gemini-3.5 models not supported on firestore-multimodal-genai extension

[REQUIRED] Step 2: Describe your configuration

Extension name: firestore-multimodal-genai
Extension version: 1.0.5
Configuration values:Provider: vertex-ai
Gemini model: gemini-3.5-flash-lite
Cloud Functions location: us-central1
Vertex AI API Location (Optional): global

[REQUIRED] Step 3: Describe the problem

Firebase Support reviewed this issue and identified a likely root cause: gemini-3.5-flash-lite is currently missing from the supported modelReferences array in the extension client implementation:

https://github.com/GoogleCloudPlatform/firebase-extensions/blob/b9a2838a17bafcc8b4567a6f7cbd60b071f9c02f/firestore-multimodal-genai/functions/src/generative-client/genkit.ts#L102

In the same project and extension setup, gemini-2.5-flash works, but gemini-3.5-flash-lite fails.

Steps to reproduce:

Configure the firestore-multimodal-genai extension with:
Provider = vertex-ai
Gemini model = gemini-3.5-flash-lite
Cloud Functions location = us-central1
Vertex AI API Location (Optional) = global

Trigger document processing through the extension.

Expected result
gemini-3.5-flash-lite should be recognized as a supported model and generate content successfully through the extension.

Actual result
The extension fails to generate content.

Relevant logs:
Error: [firestore-multimodal-genai] Error calling Gemini API for document 'blah': failed to generate content, see function logs for details
SyntaxError: Unexpected token '<', ")
at parseJSONFromBytes (node:internal/deps/undici/undici:5880:19)
at successSteps (node:internal/deps/undici/undici:5861:27)
at fullyReadBody (node:internal/deps/undici/undici:4753:9)
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
at async consumeBody (node:internal/deps/undici/undici:5870:7)
at async throwErrorIfNotOK (/workspace/node_modules/post_fetch_processing.js:29:27)
at async generateContentStream (/workspace/node_modules/generate_content.js:99:5)
at async VertexLanguageClient.generate (/workspace/lib/generative-client/vertex_ai.js:63:36)
at async /workspace/lib/index.js:71:24

Firebase Support advised filing this GitHub issue because gemini-3.5-flash-lite appears to be missing from the extension’s supported model list.

I realize extensions are being deprecated but the earlier gemini models are being deprecated earlier so can we get a quick update to support the new models?

Start in firestore-multimodal-genai/functions/src/generative-client/genkit.ts around line 102, where the supported modelReferences array is identified. Reproduce the extension configuration with Vertex AI and gemini-3.5-flash-lite, then verify that the model is recognized and document processing generates content successfully.

Written by the indexing model from the issue text.