Great question — you’re right: in Prefect 3.x, tags in decorators are static and the curly-brace templating you can use for run names isn’t supported for tags. Good news: you have two solid options for setting tags dynamically at runtime. 1) Use the tags context manager at the call site - Wrap the task submission (or call) in a

with tags(...):

block. Any task runs created in that block inherit those tags. - This is the most common way to drive tag-based concurrency limits or to scope tags to specific invocations. Example:

from prefect import flow, task, tags

@task
def process(item):
    ...

@flow
def my_flow(customer_id: str, items: list[str]):
    runtime_tag = f"customer:{customer_id}"
    # Apply to all tasks in this block
    with tags(runtime_tag, "priority:high"):
        for item in items:
            process.submit(item)  # each run gets the dynamic tags

    # Or per-invocation if tags differ per item
    for item in items:
        with tags(f"item:{item}"):
            process.submit(item)

Notes: - Put the

with tags(...)

block in the flow (or the parent task) that creates the task run(s). Using it inside the body of a task won’t change that task’s own tags, but it will affect any nested tasks created within it. 2) Create a runtime-cloned task with with_options - You can create a “cloned” Task object at runtime with different tags, then call or submit it. Example:

from prefect import flow, task

@task
def process(item):
    ...

@flow
def my_flow(customer_id: str, items: list[str]):
    runtime_tag = f"customer:{customer_id}"
    dynamic_process = process.with_options(tags=[runtime_tag, "priority:high"])

    for item in items:
        dynamic_process.submit(item)

This is useful if you want to set once and reuse within the flow run, but still compute the tags dynamically. When to use which: - Want tags to apply to a whole block of submissions? Use

with tags(...)

. - Want a single “dynamic default” task for the whole flow run? Use

with_options(...)

. A couple of reminders: - You can pass multiple tags:

with tags("a", "b")

or

with tags(*tag_list)

. - You cannot change tags after a task run has started. - If you’re using tags for concurrency limits, this pattern is exactly what you want. See: Tag-based concurrency limits in Prefect 3.x. If you can share how you’re using tags (e.g., concurrency limits, organization, filtering), I can suggest a pattern tailored to your use case.