Introducing Token Limiting for Mastra Agents

You can now cap token usage with TokenLimiterProcessor — a processor that enforces a limit on inputs and generated responses. Configure it as an inputProcessor to trim message history when it exceeds the cap, or as an outputProcessor to abort or truncate the response mid-stream.

Strategies range from a silent truncate to a hard abort. Additional configuration lets you pick between best-fit and contiguous trimming for inputs, and whole-response or per-stream-part for outputs.

Without a token limiter, a growing message history can bloat the model’s context window and get rejected mid-turn. Similarly, a long response can exceed the length expected by a UI or downstream service. With TokenLimiterProcessor you can catch both — trim the history before it hits the LLM, or stop the response the moment it crosses the threshold.