Fiddler LangGraph SDK - Fiddler Documentation

Instrument your LangGraph agent applications and custom AI workflows with OpenTelemetry-based tracing for comprehensive agentic observability. The Fiddler LangGraph SDK provides three instrumentation approaches — auto-instrumentation for LangGraph workflows, decorator-based tracing for custom functions, and manual span creation for fine-grained control — capturing every step from thought to action to execution.

What you’ll need

Fiddler account (cloud or on-premises)
Python 3.10-3.14
LangGraph or LangChain application
Fiddler API key and application ID

Quick start

Get monitoring in 3 steps:

# Step 1: Install
pip install fiddler-langgraph

# Step 2: Initialize the Fiddler client
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

fdl_client = FiddlerClient(
    application_id='your-app-id',  # Must be valid UUID4
    api_key='your-api-key',
    url='https://your-instance.fiddler.ai'
)

# Step 3: Instrument your application
instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

# Your existing LangGraph code runs normally
# Traces will automatically be sent to Fiddler

That’s it! Your agent traces are now flowing to Fiddler.

This Quick Start uses auto-instrumentation for LangGraph applications. For custom functions or fine-grained control, see Instrumentation Methods below.

What gets monitored

The LangGraph SDK automatically captures:

Hierarchical tracing

Application Level - Overall system performance and health
Session Level - User interaction and conversation flows
Agent Level - Individual agent behavior and decisions
Span Level - Tool calls, LLM requests, state transitions

Agent lifecycle stages

Every agent operation is tracked through five observable stages:

Thought - Data ingestion, context retrieval, information interpretation
Action - Planning processes, tool selection, decision-making
Execution - Task performance, API calls, external integrations
Reflection - Self-evaluation, learning signals, adaptation
Alignment - Trust validation, safety checks, policy enforcement

Captured data

Agent state transitions and decision points
Tool invocations with inputs and outputs
LLM API calls with prompts and responses
Execution times and latency metrics
Error traces and exception handling
Custom metadata and tags

Application setup

Before instrumenting your application, you must create an application in Fiddler and obtain your Application ID:

1. Create your application in Fiddler

Log in to your Fiddler instance and navigate to GenAI Applications, then click Add Application and follow the onboarding wizard to create your application.

GenAI Applications page with Add Application button

2. Copy your Application ID

After creating your application, copy the Application ID from the GenAI Applications page using the copy icon next to the ID. This must be a valid UUID4 format (for example, 550e8400-e29b-41d4-a716-446655440000). You’ll need this for initialization.

GenAI Applications page showing Application ID column with copy icons

3. Get your access token

Go to Settings > Credentials and copy your access token. You’ll need this for initialization.

Fiddler Settings- Credentials tab showing admin's access token

Detailed setup

Installation

pip install fiddler-langgraph

Framework Compatibility:

LangGraph: >= 0.3.28 and <= 1.1.0 OR LangChain: >= 0.3.28 and <= 1.1.0
Python: 3.10, 3.11, 3.12, or 3.13
OpenTelemetry: API and SDK >= 1.28.0 and <= 1.39.1 (installed automatically)

Configuration

Direct initialization (Recommended)

from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

fdl_client = FiddlerClient(
    application_id='your-app-id',        # Required (UUID4 format)
    api_key='your-api-key',              # Required
    url='https://your-instance.fiddler.ai'  # Required
)

instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

Using environment variables

You can use environment variables instead of hardcoding credentials:

import os
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

fdl_client = FiddlerClient(
    application_id=os.getenv("FIDDLER_APPLICATION_ID"),
    api_key=os.getenv("FIDDLER_API_KEY"),
    url=os.getenv("FIDDLER_URL")
)

instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

Environment Variables Reference:

Variable	Description	Example
`FIDDLER_API_KEY`	Your Fiddler API key	`fid_...`
`FIDDLER_APPLICATION_ID`	Your application UUID4	`550e8400-e29b-41d4-a716-446655440000`
`FIDDLER_URL`	Your Fiddler instance URL	`https://your-instance.fiddler.ai`

