PrefectHQ/prefect 3.4.19

3.4.19 - Pay No Attention To That GCL Behind The Curtain

on GitHub

Released on September 19, 2025

Enhancements ➕➕

• split deploy.py into a module by @zzstoatzz in #18925
• Add minimal V1→V2 concurrency adapter by @zzstoatzz in #18971
• Update task concurrency slot orchestration rules to work with global concurrency limits by @desertaxle in #18983
• Update task engine to use GCLs to limit task concurrency by @desertaxle in #18982
• Migrate V1 concurrency limits to V2 format in database by @zzstoatzz in #18968
• Add pagination support to lease storage read_active_lease_ids by @zzstoatzz in #18973
• Add list_holders_for_limit to ConcurrencyLeaseStorage protocol by @zzstoatzz in #18970

Bug Fixes 🐞

• Fix set_working_directory to return absolute path by @desertaxle in #18932
• Silence retryable SQLite lock errors by @zzstoatzz in #18957
• Fix wait() to monitor all futures concurrently with timeout by @zzstoatzz in #18960
• Fix blocks not registering schema for nested Blocks in piped union types by @GalLadislav in #18920
• Fix atomicity issue in GCL-backed tag-based concurrency limits by @desertaxle in #18991

Development & Tidiness 🧹

• Add Python environment setup to Claude workflow by @desertaxle in #18931
• Add models for validating loaded prefect.yaml files by @desertaxle in #18941
• Replace pre-push docs generation with GitHub Action by @desertaxle in #18930
• Install mdxify explicitly in CI by @desertaxle in #18954
• Add starlette status code compatibility layer by @zzstoatzz in #18963

Documentation 📓

• fix: add redirect setting to docs.json to fix /latest path 404s by @zzstoatzz in #18945
• fix: add errors.404.redirect setting to fix /latest path 404s by @zzstoatzz in #18946

Full Changelog: 3.4.18...3.4.19