Improve Anthropic Vertex Claude content block handling

[daewoongoh]

Related GitHub Issue

Closes: #788

Description

This PR improves how completion response content blocks are handled when using Claude models through Anthropic Vertex.

The previous implementation only checked response.content[0], assuming that the first content block would always be a text block. This works for common text-only responses, but it is less defensive when Claude returns an empty content array or includes non-text blocks, such as thinking, before the actual text response.

This change updates the logic to search for the first available text block in the response content array. If no text block exists, it safely returns an empty string, preserving the existing fallback behavior.

Main changes:

• Updated Anthropic Vertex completePrompt to find the first text block instead of only checking response.content[0].
• Safely handles empty content arrays.
• Added test coverage for empty Claude content responses.
• Added test coverage for mixed Claude content responses where a non-text block appears before a text block.

Test Procedure

Added unit tests for the following cases:

1. Claude returns an empty content array and completePrompt returns an empty string.
2. Claude returns mixed content blocks and completePrompt returns the first text block.

Test command:

pnpm test src/api/providers/__tests__/anthropic-vertex.spec.ts

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Testing: New and/or updated tests have been added to cover my changes (if applicable).
• Documentation Impact: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Screenshots / Videos

N/A

Documentation Updates

• No documentation updates are required.

Additional Notes

This change aligns Anthropic Vertex completion handling with other providers by extracting the first available text block instead of assuming the first content block is always text.

Get in Touch

hehegwk_23849

Summary by CodeRabbit

• Bug Fixes
  • Improved prompt completion handling for Claude/Vertex responses so text is extracted correctly even when non-text content appears first.
  • Empty responses now return an empty string instead of failing or returning unexpected output.
  • Added test coverage for empty content and mixed content responses to prevent regressions.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 6d0a1f2f-3706-488e-87a2-5d0ae0b17416

📥 Commits

Reviewing files that changed from the base of the PR and between 1c728e7 and 2e8850e.

📒 Files selected for processing (2)

• src/api/providers/__tests__/anthropic-vertex.spec.ts
• src/api/providers/anthropic-vertex.ts

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📝 Walkthrough

Walkthrough

AnthropicVertexHandler.completePrompt now searches the response content array for the first block with type "text" and returns its text, falling back to an empty string if none exists, replacing the previous assumption that the first element was always text. Corresponding tests were added and one test reformatted.

Changes

Text Block Extraction Fix

Layer / File(s)	Summary
Safe text block extraction src/api/providers/anthropic-vertex.ts	completePrompt now finds the first "text"-typed content block instead of indexing the first element, returning "" if none is found.
Test coverage for edge cases src/api/providers/__tests__/anthropic-vertex.spec.ts	Added tests for empty content array and mixed thinking/text content blocks; reformatted an unrelated test call for readability.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Suggested labels: awaiting-review

Suggested reviewers: taltas, JamesRobert20, navedmerchant, hannesrudolph, edelauna

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately summarizes the provider-specific Claude content block handling fix.
Description check	✅ Passed	The PR description follows the template and covers the issue link, change summary, testing, checklist, screenshots, notes, and docs status.
Linked Issues check	✅ Passed	The code and tests match issue #788 by finding the first text block and returning an empty string for empty or textless content.
Out of Scope Changes check	✅ Passed	The changes stay focused on Anthropic Vertex parsing and regression tests, with no unrelated scope added.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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