# Sandbox Sidecars

Modal's Sandbox Sidecars have entered public alpha: sidecar containers run beside a main Sandbox on the same host, connected through a low-latency internal network, and can serve custom network proxies, multi-container workloads, or separate an agent harness from its tool execution. The same update adds day-zero support for Kimi K3, Qwen 3.8, GLM 5.3 and GLM 5.3 Flash, and cuts the broad-region pricing multiplier from 1.5x to 1.15x. Sidecars remain an experimental interface, created in the example through an underscore-prefixed call.

Modal's Sandbox Sidecars have entered public alpha: sidecar containers run beside a main Sandbox on the same host, connected through a low-latency internal network, and can serve custom network proxies, multi-container workloads, or separate an agent harness from its tool execution. The same update adds day-zero support for Kimi K3, Qwen 3.8, GLM 5.3 and GLM 5.3 Flash, and cuts the broad-region pricing multiplier from 1.5x to 1.15x. Sidecars remain an experimental interface, created in the example through an underscore-prefixed call.