---
title: "Runtime Roundup: VM Sandboxes, Multi-node clusters, and more"
description: "Modal announced several new features at its inaugural Runtime conference. VM Sandboxes provide agents with full Linux computer access, supporting Docker stacks, databases, graphical environments, and kernel experimentation, already used at Linear, Legora, and Snorkel for coding agents and evals. Sandbox Sidecars run alongside main sandboxes with isolation but share a host, allowing agent code in the main sandbox while trusted operations run in a sidecar the agent cannot access, avoiding network round trips in execution-heavy loops. Modal Clusters, now generally available via @modal.clustered, enable multi-node jobs for training or serving trillion-parameter models, powering post-training at Decagon and real-time inference at Runway. Sticky Sessions maintain client state by routing to the same container using a session token, critical for voice model serving, while Endpoint Candidates allow mirroring production traffic to compare quality, latency, throughput, and cost before promoting."
---

# Runtime Roundup: VM Sandboxes, Multi-node clusters, and more

[Modal](https://yomu.fyi/company/modal) · Oct 1, 2026

**Type:** Announcement

## Summary

Modal announced several new features at its inaugural Runtime conference. VM Sandboxes provide agents with full Linux computer access, supporting Docker stacks, databases, graphical environments, and kernel experimentation, already used at Linear, Legora, and Snorkel for coding agents and evals. Sandbox Sidecars run alongside main sandboxes with isolation but share a host, allowing agent code in the main sandbox while trusted operations run in a sidecar the agent cannot access, avoiding network round trips in execution-heavy loops. Modal Clusters, now generally available via @modal.clustered, enable multi-node jobs for training or serving trillion-parameter models, powering post-training at Decagon and real-time inference at Runway. Sticky Sessions maintain client state by routing to the same container using a session token, critical for voice model serving, while Endpoint Candidates allow mirroring production traffic to compare quality, latency, throughput, and cost before promoting.

## Takeaways

- VM Sandboxes give agents a full Linux computer environment, supporting Docker stacks, databases, dev servers, graphical environments, and kernel work, already used by Linear, Legora, and Snorkel for coding agents and evals.
- Sandbox Sidecars run alongside the main sandbox with isolation but share a host, letting agent code run while credentials and harness logic run in an inaccessible sidecar, cutting network round trips.
- Modal Clusters via @modal.clustered enable multi-node coordinated containers for training or serving trillion-parameter models, used by Decagon for post-training and Runway for real-time inference.

## FAQ

### How do Sandbox Sidecars differ from regular sandboxes?

Sandbox Sidecars run on the same host as the main sandbox but with the same isolation. Agent code runs in the main sandbox while trusted operations like credentials run in the sidecar, inaccessible to the agent. Communication stays local to avoid network round trips.

### What is the deployment primitive for multi-node clusters on Modal?

Modal Clusters are deployed using a single decorator, @modal.clustered. They support jobs across several coordinated containers, such as training or serving trillion-parameter models.

### How do Sticky Sessions work in Modal?

By passing a session token with application requests, clients route back to the same running container they started on, maintaining state across requests. This is critical for real-time use cases like voice model serving.

**Tags:** [AI Agents](https://yomu.fyi/topic/ai-agents), [Containers](https://yomu.fyi/topic/containers), [Modal](https://yomu.fyi/topic/modal), [Real-time](https://yomu.fyi/topic/real-time)

- Source: [Modal](https://modal.com/blog/runtime-product-update-sandbox-endpoints)
- Source URL: https://modal.com/blog/runtime-product-update-sandbox-endpoints
- Ingested by Yomu: 2026-10-01T21:00:15.435Z

[Read original post](https://modal.com/blog/runtime-product-update-sandbox-endpoints)