LangSmith Fetch

LangSmith Fetch is CLI for fetching threads or traces from LangSmith projects. It is designed to be easily used by humans or code agents to programmatically fetch LangSmith data for testing and debugging.

🚀 Quickstart

pip install langsmith-fetch

Set your LangSmith API key and project name:

export LANGSMITH_API_KEY=lsv2_...
export LANGSMITH_PROJECT=your-project-name
export LANGSMITH_ENDPOINT=your-langsmith-api-url # setting this if you use self-host langsmith

That's it! The CLI will automatically fetch traces or threads in LANGSMITH_PROJECT.

Fetch recent traces to directory (recommended):

langsmith-fetch traces ./my-traces --limit 10

Fetch specific trace by ID:

langsmith-fetch trace 3b0b15fe-1e3a-4aef-afa8-48df15879cfe

Same commands work for threads:

langsmith-fetch threads ./my-threads --limit 10
langsmith-fetch thread my-thread-id

Include metadata and feedback:

langsmith-fetch traces ./my-traces --limit 10 --include-metadata --include-feedback

For code agents:

Use langsmith-fetch to fetch recent LangSmith traces. Run langsmith-fetch --help for usage details.

Commands

Flags

Output Formats

• pretty (default): Human-readable Rich panels with color and formatting
• json: Pretty-printed JSON with syntax highlighting
• raw: Compact single-line JSON for piping to tools like jq

Concepts

LangSmith organizes data into three levels:

• Runs: Individual LLM calls or tool executions
• Traces: A collection of runs representing a single execution path (one trace contains multiple runs)
• Threads: A collection of traces representing a conversation or session (one thread contains multiple traces)

Configuration

langsmith-fetch requires only LANGSMITH_PROJECT env var. It automatically looks up the Project UUID and saves both to ~/.langsmith-cli/config.yaml.

Finding IDs in LangSmith UI:

Project UUID (automatic lookup via LANGSMITH_PROJECT):

Trace ID (for fetching specific traces):

Thread ID (for fetching specific threads):

Tests

Run the test suite:

# Install with test dependencies
pip install -e ".[test]"

# Or with uv
uv sync --extra test

# Run all tests
pytest tests/

# Run with verbose output
pytest tests/ -v

# Run with coverage
pytest tests/ --cov=langsmith_cli

The test suite includes 71 tests covering:

• All CLI commands (traces, trace, thread, threads, config)
• All output formats (pretty, json, raw)
• Config management and storage
• Project UUID lookup and caching
• API fetching and error handling
• Time filtering and SDK integration
• Edge cases and validation

License

MIT