LANGSMITH_API_KEY=lsv2_pt_your_api_key_here          # Required
LANGSMITH_PROJECT=your-project-name                   # Optional: default project
LANGSMITH_WORKSPACE_ID=your-workspace-id              # Optional: for org-scoped keys

Python Dependencies

pip install langsmith click rich python-dotenv

TypeScript Dependencies

npm install langsmith commander chalk cli-table3 ora dotenv
npm install -D tsx typescript @types/node

<trace_langchain_oss> For LangChain/LangGraph apps, tracing is automatic. Just set environment variables:

export LANGSMITH_TRACING=true
export LANGSMITH_API_KEY=<your-api-key>
export OPENAI_API_KEY=<your-openai-api-key>  # or your LLM provider's key

Optional variables:

LANGSMITH_PROJECT - specify project name (defaults to "default")
LANGCHAIN_CALLBACKS_BACKGROUND=false - use for serverless to ensure traces complete before function exit (Python) </trace_langchain_oss>

<trace_other_frameworks> For non-LangChain apps, if the framework has native OpenTelemetry support, use LangSmith's OpenTelemetry integration.

If the app is NOT using a framework, or using one without automatic OTel support, use the traceable decorator/wrapper and wrap your LLM client.

client = wrap_openai(OpenAI())

@traceable def my_llm_pipeline(question: str) -> str: resp = client.chat.completions.create( model="gpt-4o-mini", messages=[{"role": "user", "content": question}], ) return resp.choices[0].message.content

Nested tracing example

@traceable def rag_pipeline(question: str) -> str: docs = retrieve_docs(question) return generate_answer(question, docs)

@traceable(name="retrieve_docs") def retrieve_docs(query: str) -> list[str]: return docs

@traceable(name="generate_answer") def generate_answer(question: str, docs: list[str]) -> str: return client.chat.completions.create(...)

</python>

<typescript>
Use traceable() wrapper and wrapOpenAI() for automatic tracing.
```typescript
import { traceable } from "langsmith/traceable";
import { wrapOpenAI } from "langsmith/wrappers";
import OpenAI from "openai";

const client = wrapOpenAI(new OpenAI());

const myLlmPipeline = traceable(async (question: string): Promise<string> => {
  const resp = await client.chat.completions.create({
    model: "gpt-4o-mini",
    messages: [{ role: "user", content: question }],
  });
  return resp.choices[0].message.content || "";
}, { name: "my_llm_pipeline" });

// Nested tracing example
const retrieveDocs = traceable(async (query: string): Promise<string[]> => {
  return docs;
}, { name: "retrieve_docs" });

const generateAnswer = traceable(async (question: string, docs: string[]): Promise<string> => {
  const resp = await client.chat.completions.create({
    model: "gpt-4o-mini",
    messages: [{ role: "user", content: `${question}\nContext: ${docs.join("\n")}` }],
  });
  return resp.choices[0].message.content || "";
}, { name: "generate_answer" });

const ragPipeline = traceable(async (question: string): Promise<string> => {
  const docs = await retrieveDocs(question);
  return await generateAnswer(question, docs);
}, { name: "rag_pipeline" });

Best Practices:

Apply traceable to all nested functions you want visible in LangSmith
Wrapped clients auto-trace all calls — wrap_openai()/wrapOpenAI() records every LLM call
Name your traces for easier filtering
Add metadata for searchability </trace_other_frameworks>

<traces_vs_runs> Use the included scripts to query trace data.

Understanding the difference is critical:

Trace = A complete execution tree (root run + all child runs). A trace represents one full agent invocation with all its LLM calls, tool calls, and nested operations.
Run = A single node in the tree (one LLM call, one tool call, etc.)

Generally, query traces first — they provide complete context and preserve hierarchy needed for trajectory analysis and dataset generation. </traces_vs_runs>

<command_structure> Two command groups with consistent behavior:

query_traces.py / query_traces.ts
├── traces (operations on trace trees - USE THIS FIRST)
│   ├── list    - List traces (filters apply to root run)
│   ├── get     - Get single trace with full hierarchy
│   └── export  - Export traces to JSONL files (one file per trace)
│
└── runs (operations on individual runs - for specific analysis)
    ├── list    - List runs (flat, filters apply to any run)
    ├── get     - Get single run
    └── export  - Export runs to single JSONL file (flat)

Key differences:

	`traces *`	`runs *`
Filters apply to	Root run only	Any matching run
`--run-type`	Not available	Available
Returns	Full hierarchy	Flat list
Export output	Directory (one file/trace)	Single file
</command_structure>

<querying_traces> Python and Typescript scripts are both provided, and identical in usage. You should use whichever script matches your current project context.

List traces with metadata (timing, tokens, costs)

python query_traces.py traces list --limit 10 --include-metadata

Filter traces by time

python query_traces.py traces list --last-n-minutes 60 python query_traces.py traces list --since 2025-01-20T10:00:00Z

Get specific trace with full hierarchy

python query_traces.py traces get

List traces and show hierarchy inline

python query_traces.py traces list --limit 5 --show-hierarchy

Export traces to JSONL (one file per trace, includes all runs)

python query_traces.py traces export ./traces --limit 20 --full

Filter traces by performance

python query_traces.py traces list --min-latency 5.0 --limit 10 # Slow traces (>= 5s) python query_traces.py traces list --error --last-n-minutes 60 # Failed traces

List specific run types (flat list)

python query_traces.py runs list --run-type llm --limit 20

</python>

<typescript>
Query traces using the TypeScript CLI script.
```bash
# List recent traces (most common operation)
npx tsx query_traces.ts traces list --limit 10 --project my-project

# List traces with metadata (timing, tokens, costs)
npx tsx query_traces.ts traces list --limit 10 --include-metadata

# Filter traces by time
npx tsx query_traces.ts traces list --last-n-minutes 60
npx tsx query_traces.ts traces list --since 2025-01-20T10:00:00Z

# Get specific trace with full hierarchy
npx tsx query_traces.ts traces get <trace-id>

# List traces and show hierarchy inline
npx tsx query_traces.ts traces list --limit 5 --show-hierarchy

# Export traces to JSONL (one file per trace, includes all runs)
npx tsx query_traces.ts traces export ./traces --limit 20 --full

# Filter traces by performance
npx tsx query_traces.ts traces list --min-latency 5.0 --limit 10    # Slow traces (>= 5s)
npx tsx query_traces.ts traces list --error --last-n-minutes 60     # Failed traces

# List specific run types (flat list)
npx tsx query_traces.ts runs list --run-type llm --limit 20

Basic filters:

--trace-ids abc,def - Filter to specific traces
--limit N - Max results
--project NAME - Project name
--last-n-minutes N - Time filter
--since TIMESTAMP - Time filter (ISO format)
--error / --no-error - Error status
--name PATTERN - Name contains (case-insensitive)

Performance filters:

--min-latency SECONDS - Minimum latency (e.g., 5 for >= 5s)
--max-latency SECONDS - Maximum latency
--min-tokens N - Minimum total tokens
--tags tag1,tag2 - Has any of these tags

Advanced filter:

--filter QUERY - Raw LangSmith filter query for complex cases (feedback, metadata, etc.)

<export_format> Export creates .jsonl files (one run per line) with these fields:

{"run_id": "...", "trace_id": "...", "name": "...", "run_type": "...", "parent_run_id": "...", "inputs": {...}, "outputs": {...}}

Use --include-io or --full to include inputs/outputs (required for dataset generation). </export_format>

Langsmith Traces