3.5.0 - 🎃 The Exorcism of Python 3.9 👻

Released on October 31, 2025

With the removal of Python 3.9 support, Prefect now requires Python 3.10 or later. This means you can finally say goodbye to from __future__ import annotations in your workflow code—native type annotations are now standard! This release also removes several long-deprecated features, including Runner functionality and system Blocks. Check the Breaking Changes section below for details.

Enhancements ➕➕

• Add on_running hook support for tasks by @zzstoatzz in #19277
• Allow using Field descriptions directly in Flow parameters (#13912) by @jmesterh in #19281
• Add PREFECT_SERVER_UI_SHOW_PROMOTIONAL_CONTENT setting by @zzstoatzz in #19299

Breaking Changes ⚠️

• Remove Python 3.9 support by @desertaxle in #19273
• Remove deprecated Runner functionality and system Blocks by @desertaxle in #19307

Bug Fixes 🐞

• Fix forward reference resolution in ValidatedFunction by @desertaxle in #19289
• Fix datetime parameter serialization in run_deployment by @zzstoatzz in #19278
• Fix time zone normalization bug in interval schedules by @zzstoatzz in #19301
• Fix multiprocessing deadlock after using prefect_test_harness on Linux by @zzstoatzz in #19116

Development & Tidiness 🧹

• Update typer minimum to 0.16.0 for click>=8.2 compatibility by @zzstoatzz in #19269
• Remove weird language by @zzstoatzz in #19271
• Update just recipes to use 3.10 for lowest python by @zzstoatzz in #19297
• Fix duration in generate_deprecation_message by @desertaxle in #19314
• Fix RRuleSchedule test flakiness from DST-dependent date by @zzstoatzz in #19305
• Add debug log for fork handler registration failure by @zzstoatzz in #19311

Documentation 📓

• Add global concurrency limits concept doc and refactor how-to guide by @desertaxle in #19231

Full Changelog: 3.4.25...3.5.0

3.4.26.dev6: Nightly Development Release

What's Changed

Bug Fixes 🐞

• Fix multiprocessing deadlock after using prefect_test_harness on Linux by @zzstoatzz in #19116

Uncategorized

• Call pods containers in ECS by @leetrout in #19310

Full Changelog: 3.4.26.dev5...3.4.26.dev6

3.4.26.dev5: Nightly Development Release

What's Changed

Enhancements ➕➕

• Allow using Field descriptions directly in Flow parameters (#13912) by @jmesterh in #19281

Bug Fixes 🐞

• Fix time zone normalization bug in interval schedules by @zzstoatzz in #19301
• fix: RRuleSchedule test flakiness from DST-dependent date by @zzstoatzz in #19305

Uncategorized

• Auto-update documentation by @github-actions[bot] in #19303
• add option to disable the Kubernetes worker observer and pod event replication by @levzem in #19282

New Contributors

• @jmesterh made their first contribution in #19281

Full Changelog: 3.4.26.dev4...3.4.26.dev5

3.4.26.dev4: Nightly Development Release

What's Changed

Development & Tidiness 🧹

• update just recipes to use 3.10 for lowest python by @zzstoatzz in #19297

Uncategorized

• Add PREFECT_SERVER_UI_SHOW_PROMOTIONAL_CONTENT setting by @zzstoatzz in #19299
• Auto-update documentation by @github-actions[bot] in #19300

Full Changelog: 3.4.26.dev3...3.4.26.dev4

3.4.26.dev3: Nightly Development Release

What's Changed

Enhancements ➕➕

• Add on_running hook support for tasks by @zzstoatzz in #19277

Bug Fixes 🐞

• Fix forward reference resolution in ValidatedFunction by @desertaxle in #19289
• Fix datetime parameter serialization in run_deployment by @zzstoatzz in #19278

