🟡 Using BAML in Elixir with OpenAPI and Custom Client Registry boundary #questions

🟡 Using BAML in Elixir with OpenAPI and Custom Cl...

kirakos6970

12/04/2025, 11:31 AM

Hi, I am trying to use BAML in Elixir. I need to be able to pass my custom client registry, since I use an LLM proxy and need custom additional header, and this is not currently possible with

baml_elixir

, that's why I am considering OpenAPI option. So my first questions is, is it possible to do the OpenAPI spec generation from BAML and then Elixir code generation from OpenAPI as a separate step (compile/build time) from the Rest API serving? In other words, I want to generate the Elixir modules from BAML during build time, and then only serve the Rest API in the runtime.

greg (BAML)

12/04/2025, 6:35 PM

Hello! Yes, what I think you're describing is the normal OpenAPI client setup. You edit your BAML code, regenerate the open-api spec, regenerate the elixer client from the open-api spec, and the BAML server (which has been watching your .baml files for changes) updates to be able to handle the new input/output schemas.

greg (BAML)

12/04/2025, 6:36 PM

In fact in your generators.baml file (if you have the same file structure from when you ran

baml-init

, if you use the openapi generator, this is an field you can use that will re-run an arbitrary command every time any .baml file updates. It's common to use this field to drive the openapi-cli. That way you get new elixer client code every time you change your .baml files.

kirakos6970

12/05/2025, 1:28 AM

Thanks for responding @greg (BAML)! I just realized I missed the very first section in the docs where it describes

baml-cli

, which has exactly what I need, separate commands for

generate

and

serve

kirakos6970

12/05/2025, 1:30 AM

My other question is, does the rest generator not support the stream routes? I see that when serving the rest API it actually does support

/stream

routes, but those are not being generated in the OpenAPI spec, or am I missing something?

greg (BAML)

12/05/2025, 7:09 AM

That's correct. OpenAPI doesn't natively support streaming, so we can't generate streaming clients, although the streaming endpoints are available from the server.

emil

01/08/2026, 6:28 PM

@kirakos6970 passing the full client registry is now supported in the latest baml_elixir version 🙂

greg (BAML)

01/09/2026, 8:09 PM

That's awesome news, @User !!!

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