Langfuse CLI (lf)

Command-line interface for the Langfuse LLM observability platform. Query traces, sessions, observations, scores, and metrics. Manage prompts with versioning and labels. Manage datasets for evaluation.

Quick Reference

lf traces list [OPTIONS]       # List traces with filters
lf traces get <ID>             # Get specific trace (--with-observations)
lf sessions list [OPTIONS]     # List sessions
lf sessions show <ID>          # Show session details (--with-traces)
lf observations list [OPTIONS] # List observations (spans/generations/events)
lf observations get <ID>       # Get specific observation
lf scores list [OPTIONS]       # List scores
lf scores get <ID>             # Get specific score
lf scores create [OPTIONS]     # Create a new score
lf metrics query [OPTIONS]     # Query aggregated metrics
lf prompts list [OPTIONS]      # List prompts
lf prompts get <NAME>          # Get prompt (by label or version)
lf prompts create-text         # Create text prompt (-m for commit message)
lf prompts create-chat         # Create chat prompt (-m for commit message)
lf prompts label <NAME> <VER>  # Set labels on prompt version
lf prompts delete <NAME>       # Delete prompt
lf datasets list [OPTIONS]     # List datasets
lf datasets get <NAME>         # Get dataset by name
lf datasets create <NAME>      # Create a new dataset
lf datasets items [OPTIONS]    # List dataset items (--dataset to filter)
lf datasets item-get <ID>      # Get dataset item by ID
lf datasets item-create        # Create dataset item (--dataset, --input required)
lf datasets runs <DATASET>     # List runs for a dataset
lf datasets run-get <DS> <RUN> # Get a specific run

Common Tasks

View Recent Traces

lf traces list --limit 20

Filter Traces by Time

# Today's traces
lf traces list --from "$(date -u +%Y-%m-%dT00:00:00Z)"

# Last 24 hours
lf traces list --from "$(date -u -v-1d +%Y-%m-%dT%H:%M:%SZ)"

# Specific date range
lf traces list --from 2024-01-15T00:00:00Z --to 2024-01-16T00:00:00Z

Filter by User or Session

lf traces list --user-id user123
lf traces list --session-id sess456
lf traces list --name "chat-completion"
lf traces list --tags production --tags v2

Analyse Costs

# Total cost over time
lf metrics query --view traces --measure total-cost --aggregation sum --granularity day

# Cost by model
lf metrics query --view observations --measure total-cost --aggregation sum --dimensions model

# Average cost per trace
lf metrics query --view traces --measure total-cost --aggregation avg

Analyse Latency

# P95 latency
lf metrics query --view traces --measure latency --aggregation p95

# Latency by trace name
lf metrics query --view traces --measure latency --aggregation avg --dimensions traceName

# Latency trends
lf metrics query --view traces --measure latency --aggregation p50 --granularity hour

Token Usage

# Total tokens
lf metrics query --view observations --measure total-tokens --aggregation sum

# Tokens by model
lf metrics query --view observations --measure total-tokens --aggregation sum --dimensions model

# Input vs output tokens
lf metrics query --view observations --measure input-tokens --aggregation sum
lf metrics query --view observations --measure output-tokens --aggregation sum

Investigate Specific Trace

# Get trace details
lf traces get tr-abc123

# Get trace with all observations included
lf traces get tr-abc123 --with-observations

# See all observations in a trace
lf observations list --trace-id tr-abc123

# Check scores for a trace
lf scores list --name accuracy

Create Scores

# Score a trace
lf scores create --name accuracy --value 0.95 --trace-id tr-abc123

# Score an observation with comment
lf scores create --name relevance --value 0.8 \
  --observation-id obs-xyz789 --comment "Good but could be more specific"

