Yes. While

flow.deploy()

doesn’t take a headers argument, in Prefect 3.x you can add custom HTTP headers to every API request (including deploy) via client settings. Ways to set them: - Environment variable (applies to the current process)

export PREFECT_CLIENT_CUSTOM_HEADERS='{"X-My-Header":"foo","X-Another":"bar"}'

Then run your deployment code or CLI and Prefect will include these headers on all API calls. - Profile TOML (persistent across sessions) In your profile (e.g., ~/.prefect/profiles.toml or a project prefect.toml):

[client.custom_headers]
  X-My-Header = "foo"
  X-Another = "bar"

- Programmatic (for your own client usage) If you create a client yourself, you can pass httpx settings:

from prefect.client.orchestration import PrefectClient

  client = PrefectClient(
      api="<https://api.prefect.cloud>",
      httpx_settings={"default_headers": {"X-My-Header": "foo"}}
  )

Note:

flow.deploy()

uses the default client from current settings; it doesn’t accept

httpx_settings

directly. If you need headers for deploy, prefer the env var or profile settings above. Example with deploy in code (env var set first):

import os
os.environ["PREFECT_CLIENT_CUSTOM_HEADERS"] = '{"X-My-Header":"foo"}'

from prefect import flow

@flow
def my_flow():
    return "hi"

# Your normal deployment call — headers will be included automatically
my_flow.from_source(
    "<https://github.com/owner/repo>",
    entrypoint="flows/my_flow.py:my_flow"
).deploy(
    name="my-deployment",
    work_pool_name="my-pool"
)

Notes: - Headers you set are merged with Prefect’s own headers; Prefect may manage some reserved headers for functionality and security. - The same setting applies to

prefect deploy

from the CLI. Docs: - Settings reference (see

client.custom_headers

) - Settings and profiles - Client API If you can share which header you need (e.g., a proxy or gateway requirement), I can suggest the cleanest setup for your environment.