---
name: llm-observability-expert
description: "Expert guide for LLM observability in production — token cost tracking, hallucination rate monitoring, latency analysis, prompt/completion logging, model comparison dashboards, and AI-specific tracing (Langfuse, Helicone, Lunary, OpenTelemetry GenAI) / Panduan ahli observabilitas LLM di produksi — pelacakan biaya token, pemantauan tingkat halusinasi, analisis latensi, logging prompt/completion, dashboard perbandingan model, dan tracing khusus AI."
author: "Roedy Rustam"
version: "4.4.2"

---

# llm-observability-expert — vibes-plug Skill

[English](#english) | [Bahasa Indonesia](#bahasa-indonesia)

---

<a name="english"></a>
## English

### Orchestration & Integration
- **Upstream Orchestrators**: Works under `brainstorming` (AI & LLM Integration matrix row) and `zero-to-prod-orchestrator` (Phase 7 - Monitoring & Production Telemetry) to provide observability for AI applications.
- **Downstream Cooperating Skills**:
  - `data-telemetry-expert` — Extend OpenTelemetry instrumentation with LLM-specific spans and metrics.
  - `llm-finops-router` — Feed real-time cost data to the FinOps router for dynamic model selection.
  - `kv-cache-prefix-optimizer` — Monitor cache hit rates to detect prefix cache invalidation.
  - `logging-error-tracking-expert` — Integrate LLM traces with Sentry error tracking and Pino structured logs.
  - `ai-safety-governance-expert` — Log and audit AI outputs for compliance with safety policies.
  - `adaptive-model-cascade` — Feed model latency and error statistics to dynamic model cascading routers.
  - `session-memory-manager` — Store AI session traces and token usage checkpoints.

### Description
Production observability framework for LLM-powered applications. Addresses the biggest blind spot in 2026 AI applications: teams deploy AI features to production with zero visibility into token costs, hallucination rates, latency distributions, cache hit ratios, or user satisfaction scores. This skill provides the instrumentation patterns, tool integrations, and dashboard architectures to make LLM behavior fully observable.

### Trigger Conditions
Activate this skill when:
- Deploying any LLM-powered feature to production (chatbots, AI assistants, code generators, content tools).
- Investigating unexplained cost spikes in AI API billing.
- Debugging hallucination reports or quality degradation in AI outputs.
- Building dashboards to monitor AI feature health and cost efficiency.
- Comparing model performance (latency, quality, cost) across providers.

---

### Core Concepts & Patterns

#### 1. LLM Observability Stack (2026)

| Layer | Tool | Purpose |
| :--- | :--- | :--- |
| **Tracing** | Langfuse / Helicone / Lunary | End-to-end trace of LLM calls, including prompt, completion, tokens, latency, and metadata |
| **Cost Tracking** | Helicone / LiteLLM Proxy / Custom | Real-time token cost aggregation by model, feature, user, and tenant |
| **Quality Metrics** | Langfuse Scores / Custom Evals | Hallucination rate, factuality score, user satisfaction (thumbs up/down) |
| **Alerting** | Grafana / PagerDuty / Custom | Cost anomaly alerts, latency SLA breaches, error rate spikes |
| **Logs** | OpenTelemetry + Axiom/Datadog | Structured logs with prompt/completion pairs for debugging |

#### 2. Core Metrics to Track

```typescript
export interface LLMCallMetrics {
  traceId: string;
  spanId: string;
  timestamp: string;

  // Model & Provider
  model: string;
  provider: 'openai' | 'anthropic' | 'google' | 'custom';

  // Token Economics
  promptTokens: number;
  completionTokens: number;
  cachedTokens: number;
  totalCost: number;
  cacheHitRate: number;

  // Latency
  timeToFirstToken: number;
  totalLatency: number;
  tokensPerSecond: number;

  // Quality Signals
  userFeedback?: 'positive' | 'negative' | null;
  hallucinationDetected?: boolean;
  toolCallSuccess?: boolean;
  retryCount: number;

  // Context
  feature: string;
  userId?: string;
  tenantId?: string;
  sessionId: string;
}
```

