Best cheap/free LLM API for rewriting 5,000 technical texts now that open code can't be used as an API anymore?

Hi,

I have around 5,000 texts that need proofreading and rewriting. They are mostly user manuals/instructions, so I need a reasonably smart and reliable model. Hallucinations or changing the actual meaning of the instructions would obviously be a problem.

Until now, I was using some of the free models through the OpenCode Zen/Go APIs. From what I understand, Go can no longer really be used as a general-purpose API outside supported clients.

What are the best alternatives now?

I'm specifically looking for:

• API access
• a model good enough for careful rewriting/proofreading
• extremely cheap, ideally free
• high enough limits to process ~5,000 texts

I don't need a frontier model if a smaller model can reliably preserve the original meaning.

Are there any genuinely unlimited or very high-limit free APIs left? Or any dirt-cheap models/providers you would recommend for this kind of batch processing?

Thanks!