add langfuse_filter_function_v3

functions/filters/langfuse/README.md

@@ -0,0 +1,53 @@
+# Langfuse Filter Function v3
+
+**Author:** YetheSamartaka  
+**Version:** 1.0.0  
+**License:** MIT  
+**Date:** 2025-10-27  
+
+---
+
+## Overview
+
+A filter plugin for **Open WebUI (v0.6.32+)** that integrates with **Langfuse v3** for telemetry, tracing, and analytics.  
+It logs chat sessions, user inputs, model responses, and token usage directly to Langfuse (Cloud or local).
+
+---
+
+## Features
+
+- Automatic trace creation per chat session  
+- Logs user input and assistant responses  
+- Tracks token usage (input/output)  
+- Supports Langfuse Cloud or local instance  
+- Optional debug mode with console logs  
+- Custom tags and metadata injection  
+
+## How It Works
+
+### `inlet()`
+- Called **before** LLM execution  
+- Creates or updates a Langfuse trace  
+- Logs user input and metadata  
+
+### `outlet()`
+- Called **after** LLM execution  
+- Logs assistant response and token usage  
+- Finalizes and flushes the trace  
+
+---
+
+## Integration (Open WebUI)
+
+1. Athis file into `filters/langfuse_filter_v3.py` in your Open WebUI instance.  
+2. In **Admin → Functions**, add a new function and select either put it there manually or Import it From Link 
+3. Set your Langfuse keys and host in the **Valves** settings.  
+4. Save and enable it and then either set it as Global or for specific models
+
+All chat activity will then be automatically logged in **Langfuse**.
+
+---
+
+## License
+
+**MIT License**