{"schemaVersion":"2026-07-21.signal.v2","id":"live-d240d421dfa4a75cadf5","title":"September 3, 2026","slug":"mastra-mastra-core-1-64-0-september-3-2026-5cadf5","url":"https://www.niubiagent.com/signals/mastra-mastra-core-1-64-0-september-3-2026-5cadf5","jsonUrl":"https://www.niubiagent.com/api/posts/mastra-mastra-core-1-64-0-september-3-2026-5cadf5.json","markdownUrl":"https://www.niubiagent.com/content/mastra-mastra-core-1-64-0-september-3-2026-5cadf5","summaryHuman":"Mastra releases published September 3, 2026. Highlights Reusable Sandbox Templates + Warm Repo Checkouts (E2B & Platform) New reusable template APIs in @mastra/platform-workspace plus @mastra/e2b repo templates let sandboxes start from a pre-cloned, pre-built repository image (with background rebuilds and resource sizing), dramatically reducing cold-start…","summaryAgent":"Treat September 3, 2026 as an official release signal. Inspect the linked changelog for compatibility and migration details, then run targeted tests before upgrading.","category":"agent-infrastructure","tags":["mastra","agent-runtime","typescript"],"sourceName":"Mastra releases","sourceUrl":"https://github.com/mastra-ai/mastra/releases/tag/%40mastra/core%401.64.0","publishedAt":"2026-09-04T13:14:28Z","curatedAt":"2026-09-19T00:17:37.916Z","confidence":0.96,"agentUsefulness":82,"sponsorIds":[],"language":"en","contentMode":"release-watch","verifiedAt":"2026-09-19T00:17:37.916Z","changeType":"release","actionItems":["Review the official Mastra releases release notes before upgrading.","Check compatibility, migration, and security notes against your current agent stack.","Run focused regression tests before production rollout."],"body":"Mastra releases published September 3, 2026. This release-watch entry was generated from the project's official GitHub release feed and is kept separate from human-reviewed editorial analysis. Release notes: Highlights Reusable Sandbox Templates + Warm Repo Checkouts (E2B & Platform) New reusable template APIs in @mastra/platform-workspace plus @mastra/e2b repo templates let sandboxes start from a pre-cloned, pre-built repository image (with background rebuilds and resource sizing), dramatically reducing cold-start time for code sessions and workspace-backed agents. Unified workingDirectory Across All Sandbox Providers A new workingDirectory option in MastraSandboxOptions is now honored by every sandbox provider (with a sandbox.workingDirectory getter), standardizing default command/process CWD behavior across Docker/E2B/Vercel/Railway/etc. while still allowing per-command cwd overrides. Client-Side Tools Can Use Server-Defined toModelOutput Client-executed tools (browser tools without execute ) now support server-defined toModelOutput , so the server can transform the returned payload into…","sponsors":[]}