feat(ai): Chat history and auto function calling for server templates

[hsubox76]

Based on initial work in #9742

API design doc (internal): https://docs.google.com/document/d/1ecqEdvMMkx1QSInhPVmqF9yOXSJaCgGlnxOc9GshcEY/edit?resourcekey=0-t1kgF5b2FKpRexQGQVc58Q&tab=t.qqsqzzhfm8vt

• Created a new TemplateChatSession.
• To avoid code duplication, extracted most of the functionality of ChatSession to a ChatSessionBase abstract class and allowed ChatSession and TemplateChatSession to extend it and add a few methods and types specific to their use cases.
• Did not add integration test yet as the prod server won't be available until release, but tested against staging server manually.

[changeset-bot]

🦋 Changeset detected

Latest commit: a0b3839

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@firebase/ai	Minor
firebase	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[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 significantly enhances the AI SDK by introducing robust chat history management and automatic function calling capabilities specifically for server-side templates. By refactoring core chat logic into a shared base class and providing a dedicated TemplateChatSession, it streamlines the development of interactive AI experiences that leverage predefined templates and external tools, making AI interactions more dynamic and stateful.

Highlights

• Template Chat Sessions: Introduced TemplateChatSession to manage chat interactions with server-side AI templates, allowing for persistent chat history.
• Automatic Function Calling for Templates: Enabled automatic function calling within TemplateChatSession, allowing the model to invoke predefined functions based on chat context.
• Refactored Chat Logic: Created a new abstract base class, ChatSessionBase, to centralize common chat session logic, including history management and automatic function calling, which ChatSession and TemplateChatSession now extend.
• New startChat() Method: Added a startChat() method to TemplateGenerativeModel for easily initiating a new TemplateChatSession.
• Typo Correction: Corrected a typo from maxSequentalFunctionCalls to maxSequentialFunctionCalls in RequestOptions.

🧠 New Feature in Public Preview: You can now enable Memory to help Gemini Code Assist learn from your team's feedback. This makes future code reviews more consistent and personalized to your project's style. Click here to enable Memory in your admin console.

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 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 counter productive. 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. ↩

[gemini-code-assist]

Code Review

This pull request introduces TemplateChatSession and ChatSessionBase to enable template-based chat functionality and centralize common chat session logic. The TemplateGenerativeModel now supports starting a chat session via startChat(). The ChatSession class has been refactored to extend ChatSessionBase. New types like StartTemplateChatParams and TemplateGenerateContentRequest are added to support this feature, and a typo in maxSequentalFunctionCalls was corrected to maxSequentialFunctionCalls. Review feedback highlights a potential TypeError crash in ChatSessionBase when handling response.candidates[0].content if it's null or undefined. Additionally, ChatSessionBase should be exported for better extensibility, and public interfaces like StartTemplateChatParams and TemplateGenerateContentRequest require TSDoc comments for their properties. The _formatRequest method in TemplateChatSession can be made more type-safe, and the [key: string]: unknown; index signature in TemplateGenerateContentRequest should be reconsidered for a more type-safe approach.

[DellaBitta]

👍

[rachelsaunders]

Are there any changes that a dev needs to do within their code for regular chat (like non-server prompt template chat) to accommodate this change?

[hsubox76]

This is a result of doing something that makes the code work better and makes the documentation messier - making ChatSession and TemplateChatSession extend a base class, ChatSessionBase, in order to avoid duplicate code. Unfortunately that means a method shared by both extended classes (getHistory) is only going to be found by clicking through to ChatSessionBase, which is linked above.

[rachelsaunders]

But no changes for the developer in their actual source code for their app, right?

[hsubox76]

Nope, just harder to read the documentation.

[rachelsaunders]

nit - ChatSession should be tagged as code

[hsubox76]

Done, also rewrote to reflect this is a base class for multiple ChatSession variants and not just literally ChatSession (it's only two right now but it could be more in the future).