Instrumentation methods

The Fiddler LangGraph SDK provides three instrumentation approaches. Choose the one that fits your application:

Approach	Best For	Key API
Auto-Instrumentation	LangGraph and LangChain applications	`LangGraphInstrumentor`
Decorator-Based	Custom Python functions, mixed workflows	`@trace()`, `get_current_span()`
Manual	Fine-grained span lifecycle control	`start_as_current_span()`, `start_span()`

You can combine all three approaches in the same application. For example, use auto-instrumentation for your LangGraph graph and decorators for custom helper functions that the graph calls.

Auto-Instrumentation

Auto-instrumentation captures LangGraph and LangChain workflows automatically. Initialize the instrumentor once, and all graph invocations produce traces with no additional code changes.

from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)

instrumentor = LangGraphInstrumentor(client)
instrumentor.instrument()

# Your LangGraph/LangChain code runs normally — traces are captured automatically

When to use: Your application uses LangGraph StateGraph or LangChain runnables and you want comprehensive tracing with zero instrumentation code. See the Quick Start section above for a complete walkthrough, or the Advanced Usage section for context enrichment and production configuration.

Decorator-based instrumentation

Use the @trace() decorator to instrument individual Python functions. This is the recommended approach for custom functions that are not part of a LangGraph graph, such as standalone LLM calls, tool implementations, or orchestration logic.

from openai import OpenAI
from fiddler_langgraph import FiddlerClient, trace, get_current_span

client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)

openai_client = OpenAI()  # Assumes OPENAI_API_KEY is set in environment
# vector_store: a pre-configured vector database client (e.g., Pinecone, Chroma, Weaviate)

@trace(as_type="generation", model="gpt-4o", system="openai")
def call_llm(prompt: str) -> str:
    span = get_current_span(as_type="generation")
    if span:
        span.set_user_prompt(prompt)
    response = openai_client.chat.completions.create(
        model="gpt-4o",
        messages=[{"role": "user", "content": prompt}]
    )
    result = response.choices[0].message.content
    if span:
        span.set_completion(result)
    return result

@trace(as_type="tool", name="search_knowledge_base")
def search_kb(query: str) -> list[str]:
    span = get_current_span(as_type="tool")
    if span:
        span.set_tool_input({"query": query})
    results = vector_store.search(query)
    if span:
        span.set_tool_output(results)
    return results

@trace(name="handle_request")
def handle_request(user_input: str) -> str:
    context = search_kb(user_input)       # Child span (tool)
    response = call_llm(user_input)       # Child span (generation)
    return response                        # Parent span auto-closes

When to use: You have custom Python functions — LLM wrappers, tool implementations, or orchestration logic — that you want to trace with full control over span metadata.

`@trace()` Arguments

Argument	Type	Default	Description
`name`	`str`	Function name	Custom span name
`as_type`	`str`	`"span"`	Span type: `"span"`, `"generation"`, `"chain"`, or `"tool"`
`capture_input`	`bool`	`True`	Automatically capture function arguments as span input
`capture_output`	`bool`	`True`	Automatically capture return value as span output
`model`	`str`	`None`	LLM model name (sets `gen_ai.request.model`)
`system`	`str`	`None`	LLM provider such as `"openai"` or `"anthropic"` (sets `gen_ai.system`)
`user_id`	`str`	`None`	User identifier
`version`	`str`	`None`	Service version string
`client`	`FiddlerClient`	`None`	Explicit client instance (defaults to the global singleton)

Accessing the current span

Inside a decorated function, call get_current_span() to access the active span and add metadata:

from fiddler_langgraph import get_current_span

@trace(as_type="generation")
def my_llm_call(prompt: str) -> str:
    span = get_current_span(as_type="generation")
    if span:
        span.set_user_prompt(prompt)
        span.set_model("gpt-4o")
        span.set_system("openai")
    # ... make your LLM call ...
    if span:
        span.set_completion(result)
        span.set_usage(input_tokens=50, output_tokens=120)
    return result

Pass as_type to get a type-specific wrapper with semantic helper methods. See Span Types and Helper Methods for the full list.

