Fix execution failures with NULL dag_run.conf during upgrades from earlier versions (#56729)
Fix memory leak in remote logging connection cache (#56695)
Fix DAG processor crash with pre-import module optimization enabled (#56779)
Fix scheduler crash with email notifications (#56431)
Fix scheduler crash during 3.0 to 3.1 migration when retry_delay is None (#56236)
Fix task retries executing wrong method after deferred state (#56737)
Fix retry callbacks not executing for externally killed tasks (#56607)
Fix custom timetable generate_run_id not called for manual triggers (#56699)
Fix KeyError when accessing retry_delay on MappedOperator without explicit value (#56605)
Fix task-sdk connection error handling to match airflow-core behavior (#56653)
Fix topological sort for Grid View (#56963)
Fix get_ti_count and get_task_states access in callback requests (#56860)
Fix Connection or Variable access in Server context (#56602)
Fix .airflowignore order precedence (#56832)
Fix migration errors for Pydantic 2.12.0 compatibility (#56581)
Fix: Correctly parse JSON for --dag_run_conf in airflow dags backfill CLI (#56599)
UI: Fix note modal does not change markdown text after change (#56092)
UI: Fix Grid for cleared runs when tasks were removed (#56297)
UI: Fix log text selection contrast in light mode (#56893)
UI: Fix Advanced Search button overlap in DAG List View (#56777)
UI: Fix view for many DAG tags (#55604)
UI: Fix asset name text overflow in DAGs list view (#55914)
UI: Fix auto refresh when only 1 dag run is running (#56649)
UI: Fix UI keeps poking pools API when no permission (#56626)
UI: Fix multi-line drag selection in task log view (#56300)
UI: Fix task named 'root' causes blue screen on hover (#56926)
UI: Fix cron expression display for Day-of-Month and Day-of-Week conflicts (#56255)
UI: Fix Grid view performance issues with SerializedDagModel query optimization (#56938)
Fix: Gracefully handle FastAPI plugins with empty url_prefix (#55262)
Fix: Allow mapped tasks to accept zero-length inputs on rerun (#56162)
Fix: Enable API to clear task instances by specifying map indexes (#56945)
Fix: Add max_retry_delay to MappedOperator model (#56951)
Fix: Use name passed to @asset decorator when fetching the asset (#56611)
UI: Add English as a fallback locale (#56934)

Miscellaneous

Add Greek UI translation (#56724)
Add Thai UI translation (#56946)
Add Polish translations (#56825)
Close German translation gaps for full UI translation (#56981)
Fix Hebrew typo in translations (#56168)
Improve DAG and task missing error handling in callbacks (#56725)
Improve UI retry strategy on client errors (#56638)
Improve get dag grid structure endpoint speed (#56937)
Optimize grid structure query with DISTINCT for dag_version_id lookup (#56565)
Add configurable timeout for Execution API requests (#56969)
Prevent unnecessary kubernetes client imports in workers (#56692)
Lazy import PodGenerator for deserialization (#56733)
Serialize pydantic models in json mode for JSON serialization compatibility (#56939)
Update authentication to handle JWT token in backend (#56677)
Update bulk API permission check to handle action_on_existence (#56672)
Migrate CreateAssetEventsBody to Pydantic v2 ConfigDict (#56772)
Restore timetable active_runs_limit check (#56922)
Add is_favorite to UI dags list (#56341)
Add executor, hostname, and queue columns to TaskInstances page (#55922)
Add resize function for DAG Documentation (#56344)
Add optional pending dag runs check to auto refresh (#56648)
Add auto refresh to backfill banner (#56774)
UI: Add Expand/Collapse all to XComs page (#56285)
UI: Update recent runs bar chart and improve responsiveness (#56314)
UI: Update duration format to show milliseconds (#56961)
UI: Modify min width for task names in grid view (#56952)
UI: Use Task Display Name in Graph if existing (#56511)
UI: Use Task Display Name in Grid if existing (#56410)
UI: Use TI duration from database instead of UI calculated (#56329)
UI: Make DAG Run ID visible in DAG Header Card (#56409)
UI: Modify calendar cell colors (#56161)
UI: Modify log highlight color (#56894)
UI: Fix show appropriate time units in grid view (#56414)
UI: Reduce default columns of DAG Run and Task Instance lists (#55968)
UI: Add expand and collapse functionality for task groups (#56334)
UI: Avoid using rem for icons for Safari compatibility (#56304)
UI: Add ANSI support to log viewer (#56721)
UI: Support Dynamic UI Alerts (#56259)
UI: Disable Gantt view by default (#56242)
UI: Use welcome on dashboard instead of airflow (#56074)
UI: Improve clipboard button visibility with hover effect (#56484)
UI: Allow sub-pages in React UI plugins (#56485)
Include task instance id in log printed by supervisor (#56383)
Emit log stream stopped warning as ndjson (#56480)
Detect interactive terminal to set colored logging with override env variable support (#56157)
Add back deprecation warning for sla_miss_callback (#56127)
Move natsort dependency to airflow-core (#56582)
Added missing babel dependency in Task SDK (#56592)
Remove unused dagReports API endpoint (#56621)

Doc Only Changes

Improve API sort documentation (#56617)
Improve API doc for ordering query param (#55988)
Add Audit Logs detailed documentation (#56719)
Update serializer document to reflect latest changes in codebase (#56857)
Update ASF logos in documentation to the new Oak logo (#56601)
Enhance triggering_asset_event retrieval documentation in DAGs (#56957)
Remove self-reference in best practices documentation (#56111)
Fix supported Python versions in README (#56734)

Full Changelog: https://github.com/apache/airflow/compare/3.1.0...3.1.1