#### 3. Langfuse Integration (TypeScript)

```typescript
import { Langfuse } from 'langfuse';

const langfuse = new Langfuse({
  publicKey: process.env.LANGFUSE_PUBLIC_KEY!,
  secretKey: process.env.LANGFUSE_SECRET_KEY!,
  baseUrl: process.env.LANGFUSE_BASE_URL,
});

export function traceLLMCall<T>(
  featureName: string,
  userId: string,
  fn: (trace: ReturnType<typeof langfuse.trace>) => Promise<T>
): Promise<T> {
  const trace = langfuse.trace({
    name: featureName,
    userId,
    metadata: { environment: process.env.NODE_ENV },
  });

  return fn(trace).finally(() => langfuse.flush());
}

// Usage in API route with graceful availability fallback:
export async function handleChatRequest(req: Request) {
  const { message, userId } = await req.json();

  return traceLLMCall('chat-assistant', userId, async (trace) => {
    let activeModel = 'gemini-4-pro';
    let response: { text: string; usage: { promptTokens: number; completionTokens: number; totalTokens: number } };

    try {
      response = await callLLM(message, activeModel);
    } catch (err) {
      // Invariant: Gracefully fall back to Gemini 3.8 Flash if Gemini 4 Pro is unprovisioned/unavailable
      console.warn('[LLMObservability] Gemini 4 Pro unavailable. Falling back to Gemini 3.8 Flash:', err);
      activeModel = 'gemini-3.8-flash';
      trace.update({ metadata: { fallbackTriggered: true, originalModel: 'gemini-4-pro', fallbackModel: activeModel } });
      response = await callLLM(message, activeModel);
    }

    const generation = trace.generation({
      name: 'chat-completion',
      model: activeModel,
      input: message,
    });

    generation.end({
      output: response.text,
      usage: {
        promptTokens: response.usage.promptTokens,
        completionTokens: response.usage.completionTokens,
        totalTokens: response.usage.totalTokens,
      },
    });

    return new Response(JSON.stringify({ text: response.text }));
  });
}
```

#### 4. Cost Anomaly Detection

```typescript
export interface CostAlert {
  type: 'daily_budget_exceeded' | 'cost_per_call_spike' | 'cache_hit_drop';
  severity: 'warning' | 'critical';
  currentValue: number;
  threshold: number;
  message: string;
}

export function detectCostAnomalies(
  metrics: LLMCallMetrics[],
  dailyBudget: number,
  expectedCacheHitRate: number
): CostAlert[] {
  const alerts: CostAlert[] = [];

  const dailyCost = metrics.reduce((sum, m) => sum + m.totalCost, 0);
  if (dailyCost > dailyBudget) {
    alerts.push({
      type: 'daily_budget_exceeded',
      severity: 'critical',
      currentValue: dailyCost,
      threshold: dailyBudget,
      message: `Daily AI cost $${dailyCost.toFixed(2)} exceeds budget $${dailyBudget.toFixed(2)}`,
    });
  }

  const avgCacheHit = metrics.reduce((sum, m) => sum + m.cacheHitRate, 0) / metrics.length;
  if (avgCacheHit < expectedCacheHitRate * 0.7) {
    alerts.push({
      type: 'cache_hit_drop',
      severity: 'warning',
      currentValue: avgCacheHit,
      threshold: expectedCacheHitRate,
      message: `Cache hit rate dropped to ${(avgCacheHit * 100).toFixed(1)}% (expected ${(expectedCacheHitRate * 100).toFixed(1)}%)`,
    });
  }

  return alerts;
}
```

#### 5. Dashboard Architecture

```
┌──────────────────────────────────────────────────────┐
│                  AI OPERATIONS DASHBOARD              │
├──────────────┬───────────────┬────────────────────────┤
│ COST CENTER  │ QUALITY       │ PERFORMANCE            │
├──────────────┼───────────────┼────────────────────────┤
│ Daily spend  │ Hallucination │ P50/P95/P99 latency    │
│ by model     │ rate (24h)    │ by model               │
│              │               │                        │
│ Cost per     │ User feedback │ Tokens/second           │
│ feature      │ ratio (+/-)   │ throughput              │
│              │               │                        │
│ Cache hit    │ Tool call     │ Time-to-first-token     │
│ rate trend   │ success rate  │ distribution            │
│              │               │                        │
│ Token volume │ Retry rate    │ Error rate by           │
│ by tenant    │ by feature    │ provider                │
└──────────────┴───────────────┴────────────────────────┘
```

