If your use case requires using Swagger UI for the OAuth client credentials flow, and Swagger UI only supports the

client_secret_basic

authentication mechanism, you should configure your OAuth2 client to use

client_secret_basic

. By default, Ory Hydra and Ory Network clients are set to use

client_secret_basic

, which means the client ID and secret are sent in the HTTP Authorization header. If your client is currently set to

client_secret_post

, authentication will fail with Swagger UI, as it does not support this method. To resolve this, update your OAuth2 client to use

client_secret_basic

as the

token_endpoint_auth_method

. You can do this using the Ory CLI or Hydra CLI with the appropriate flag:

ory update oauth2-client --token-endpoint-auth-method client_secret_basic

or

hydra update client --token-endpoint-auth-method client_secret_basic

This change will ensure compatibility with Swagger UI, as it expects credentials in the HTTP header, not the POST body. If you continue using

client_secret_post

, Swagger UI will not be able to authenticate successfully with your OAuth2 server [Client auth fails because Wrong token_endpoint_auth_method](https://www.ory.sh/docs/hydra/debug/token-endpoint-auth-method). In summary: Yes, you should switch to

client_secret_basic

if you want to use Swagger UI for the OAuth client credentials flow.

Based on the provided knowledge sources, it is not possible to enable multiple authentication methods simultaneously for a single OAuth client in Ory Hydra. The client must be configured with a single value for the

token_endpoint_auth_method

parameter, such as

client_secret_basic

,

client_secret_post

,

private_key_jwt

, or

none

. The documentation and CLI options only allow specifying one method at a time, and there is no mention of supporting multiple methods for a single client. If you attempt to use a method that is not configured for the client, authentication will fail [Client auth fails because Wrong token_endpoint_auth_method](https://www.ory.sh/docs/hydra/debug/token-endpoint-auth-method). If you need to support multiple authentication methods, you would need to create separate clients, each configured with the desired method.

@chilly-king-10285 How to set the authentication method for OAuth clients in the Docker Hydra YAML config?

To set the authentication method for OAuth clients in Ory Hydra when using Docker and YAML configuration, you do not set this directly in the Docker Compose YAML file. Instead, you configure the authentication method when creating the OAuth client, typically using the Hydra CLI or Ory CLI, which you can run inside your Docker container. For example, to set the authentication method to

client_secret_post

, you would run:

docker-compose -f quickstart.yml exec hydra \   hydra create client \   --endpoint <http://127.0.0.1:4445> \   --grant-type authorization_code,refresh_token \   --response-type code,id_token \   --scope openid,offline_access \   --redirect-uri <http://your-app/callback> \   --token-endpoint-auth-method client_secret_post

Replace

client_secret_post

with your desired method (e.g.,

client_secret_basic

,

private_key_jwt

, or

none

). The

--token-endpoint-auth-method

flag is used to specify the authentication method for the client at the token endpoint [hydra create client options](https://www.ory.sh/docs/hydra/cli/hydra-create-client#options) [GitLab Hydra integration example](https://www.ory.sh/docs/hydra/self-hosted/gitlab). Summary: You set the authentication method for OAuth clients by specifying the

--token-endpoint-auth-method

flag when creating the client via the CLI, not directly in the Docker Compose YAML file.