Documentation 📓

• Remove Python 3.9 support by @desertaxle in #19273

Uncategorized

• Auto-update documentation by @github-actions[bot] in #19291

Full Changelog: 3.4.26.dev2...3.4.26.dev3

3.4.26.dev2: Nightly Development Release

What's Changed

Development & Tidiness 🧹

• rm weird language by @zzstoatzz in #19271

Uncategorized

• Auto-update documentation by @github-actions[bot] in #19272
• chore(cicd): Update Dockerhub token for prefect-aws image builds by @jamiezieziula in #19274

Full Changelog: 3.4.26.dev1...3.4.26.dev2

3.4.26.dev1: Nightly Development Release

What's Changed

Development & Tidiness 🧹

• update typer minimum to 0.16.0 for click 8.2+ compatibility by @zzstoatzz in #19269

Full Changelog: 3.4.25...3.4.26.dev1

3.4.25 - A slice of π-thon

Released on October 23, 2025

Enhancements ➕➕

• Add Python 3.14 support by @desertaxle in #19119
• Unify sync and async client methods by @hanhwanglim in #19217

Bug Fixes 🐞

• Upgrade Docker image SQLite to 3.50.4 to address CVE-2025-6965 by @desertaxle in #19214
• Fix GitLab credentials for self-hosted instances and deploy tokens by @zzstoatzz in #19227
• Make MemoryLockManager serializable with cloudpickle by @desertaxle in #19246
• Suppress noisy concurrency warnings for automatic tag-based checks by @desertaxle in #19254
• Fix work pool env vars being overwritten by variable defaults by @desertaxle in #19258

Development & Tidiness 🧹

• Fix non-deterministic test flake in PREFECT_EXPERIMENTS_PLUGINS_ALLOW tests by @zzstoatzz in #19203
• Add generate-cli-docs to justfile by @desertaxle in #19245
• Add uv and gh as allowed tools for Claude in GitHub Actions by @desertaxle in #19210
• Refactor git credential formatting to fix leaky abstraction by @zzstoatzz in #19236

Documentation 📓

• Correct worker --limit argument documentation by @desertaxle in #19244
• Add pydantic-ai data analyst example by @desertaxle in #19209
• Update Prefect MCP status in docs by @zzstoatzz in #19213
• Correct Modal dashboard link by @jesse-c in #19240
• Fix repository name capitalization in README example by @gowtham1412-p in #19260

Full Changelog: 3.4.24...3.4.25

3.4.25.dev5: Nightly Development Release

What's Changed

Enhancements ➕➕

• Correct worker --limit argument documentation by @desertaxle in #19244

Bug Fixes 🐞

• Make MemoryLockManager serializable with cloudpickle by @desertaxle in #19246

Development & Tidiness 🧹

• Add generate-cli-docs to justfile by @desertaxle in #19245

Documentation 📓

• docs: Correct Modal dashboard link by @jesse-c in #19240

Uncategorized

• Auto-update documentation by @github-actions[bot] in #19234
• Auto-update documentation by @github-actions[bot] in #19251

Full Changelog: 3.4.25.dev4...3.4.25.dev5

3.4.25.dev4: Nightly Development Release

What's Changed

Enhancements ➕➕

• Kubernetes: allow opt-out of rescheduling on SIGTERM by setting PREFECT_FLOW_RUN_EXECUTE_SIGTERM_BEHAVIOR by @svatopluk-sperka in #19223
• Unify sync and async client methods by @hanhwanglim in #19217
• Upgrade Docker image SQLite to 3.50.4 to address CVE-2025-6965 by @desertaxle in #19214

Bug Fixes 🐞

• Fix GCS bundle upload/download to use filename methods by @desertaxle in #19224
• fix gitlab credentials for self-hosted instances and deploy tokens by @zzstoatzz in #19227

Uncategorized

• Auto-update documentation by @github-actions[bot] in #19228

New Contributors

• @svatopluk-sperka made their first contribution in #19223

Full Changelog: 3.4.25.dev3...3.4.25.dev4