---

### Best Practices

1. **Instrument Every LLM Call**: No LLM call should go untraced. Wrap all provider SDK calls in an observability layer.
2. **Track Cost Per Feature, Not Just Total**: Aggregate costs by feature name to identify the most expensive AI functions.
3. **Set Budget Alerts Early**: Configure daily/weekly cost alerts before going to production, not after the first billing shock.
4. **Collect User Feedback Signals**: Implement thumbs up/down buttons on AI outputs and log them as quality scores in Langfuse.
5. **Monitor Cache Hit Rates**: A drop in cache hit rate directly increases costs — alert on deviations from baseline.
6. **Track Model Availability Fallbacks**: When Gemini 4 falls back to Gemini 3.8 Flash or Claude Opus 5.5 falls back to Claude Opus 4.6, tag trace metadata with `fallbackTriggered: true` to observe provider availability and SLA compliance.

---

### Common Pitfalls to Avoid

| Anti-Pattern | Consequence | Remedy |
| :--- | :--- | :--- |
| No observability in production AI features | Zero visibility into costs, quality, or failures | Instrument every LLM call with Langfuse/Helicone |
| Logging full prompts without PII filtering | GDPR/PDPA violation from stored user data | Apply PII scrubbing before logging |
| No cost alerting | Surprise $10k+ monthly bills | Set daily budget alerts with automatic circuit breakers |
| Tracking only latency, ignoring quality | Low-latency but high-hallucination responses | Track factuality scores alongside latency |

### Sovereign Execution, Token Efficiency & Invariants
| Dimension | Sovereign Mandate & Deterministic Contract |
| :--- | :--- |
| **Frontier Model Cascade** | Medium / High (`GPT-5.6 Sol Medium`, `Gemini 4 Argon`, `Claude Sonnet 5.5 High`, `Grok 4.7 High Fast`) |
| **Availability Fallback** | `Gemini 4 Argon/Pro` -> `Gemini 3.8 Flash`; `Claude Opus 5.5` -> `Claude Opus 4.6` (Zero unhandled missing-model errors) |
| **KV-Cache & Token Protocol** | Pin static instructions & schemas at prompt prefix (`kv-cache-prefix-optimizer`); pass surgical `CONTEXT_MAP.md` slices (<250 tokens/call) during Swarm Fan-Out |
| **SaaT CLI & MCP Dispatch** | CLI: `vibes skill exec llm-observability-expert <audit\|eval\|verify\|generate\|blueprint>` / MCP: `vibes_skill_dispatch`, `vibes_ast_query`, `vibes_compile_cache`, `vibes_optimize_budget`, `vibes_verify_gate` |
| **NFR & Anti-Slop Invariants** | P99 API Gateway Latency < 85ms, OpenAPI 3.1 / TypeSpec strict schema parity, RFC 9457 Problem Details error contracts, Idempotency-Key enforcement; 100% complete zero-placeholder output verified via `node scripts/check-anti-slop.js --strict` |

---


---

<a name="bahasa-indonesia"></a>
## Bahasa Indonesia

### Integrasi Orkestrasi
- **Orkestrator Hulu**: Beroperasi di bawah arahan `brainstorming` (baris "AI & LLM Integration" pada Matriks Orkestrasi) dan `zero-to-prod-orchestrator` (Fase 7 - Pemantauan & Telemetri Produksi) untuk menyediakan observabilitas aplikasi AI.
- **Skill Hilir & Kerja Sama**:
  - `data-telemetry-expert` — Memperluas instrumentasi OpenTelemetry dengan span dan metrik khusus LLM.
  - `llm-finops-router` — Mengirim data biaya real-time ke router FinOps untuk pemilihan model dinamis.
  - `kv-cache-prefix-optimizer` — Memantau cache hit rate untuk mendeteksi invalidasi prefix cache.
  - `logging-error-tracking-expert` — Mengintegrasikan trace LLM dengan pelacakan error Sentry dan log Pino.
  - `ai-safety-governance-expert` — Mencatat dan mengaudit output AI untuk kepatuhan kebijakan keamanan.
  - `adaptive-model-cascade` — Menyalurkan statistik latensi dan error model ke router cascade model.
  - `session-memory-manager` — Menyimpan trace sesi AI dan checkpoint penggunaan token.

