Short answer: In Prefect 3.x, placeholders like

{{ prefect.variables.* }}

in prefect.yaml are rendered when you run

prefect deploy

. There isn’t a flag or escape to keep them for runtime evaluation, and workers do not re-template deployment job variables at run time. Details and options: - What gets rendered when: - build and push sections: all placeholders are resolved at deploy time - pull section: block references (and variables used there) are resolved at runtime by the worker - deployment.job_variables (e.g., ECS

image

): treated as static infra overrides; they’re not re-rendered at runtime Docs: - prefect.yaml mechanics - Prefect Variables What you can do instead: - If you truly need runtime resolution, move that usage into the

pull

section (that code runs on the worker at execution time and can reference Prefect Variables). - If this value is for infrastructure (e.g., ECS job_variables.image), it must be concrete when the worker submits the run. In that case you’ll need to: - re-run

prefect deploy

when the variable changes, or - programmatically update the deployment’s infra overrides via the API before runs - For values used inside your flow code (not infra), fetch at runtime:

from prefect import flow
  from prefect.variables import Variable

  @flow
  def my_flow():
      registry = Variable.get("ecr-registry")
      # build your string here at runtime

Could you share where in your prefect.yaml you’re using

{{ prefect.variables.ecr-registry }}

? For example, is it in

deployment: job_variables.image

for an ECS work pool, or inside a

pull

step? With that, I can suggest the best pattern for your setup.