Always check if span: before calling helper methods. get_current_span() returns None if no Fiddler span is active — for example, during unit tests or when the client is not initialized.

Async support

The @trace() decorator works with both sync and async functions. No additional configuration is needed:

@trace(as_type="generation", model="gpt-4o", system="openai")
async def async_llm_call(prompt: str) -> str:
    span = get_current_span(as_type="generation")
    if span:
        span.set_user_prompt(prompt)
    response = await openai_client.chat.completions.create(
        model="gpt-4o",
        messages=[{"role": "user", "content": prompt}]
    )
    result = response.choices[0].message.content
    if span:
        span.set_completion(result)
    return result

Automatic parent-child relationships

Nested decorated functions create proper span hierarchies automatically. The outer function becomes the parent span, and inner calls become child spans:

@trace(name="agent_workflow", as_type="chain")
def run_agent(query: str) -> str:
    context = retrieve_docs(query)    # Child span
    answer = generate_answer(context) # Child span
    return answer                     # Parent span

@trace(as_type="tool")
def retrieve_docs(query: str) -> list[str]:
    # Automatically a child of "agent_workflow"
    return vector_db.search(query)

@trace(as_type="generation", model="gpt-4o")
def generate_answer(context: list[str]) -> str:
    # Also a child of "agent_workflow"
    return llm.generate(context)

Manual instrumentation

Create spans manually using context managers or explicit start/end calls. This gives you full control over span lifecycle — useful for dynamic span creation, conditional instrumentation, or code where decorator syntax does not apply.

Context manager (automatic lifecycle)

Use start_as_current_span() to create a span that ends automatically when the block exits:

from openai import OpenAI
from fiddler_langgraph import FiddlerClient

openai_client = OpenAI()  # Assumes OPENAI_API_KEY is set in environment

client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)

with client.start_as_current_span("llm_call", as_type="generation") as span:
    span.set_model("gpt-4o")
    span.set_system("openai")
    span.set_user_prompt("What is the capital of France?")

    response = openai_client.chat.completions.create(
        model="gpt-4o",
        messages=[{"role": "user", "content": "What is the capital of France?"}]
    )

    span.set_completion(response.choices[0].message.content)
    span.set_usage(
        input_tokens=response.usage.prompt_tokens,
        output_tokens=response.usage.completion_tokens
    )
# Span ends automatically here

Explicit span control

Use start_span() when you need to manage span lifecycle manually — for example, in callback-driven or event-based code:

span = client.start_span("background_task", as_type="tool")
try:
    span.set_tool_name("data_processor")
    span.set_tool_input({"file": "data.csv"})
    result = process_file("data.csv")
    span.set_tool_output(result)
finally:
    span.end()  # Must call end() explicitly

Always call span.end() when using start_span(). Forgetting to end a span causes a resource leak. Prefer start_as_current_span() unless you need explicit lifecycle control.

When to use: You need explicit control over when spans start and end — for example, in callback-driven code, conditional spans, or complex control flow where decorators do not fit.

Span types and helper methods

Both decorator and manual instrumentation support four span types. Set the as_type parameter to select a type, which determines which semantic helper methods are available on the span wrapper.