### Deskripsi
Kerangka observabilitas produksi untuk aplikasi berbasis LLM. Mengatasi blind spot terbesar di aplikasi AI 2026: tim men-deploy fitur AI ke produksi tanpa visibilitas terhadap biaya token, tingkat halusinasi, distribusi latensi, rasio cache hit, atau skor kepuasan pengguna.

### Kondisi Pemicu
Aktifkan skill ini ketika:
- Men-deploy fitur berbasis LLM ke produksi (chatbot, asisten AI, generator kode).
- Menginvestigasi lonjakan biaya tak terduga di tagihan API AI.
- Men-debug laporan halusinasi atau degradasi kualitas output AI.
- Membangun dashboard untuk memonitor kesehatan fitur AI.

---

### Konsep Inti & Pola Praktik

#### 1. Metrik Inti yang Dilacak
Setiap panggilan LLM harus mencatat: traceId, model, provider, token (prompt/completion/cached), biaya total, cache hit rate, TTFT, latensi total, feedback pengguna, deteksi halusinasi, dan konteks fitur/user/tenant.

#### 2. Integrasi Langfuse
Gunakan Langfuse untuk tracing end-to-end setiap panggilan LLM, termasuk input prompt, output completion, penggunaan token, dan latensi.

#### 3. Deteksi Anomali Biaya
Implementasikan alert otomatis untuk: anggaran harian terlampaui, lonjakan biaya per-panggilan, dan penurunan cache hit rate.

---

### Praktik Terbaik

1. **Instrumenkan Setiap Panggilan LLM**: Tidak ada panggilan LLM yang boleh tidak dilacak.
2. **Lacak Biaya Per Fitur**: Agregasikan biaya berdasarkan nama fitur untuk mengidentifikasi fungsi AI termahal.
3. **Atur Alert Anggaran Sejak Awal**: Konfigurasikan alert biaya harian/mingguan sebelum ke produksi.
4. **Kumpulkan Sinyal Feedback Pengguna**: Implementasikan tombol thumbs up/down pada output AI.
5. **Pantau Pengalihan Ketersediaan (Fallback)**: Saat model Gemini 4 dialihkan ke Gemini 3.8 Flash atau Claude Opus 5.5 ke Claude Opus 4.6, sematkan metadata `fallbackTriggered: true` pada trace untuk memantau SLA ketersediaan dan variasi biaya.

### Matriks Eksekusi Berdaulat, Efisiensi Token & Invarian
| Dimensi | Mandat Berdaulat & Kontrak Deterministik |
| :--- | :--- |
| **Kaskade Model Frontier** | Medium / High (`GPT-5.6 Sol Medium`, `Gemini 4 Argon`, `Claude Sonnet 5.5 High`, `Grok 4.7 High Fast`) |
| **Invarian Fallback Ketersediaan** | `Gemini 4 Argon/Pro` -> `Gemini 3.8 Flash`; `Claude Opus 5.5` -> `Claude Opus 4.6` (Bebas gagal saat model belum tersedia/kuota penuh) |
| **Protokol Hemat Token & KV-Cache** | Kunci instruksi & skema statis di prefix awal (`kv-cache-prefix-optimizer`); kirim potongan `CONTEXT_MAP.md` (<250 token/panggilan) saat Fan-Out |
| **Eksekusi SaaT CLI & MCP** | CLI: `vibes skill exec llm-observability-expert <audit\|eval\|verify\|generate\|blueprint>` / MCP: `vibes_skill_dispatch`, `vibes_ast_query`, `vibes_compile_cache`, `vibes_optimize_budget`, `vibes_verify_gate` |
| **Invarian NFR & Anti-Slop** | Latensi P99 API < 85ms, paritas skema ketat OpenAPI 3.1 / TypeSpec, kontrak error RFC 9457 Problem Details, penegakan Idempotency-Key; kode 100% tuntas tanpa placeholder diverifikasi melalui `node scripts/check-anti-slop.js --strict` |