Answer generation model versions and lifecycle

Vertex AI Search offers multiple model versions for you to choose when generating answers. You can choose the model versions when using search summaries and answers and follow-ups.

Available models

Vertex AI Search uses two types of models for question and answering use cases:

Vertex AI LLM models that have been tested on question and answering tasks
Vertex AI Search models that are based on Vertex AI LLM models and further trained to address question and answering tasks

Vertex AI Search models share the same discontinuation date as their base Vertex AI LLM models. The base LLM model is available for six months after the release date of the next version of the model, per the Vertex AI model lifecycle policy. Leave enough time to migrate to new models before the discontinuation dates.

The following table lists model version specifications. When you set a model specification, the API uses the specified model to generate answers.

Model version	Generic			Healthcare
Model version	Description	Context window	Discontinuation date	Description	Context window	Discontinuation date
`stable`	The default model choice if the model version is not set. The `stable` model specification points to `gemini-1.5-flash-001/answer_gen/v1`. The model designated as `stable` changes periodically as new models and versions become available.	128K	N/A	The default model choice if the model version is not set. The `stable` model specification points to `gemini-1.5-flash-001/answer_gen/v1`. The model designated as `stable` changes periodically as new models and versions become available.	128K	N/A
`gemini-1.0-pro-001/answer_gen/v1`	Points to the `gemini-1.0-pro-001` model. The model is frozen after release.	32K	April 9, 2025	Not Available
`gemini-1.0-pro-002/answer_gen/v1`	A Vertex AI Search based on the `gemini-1.0-pro-002` model with additional training to address question and answering tasks. The model is frozen after release.	32K	April 9, 2025	A Vertex AI Search model based on the `gemini-1.0-pro-002 model` with additional training to address question and answering tasks. The model is frozen after release.	32K	April 9, 2025
`gemini-1.5-flash-001/answer_gen/v1`	A Vertex AI Search model based on the `gemini-1.5-flash-001` model with additional tuning to address question and answering tasks. The model is frozen after release.	128K	May 24, 2025	A Vertex AI Search model based on the `gemini-1.5-flash-001` model with additional tuning to address question and answering tasks. The model is frozen after release.	128K	May 24, 2025
`gemini-1.5-flash-001/answer_gen/v2`	A Vertex AI Search model based on the `gemini-1.5-flash-001` model with additional tuning (version 2) on blended structured and unstructured data to address question and answering tasks. The model is frozen after release.	128K	May 24, 2025	Not Available
`gemini-1.5-flash-002/answer_gen/v1`	A Vertex AI Search model based on the `gemini-1.5-flash-002` model with additional tuning to address question and answering tasks. The model is frozen after release.	128K	Sept 24, 2025	Not Available
`medlm-medium/answer_gen/v1`	Not Available			MedLM models have been trained on large-scale publicly available web information, public datasets and de-identified licenced private datasets with health and medical information.	32k	November 16, 2024
`preview`	The preview model specification points to the latest gemini-1.5-pro-002 model. The preview model is subject to change without notification. If you use this model, you might see changes in the responses when the model changes. If you want more consistency in the responses, select a specific model.	128K	N/A	`medlm-medium/answer_gen/v1`	32k	N/A

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