Type	Wrapper Class	Use For
`"span"`	`FiddlerSpan`	Generic operations, orchestration
`"generation"`	`FiddlerGeneration`	LLM calls (prompts, completions, token usage)
`"chain"`	`FiddlerChain`	Multi-step workflows, processing chains
`"tool"`	`FiddlerTool`	Tool or function calls (name, input, output)

Common methods (all types)

Method	Description
`set_input(data)`	Set input data (auto-serializes dicts and lists to JSON)
`set_output(data)`	Set output data (auto-serializes dicts and lists to JSON)
`set_attribute(key, value)`	Set a custom span attribute
`set_agent_name(name)`	Set the agent name (`gen_ai.agent.name`)
`set_agent_id(id)`	Set the agent ID (`gen_ai.agent.id`)
`set_conversation_id(id)`	Set the conversation ID (`gen_ai.conversation.id`)
`record_exception(exception)`	Record an error on the span

Generation methods (`FiddlerGeneration`)

Method	Sets Attribute
`set_model(name)`	`gen_ai.request.model`
`set_system(provider)`	`gen_ai.system`
`set_system_prompt(text)`	`gen_ai.llm.input.system`
`set_user_prompt(text)`	`gen_ai.llm.input.user`
`set_completion(text)`	`gen_ai.llm.output`
`set_usage(input_tokens, output_tokens, total_tokens)`	`gen_ai.usage.*`
`set_context(text)`	`gen_ai.llm.context`
`set_messages(messages)`	`gen_ai.input.messages`
`set_output_messages(messages)`	`gen_ai.output.messages`
`set_tool_definitions(definitions)`	`gen_ai.tool.definitions`

Tool methods (`FiddlerTool`)

Method	Sets Attribute
`set_tool_name(name)`	`gen_ai.tool.name`
`set_tool_input(data)`	`gen_ai.tool.input`
`set_tool_output(data)`	`gen_ai.tool.output`
`set_tool_definitions(definitions)`	`gen_ai.tool.definitions`

For complete API documentation, see the LangGraph SDK API Reference.

Context isolation

The Fiddler LangGraph SDK maintains its own isolated OpenTelemetry context. Fiddler traces do not interfere with other OpenTelemetry tracers that may be active in your application, and vice versa. Each FiddlerClient creates a private Context instance. All span creation, parent-child linking, and context propagation happen within this isolated context. When you use @trace(), start_as_current_span(), or start_span(), the SDK manages context attachment and detachment automatically. You can verify whether a span belongs to Fiddler using is_fiddler_span():

from fiddler_otel.utils import is_fiddler_span
from opentelemetry import trace

otel_span = trace.get_current_span()
if is_fiddler_span(otel_span):
    print("This span belongs to Fiddler")

This isolation matters if your application uses other OpenTelemetry-based observability tools (such as Datadog, Honeycomb, or custom OTel exporters). Fiddler traces remain completely separate, so you can run multiple tracing systems side by side without conflicts.

Global client pattern

The Fiddler SDK uses a singleton pattern for FiddlerClient. The first client created in your process is automatically registered as the global default. Retrieve it anywhere using get_client():

from fiddler_langgraph import FiddlerClient, get_client

# Initialize once (automatically registered as global singleton)
client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)

# Retrieve anywhere in your application
def some_utility_function():
    fdl_client = get_client()  # Returns the same client instance
    with fdl_client.start_as_current_span("utility_op") as span:
        span.set_attribute("source", "utility")
        # ... your logic ...

The @trace() decorator uses get_client() internally, so you do not need to pass a client to each decorated function. As long as a FiddlerClient has been created somewhere in your application, all @trace() decorators and get_current_span() calls work automatically.

There is no set_current_client() function. The singleton is set automatically during FiddlerClient initialization. If you create multiple clients, only the first one becomes the global default. Pass an explicit client argument to @trace() to use a different client.

