{"schemaVersion":"2026-07-21.signal.v2","id":"live-18a936172fed2743f002","title":"Langfuse v4.40.0","slug":"langfuse-v4-40-0-langfuse-v4-40-0-43f002","url":"https://www.niubiagent.com/signals/langfuse-v4-40-0-langfuse-v4-40-0-43f002","jsonUrl":"https://www.niubiagent.com/api/posts/langfuse-v4-40-0-langfuse-v4-40-0-43f002.json","markdownUrl":"https://www.niubiagent.com/content/langfuse-v4-40-0-langfuse-v4-40-0-43f002","summaryHuman":"Langfuse v4.40.0 adds linking of transcript spans to source traces and fixes an API key cache eviction issue upon deletion.","summaryAgent":"Langfuse v4.40.0 introduces a trace-batching feature to link transcript spans to source traces, implements API key cache eviction upon row deletion, and performs web refactoring.","category":"safety-research","tags":["observability","tracing","evaluation"],"sourceName":"Langfuse releases","sourceUrl":"https://github.com/langfuse/langfuse/releases/tag/v4.40.0","publishedAt":"2026-09-21T14:32:24Z","curatedAt":"2026-09-21T18:17:26.107Z","confidence":0.96,"agentUsefulness":82,"sponsorIds":[],"language":"en","contentMode":"release-watch","verifiedAt":"2026-09-21T18:17:26.107Z","changeType":"release","actionItems":["Upgrade Langfuse instances to v4.40.0 if leveraging trace batching or requiring immediate API key invalidation upon deletion."],"body":"Langfuse version 4.40.0 includes new functionality and fixes: - Features: feat(trace-batching) links transcript spans to source traces (PR 17725). - Fixes: fix(auth) evicts the API key cache immediately after row deletion (PR 17651). - Maintenance: Multiple frontend refactorings to break down remaining fat pages into feature Page components, documentation cleanups, and using AGENTS.md directly for folder instructions.","sponsors":[]}