Using content_pdf_file with a chat_openai object

[brynhum]

I have the following code snippet:

proofreader <- chat_openai(system_prompt = "You are a proofreader.")

proofreader$chat(
  "Find the issues in this file",
  content_pdf_file(fname)
)

Running it yields this error:

Error: Can't find method for generic `as_json(provider, x)`:
- provider: <ellmer::ProviderOpenAI>
- x       : <ellmer::ContentPDF>

I understand from the documentation for content_pdf_file that not all providers support PDF input, but according to OpenAI, direct PDF support was added in March 2025.

Is it possible to hook this up so that content_pdf_file works with chat_openai?

(Additional note: I think the above error message could also be improved to simply say that content_pdf_file is not yet supported for OpenAI chat objects.)