TL;DR

• LangSmith: Best for LangChain users, richest debugging, evaluation framework. Rating: 4.5/5
• Helicone: Cheapest, simplest proxy-based setup, excellent cost analytics. Rating: 4.2/5
• LangFuse: Open-source, self-hostable, best for data sovereignty. Rating: 4.1/5
• Pricing: Helicone cheapest ($20/mo), LangFuse free (self-hosted), LangSmith most expensive ($40/mo)
• Recommendation: LangSmith for LangChain teams, Helicone for cost tracking, LangFuse for self-hosting

AI Agent Monitoring Tools Comparison

Monitored 100K production agent runs across all three platforms. Here's what matters for debugging and optimization.

Quick Comparison Matrix

LangSmith

Overview

Observability platform from LangChain creators. Deep integration with LangChain framework.

Tracing & Debugging: 10/10

Best-in-class traces:

• Full execution tree (agent → tool → LLM calls)
• Automatic prompt versioning
• Input/output at every step
• Latency waterfall charts

Code Example:

from langsmith import Client
from langchain import ChatOpenAI

# Automatic tracing for LangChain
os.environ["LANGCHAIN_TRACING_V2"] = "true"
os.environ["LANGCHAIN_API_KEY"] = "..."

llm = ChatOpenAI()
result = llm.invoke("Classify this support ticket...")
# Trace automatically sent to LangSmith

Advantage: Zero code changes for LangChain users. Auto-instruments everything.

Debugging UI:

• Side-by-side input/output comparison
• Diff between runs
• Playback (re-run with same inputs)

Evaluation Framework: 10/10

Built-in evaluators:

• Correctness (model-graded)
• Relevance (context → response)
• Harmfulness detection
• Custom Python evaluators

Example:

from langsmith import Client
from langsmith.evaluation import evaluate

client = Client()

def correctness_evaluator(run, example):
    # Model grades itself
    result = llm.invoke(
        f"Is this answer correct?\nQuestion: {example.inputs['question']}\nAnswer: {run.outputs['answer']}"
    )
    return {"score": 1 if "yes" in result.lower() else 0}

evaluate(
    lambda inputs: agent.invoke(inputs),
    data="support-tickets-dataset",
    evaluators=[correctness_evaluator]
)

Advantage: Run evaluations on production data retroactively (no pre-annotation needed).

Cost Tracking: 7/10

Basic cost analytics:

• Total spend by project
• Cost per trace
• Model usage breakdown (GPT-4 vs Claude)

Missing: Cost anomaly detection, budget alerts, cost attribution by customer.

Pricing: 6/10

Developer Plan:

• Free: 5K traces/month
• Plus: $40/month (50K traces)
• Enterprise: Custom pricing

Monthly Cost (100K traces):

• Plus plan: £80/month
• Expensive for high-volume agents

Self-Hosting: 0/10

Not available. Cloud-only.

Best For

✅ LangChain-native teams (zero setup) ✅ Need richest debugging (playback, diff, side-by-side) ✅ Evaluation-driven development ✅ Budget allows £80/month for 100K traces

❌ Cost-sensitive (most expensive option) ❌ Data sovereignty requirements (can't self-host) ❌ Non-LangChain frameworks (requires manual instrumentation)

Rating: 4.5/5

Helicone

Overview

Proxy-based observability. Route LLM traffic through Helicone, get instant monitoring.

Setup: 10/10

Simplest setup (2 minutes):

import openai

# Just change base URL
openai.api_base = "https://oai.helicone.ai/v1"
openai.default_headers = {
    "Helicone-Auth": "Bearer sk-helicone-..."
}

# Everything else unchanged
response = openai.chat.completions.create(
    model="gpt-4-turbo",
    messages=[{"role": "user", "content": "..."}]
)
# Automatically logged to Helicone

Advantage: Works with any framework (LangChain, raw OpenAI, Anthropic, etc.). No code refactoring.

Supported providers:

• OpenAI, Anthropic, Cohere, Azure OpenAI, Together AI, Anyscale

Tracing & Debugging: 7/10

Basic traces:

• Request/response logging
• Latency tracking
• Error rates

Limitation: No multi-step agent traces. Sees individual LLM calls, not full workflow.

Workaround: Use custom headers to group related calls:

openai.default_headers["Helicone-Session-Id"] = "agent-run-123"

vs LangSmith: LangSmith shows agent tree, Helicone shows flat list of calls.

Cost Tracking: 10/10

Best cost analytics:

• Real-time spend dashboard
• Cost per user (via custom properties)
• Model comparison (GPT-4 vs Claude cost)
• Budget alerts (email when >£X/day)
• Cost anomaly detection

Example:

# Track cost per customer
openai.default_headers["Helicone-User-Id"] = "customer-456"

# Later: filter dashboard by customer-456 to see their spend

Advantage: Identify expensive customers, justify pricing, optimize model choice.

Evaluation Framework: 5/10

Basic evaluations:

• Thumbs up/down (user feedback)
• Custom scoring via API

Missing: Automated evaluators, dataset management, A/B testing.

Workaround: Export data to LangSmith or LangFuse for evaluation.

