---
title: How do I make my project ready for the upgrade to Langfuse v4?
sidebarTitle: Make your project ready for the upgrade to Langfuse v4
description: Upgrade to Langfuse v4 by updating ingestion, migrating the v3 features you use, and completing the rollout for your deployment.
tags: [platform]
---
# Make your project ready for the upgrade to Langfuse v4 [#make-your-project-ready-for-the-upgrade-to-langfuse-v4]
Langfuse v4 uses an observations-first data model. The [v4 overview](/docs/v4) explains what changed. New managed projects already use v4 and need no migration.
For existing projects, complete the applicable steps below.
## 1. Upgrade trace ingestion [#ingestion]
Move off legacy ingestion before the v4 cutover on November 16, 2026 (2026-11-16) (Langfuse Cloud; self-hosted deployments control their own timeline, see [step 3](#rollout)). Deprecated SDKs can delay data by up to 15 minutes.
| Your setup | Do this |
| ----------------------------------------------------------- | -------------------------------------------------------------------------------------------------------- |
| Python SDK below 4.7.0 | [Upgrade the Python SDK](/docs/observability/sdk/upgrade-path) to 4.7.0 or later. |
| JS/TS SDK below 5.4.0 | [Upgrade the JS/TS SDK](/docs/observability/sdk/upgrade-path) to 5.4.0 or later. |
| Custom REST or OpenTelemetry ingestion | [Migrate custom ingestion](/integrations/native/opentelemetry/migration-to-v4) to the v4 OTLP/HTTP path. |
## 2. Migrate the v3 features you use [#features]
Only follow the rows that apply to your project.
| Check | Do this |
| ------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| APIs | [Migrate deprecated API calls](/faq/all/deprecated-api-migration) to the supported Observations, Metrics, Scores, and Experiments APIs. |
| Evaluators | [Move trace-level evaluators](/faq/all/llm-as-a-judge-migration) to observation targets and legacy-dataset evaluators to experiment targets. |
| Exports | [Switch blob storage exports](/docs/api-and-data-platform/features/export-to-blob-storage#upgrade-path) to enriched observations. |
| Integrations | Switch [PostHog](/integrations/analytics/posthog#migrate-export-source) and [Mixpanel](/integrations/analytics/mixpanel#migrate-export-source) to enriched observations. |
## 3. Complete the rollout [#rollout]
### Langfuse Cloud projects [#managed]
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.
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).
### Self-hosted deployments [#self-hosted]
Self-hosted v4 is generally available. Follow the [v3 to v4 upgrade guide](/self-hosting/upgrade/upgrade-guides/upgrade-v3-to-v4) to migrate your deployment; the `legacy` and `dual` write modes let you schedule each migration step independently.
If you deploy with the [Langfuse Helm chart](/self-hosting/deployment/kubernetes-helm) and run its bundled ClickHouse, [upgrade the chart from v1 to v2](/self-hosting/deployment/kubernetes-helm#chart-v1-to-v2) first. The v1 chart cannot bring its bundled ClickHouse to a v4-compatible version.
There is no forced cutover date. Langfuse v3 receives security patches through January 2027. The [self-hosted compatibility matrix](/self-hosting/upgrade/versioning#sdk-server) lists supported SDKs and APIs.
## 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).
---
## 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/faq/all/upgrade-to-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 .