# Langfuse: Hermes Agent plugin

> Langfuse observability for Hermes: one trace per turn, one generation per LLM call (usage and cost from Hermes' own pricing, cache and reasoning tokens included), one observation per tool call and subagent.

Canonical: https://hermeswatcher.com/plugins/langfuse  
Tier: Official  
Official page (Nous Research): https://hermes-agent.nousresearch.com/docs/plugins/langfuse  
Last updated in catalog: 2026-10-23

Langfuse observability for Hermes: one trace per turn, one generation per LLM call (usage and cost from Hermes' own pricing, cache and reasoning tokens included), one observation per tool call and subagent. Content capture is sanitized by default (metadata-only and full are opt-in); sends traces only to the Langfuse project whose keys you set. Formerly built into Hermes core as observability/langfuse; existing users are migrated automatically.

## How to install

1. Install it. Hermes asks for any API keys it needs (this one needs `HERMES_LANGFUSE_PUBLIC_KEY`, `HERMES_LANGFUSE_SECRET_KEY`), then asks whether to turn it on.

```bash
hermes plugins install langfuse
```

2. Said no? Turn it on later:

```bash
hermes plugins enable langfuse
```

3. Restart Hermes so it loads the plugin.

Some plugins also need a sign-in or settings: see the official page. Memory plugins ask whether to become your memory provider instead. Steps follow the official plugins guide: https://hermes-agent.nousresearch.com/docs/user-guide/features/plugins

## Facts

- Category: Cost, speed & monitoring
- Maintained by: NousResearch (Official)
- Needs: `HERMES_LANGFUSE_PUBLIC_KEY`, `HERMES_LANGFUSE_SECRET_KEY` (API keys)
- Requires Hermes: `>=0.21.7`
- Version: 2.0.0
- In the catalog since: 2026-10-12, updated 2026-10-23

## Links

- [Full setup and settings (official page)](https://hermes-agent.nousresearch.com/docs/plugins/langfuse)
- [Source code](https://github.com/NousResearch/hermes-official-plugins/tree/main/langfuse)
- [All plugins](https://hermeswatcher.com/plugins.md)

---

HermesWatcher is an independent guide. It is not affiliated with or endorsed by Nous Research. The [official Hermes Agent documentation](https://hermes-agent.nousresearch.com/docs) and [repository](https://github.com/NousResearch/hermes-agent) from Nous Research are the authority; each page here lists the official sources it was written from. If this site and the official docs disagree, trust the official docs. Index for agents: https://hermeswatcher.com/llms.txt