Short answer: your trigger shape looks right, but two common gotchas usually prevent it from firing: - Using the deployment name instead of the UUID in

match_related.prefect.resource.id

- Expecting retroactive behavior after enabling the automation What to check 1) Verify you’re filtering by the correct deployment resource - The filter must use the deployment’s UUID resource id: -

prefect.resource.id

should be exactly

prefect.deployment/<deployment_id>

or

prefect.deployment.<deployment_id>

depending on your environment formatting (both are supported; Prefect typically uses the dot form). - Quick way to get the deployment ID:

prefect deployment inspect "flow_name/deployment_name"

This prints a dict with

'id': 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'

. 2) Confirm the actual event name - Open the Events view and click on the flow-run that just finished from Deployment A. Check the exact event name; it should be

prefect.flow-run.Completed

and the Related resources should include the deployment: - Related resource id:

prefect.deployment.<deployment_id>

- If you see a different spelling, update

expect

accordingly. 3) Make sure the automation was enabled before the event occurred - Automations do not backfill; they only react to events that occur while the automation is enabled. - Enabling/disabling takes effect quickly; there’s no long-lived cache. Expect a small propagation delay (a few seconds), but not minutes. 4) Validate the action configuration - Ensure “Run Deployment B” points to the correct deployment (UUID), and that B’s work pool/infra is available. - If B needs parameters, configure them in the action. Your JSON with a few best‑practice tweaks - It’s fine as-is, but here’s a complete example including an action section to cross-check your setup:

{
  "name": "Run B when A completes",
  "description": "Runs Deployment B when any flow run from Deployment A completes",
  "enabled": true,
  "triggers": {
    "type": "compound",
    "require": "any",
    "within": 0,
    "triggers": [
      {
        "type": "event",
        "expect": [
          "prefect.flow-run.Completed"
        ],
        "posture": "Reactive",
        "match": {},
        "match_related": {
          "prefect.resource.id": "prefect.deployment.<A-DEPLOYMENT-UUID>"
        },
        "after": [],
        "for_each": [],
        "threshold": 1,
        "within": 0
      }
    ]
  },
  "actions": [
    {
      "type": "run-deployment",
      "deployment_id": "<B-DEPLOYMENT-UUID>",
      "parameters": {}
    }
  ]
}

Troubleshooting steps if it still doesn’t fire - Trigger a quick test run of A, then immediately check the Events view for that run and verify: - Event appears as

prefect.flow-run.Completed

- Related includes

prefect.deployment.<A-UUID>

- Check the automation’s Recent activity to see whether the trigger matched and whether the action attempted to run. - Confirm A’s terminal state is actually Completed (not, e.g., Failed or Cancelled). If you want to react to any terminal outcome, use multiple expects:

"expect": [
    "prefect.flow-run.Completed",
    "prefect.flow-run.Failed",
    "prefect.flow-run.Cancelled"
  ]

On caching of enable/disable - There is no caching you need to manually invalidate. Changes take effect almost immediately; allow a few seconds for propagation. They won’t apply to past events. If you can share: - The exact Related resources block from a completed flow-run of A - The UUIDs you’re using for A and B I can sanity-check the filter and action values.