Advanced usage

Adding context and metadata

Enrich traces with custom context and conversation tracking:

from fiddler_langgraph import set_llm_context, clear_llm_context, set_conversation_id
import uuid

# Set descriptive context for LLM processing
set_llm_context(model, 'Customer support conversation')

# Set conversation ID for tracking multi-turn conversations
conversation_id = str(uuid.uuid4())
set_conversation_id(conversation_id)

Clearing LLM context for non-RAG steps

In multi-step agent workflows, context set after a RAG retrieval step leaks into subsequent non-RAG LLM calls (tool planning, routing, etc.), causing unintended faithfulness evaluation. Use clear_llm_context() to explicitly remove context before non-RAG steps:

from fiddler_langgraph import set_llm_context, clear_llm_context

# After RAG retrieval — attach context for faithfulness evaluation
set_llm_context(llm, retrieved_documents)
response = llm.invoke(rag_prompt)  # faithfulness evaluated

# Before non-RAG steps — clear context to skip faithfulness evaluation
clear_llm_context(llm)
plan = llm.invoke(planning_prompt)  # no faithfulness evaluation

clear_llm_context(llm) is equivalent to set_llm_context(llm, None).

Custom span and session attributes

Add custom attributes to individual spans or entire sessions:

from fiddler_langgraph import add_span_attributes, add_session_attributes

# Add attributes to specific spans
add_span_attributes({
    "user_id": "user_123",
    "request_type": "billing_inquiry"
})

# Add attributes that persist across all spans in a session
add_session_attributes({
    "session_type": "premium",
    "feature_flags": ["new_ui", "advanced_mode"]
})

Sampling configuration

Control trace sampling for high-volume applications:

from opentelemetry.sdk.trace import sampling
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

# Sample 10% of traces
sampler = sampling.TraceIdRatioBased(0.1)

fdl_client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai",
    sampler=sampler
)

instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

For production deployments, consider these sampling strategies:

High-volume applications: Sample 5-10% (TraceIdRatioBased(0.05))
Development/testing: Sample 100% (default - no sampler specified)
Cost optimization: Sample 1-5% (TraceIdRatioBased(0.01))

Production configuration

For high-volume production applications, configure span limits and batch processing:

import os
from opentelemetry.sdk.trace import SpanLimits, sampling
from opentelemetry.exporter.otlp.proto.http.trace_exporter import Compression
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

# Configure batch processing BEFORE initializing FiddlerClient
os.environ['OTEL_BSP_MAX_QUEUE_SIZE'] = '500'         # Increased from default 100
os.environ['OTEL_BSP_SCHEDULE_DELAY_MILLIS'] = '500'  # Faster export than default 1000ms
os.environ['OTEL_BSP_MAX_EXPORT_BATCH_SIZE'] = '50'   # Larger batches than default 10

# Increase span limits to capture more data
production_limits = SpanLimits(
    max_events=128,                   # Default: 32
    max_span_attributes=128,          # Default: 32
    max_span_attribute_length=8192,   # Default: 2048
)

# Sample 5-10% of traces
production_sampler = sampling.TraceIdRatioBased(0.05)

fdl_client = FiddlerClient(
    application_id=os.getenv("FIDDLER_APPLICATION_ID"),
    api_key=os.getenv("FIDDLER_API_KEY"),
    url=os.getenv("FIDDLER_URL"),
    span_limits=production_limits,
    sampler=production_sampler,
    compression=Compression.Gzip,
)

instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

Offline / S3 Routing Mode

Use this mode when traces must be routed through an intermediate store (such as Amazon S3) before reaching Fiddler, rather than being sent directly. This is the correct approach when your security or network policies require all data to pass through a controlled intermediary.

otlp_enabled=False — disables all direct OTLP export to Fiddler. api_key and url are not required in this mode.
otlp_json_capture_enabled=True — writes traces to local .json files in standard OTLP JSON format (ExportTraceServiceRequest envelope). These files are directly consumable by the Fiddler S3 connector with no reformatting.
application_id is still required — even though no data is sent to Fiddler directly, the S3 connector uses the application_id embedded in the trace files to route ingested traces to the correct application in Fiddler.

from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

# No api_key or url needed — traces go to local files only
fdl_client = FiddlerClient(
    application_id="YOUR_APPLICATION_ID",   # UUID4 — required for S3 connector routing
    otlp_enabled=False,                      # Disables direct export to Fiddler
    otlp_json_capture_enabled=True,          # Writes OTLP JSON files locally
    otlp_json_output_dir="./fiddler_traces", # Directory for output files (default: 'fiddler_traces')
)

instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

# Your LangGraph code runs normally — traces are written to ./fiddler_traces/*.json

Upload the generated .json files from otlp_json_output_dir to your S3 bucket. The Fiddler S3 connector reads them directly.

