified in threads |

Grep patterns:

• Go unsafe: type.*struct\s*{[^}]*map\[ without sync.Mutex in same struct
• Python unsafe: global\s+\w+ in function + threading.Thread in same file

Severity: HIGH (data corruption possible)

Recommendation: Use thread-safe primitives

Effort: M

5. Deadlock Potential

What: Lock acquisition in inconsistent order

Detection Patterns:

| Issue | Grep | Example | |-------|------|---------| | Nested locks | with\s+\w+_lock:.*with\s+\w+_lock: (multiline) | Lock A then Lock B | | Lock in loop | for.*:.*\.acquire\(\) | Lock acquired repeatedly without release | | Lock + external call | .acquire\(\) followed by await or requests. | Holding lock during I/O |

Severity: HIGH (deadlock freezes application)

Recommendation: Consistent lock ordering, timeout locks (asyncio.wait_for)

Effort: L

6. Blocking I/O in Event Loop (Python asyncio)

What: Synchronous blocking calls inside async functions

Detection Patterns:

| Blocking Call | Grep in async def | Replacement | |---------------|---------------------|-------------| | time.sleep | time\.sleep inside async def | await asyncio.sleep | | requests. | requests\.(get\|post) inside async def | httpx or aiohttp | | open() file | open\( inside async def | aiofiles.open |

Severity:

• HIGH: Blocks entire event loop
• MEDIUM: Minor blocking (<100ms)

Recommendation: Use async alternatives

Effort: S-M

Scoring Algorithm

MANDATORY READ: Load shared/references/audit_scoring.md for unified scoring formula.

Output Format

MANDATORY READ: Load shared/templates/audit_worker_report_template.md for file format.

Write report to {output_dir}/628-concurrency.md with category: "Concurrency" and checks: race_conditions, missing_await, resource_contention, thread_safety, deadlock_potential, blocking_io.

Return summary to coordinator:

Report written: docs/project/.audit/628-concurrency.md
Score: X.X/10 | Issues: N (C:N H:N M:N L:N)

Reference Files

• Worker report template: shared/templates/audit_worker_report_template.md
• Audit scoring formula: shared/references/audit_scoring.md
• Audit output schema: shared/references/audit_output_schema.md

Critical Rules

• Do not auto-fix: Report only, concurrency fixes require careful human review
• Language-aware detection: Use language-specific patterns (Go sync.Mutex, Python asyncio.Lock, Java synchronized)
• Effort realism: S = <1h, M = 1-4h, L = >4h
• Critical path escalation: Race conditions in payment/auth = CRITICAL, regardless of other factors
• Exclusions: Skip test files, skip single-threaded CLI tools, skip generated code

Definition of Done

• contextStore parsed (language, concurrency model, output_dir)
• All 6 checks completed (race conditions, missing await, resource contention, thread safety, deadlock potential, blocking I/O)
• Findings collected with severity, location, effort, recommendation
• Score calculated per shared/references/audit_scoring.md
• Report written to {output_dir}/628-concurrency.md (atomic single Write call)
• Summary returned to coordinator

Version: 3.0.0 Last Updated: 2025-12-23