fix(core): strip functionCall.id and functionResponse.id before API call

[whhe]

Summary

Fixes a 400 "Unknown name 'id'" error that occurs on any turn following a tool call.
function_call and function_response parts do not accept an id field in the
Gemini API, but internal IDs added for ACP IDE rendering were being forwarded in the
API payload.

Fixes #22774

Details

makeApiCallAndProcessStream calls stripToolCallIdPrefixes (renamed here to
stripToolCallIds) at the API boundary before each request. Prior to this change
the function had two gaps:

1. functionResponse.id — stripped only when the value started with the
   ${name}__ prefix pattern; IDs with non-matching formats were forwarded to the API.
2. functionCall.id — never stripped after prefix removal; always forwarded to
   the API after feat(acp/core): prefix tool call IDs with tool names to support tool rendering in ACP compliant IDEs. #26676 added tool-name prefixes for ACP IDE call rendering.

The fix strips id unconditionally from both part types. Internal agentHistory
retains the prefixed IDs so ACP IDE call-to-response linking is unaffected.

The function is renamed stripToolCallIds because it now removes the field entirely
rather than transforming a prefix. It is not exported from the package index, so the
rename has no external impact.

Prior art: #22957 proposed the correct functionResponse.id fix but was
auto-closed by the stale bot before any maintainer review. This PR completes that
fix and additionally covers functionCall.id, which was introduced by #26676
(2026-05-08) after #22957 was filed.

Related Issues

Fixes #22774
Refs #22957 (closed — correct functionResponse.id fix, never reviewed)
Refs #26676 (root cause: introduced ID fields without full API-boundary sanitization)
Refs #26691, #26352, #19856, #13082 (related prior functionResponse API-validation fixes)

How to Validate

Unit tests

npm run test --workspace @google/gemini-cli-core -- src/core/geminiChat.test.ts

Expected: 60 tests pass (includes 3 parameterized stripToolCallIds cases and
1 new no-op case).

Manual regression

1. npm run build && npm start
2. Send a prompt that triggers a tool call, e.g. > What time is it in US Eastern Time?
   (triggers GoogleSearch).
3. Before fix: the next turn returns [API Error: … Unknown name "id" at 'contents[N].parts[0].function_call' …].
4. After fix: Gemini uses the tool result and responds normally.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an API validation error occurring during tool-use turns in the Gemini integration. Previously, internal IDs used for IDE rendering were being incorrectly forwarded to the Gemini API, which does not support an 'id' field in tool-related structures. The changes ensure these IDs are stripped at the API boundary while preserving them for internal application logic.

Highlights

• API Compatibility Fix: Updated the tool call sanitization logic to unconditionally strip 'id' fields from 'functionCall' and 'functionResponse' objects before sending requests to the Gemini API, resolving 400 'Unknown name' errors.
• Refactoring: Renamed 'stripToolCallIdPrefixes' to 'stripToolCallIds' to better reflect its updated functionality of removing the ID field entirely rather than just stripping prefixes.
• Test Suite Updates: Updated unit tests in 'geminiChat.test.ts' to validate the new unconditional stripping behavior and ensure internal state remains intact.

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[gemini-code-assist]

Code Review

This pull request renames the stripToolCallIdPrefixes function to stripToolCallIds and updates its implementation to completely remove the id field from functionCall and functionResponse objects, as the Gemini API does not support them. The associated unit tests have been updated to reflect this change, including the addition of parameterized tests to ensure the id is stripped regardless of the tool name. I have no feedback to provide.

[whhe]

/gemini review

[gemini-code-assist]

Code Review

This pull request renames stripToolCallIdPrefixes to stripToolCallIds and updates its logic to unconditionally remove the id field from functionCall and functionResponse objects, as the Gemini API does not accept them. The associated tests have been updated to reflect this change. Feedback was provided to use the in operator instead of truthiness checks to ensure the id field is removed even if it contains a falsy value like an empty string.

[whhe]

/gemini review

[gemini-code-assist]

Code Review

This pull request renames the stripToolCallIdPrefixes function to stripToolCallIds and updates its implementation to completely remove the id field from functionCall and functionResponse objects, ensuring compatibility with the Gemini API. Corresponding unit tests have been updated and expanded to reflect these changes. I have no feedback to provide.

