fix: set anthropic beta headers in vertex requests headers as well

[TejasGhatte]

Summary

This PR adds proper anthropic-beta header propagation for Vertex AI's Responses and ResponsesStream endpoints, ensuring beta feature headers are correctly filtered and applied when making Anthropic-on-Vertex requests.

Changes

• Applied FilterBetaHeadersForProvider and MergeBetaHeaders logic to the Vertex Responses method, replacing the previous unconditional SetExtraHeaders behavior with explicit beta header setting or deletion.
• Applied the same beta header logic to ResponsesStream, injecting the filtered beta headers into the request headers map before streaming begins.
• Removed an unnecessary blank line in Responses after the bifrostErr check.
• Removed redundant parentheses around a boolean condition in ChatCompletionStream.

Type of change

• Bug fix
• Feature
• Refactor
• Documentation
• Chore/CI

Affected areas

• Core (Go)
• Transports (HTTP)
• Providers/Integrations
• Plugins
• UI (React)
• Docs

How to test

Send a request to the Vertex Responses or ResponsesStream endpoint using an Anthropic model that requires a beta header (e.g., a model requiring interleaved-thinking-20250522). Verify that the anthropic-beta header is correctly set in the outgoing request and that the response is successful.

go test ./...

Breaking changes

• Yes
• No

Related issues

Security considerations

No security implications. Changes are limited to header propagation logic for Vertex AI Anthropic requests.

Checklist

• I read docs/contributing/README.md and followed the guidelines
• I added/updated tests where appropriate
• I updated documentation where needed
• I verified builds succeed (Go and UI)
• I verified the CI pipeline passes locally if applicable

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: e7ca6e4c-081b-4dc7-89e7-e9de0ab7f66a

📥 Commits

Reviewing files that changed from the base of the PR and between a75995b and 718f38c.

📒 Files selected for processing (1)

• core/providers/vertex/vertex.go

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Improved header handling for the Vertex provider: beta headers are now computed from merged context/network extras, set as a comma-joined header when present, and removed when none remain.

• Refactor

  • Simplified conditional logic to streamline branching and improve maintainability.

Walkthrough

The Vertex provider now explicitly filters merged network/context beta headers and sets or deletes anthropic.AnthropicBetaHeader in the Anthropic Responses flow. A redundant-parentheses cleanup was applied to the Gemini model check and a small context boundary was adjusted before extracting projectID and region.

Changes

Vertex Anthropic Beta Header Management

Layer / File(s)	Summary
Anthropic beta header filtering in Responses core/providers/vertex/vertex.go	Filters merged network + context extra headers for Vertex-scoped beta headers; sets anthropic.AnthropicBetaHeader to a comma-joined string when present, otherwise deletes the header (lines 1046–1051).
Minor cleanups and context adjustments core/providers/vertex/vertex.go	Removes redundant parentheses from the Gemini model check (line 913) and adjusts a small boundary/context before projectID/region extraction in Anthropic Responses (line 1018).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Suggested reviewers

• danpiths
• akshaydeo

Poem

🐰 I hopped through headers, sharp and neat,
Trimmed beta strings to make them meet,
Brushed off a parenthesis, light and quick,
Adjusted a boundary, small but slick,
Vertex and Anthropic—my tidy little feat!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: setting anthropic beta headers in Vertex requests, matching the core modification in the changeset.
Description check	✅ Passed	The description comprehensively covers the purpose, detailed changes, type, affected areas, testing instructions, breaking changes, and security considerations, matching the template structure.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 05-19-fix_set_anthropic_beta_headers_in_vertex_requests_headers_as_well

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.12.2)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[TejasGhatte]

• fix: set anthropic beta headers in vertex requests headers as well #3585 👈 (View in Graphite)
• dev

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Confidence Score: 5/5

Safe to merge — the change is a targeted header-propagation fix that follows the established pattern used by the direct Anthropic provider path.

The new beta-header block in Responses mirrors identical logic elsewhere in the codebase, operates on the same inputs, and is ordered correctly after SetExtraHeaders (which already excludes the beta header). ResponsesStream delegates to HandleAnthropicResponsesStream, which handles the header internally, so no parallel risk there. No data paths, auth flows, or external contracts are affected beyond header forwarding.

No files require special attention.

Important Files Changed

Filename	Overview
core/providers/vertex/vertex.go	Adds proper anthropic-beta header filtering and propagation in the Responses method; also removes unnecessary parentheses in ChatCompletionStream and a stray blank line. Changes follow the same FilterBetaHeadersForProvider + MergeBetaHeaders pattern used elsewhere in the codebase.

_{Reviews (2): Last reviewed commit: "fix: set anthropic beta headers in verte..." | Re-trigger Greptile}

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[akshaydeo]

Merge activity

• May 19, 10:34 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• May 19, 10:34 AM UTC: @akshaydeo merged this pull request with Graphite.