[Bug]:Codegen in 3.0.78 fails with JsonParseException: Unrecognized token 'openapi':

Description

Codegen failing with exception:

[main] ERROR io.swagger.parser.SwaggerCompatConverter - failed to read resource listing
com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'openapi': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')

This worked prior to 3.0.78

Swagger Codegen Version

3.0.78

Language / Generator

java

OpenAPI/Swagger Spec

I can not determine what is the relevant part of the api spec. It passes validation, e.g. in swagger editor

See - https://gist.github.com/195858/44676d1bf4dbc0b74183258df67c502f

Related Issues / Repos

Environment

• OS: Ubuntu/github action, MacOs
• Java Version: odk 25
• Build Tool:CLI
• Swagger Codegen CLI version: 3.0.78 (installed via brew install swagger-codegen_

Additional Context

Checklist

• I have searched the existing issues to make sure this is not a duplicate.
• I have included a minimal and reproducible spec example.
• [ x I have explained how to reproduce the issue.
• I have specified which generator/language is affected.

Start with SwaggerCompatConverter and reproduce the failure using the referenced gist, Swagger Codegen CLI 3.0.78, and the reported environments. Compare this behavior with the prior release and inspect why the valid OpenAPI document is being parsed as JSON; done means the CLI accepts the document and code generation completes.