Mix release in prod creates bad sys.config


I will try to make a small example, but first I would like to check that this is not a know bug. Which should have been possible to find here…

Elixir 1.15, Mix 1.15.6 (compiled with Erlang/OTP 26), umberella project
MIX_ENV=prod mix release
creates a sys.config with, among others, {logger, [... ,{metadata,[mfa]}]}
Trying to start this release:

=CRASH REPORT==== 1-Nov-2023::10:07:38.785472 ===
    initial call: application_master:init/4
    pid: <0.1827.0>
    registered_name: []
    exception exit: {bad_return,
                          [{error_info,#{module => erl_stdlib_errors}}]},
      in function  application_master:init/4 (application_master.erl, line 142)

MIX_ENV=dev does not have the problem, neither did prod in Elixir 1.14.

It seems you have invalid Logger configuration.

You were defining config :logger, metadata: [:mfa], but this has no meaning on previous Elixir versions. Elixir v1.15 assigns a meaning to this key to specify key-value pairs of global metadata.

You probably want to move your metadata key to a backend/handler, such as config :logger, :console, metadata: [:mfa].

Thank you very much.
Yes, I have (inherited) config/prod.exs with metadata: [:mfa]
I do not know what it does and will remove it.