Each batch of spans is written to a separate timestamped .json file in the output directory. The directory is created automatically if it does not exist.

Do not confuse console_tracer or jsonl_capture_enabled with this mode. Both of those flags are additive — they add a local output on top of the existing OTLP export to Fiddler but do not disable it. Only otlp_enabled=False fully stops direct export to Fiddler.

Flush and shutdown handling

The SDK uses OpenTelemetry’s batch span processor, which buffers spans in memory and exports them on a schedule. To avoid losing buffered spans when your process exits, use explicit flush and shutdown:

Process exit: The SDK registers an atexit handler that flushes and shuts down the tracer when the process exits. For short scripts or environments where atexit may not run (e.g. SIGKILL, forked processes), call force_flush() and shutdown() explicitly—for example in a try/finally or signal handler.
Long-running servers (e.g. FastAPI, uvicorn): On graceful shutdown (SIGTERM), call the Fiddler client’s shutdown so pending spans are exported before the process exits. From async code use ashutdown() (or aflush() then ashutdown()) so the event loop is not blocked; the sync force_flush() and shutdown() can block for up to the flush timeout (default 30 seconds).

Sync (scripts or signal handler):

# Ensure spans are sent before exit (e.g. in finally or SIGTERM handler)
fdl_client.shutdown()

Async (e.g. FastAPI/uvicorn lifespan):

# In your app's shutdown/lifespan handler (e.g. on SIGTERM)
await fdl_client.ashutdown()

Context manager (scripts): Use with FiddlerClient(...) as client: so shutdown() is called automatically when the block exits.

Example applications

Multi-agent travel planner

from langgraph.graph import StateGraph, END
from langchain_openai import ChatOpenAI
from typing import TypedDict
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

# Initialize Fiddler monitoring
fdl_client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)
instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

# Define your agent graph
class TravelState(TypedDict):
    destination: str
    budget: float
    itinerary: list

# Research agent
def research_agent(state: TravelState):
    # Agent logic - automatically traced
    return {"research_complete": True}

# Booking agent
def booking_agent(state: TravelState):
    # Agent logic - automatically traced
    return {"bookings": [...]}

# Build graph
graph = StateGraph(TravelState)
graph.add_node("research", research_agent)
graph.add_node("booking", booking_agent)
graph.add_edge("research", "booking")
graph.add_edge("booking", END)

# Run - traces automatically sent to Fiddler
app = graph.compile()
result = app.invoke({"destination": "Paris", "budget": 5000})

View the Advanced Observability Notebook → | Custom Instrumentation Notebook →

Customer support agent with tools

from langchain.tools import Tool
from langchain_openai import ChatOpenAI
from langgraph.prebuilt import create_react_agent
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

# Initialize Fiddler monitoring
fdl_client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)
instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

# Define tools - calls automatically traced
tools = [
    Tool(name="search_kb", func=search_knowledge_base),
    Tool(name="create_ticket", func=create_support_ticket),
    Tool(name="escalate", func=escalate_to_human)
]

# Create agent - instrumentation is automatic
model = ChatOpenAI(model="gpt-4o")
agent = create_react_agent(model, tools)

# Run agent - full trace in Fiddler
response = agent.invoke({
    "messages": [{"role": "user", "content": "My order is delayed"}]
})

Viewing your data

After running your instrumented application:

