Defer sandbox acquisition and thread directory creation until first use to improve performance and reduce resource usage.
Changes:
- Add lazy_init parameter to SandboxMiddleware (default: true)
- Add ensure_sandbox_initialized() helper for lazy sandbox acquisition
- Update all sandbox tools to use lazy initialization
- Add lazy_init parameter to ThreadDataMiddleware (default: true)
- Create thread directories on-demand in AioSandboxProvider
- LocalSandbox already creates directories on write (no changes needed)
Benefits:
- Saves 1-2s Docker container startup for conversations without tools
- Reduces unnecessary directory creation and file system operations
- Backward compatible with lazy_init=false option
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>
