fix(openai-compat): decode base64 string data

[aayush-kapoor]

Background

reported in issue #12965

we decoded the base64 data properly in the anthropic provider but not in openai-compat

Summary

• added convertBase64ToUint8Array to properly decode the string before converting to text
• replaced Buffer.from(data, 'base64').toString('utf-8') with the edge-runtime-safe equivalent using convertBase64ToUint8Array

Manual Verification

na

Checklist

• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added (for bug fixes / features - run pnpm changeset in the project root)
• I have reviewed this pull request (self-review)

Related Issues

fixes #12965

[felixarntz]

@aayush-kapoor

we decoded the base64 data properly in the anthropic provider but not in openai-compat

the only production code change here is in the Anthropic provider - that seems to conflict with your statement? or maybe I'm misunderstanding?

[aayush-kapoor]

the only production code change here is in the Anthropic provider - that seems to conflict with your statement? or maybe I'm misunderstanding?

im not sure i understand? what i meant was - previously, decoding was done for properly in anthropic provider but we missed to do it in openai compat. the current change in packages/anthropic/src/convert-to-anthropic-messages-prompt.ts is only to ensure we don't use a node specific api for this

[felixarntz]

@aayush-kapoor ah my bad. I didn't actually see the OpenAI compatible non-test code change before 🤦‍♂️

All good!

[vercel-ai-sdk]

🚀 Published in:

Package	Version
@ai-sdk/alibaba	1.0.8
@ai-sdk/amazon-bedrock	4.0.72
@ai-sdk/anthropic	3.0.53
@ai-sdk/baseten	1.0.36
@ai-sdk/cerebras	2.0.37
@ai-sdk/deepinfra	2.0.37
@ai-sdk/fireworks	2.0.38
@ai-sdk/google-vertex	4.0.71
@ai-sdk/huggingface	1.0.35
@ai-sdk/moonshotai	2.0.8
@ai-sdk/openai-compatible	2.0.33
@ai-sdk/togetherai	2.0.37
@ai-sdk/vercel	2.0.35
@ai-sdk/xai	3.0.64