Supercharge Alter with Sub-agents! (+ Gemini 3 Flash & Mistral Creative)
For Christmas, we are offering you some Russian dolls.
Samuel ROY & Olivier Legris
December 19, 2025
Hey everyone,
Exciting news, Alter now supports sub-agents, enabling you to trigger multiple Alter actions within a single conversation.
Sub-agents let you create complex workflows and get more done, faster. Imagine having a team of experts working for you, all within a single Alter chat.
How to Use Sub-Agents
You can find the “Run Action” tool in your local tools
Open Tool Manager → Local Tools → Alter and find the "Run Action" tool.
The "Run Action" tool allows you to trigger other Alter actions within a conversation.
Grant access to the "Run Action" tool within a custom Alter action (e.g., "Council").
Invoke other actions by their ID in the system prompt. Use the action name for built-in actions, and find the ID for custom actions in the General settings.
Sub-agents performance really depends on the models you are using!
Ideally use /best, but some models tend to run sub-agents sequentially rather than in parallel (yes GLM 4.6, I’m looking at you)
How we use it at Alter
Council Strategy: Invoke multiple experts when brainstorming on an idea
Meeting Reporting on steroids: Based on the nature of the meeting, the meeting report actions will create Linear issues and/or Notion entries from the discussion.
MCP experts: Call the Google Spreadsheet specialist when you need to do some data manipulation on our analytics file and business plan.
Be very careful with your payloads for each Alter Action, especially with tool enabled.
For optimal performance, only select the tools you need per action.
New models in Alter this week
Gemini 3 Flash Preview and Mistral Small Creative are now available.
Have fun also playing with Cerebras GLM 4.6 :)
Cheers,
Sam & Olivier
Full Changelog
New Features & Enhancements
Run Action Tool: Run Alter actions as sub-agents within conversations, enabling complex multi-step workflows and parallel task execution
Stop Tool Calls: Added ability to stop tool calls mid-execution, similar to text streaming cancellation
Internationalization: Added support for Spanish and Chinese (Simplified and Traditional) languages with comprehensive translations across the app
Localized Tool Names: Tool names and descriptions are now translated and localized
Flow Messages Localization: Flow messages in conversation view are now localized
Faster Microphone Start: Improved microphone start performance
Screen Capture: Automatic restart of screen capture streams when the system stops them
New Models: Gemini 3.0 Flash and Mistral Small Creative
Bug Fixes & Stability
Notch: Fixed indexing indicator not showing when triggered manually
Microphone: Avoid low audio cutoff when transcriptions are coming in
MCP Tools: Return proper ToolError when no response is received from MCP tools
Crash Fixes: Fixed crash when saving messages
Data Races: Fixed data race in Models service