# Categorical score
lf scores create --name sentiment --value 1 \
  --data-type CATEGORICAL --trace-id tr-abc123

# Boolean score
lf scores create --name approved --value 1 \
  --data-type BOOLEAN --trace-id tr-abc123

Manage Prompts

# List all prompts
lf prompts list

# Filter by label or tag
lf prompts list --label production
lf prompts list --tag summarisation

# Get production version of a prompt
lf prompts get my-prompt

# Get specific version or label
lf prompts get my-prompt --version 3
lf prompts get my-prompt --label staging

# Get raw content (for piping)
lf prompts get my-prompt --raw > prompt.txt

Create and Update Prompts

# Create text prompt from file
lf prompts create-text --name my-prompt -f prompt.txt

# Create with commit message documenting the change
lf prompts create-text --name my-prompt -f prompt.txt \
  -m "Add context about user preferences"

# Create from stdin
echo "You are a helpful assistant." | lf prompts create-text --name my-prompt

# Create with labels and config
lf prompts create-text --name my-prompt -f prompt.txt \
  --labels production --tags summarisation \
  --config '{"model": "gpt-4", "temperature": 0.7}'

# Create chat prompt from JSON
lf prompts create-chat --name chat-prompt -f messages.json

# Label a version as production
lf prompts label my-prompt 5 --labels production

# Delete a prompt
lf prompts delete old-prompt
lf prompts delete my-prompt --version 2

Manage Datasets

Datasets store input/output pairs for evaluation. Items can be created manually or from existing traces.

# List all datasets
lf datasets list

# Create a dataset
lf datasets create my-eval-dataset -d "Test cases for summarisation"

# Create with metadata
lf datasets create my-eval-dataset \
  -d "Test cases for summarisation" \
  -m '{"version": "1.0", "owner": "team-ml"}'

# Get dataset details
lf datasets get my-eval-dataset

Add Dataset Items

# Create item with input and expected output
lf datasets item-create --dataset my-eval-dataset \
  --input '{"text": "Long article content..."}' \
  --expected-output '{"summary": "Brief summary..."}'

# Create item from existing trace
lf datasets item-create --dataset my-eval-dataset \
  --input '{"prompt": "Summarise this"}' \
  --source-trace-id tr-abc123

# Create item with metadata
lf datasets item-create --dataset my-eval-dataset \
  --input '{"text": "Content"}' \
  --expected-output '{"result": "Expected"}' \
  --metadata '{"category": "short-form", "difficulty": "easy"}'

# List items in a dataset
lf datasets items --dataset my-eval-dataset

# Get specific item
lf datasets item-get item-abc123

View Dataset Runs

Runs represent evaluation executions against a dataset.

# List runs for a dataset
lf datasets runs my-eval-dataset

# Get details of a specific run
lf datasets run-get my-eval-dataset run-2024-01-15

Output Formats

All list and query commands support output format selection:

lf traces list --format table    # Default, human-readable
lf traces list --format json     # Machine-readable, full details
lf traces list --format csv      # Spreadsheet-compatible
lf traces list --format markdown # Documentation-friendly

Save to file:

lf traces list --format json --output traces.json

Configuration

The CLI uses profile-based configuration. Credentials resolve in order:

1. CLI arguments (--public-key, --secret-key, --host)
2. Environment variables (LANGFUSE_PUBLIC_KEY, LANGFUSE_SECRET_KEY, LANGFUSE_HOST)
3. Config file profile (~/.config/langfuse/config.yml)

Setup Profile

lf config setup

Use Specific Profile

lf traces list --profile production

Metrics Query Deep Dive

The metrics command provides aggregated analytics:

Required parameters:

• --view: traces or observations
• --measure: What to measure
• --aggregation: How to aggregate

Measures:

• count - Number of items
• latency - Duration in milliseconds
• input-tokens, output-tokens, total-tokens - Token counts
• input-cost, output-cost, total-cost - Cost in USD

Aggregations:

• count - Total count
• sum - Total sum
• avg - Average
• p50, p95, p99 - Percentiles
• histogram - Distribution buckets

Dimensions (group by):

• traceName, model, environment, version, release

Granularity (time bucketing):

• auto, minute, hour, day, week, month

Additional Resources

For complete CLI documentation including all options:

• references/cli-reference.md - Full command reference with all flags