Langfuse Skills

---
name: langfuse
description: >-
  Interact with Langfuse and access its documentation: tracing, monitoring, creating datasets, running experiments, and evaluating AI applications. Use when needing to (1) query or modify Langfuse data, (2) look up Langfuse documentation, concepts, integration guides, a feature or SDK usage, or (3) do any AI engineering task (AI observability, prompt engineering/management, evaluation and evaluator management, experimentation, dataset management, evaluation-driven CI/CD, feedback collection). Invoke it for tasks in this scope even when Langfuse is not configured or explicitly mentioned.
allowed-tools:
  - WebFetch(domain:langfuse.com)
  - Bash(curl *langfuse.com/*)
  - Bash(npx langfuse-cli api __schema *)
  - Bash(npx langfuse-cli api * --help *)
  - Bash(npx langfuse-cli api * list *)
  - Bash(npx langfuse-cli api * get *)
  - Bash(bunx langfuse-cli api __schema *)
  - Bash(bunx langfuse-cli api * --help *)
  - Bash(bunx langfuse-cli api * list *)
  - Bash(bunx langfuse-cli api * get *)
---

# Langfuse

This skill helps you use Langfuse effectively across all common workflows: instrumenting applications, migrating prompts, debugging traces, and accessing data programmatically.

## Core Principles

Follow these principles for ALL Langfuse work:

1. **Documentation First**: NEVER implement based on memory. Always fetch current docs before writing code (Langfuse updates frequently) See the section below on how to access documentation.
2. **CLI for Data Access**: Use `langfuse-cli` when querying/modifying Langfuse data. See the section below on how to use the CLI.
3. **Best Practices by Use Case**: Read the relevant reference below use-case-specific guidelines before asking the user for more details or implementing.
4. **Use latest Langfuse versions**: Unless the user specified otherwise or there's a good reason, always use the latest version of Langfuse SDKs/APIs. Even if you're only creating a plan for another agent to execute, be explicit about the exact version to use.
5. **If you guide the user through UI** and are unsure about a label or location, inspect the user’s screenshots or ask to see the relevant screen. Do not assume UI labels have the exact same names as API, SDK, or CLI fields.


## Use case specific references

- instrumenting an existing function/application: references/instrumentation.md
- creating or getting to a good (evaluation) dataset to measure quality or test for regressions in AI systems: references/create-dataset.md
- migrating prompts from a codebase into Langfuse: references/prompt-migration.md
- creating a prompt or changing any part of an existing prompt, including small edits and debugging/tuning: references/prompt-engineering.md
- setting up evals when the user needs to identify gaps across signal capture, monitoring, and evaluator metrics ("I have traces, how do I set up evals?"): references/setting-up-evals.md
- capturing user feedback signals (explicit ratings, behavioral events, conversation signals, task outcomes) as scores: references/user-feedback.md
- further tips on using the Langfuse CLI: references/cli.md
- preparing a Langfuse project for the v4 platform migration: references/v4-project-migration.md
- calibrating a new or existing LLM-as-a-Judge against labeled examples, iterating on its prompt, and deploying the approved judge: references/judge-calibration.md
- systematic error analysis when requested directly or eval setup still lacks concrete failure modes after agent-led trace inspection: references/error-analysis.md
- setting up CI/CD experiment gates with `langfuse/experiment-action`: references/ci-cd.md
- optimizing the cost of an LLM application or AI agent: references/cost-optimization.md
- submitting feedback about this skill: references/skill-feedback.md


## 1. Langfuse API via CLI

Use the `langfuse-cli` to interact with the full Langfuse REST API from the command line. Run via npx (no install required):

Start by discovering the schema and available arguments:

```bash
# Discover all available resources
npx langfuse-cli api __schema

# List actions for a resource