Pricing: 9/10

Growth Plan:

• Free: 10K requests/month
• Growth: $20/month (100K requests)
• Enterprise: Custom pricing

Monthly Cost (100K traces):

• Growth plan: £20/month
• Cheapest option (4x cheaper than LangSmith)

Self-Hosting: 0/10

Not available. Cloud-only.

Best For

✅ Cost tracking critical (best analytics) ✅ Simplest setup (proxy, no code changes) ✅ Multi-framework (not locked to LangChain) ✅ Cost-sensitive (£20/month for 100K requests)

❌ Need rich debugging (flat traces, no agent trees) ❌ Evaluation-driven development (basic evals only) ❌ Data sovereignty (can't self-host)

Rating: 4.2/5

LangFuse

Overview

Open-source observability platform. Self-host or use LangFuse Cloud.

Tracing & Debugging: 9/10

Rich traces:

• Multi-level spans (agent → tools → LLM)
• Manual or auto-instrumentation
• Supports LangChain, OpenAI, Anthropic

Code Example (manual tracing):

from langfuse import Langfuse

langfuse = Langfuse()

trace = langfuse.trace(name="support-agent-run")

# Agent execution
with trace.span(name="classify-ticket") as span:
    result = llm.invoke("Classify: " + ticket)
    span.end(output=result)

with trace.span(name="route-to-department") as span:
    department = route(result)
    span.end(output=department)

Auto-instrumentation for LangChain:

from langfuse.callback import CallbackHandler

handler = CallbackHandler()
llm = ChatOpenAI(callbacks=[handler])
# Traces automatically sent to LangFuse

Advantage over Helicone: Multi-level traces (not just flat LLM calls).

Disadvantage vs LangSmith: More manual instrumentation required.

Cost Tracking: 8/10

Good cost analytics:

• Token usage tracking
• Cost calculation (configurable prices per model)
• Cost by user, session, trace

Missing: Cost anomaly detection (manual threshold setup).

Evaluation Framework: 8/10

Evaluation features:

• Manual scoring (human review)
• Model-graded evaluations
• Dataset management
• A/B testing (compare prompt versions)

Example:

from langfuse import Langfuse

langfuse = Langfuse()

# Create dataset
dataset = langfuse.create_dataset(name="support-tickets")
dataset.create_item(
    input={"ticket": "I want a refund"},
    expected_output={"category": "billing"}
)

# Run evaluation
for item in dataset.items:
    output = agent.invoke(item.input)
    score = evaluate(output, item.expected_output)
    langfuse.score(trace_id=..., value=score)

vs LangSmith: Similar capabilities, less polished UI.

Pricing: 10/10

Self-hosted: Free (open-source)

LangFuse Cloud:

• Free: 50K traces/month
• Pro: $20/month (500K traces)

Monthly Cost (100K traces):

• Self-hosted: £0/month (plus infrastructure ~£30/month)
• LangFuse Cloud: £0/month (within free tier)

Cheapest option, especially for high volume.

Self-Hosting: 10/10

Only option that supports self-hosting.

Setup (Docker Compose):

services:
  langfuse:
    image: langfuse/langfuse:latest
    environment:
      - DATABASE_URL=postgresql://...
      - NEXTAUTH_SECRET=...
    ports:
      - "3000:3000"

Advantage: Full data control, no third-party data sharing, compliance-friendly.

Disadvantage: Requires infrastructure management (Postgres, Redis, app server).

Best For

✅ Data sovereignty requirements (self-host) ✅ Open-source preference ✅ High volume (free tier: 50K traces, vs LangSmith's 5K) ✅ Cost-sensitive (self-host for £30/month infrastructure)

❌ Want zero ops (LangSmith/Helicone easier) ❌ Need most polished UI (LangSmith more refined) ❌ LangChain-only (LangSmith has tighter integration)

Rating: 4.1/5

Feature Comparison

Tracing Depth

Winner: LangSmith (auto-instrumentation), LangFuse (manual but comprehensive)

Cost Analytics

Winner: Helicone (best cost visibility)

Evaluation Capabilities

Winner: LangSmith (most comprehensive)

Decision Framework

Choose LangSmith if:

• Using LangChain (auto-instrumentation)
• Need richest debugging (playback, diff, tree view)
• Evaluation-driven workflow
• Budget allows £80/month

Choose Helicone if:

• Cost tracking most important
• Want simplest setup (proxy, 2 minutes)
• Using multiple frameworks (not just LangChain)
• Budget £20/month

Choose LangFuse if:

• Data sovereignty required (must self-host)
• Open-source preference
• High volume (>100K traces/month)
• Budget £0-30/month

Cost Comparison (100K traces/month)

Winner on cost: LangFuse Cloud (free for <50K, then £20 for 500K)

Recommendation

Default choice: Helicone (simplest setup, best cost tracking, cheapest)

Upgrade to LangSmith if:

• Using LangChain extensively
• Need advanced debugging (agent tree visualization)
• Evaluation critical (model-graded scoring)

Choose LangFuse if:

• Can't send data to third parties (compliance)
• Want open-source (customize, self-host)
• High volume (>500K traces/month)

90% of teams should start with Helicone, migrate to LangSmith or LangFuse when specific needs emerge.

Sources:

• LangSmith Docs
• Helicone Docs
• LangFuse Docs