Fix scheduler heartbeat timeout failures with intermittent DetachedInstanceError crashes (#53838) (#53858)
Fix connection editing where sensitive fields like passwords and extras were lost when updating connections (#53943) (#53973)
Fix BaseOperator on_kill functionality not working when tasks are killed externally in TaskSDK (#53718) (#53832)
Fix TaskInstance notes not refreshing automatically without manual page refresh (#53307) (#54025)
Fix invalid execution API URLs causing failures in task supervisor (#53082) (#53518)
Fix task failure callbacks not running on DAG Processor when tasks are externally killed (#53058) (#53143)
Fix task_success_overtime configuration option not being configurable (#53342) (#53351)
Fix CSS warning for nth-child selector (#53982) (#54000)
Fix DAG filtering where "all" option did not show all DAGs as expected (#53656) (#53672)
Fix accordion child contents not being visible when content overflows (#53595) (#53602)
Fix navbar positioning for anchor calculations (#52016) (#53581)
Fix DagBag safe mode configuration resolution in DAG processor (#52694) (#53507)
Fix large log reading causing out-of-memory issues in API server (#49470) (#53167)
Fix connection exceptions consistency between Airflow 2.x and 3.x (#52968) (#53093)
Remove unnecessary group_by clause in event logs query for performance (#53733) (#53807)
Allow remote logging providers to load connections from API Server (#53719) (#53761)
Add certificate support for API server client communication with self-signed certificates (#53574) (#53793)
Respect apps flags for API server command configuration (#52929) (#53775)
Skip empty DAG run configuration rows and set statement timeout (#50788) (#53619)
Remove incorrect warning for BaseOperator.executor attribute (#53496) (#53519)
Add back DAG parsing pre-import optimization for improved performance (#50371) (#52698)
Flexible form use ReactMarkdown instead of default Markdown component (#54032) (#54040)
Unconditionally disable start_from_trigger functionality (#53744) (#53750)
Serialize NaN and infinity values to string (#53835) (#53844)
Make log redaction safer in edge case when redaction has an error (#54046) (#54048)
Flexible form use ReactMarkdown instead of default Markdown component (#54032) (#54040)
Fix inconsistent casing in UI of decorated tasks (#54056) (#54092)

Miscellaneous

Fix AIRFLOW_API_APPS constant in API server command (#54007) (#54012)
Add deprecation notice for using Connection from models in favor of SDK approach (#53594) (#53621)
Remove remnants of ~= used in requires-python configuration (#52985) (#52987)
Remove upper-binding for "python-requires" specification (#52980) (#52984)
Update GitPython from 3.1.44 to 3.1.45 (#53725) (#53731)(#53724) (#53732)

Doc Only Changes

Update DAG author documentation to use "DAG author" terminology (#53857) (#53950)
Update architecture diagrams labels from "Webserver(s)" to "API Server(s)" (#53917) (#54020)
Remove bold formatting for Public Interface documentation in Airflow 3.0+ (#53955) (#53964)
Add user-facing documentation for running separate Task Execution API server (#53789) (#53794)
Add documentation for self-signed certificate configuration (#53788) (#53792)
Update systemd unit files and documentation for Airflow 3.0 compatibility (#52294) (#53609)
Update public interface documentation to reflect airflow.sdk and AIP-72 changes (#52197) (#53117)
Update BaseOperator documentation string for clarity (#53403) (#53404)
Remove extra slash from endpoint URL formatting (#53755) (#53764)
Clarify our security model for sensitive connection information (#54088) (#54100)

Full Changelog: https://github.com/apache/airflow/compare/3.0.3...3.0.4