# Langfuse v4.39.0

Category: safety-research
Published: 2026-09-21T11:21:23Z
Source: [Langfuse releases](https://github.com/langfuse/langfuse/releases/tag/v4.39.0)
Agent usefulness: 82/100
Confidence: 0.96
Content mode: release-watch
Verified: 2026-09-21T12:17:45.988Z
Tags: observability, tracing, evaluation

## Human Summary
Langfuse releases published Langfuse v4.39.0. What's Changed Features feat(web): publish event-loop delay for autoscaling by @sumerman in 17632 feat(automations): filter prompt events by label by @tobi12345 in 17612 feat(ai-gateway): add phase spans so request traces have no gaps by @hassiebp in 17640 feat(ai-gateway): record Codex client metadata as agent…

## Agent Summary
Treat Langfuse v4.39.0 as an official release signal. Inspect the linked changelog for compatibility and migration details, then run targeted tests before upgrading.

## Body
Langfuse releases published Langfuse v4.39.0. This release-watch entry was generated from the project's official GitHub release feed and is kept separate from human-reviewed editorial analysis. Release notes: What's Changed Features feat(web): publish event-loop delay for autoscaling by @sumerman in 17632 feat(automations): filter prompt events by label by @tobi12345 in 17612 feat(ai-gateway): add phase spans so request traces have no gaps by @hassiebp in 17640 feat(ai-gateway): record Codex client metadata as agent metadata by @hassiebp in 17641 feat(auth): authorize every ingestion event through the policy core by @marksalpeter in 16715 feat(otel): simulate worker admission in shadow mode by @sumerman in 17437 feat: return conversation history and current turn per thread by @marliessophie in 17613 feat(langchain): add serialized generation result fixture for LangChain messages normalization by @marliessophie in 17589 feat(in-app-agent): support Vertex AI for instance AI features by @toyayuto in 17390 feat(api): route prompt public handlers through the auth seam by @marksalpeter in 17533…

## Recommended actions
- Review the official Langfuse releases release notes before upgrading.
- Check compatibility, migration, and security notes against your current agent stack.
- Run focused regression tests before production rollout.

## Sponsors
No sponsor placement attached.

## Agent-readable Sponsor Surface
Sponsor inventory is available at /api/sponsors.json with useCases, pricing, API/docs URLs, targetAgents, constraints, CTA URL, commercial disclosure fields, sourceOfTruthUrl, constraintsLastVerifiedAt, constraintsRefreshCadence, driftHandlingPolicy, and constraintPolicy.