Change AI Assistant to use new API introduced in Drupal AI ~1.2.0

Problem/Motivation

Drupal AI 1.2.3 was released on 12 Nov 2025 by marcus_johansson, introducing the improved AI Assistant API and continuing the deprecation of the legacy 1.0.0 API.

When visiting:
/admin/config/ai/ai-assistant/ai_agent_assistant

the following warning appears:

Warning: This assistant is using the old AI Assistant API for 1.0.0. Please create a new one and migrate the settings to the new one. The old one will be removed in 2.0.0.

Proposed resolution

• Change drupal/ai and drupal/ai_agents to ~1.2.0 in the composer.json file
• Create a new AI Assistant entity using the new API structure introduced in AI 1.2.x.
• Remove or disable the old assistant to avoid breakage with AI 2.0.

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ✅ Release varbase-10.1.0-rc1, varbase_ai_agents-1.0.4

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• chore(ai): #3558339 Changed AI Assistant to use new API introduced in Drupal AI ~1.2.0