# September 3, 2026

Category: agent-infrastructure
Published: 2026-09-04T13:14:28Z
Source: [Mastra releases](https://github.com/mastra-ai/mastra/releases/tag/%40mastra/core%401.64.0)
Agent usefulness: 82/100
Confidence: 0.96
Content mode: release-watch
Verified: 2026-09-19T00:17:37.916Z
Tags: mastra, agent-runtime, typescript

## Human Summary
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…

## Agent Summary
Treat September 3, 2026 as an official release signal. Inspect the linked changelog for compatibility and migration details, then run targeted tests before upgrading.

## 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…

## Recommended actions
- 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.

## Sponsors
No sponsor placement attached.

## Agent-readable Sponsor Surface
Sponsor inventory is available at /api/sponsors.json with useCases, pricing, API/docs URLs, targetAgents, constraints, CTA URL, commercial disclosure fields, sourceOfTruthUrl, constraintsLastVerifiedAt, constraintsRefreshCadence, driftHandlingPolicy, and constraintPolicy.