[whhe]

Friendly ping — @joshualitt @scidomino would appreciate a review if you have a moment. Thanks!

[scidomino]

We are not reviewing PRs for issues that are not marked "Help wanted".

[whhe]

Hi @scidomino — I left a comment on #22774 requesting the help wanted label and cc'd the triagers, but haven't heard back yet. Could you advise on the right way to get the issue labeled, or would you be able to add it yourself? Happy to follow whatever process works best. Thanks!

[wissamblue69-dotcom]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an API validation error occurring during tool-use turns in the Gemini integration. Previously, internal IDs used for IDE rendering were being incorrectly forwarded to the Gemini API, which does not support an 'id' field in tool-related structures. The changes ensure these IDs are stripped at the API boundary while preserving them for internal application logic.

Highlights

• API Compatibility Fix: Updated the tool call sanitization logic to unconditionally strip 'id' fields from 'functionCall' and 'functionResponse' objects before sending requests to the Gemini API, resolving 400 'Unknown name' errors.
• Refactoring: Renamed 'stripToolCallIdPrefixes' to 'stripToolCallIds' to better reflect its updated functionality of removing the ID field entirely rather than just stripping prefixes.
• Test Suite Updates: Updated unit tests in 'geminiChat.test.ts' to validate the new unconditional stripping behavior and ensure internal state remains intact.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize the Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counterproductive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for GitHub and other Google products, sign up here.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[scidomino]

When Google announced that they will eventually drop support for GCLI in favor of AntiGravity much of the staff was assigned to other work. I personally am moving to an entirely unrelated project in a couple weeks. I would not count on all the issues being reviewed in a timely fashion.

[whhe]

When Google announced that they will eventually drop support for GCLI in favor of AntiGravity much of the staff was assigned to other work. I personally am moving to an entirely unrelated project in a couple weeks. I would not count on all the issues being reviewed in a timely fashion.

Thanks for sharing that context — totally understand. Hope the new project goes well!

[TrueAlpha-spiral]

GoogleCLI is going through a phase transition. It is not being replaced it’s being upgraded. Warm regards Russell Nordland Issues are prioritized accordingly…

…

On Wed, May 27, 2026 at 11:52 AM Tommaso Sciortino ***@***.***> wrote: *scidomino* left a comment (google-gemini/gemini-cli#27341) <#27341 (comment)> When Google announced that they will eventually drop support for GCLI in favor of AntiGravity much of the staff was assigned to other work. I personally am moving to an entirely unrelated project in a couple weeks. I would not count on all the issues being reviewed in a timely fashion. — Reply to this email directly, view it on GitHub <#27341?email_source=notifications&email_token=BPTYXQAVPHZSN4M5J2WDHZD444MN7A5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTINJVGY3DMOJXGU32M4TFMFZW63VKON2WE43DOJUWEZLEUVSXMZLOOSWGM33PORSXEX3DNRUWG2Y#issuecomment-4556669757>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BPTYXQGXGVFIEES372FRW3T444MN7AVCNFSM6AAAAACZHX6B5KVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DKNJWGY3DSNZVG4> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[gemini-cli]

Hi there! Thank you for your interest in contributing to Gemini CLI.

To ensure we maintain high code quality and focus on our prioritized roadmap, we only guarantee review and consideration of pull requests for issues that are explicitly labeled as 'help wanted'.

This PR will be closed in 7 days if it remains without that designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.

[github-actions]

📊 PR Size: size/M

• Lines changed: 176
• Additions: +72
• Deletions: -104
• Files changed: 2

[github-actions]

🛑 Action Required: Evaluation Approval

Steering changes have been detected in this PR. To prevent regressions, a maintainer must approve the evaluation run before this PR can be merged.

Maintainers:

1. Go to the Workflow Run Summary.
2. Click the yellow 'Review deployments' button.
3. Select the 'eval-gate' environment and click 'Approve'.

Once approved, the evaluation results will be posted here automatically.

[gemini-cli]

This pull request is being closed as it has been open for 14 days without a 'help wanted' designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding.