Mastra 1.67.0 adds a persisted workflow-builder agent and @mastra/connect, which turns platform integrations into tools your app never holds secrets for
The 2026-09-15 @mastra/core 1.67.0 release enables a Studio Workflow Builder backend via a `workflowBuilder` editor option — a hidden editor-owned agent that authors persisted workflow definitions, with `GET /editor/workflow-builder/settings` and `POST /editor/workflow-builder/stream` endpoints gated by stored-workflow permissions. The new @mastra/connect package converts Mastra Platform integration connections into agent tools executed through the platform connection proxy, injecting credentials and refreshing tokens so application code never touches provider secrets, with live tool discovery and optional allowlisting. Tools also gained per-call background dispositions (foreground/deferred/awaited) with caller-scoped completion signals, and threads can now be reassigned to a new resourceId; note two breaking changes, `subscribeQueuedMessages` becomes `subscribeThreadEvents` and ArchilFilesystem.grep() becomes diskGrep().
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