Totally get the concern—logging every single object upload at INFO can add a lot of noise (and storage), especially when you only care about failures. Short answer: there isn’t a built-in flag on

S3Bucket.upload_from_file_object

to silence or demote these logs. But you have a few good options to suppress them cleanly in Prefect 3.x. Options (from most targeted to least invasive): 1) Create a Prefect logging config that demotes S3 logs to WARNING - Point Prefect to a custom logging config and set the

prefect_aws.s3

logger to WARNING so INFO upload messages are dropped but errors still show. - Example logging.yml:

version: 1
  disable_existing_loggers: false

  formatters:
    standard:
      format: "%(asctime)s | %(levelname)s | %(name)s | %(message)s"

  handlers:
    console:
      class: logging.StreamHandler
      formatter: standard
      level: INFO

  loggers:
    prefect:
      level: INFO
      handlers: [console]
      propagate: false

    # Demote AWS S3 logs to WARNING so INFO-level upload messages are suppressed
    prefect_aws.s3:
      level: WARNING
      handlers: [console]
      propagate: false

    # (Optional) Demote all prefect_aws logs
    prefect_aws:
      level: WARNING
      handlers: [console]
      propagate: false

- Then set:

export PREFECT_LOGGING_SETTINGS_PATH=/path/to/logging.yml

- Prefect 3 logging customization docs: Logging customization (Prefect 3) Note: If the block uses the flow/task “run logger” internally instead of the module logger, the logger name may not be

prefect_aws.s3

. If that’s the case, a message-based filter or the run-logger name would be needed. If you can paste one of the upload log lines, I can give you an exact drop-in YAML snippet. 2) Programmatically lower the S3 logger level in your flow code - Add this once at startup (before using the block):

import logging

  logging.getLogger("prefect_aws.s3").setLevel(logging.WARNING)
  # Optional: cover the whole integration
  logging.getLogger("prefect_aws").setLevel(logging.WARNING)

- This suppresses INFO-level upload logs while still surfacing warnings/errors. 3) Bypass the block’s logging and call boto3 directly using the block’s client - You can still leverage the block for credentials, but call the client directly to avoid the block’s internal log calls:

from prefect_aws.s3 import S3Bucket

  def upload_quiet(bucket: S3Bucket, fobj, key: str, **kwargs):
      client = bucket.get_s3_client()
      extra_args = kwargs.get("ExtraArgs")  # optional
      client.upload_fileobj(fobj, bucket.bucket, key, ExtraArgs=extra_args)
      return f"s3://{bucket.bucket}/{key}"

  # usage
  with open("/path/to/file.bin", "rb") as f:
      upload_quiet(my_bucket_block, f, "path/in/bucket/file.bin")

- This avoids any INFO-level upload logging performed by the block. 4) Coarse-grained (only if you’re okay with suppressing all INFO logs) - Set:

export PREFECT_LOGGING_ROOT_LEVEL=WARNING

- This cuts down on logs across the board (not just S3). Mentioning for completeness, but the above targeted options are better. If you can share: - Your Prefect version (assuming 3.x) - One example of an upload log line (to confirm the logger name) …I can provide an exact, copy/paste logging.yml or filter that surgically silences only those messages. If you’d like, I can also open a feature request to add a flag to

S3Bucket

to disable per-file INFO logs or log them at DEBUG.