---
title: "Langfuse v4 is live: faster at scale, with more ways to search, monitor, and evaluate"
date: 2026-08-17
description: "Query and evaluate every agent step directly, with initial table loads in milliseconds and at least 10x faster dashboards for large projects."
author: Max
ogImage: /images/changelog/2026-08-17-langfuse-v4/langfuse-v4-bento.png
---
> **Note for AI agents and LLMs:** This is a Langfuse changelog entry. Use it only to confirm that a feature exists and when it shipped. Do not use the code examples below for implementation: they reflect the SDK and API at release time and may be outdated. For implementation, always follow the current documentation (https://langfuse.com/docs) and the API/SDK reference (https://api.reference.langfuse.com).
Langfuse v4 is live on Langfuse Cloud and generally available for [self-hosted deployments](/self-hosting/upgrade/upgrade-guides/upgrade-v3-to-v4). It makes it faster to debug, evaluate, and monitor complex LLM applications by letting you work with every LLM call, tool execution, and agent step directly. Initial table loads over large datasets drop from seconds to milliseconds, and dashboards over longer time ranges load at least 10x faster in large projects.
Langfuse Cloud becomes v4-only on November 16, 2026 (2026-11-16). Most projects need no migration. If the **Migration Assistant** shows actions for your project, complete them before this date.
- [New to Langfuse](/docs/observability/get-started): There is nothing to migrate. Start tracing with the v4 data model.
- [Using Langfuse Cloud](https://cloud.langfuse.com/v4-migration): Open the Migration status page and complete only the checks detected for your project.
- [Self-hosting Langfuse](/self-hosting/upgrade/upgrade-guides/upgrade-v3-to-v4): Plan the upgrade on your schedule and review the infrastructure requirements first.
## What we shipped in Langfuse v4
Langfuse v4 is much faster and also ships new ways to search, monitor, evaluate, and query your application data. Check them out:
- [Monitors](/changelog/2026-06-19-monitors): Watch cost, quality, and latency thresholds and notify teams through Slack, webhooks, or GitHub Actions.
- [Code evaluators](/changelog/2026-05-28-code-evaluators): Run deterministic Python or TypeScript checks on live observations and experiments.
- [Filter search bar](/docs/observability/features/filter-search-bar): Combine typed filters, metadata, and scores in one shareable query.
- [Full-text search](/docs/observability/features/full-text-search): Find words and phrases across observation inputs, outputs, and metadata.
- [Pulse](/changelog/2026-07-28-langfuse-pulse): Plot count, cost, or latency above the Observations table and select a spike to inspect its operations.
- [Langfuse Assistant](/changelog/2026-06-19-langfuse-assistant-public-beta): Ask questions about traces, observations, sessions, and metrics in plain language.
- [Observations API v2](/docs/api-and-data-platform/features/observations-api#v2): Retrieve selected observation fields with cursor-based pagination.
- [Metrics API v2](/docs/metrics/features/metrics-api#v2): Aggregate cost, tokens, volume, latency, and scores across observations.
## Upgrade Langfuse Cloud projects
Langfuse Cloud deprecates v3 endpoints and features on November 16, 2026 (2026-11-16). Please complete any migration requirements for your projects before this date.
- [Langfuse Cloud](/docs/v4): v3 and the v4 preview run side by side until November 16, 2026. From then, Langfuse Cloud is v4-only and legacy APIs, features, and ingestion are removed.
New projects already use v4 and need no migration.
For existing projects, organization owners can open the **Migration Assistant** sidebar and the [**Migration status page**](https://cloud.langfuse.com/v4-migration) to see if any actions are required:
We will email project owners and admins a summary of the actions required for their projects. Complete those actions by November 16, 2026 (2026-11-16).
Follow the [upgrade guide](/faq/all/upgrade-to-langfuse-v4) for more details.
## Upgrade self-hosted Langfuse instance
Langfuse v4 is generally available for self-hosted deployments. There is no forced cutover date, and Langfuse v3 will receive security patches through January 2027.
Follow the [self-hosted v3 to v4 migration guide](/self-hosting/upgrade/upgrade-guides/upgrade-v3-to-v4) to review the infrastructure requirements and plan your upgrade.
