Here’s a minimal, end‑to‑end example of configuring

results.default_storage_block

to use a LocalFileSystem block in Prefect 3.x. 1) Create and save a LocalFileSystem block

from prefect.filesystems import LocalFileSystem

# Point this to where you want results written
fs = LocalFileSystem(basepath="/opt/prefect/results")
fs.save("local-results", overwrite=True)

2) Tell Prefect to use that block by default (and optionally persist results by default) - Via CLI

prefect config set results.default_storage_block="local-file-system/local-results"
prefect config set results.persist_by_default=true

- Or via environment variables

export PREFECT_RESULTS__DEFAULT_STORAGE_BLOCK="local-file-system/local-results"
export PREFECT_RESULTS__PERSIST_BY_DEFAULT=true

- Or in your prefect.toml (profile) configuration

[results]
default_storage_block = "local-file-system/local-results"
persist_by_default = true

3) Use it in a flow (results will be written to your LocalFileSystem basepath)

from prefect import flow, task

@task(persist_result=True)  # or rely on results.persist_by_default=true
def add(x, y):
    return x + y

@flow
def my_flow():
    return add(1, 2)

if __name__ == "__main__":
    my_flow()

Notes: - The setting value format is "<block_type_slug>/<block_name>". For LocalFileSystem, the type slug is

local-file-system

, so

"local-file-system/local-results"

in this example. - Make sure the path you set in

basepath

exists and is writable wherever your flow runs (e.g., worker/container/VM). - You can override storage at the task/flow level with

result_storage

if needed, but the setting above provides a global default. Docs for reference: - Results (Prefect 3.x) - prefect.filesystems API