fix(vertex/anthropic): passing beta header only for structured outputs

[aayush-kapoor]

Background

Currently, the vertex anthropic provider only checked the model ID and would pass the beta header for all models that allow structured outputs.

But vertex doesn't yet support passing these beta headers. So we would get an error like this even for a simple generateText function

This PR also addresses a bug when strict mode is enabled and the header is passed (shouldn't happen)

Summary

• only pass the beta header when actually using native output format and when using strict tools

Manual Verification

the example google-vertex-anthropic-sonnet-4-5.ts was used to verify the fix (was failing before)

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)

Future Work

ideally, we handle this shortcoming in our implementation of vertex provider

• if beta header is to be passed, we intercept it and then we could pass a providerOption saying structuredOutputMode: 'jsonTool' (continued in this PR after the comment fix(vertex/anthropic): passing beta header only for structured outputs #11015 (comment))

Related Issues

Fixes #10981

[aayush-kapoor]

all the commits till here fix the original issue.

commits after this point are to account for the change in example /examples/ai-core/src/generate-object/google-vertex-anthropic.ts which fails in the current flow

that example will fail and give an error. but to enable it for users who want to use the latest anthropic models with vertex, we force the use of JSON tool

[lgrammel]

code looks good but test changes indicate a regression might have been introduced

[aayush-kapoor]

code looks good but test changes indicate a regression might have been introduced

expected behaviour, see comment above!

[gr2m]

code changes look good but haven't tested end-to-end, I assume you did

[aayush-kapoor]

code changes look good but haven't tested end-to-end, I assume you did

not with UI example (there isn't one for vertex or structured outputs) but yes, tested with different variations of examples (passing tools, tools + object output)

[lgrammel]

why is this additional condition needed?

[aayush-kapoor]

just as an extra check - to completely rule out header being sent for functions that don't need it. otherwise it could send it for simple text gen too. i verified with expected behaviour for approx 6 different cases (combinations essentially)

[lgrammel]

This also seems to fix a bug around strict mode and setting the header. Can this either be separated out into a different PR or added to the description?

[aayush-kapoor]

This also seems to fix a bug around strict mode and setting the header. Can this either be separated out into a different PR or added to the description?

EDIT: added in the description

[AVtheking]

@aayush-kapoor why it is required to send the structured output header when strict mode is off ?