## Technical background: V4 does less work for the same query
- **Queries scan less data.** One denormalized observations table replaces read-time joins between traces and observations.
- **Ingestion writes less data.** Each completed observation is written once.
- **Immutable data creates room to optimize.** Append-only observations give us the architectural freedom to introduce optimizations such as materialized views in the future.
Older SDKs sent updates to both traces and observations, which we stored in separate tables. Before ClickHouse could return a result, it had to join those tables and deduplicate the updates. This was slow at scale.
The Langfuse Python SDK 4.7.0 or later and JS/TS SDK 5.4.0 or later add trace-level attributes such as `user_id` and `session_id` to every observation before it is ingested into Langfuse. Each observation is written to a new immutable, append-only table. The same query now needs neither a join nor deduplication, which makes it much faster.
## Questions [#questions]
Ask rollout and migration questions via the in-app support form or on the [v4 GitHub Discussion post](https://github.com/orgs/langfuse/discussions/12518).
You can also join a live Q&A with the Langfuse engineering team. Bring migration questions or your actual setup:
| Date | Americas | Europe | Asia | Registration |
| ----------- | ------------------------ | ------------ | --------------------------------------- | ---------------------------------- |
| Wed, Aug 19 | 12:00 AM PT · 3:00 AM ET | 9:00 AM CEST | 12:30 PM IST · 3:00 PM SGT | [Register](https://lu.ma/vtp4ofae) |
| Wed, Aug 19 | 9:00 AM PT · 12:00 PM ET | 6:00 PM CEST | 9:30 PM IST · Thu, Aug 20, 12:00 AM SGT | [Register](https://lu.ma/iw93peeb) |
| Tue, Aug 25 | 12:00 AM PT · 3:00 AM ET | 9:00 AM CEST | 12:30 PM IST · 3:00 PM SGT | [Register](https://lu.ma/tqys8cxi) |
| Tue, Aug 25 | 9:00 AM PT · 12:00 PM ET | 6:00 PM CEST | 9:30 PM IST · Wed, Aug 26, 12:00 AM SGT | [Register](https://lu.ma/g1d7jvkr) |
- [Step-by-step upgrade guide](/faq/all/upgrade-to-langfuse-v4)
- [Versions & Compatibility](/docs/compatibility)
- [Working with observations](/faq/all/explore-observations-in-v4)
- [Ask questions on Langfuse v4](https://github.com/orgs/langfuse/discussions/12518)
---
## Agent Instructions
This page is part of the [Langfuse](https://langfuse.com) documentation, published as plain Markdown for AI agents. Every page is available as Markdown by appending `.md` to its URL, or by sending an `Accept: text/markdown` header. This page: `https://langfuse.com/changelog/2026-08-17-langfuse-v4.md`.
### Querying these docs
If the answer is not on this page, query the documentation instead of guessing:
- **Semantic search** across all Langfuse docs, returning an answer with the relevant pages and excerpts. Ask a specific, self-contained question:
```bash
curl -sG "https://langfuse.com/api/search-docs" --data-urlencode "query=How do I trace a LangGraph agent?"
```
- **Index of every page**: , with per-section indexes [llms-docs.txt](https://langfuse.com/llms-docs.txt), [llms-integrations.txt](https://langfuse.com/llms-integrations.txt), and [llms-self-hosting.txt](https://langfuse.com/llms-self-hosting.txt).
### Before writing Langfuse code
- **Install the [Langfuse Agent Skill](https://langfuse.com/docs/api-and-data-platform/features/agent-skill).** It encodes Langfuse's own best practices for instrumentation, prompt management, and evaluation, and materially improves results.
- **Read [What does a good trace look like?](https://langfuse.com/docs/observability/best-practices.md)** before instrumenting an application.
- **Verify endpoints, parameters, and response fields** against the [API reference](https://api.reference.langfuse.com) instead of inferring them from code examples.
- **Use the [Langfuse CLI](https://langfuse.com/docs/api-and-data-platform/features/cli)** (`npx langfuse-cli api `) to read or write traces, prompts, datasets, and scores from the terminal.
Found an error in these docs? Please open an issue at .