Navigate to Fiddler UI - https://your-instance.fiddler.ai
Select “GenAI Applications” - View your application
Inspect traces - Drill down from application → session → agent → span
Analyze patterns - Use analytics to identify bottlenecks and errors

Key metrics tracked

Latency: P50, P95, P99 response times across agents
Error Rate: Percentage of failed agent executions
Token Usage: LLM token consumption per agent/session
Tool Calls: Frequency and success rate of tool invocations
State Transitions: Agent decision path analysis

Troubleshooting

Application not showing as “Active”

Check your configuration:

Ensure your application executes instrumented code
Verify your Fiddler access token and application ID are correct
Check network connectivity to your Fiddler instance

Enable console tracer for debugging:

fdl_client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai",
    console_tracer=True  # Also prints spans to console; OTLP export to Fiddler continues
)

console_tracer=True is additive — span data is printed to stdout and continues to be exported to Fiddler via OTLP. Setting this to True does not disable or suppress the OTLP export to Fiddler. Use it to visually confirm spans are being created during local development.

Network connectivity issues

Verify connectivity to your Fiddler instance:

curl -I https://your-instance.fiddler.ai

Check firewall settings:

Ensure HTTPS traffic on port 443 is allowed
Verify your Fiddler instance URL is correct

Import errors

Problem: ModuleNotFoundError: No module named 'fiddler_langgraph' Solution: Ensure you’ve installed the correct package:

pip install fiddler-langgraph

Problem: ImportError: cannot import name 'LangGraphInstrumentor' Solution: Ensure you have the correct import path:

from fiddler_langgraph import LangGraphInstrumentor

Version compatibility issues

Verify your versions match requirements:

python --version  # Should be 3.10, 3.11, 3.12, or 3.13
pip show langgraph  # Should be >= 0.3.28 and <= 1.1.0

If you have version conflicts:

pip install langgraph>=0.3.28,<=1.1.0

Invalid application ID

Problem: ValueError: application_id must be a valid UUID4 Solution: Ensure your Application ID is in proper UUID4 format:

# ❌ This will fail
fdl_client = FiddlerClient(
    application_id="invalid-id",  # Not a valid UUID4
    api_key="your-access-token",
    url="https://instance.fiddler.ai"
)

# ✅ Correct format
fdl_client = FiddlerClient(
    application_id="550e8400-e29b-41d4-a716-446655440000",  # Valid UUID4
    api_key="your-access-token",
    url="https://instance.fiddler.ai"
)

Copy the Application ID directly from the Fiddler dashboard to avoid formatting issues.

Agent shows as “UNKNOWN_AGENT”

For LangChain applications, ensure you’re setting the agent name in the config parameter:

from langchain_core.output_parsers import StrOutputParser

# Define your LangChain runnable
chat_app_chain = prompt | llm | StrOutputParser()

# Run with agent name configuration
response = chat_app_chain.invoke({
    "input": user_input,
    "history": messages,
}, config={"configurable": {"agent_name": "service_chatbot"}})

Note: LangGraph applications automatically extract agent names. This manual configuration is only needed for LangChain applications.

OpenTelemetry compatibility

The LangGraph SDK is built on OpenTelemetry Protocol (OTLP). The SDK uses standard OpenTelemetry components, allowing you to:

Integrate with existing observability infrastructure
Export traces to multiple backends (with custom configuration)
Use custom OTEL collectors and processors

All telemetry data follows OpenTelemetry semantic conventions for AI/ML workloads.

