fix(ai-gemini): remove redundant text part from functionResponse messages

[jherr]

Summary

• Fixes @tanstack/ai-gemini Error 400 when sending a functionResponse #436 — tool result messages were emitting both a { text } part and a { functionResponse } part in the same Gemini API message
• Newer models (gemini-3.1-flash-lite, gemma-4) reject this combination with a 400 error
• The fix skips emitting the redundant text part for role: "tool" messages since the content is already in the functionResponse

Test plan

• Updated existing tests to assert tool-result text parts are no longer emitted
• All 65 ai-gemini tests pass
• Full test suite (29 projects) passes

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Resolved a 400 error when sending tool results to newer Gemini models by changing how tool response messages are formatted. Tool-result content is no longer included as redundant text parts, preventing API rejections and improving reliability when delivering tool outputs to Gemini.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 4691cbaf-aa67-42a4-8dd4-87738ffb8082

📥 Commits

Reviewing files that changed from the base of the PR and between 16609f7 and c2ce593.

📒 Files selected for processing (1)

• packages/typescript/ai-gemini/tests/gemini-adapter.test.ts

🚧 Files skipped from review as they are similar to previous changes (1)

• packages/typescript/ai-gemini/tests/gemini-adapter.test.ts

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📝 Walkthrough

Walkthrough

This PR removes redundant text parts from Gemini functionResponse messages, updating the adapter to avoid including text content for tool-role messages to prevent Gemini API 400 errors.

Changes

Cohort / File(s)	Summary
Changeset Documentation /.changeset/fix-gemini-function-response.md	Adds a changeset for a patch release to document the fix removing redundant text parts from functionResponse messages for @tanstack/ai-gemini.
Adapter Logic packages/typescript/ai-gemini/src/adapters/text.ts	Adjusts GeminiTextAdapter.formatMessages so text-only message content is not converted into a text part when msg.role === 'tool'; text conversion now occurs only when msg.role !== 'tool'.
Tests packages/typescript/ai-gemini/tests/gemini-adapter.test.ts	Updates test assertions to expect functionResponse parts without redundant tool-result text parts and to assert the presence of only the follow-up text where applicable.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐇 I nibbled code in moonlight's gleam,
Removed the duplicate text from the stream.
Now Gemini nods, no 400 cry—
One clear part, and spirits fly. ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Description check	❓ Inconclusive	The PR description provides the motivation (issue #436), explains the fix, test coverage, and acknowledges generation with Claude Code; however, it doesn't follow the provided template structure.	Consider restructuring the description to explicitly follow the template with '## 🎯 Changes' section, checklist items, and '## 🚀 Release Impact' section for consistency.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: removing redundant text parts from Gemini functionResponse messages.
Linked Issues check	✅ Passed	The PR fully addresses issue #436 by preventing duplicate text and functionResponse parts in tool result messages, ensuring Gemini API compliance without 400 errors.
Out of Scope Changes check	✅ Passed	All changes directly address the issue: removing redundant text parts from functionResponse messages. The changeset, code fix, and test updates are all scope-aligned.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ 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 pr-436

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[github-actions]

🚀 Changeset Version Preview

1 package(s) bumped directly, 3 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
@tanstack/ai-gemini	0.8.6 → 0.8.7	Changeset
@tanstack/ai-code-mode-models-eval	0.0.4 → 0.0.5	Dependent
ts-svelte-chat	0.1.30 → 0.1.31	Dependent
ts-vue-chat	0.1.30 → 0.1.31	Dependent

[nx-cloud]

View your CI Pipeline Execution ↗ for commit c2ce593

Command	Status	Duration	Result
nx affected --targets=test:sherif,test:knip,tes...	✅ Succeeded	1m 58s	View ↗
nx run-many --targets=build --exclude=examples/**	✅ Succeeded	46s	View ↗

---

☁️ Nx Cloud last updated this comment at 2026-04-13 17:48:30 UTC

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commit: c2ce593