{{ event.url }} renders empty in automation Jinja templates despite #19851 fix

[fredrikhgrelland]

Bug summary

Summary

{{ event.url }} renders as an empty string in automation action Jinja templates on Prefect Cloud. The fix in #19851 (merged Dec 19, 2025)
added a url property to the server-side ReceivedEvent, but 8 months later the property still evaluates to empty when used in automation
templates.

Reproduction

Automation flow_crashed uses this template in a RunDeployment action parameter:

Link: [View Event]({{ event.url }})

Every triggered action renders this as:

Link: View Event

Evidence

• Prefect client version: 3.8.3
• Server type: Prefect Cloud
• Work pool: ECS
• Pattern: 100% of automation-triggered actions using {{ event.url }} produce empty links. Verified on issues created Aug 25-27 across
multiple deployments.

All other Jinja variables work ({{ event.id }}, {{ event.occurred }}, {{ event.resource["prefect.state-message"] }}, {{
event.related[1]["prefect.resource.name"] }}).

Analysis

PR #19851 added ReceivedEvent.url as a @Property calling url_for(self, url_type="ui"). Possible reasons it's still empty:

1. Serialization before rendering — if the Cloud automation pipeline serializes ReceivedEvent to a dict before passing it to Jinja, the
   @Property is lost and event.url resolves to undefined/empty
2. PREFECT_UI_URL not set in the server-side rendering context — url_for() returns None when this setting is absent
3. Cloud backend hasn't picked up the change — the OSS server code has the property, but the Cloud rendering pipeline may use a different
   code path

Expected behavior

{{ event.url }} should render a working URL like:

https://app.prefect.cloud/account//workspace//events/event/2026-08-27/06a8fa82-cc7f-7075-8000-ec0580300884

References

• Original request: #19526
• Fix PR: #19851

Version info

Version:              3.8.3
API version:          0.8.4
Python version:       3.11.12
Git commit:           d8f54b5c
Built:                Thu, Aug 13, 2026 06:55 PM
OS/Arch:              linux/x86_64
Profile:              dope
Server type:          cloud
Pydantic version:     2.13.4
Server:
  Database:           sqlite
  SQLite version:     3.45.1
Integrations:
  prefect-docker:     0.7.2
  prefect-cloud:      0.1.13

Additional context

No response

[mikemikimike]

Implemented and opened #22978 to preserve ReceivedEvent.url when events are serialized. The regression test verifies that the UI URL is present in JSON serialization, which allows Cloud automation templates such as {{ event.url }} to render it. Local compileall and git diff --check passed; the focused pytest was blocked by missing generated build metadata in the source checkout. GitHub Actions completed with 86 successful, 6 skipped, and 15 failed matrix jobs; the failures span unrelated server, client, and canonical test shards, so CI is classified as failing outside the changed test path. The failing run is https://github.com/PrefectHQ/prefect/actions/runs/33303542225.