3.9

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3.9.0 - Pendulum’s last swing

Released on October 21, 2026 Breaking Changes ⚠️

• Drop Python 3.10 support by @devin-ai-integration[bot] in #23324
• Remove deprecated Runner execution paths by @desertaxle in #23496
• Deprecate Pendulum datetime behavior on Python 3.11–3.12 by @devin-ai-integration[bot] in #23328

New Features 🎉

• Add Python 3.15 support by @devin-ai-integration[bot] in #23400

Enhancements ➕➕

• Add opt-in clearing for empty deployment schedules by @mifuha in #23412
• Cut CPU spent delivering events and API logs by @desertaxle in #23473
• Open a run’s artifacts directly from the Artifacts tab and run graph in ui-v2 by @JonasFockstedt in #23339
• Read automations with action types this version doesn’t know by @nathandpeterson in #23426
• Recover cancellation and suspension observers from websocket outages by @devin-ai-integration[bot] in #23421

Bug Fixes 🐞

• Keep the runner healthcheck healthy while the API is in maintenance by @jimid27 in #23325
• Skip duplicate worker submissions of runs that already hold a limit slot by @devin-ai-integration[bot] in #23341
• Fix prefect.yaml creation when optional contents is omitted by @MuhammadWaleed12 in #23334
• Check out pinned commit_sha when a git checkout already exists by @devin-ai-integration[bot] in #23374
• Preserve pytz timezone names in RRuleSchedule.from_rrule() by @devin-ai-integration[bot] in #23396
• Fix visit_collection returning another object’s cached result after id reuse by @novain-shibu in #23404
• Make *args/**kwargs optional collections in flow parameter schemas by @devin-ai-integration[bot] in #23418
• Return run input from async pause_flow_run when pause is rejected by @devin-ai-integration[bot] in #23435
• Allow Task.with_options(tags=[]) to clear existing tags by @devin-ai-integration[bot] in #23444
• Delete every deployment with prefect deployment delete --all by @devin-ai-integration[bot] in #23440
• Unwrap FieldInfo defaults for unmapped parameters in task.map() by @devin-ai-integration[bot] in #23369
• Count expect events that race or precede a proactive trigger’s window by @chrisguidry in #23445
• Respect --hours in work-pool preview and work-queue preview --pool by @LuisFigueroaG in #23300
• Raise ValueError for negative timeout in pause_flow_run by @kingsley-123 in #22761
• Fix prefect deploy dropping list items templated from step outputs by @MohammadHijjawi97 in #23381
• Copy hook lists in with_options for tasks and flows by @spicysharkco in #23442
• Return empty list from extract_instances when there is no match by @udsy19 in #23427
• Fix timeout=0 raising a TimeoutError in PrefectFutureList.result by @uinstinct in #23408
• Fix silently skipped task retries in retry_condition_fn by @uinstinct in #23397
• Fix overlapping action branches in the automation JSON schema by @devin-ai-integration[bot] in #23448
• Use min_length and max_length on request bodies so the server imports on FastAPI 0.155 by @bunchesofdonald in #23476
• Make flow run activity cells navigable by @VivekVRobo in #23352
• Render run graph artifact icons instead of black boxes in ui-v2 by @JonasFockstedt in #23348

Integrations & Dependencies 🤝

• Bump source-map-js from 1.2.1 to 1.2.2 in /ui by @dependabot[bot] in #23315
• Bump postcss-selector-parser from 6.1.2 to 6.1.4 in /ui by @dependabot[bot] in #23288
• Bump seroval from 1.6.2 to 1.6.8 in /ui-v2 by @dependabot[bot] in #23314
• Bump snowflake-connector-python from 4.7.1 to 4.7.3 by @dependabot[bot] in #23316
• Bump werkzeug from 3.1.6 to 3.1.9 by @dependabot[bot] in #23317
• Bump mako from 1.3.12 to 1.4.2 by @dependabot[bot] in #23318
• Bump multidict from 6.7.0 to 6.9.1 by @dependabot[bot] in #23319
• Bump uv from 0.12.10 to 0.12.18 in /scripts/proxy-test by @dependabot[bot] in #23365
• Bump cairosvg from 2.9.0 to 2.9.1 by @dependabot[bot] in #23363
• Bump source-map-js from 1.2.1 to 1.2.2 in /ui-v2 by @dependabot[bot] in #23364
• Bump dompurify from 3.4.12 to 3.4.16 in /ui-v2 by @dependabot[bot] in #23362
• Bump aiohttp from 3.14.3 to 3.14.4 by @dependabot[bot] in #23462
• Bump follow-redirects from 1.16.0 to 1.16.1 in /ui by @dependabot[bot] in #23480
• Bump vite from 8.2.2 to 8.3.4 in /ui by @dependabot[bot] in #23485
• Cap fastapi below 0.151 by @bunchesofdonald in #23478
• Update certifi and uv for the eMudhra CA compromise by @desertaxle in #23483

Development & Tidiness 🧹

• Keep the patched test clock timezone-aware on Python 3.12 by @chrisguidry in #23465
• Wait for the events client to confirm events before asserting in checkpoint tests by @bunchesofdonald in #23477
• Guard internal call sites against Pendulum deprecation warnings by @devin-ai-integration[bot] in #23497
• Replace dead Sanity logo URLs in bundled collection metadata by @mattiamatrix in #23409

Documentation 📓

• Fix broken in-page anchors in the events reference by @wznhf78gyf-bot in #23331
• Fix items type in the base job template customization docs by @rjafarau in #23388
• Document UnknownAction for automations and transfer skips by @devin-ai-integration[bot] in #23446
• Document held expect events for proactive triggers with after by @devin-ai-integration[bot] in #23467

Full Changelog: https://github.com/PrefectHQ/prefect/compare/3.8.8…3.9.0

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