← Back to changelog

October 14, 2026

Python SDK v5 and JS/TS SDK v6

Hassieb Pakzad

New SDK majors built for Langfuse v4, with experiment links, typed metadata filters, and compressed span export. A small upgrade for most users.

Python SDK v5 and JS/TS SDK v6 are built for Langfuse v4. For most users, upgrading is a version bump: tracing, scoring, prompts, and the integrations work as before.

• Open experiment results straight from your code: experimentUrl / experiment_url links to the comparison view.
• Filter on typed metadata: numbers and booleans keep their type, and nested objects become filterable dotted paths such as a.b.
• Send large traces with less bandwidth: span batches are gzip-compressed and processed in real time on Langfuse v4.
• Create scores in batches with api.scores.create and read them from the same namespace with api.scores.get_many / api.scores.getMany, which replace api.scores_v3 / api.scoresV3 (a breaking change; see the migration guides). The generated API client only includes the current Public API.

Upgrading

pip install --upgrade "langfuse>=5"

npm install @langfuse/client@6 @langfuse/tracing@6 @langfuse/otel@6

Both majors need Langfuse Cloud or self-hosted Langfuse v4.59.0 or later, plus Python 3.11+ or Node.js 22+. If you self-host Langfuse v3, stay on Python SDK v4 and JS/TS SDK v5. Most removed APIs were already deprecated in the previous major, so code without deprecation warnings rarely needs changes. Each migration guide opens with a short "Are you affected?" list, so you can see in a few seconds whether your code needs changes.