Fiddler Evals SDK - Evaluate LangGraph agent quality offline
Python Client SDK - Additional monitoring capabilities

Migration guides

From LangSmith

# Before (LangSmith)
import os
os.environ["LANGCHAIN_TRACING_V2"] = "true"
os.environ["LANGCHAIN_API_KEY"] = "ls_..."

# After (Fiddler - both can run simultaneously)
from fiddler_langgraph import FiddlerClient, LangGraphInstrumentor

fdl_client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)
instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

# Your LangGraph code remains unchanged

From manual tracing

If you’ve built custom tracing, migration is straightforward:

# Before (manual timing/logging)
import time
start = time.time()
result = my_agent.run()
duration = time.time() - start
log_to_system(duration, result)

# After (Fiddler SDK - automatic instrumentation)
# Initialize Fiddler client and instrumentor (once)
fdl_client = FiddlerClient(
    application_id="your-app-id",
    api_key="your-api-key",
    url="https://your-instance.fiddler.ai"
)
instrumentor = LangGraphInstrumentor(fdl_client)
instrumentor.instrument()

# Remove all manual timing/logging code
result = my_agent.run()  # Automatic instrumentation

API reference

Full SDK documentation:

LangGraph SDK Reference - Complete class and method documentation

Next steps

Now that your application is instrumented:

Explore the data: Check your Fiddler dashboard for traces, metrics, and performance insights
Learn advanced features: See our Advanced Usage Guide for complex multi-agent scenarios
Review the SDK reference: Check the Fiddler LangGraph SDK Reference for complete documentation
Optimize for production: Review configuration options for high-volume applications

​What you’ll need

​Quick start

​What gets monitored

​Hierarchical tracing

​Agent lifecycle stages

​Captured data

​Application setup

​1. Create your application in Fiddler

​2. Copy your Application ID

​3. Get your access token

​Detailed setup

​Installation

​Configuration

​Direct initialization (Recommended)

​Using environment variables

​Instrumentation methods

​Auto-Instrumentation

​Decorator-based instrumentation

​@trace() Arguments

​Accessing the current span

​Async support

​Automatic parent-child relationships

​Manual instrumentation

​Context manager (automatic lifecycle)

​Explicit span control

​Span types and helper methods

​Common methods (all types)

​Generation methods (FiddlerGeneration)

​Tool methods (FiddlerTool)

​Context isolation

​Global client pattern

​Advanced usage

​Adding context and metadata

​Clearing LLM context for non-RAG steps

​Custom span and session attributes

​Sampling configuration

​Production configuration

​Offline / S3 Routing Mode

​Flush and shutdown handling

​Example applications

​Multi-agent travel planner

​Customer support agent with tools

​Viewing your data

​Key metrics tracked

​Troubleshooting

​Application not showing as “Active”

​Network connectivity issues

​Import errors

​Version compatibility issues

​Invalid application ID

​Agent shows as “UNKNOWN_AGENT”

​OpenTelemetry compatibility

​Related integrations

​Migration guides

​From LangSmith

​From manual tracing

​API reference

​Next steps

What you’ll need

Quick start

What gets monitored

Hierarchical tracing

Agent lifecycle stages

Captured data

Application setup

1. Create your application in Fiddler

2. Copy your Application ID

3. Get your access token

Detailed setup

Installation

Configuration

Direct initialization (Recommended)

Using environment variables

Instrumentation methods

Auto-Instrumentation

Decorator-based instrumentation

`@trace()` Arguments

Accessing the current span

Async support

Automatic parent-child relationships

Manual instrumentation

Context manager (automatic lifecycle)

Explicit span control

Span types and helper methods

Common methods (all types)

Generation methods (`FiddlerGeneration`)

Tool methods (`FiddlerTool`)

Context isolation

Global client pattern

Advanced usage

Adding context and metadata

Clearing LLM context for non-RAG steps

Custom span and session attributes

Sampling configuration

Production configuration

Offline / S3 Routing Mode

Flush and shutdown handling

Example applications

Multi-agent travel planner

Customer support agent with tools

Viewing your data

Key metrics tracked

Troubleshooting

Application not showing as “Active”

Network connectivity issues

Import errors

Version compatibility issues

Invalid application ID

Agent shows as “UNKNOWN_AGENT”

OpenTelemetry compatibility

Related integrations

Migration guides

From LangSmith

From manual tracing

API reference

Next steps