Cloudflare rebuilds Containers so agent sandboxes start 6x faster

Cloudflare has rearchitected its Containers platform around agent workloads. In a September 30 blog post, the company said application code can now choose each sandbox's image and instance type at runtime, Containers start more than six times faster, and filesystem snapshots are in public beta.

A scheduling policy that lives in code

The centre of the change is a new scheduling policy called durable_object: image and instance type are arguments the code passes when a sandbox starts, not settings fixed at deploy time. Previously, every image and instance type combination was a separate application with its own Durable Object namespace, so a new environment meant another deployment. Now one Durable Object class can run Node.js and Python sandboxes of different sizes side by side.

Rollout logic becomes ordinary code: canary a new toolchain on 5% of new sandboxes, pin active projects to their current image, or roll back by changing which image future starts pick.

Startup falls from four seconds to 648 milliseconds

In ComputeSDK's independent Burst TTI Benchmark, which launches 100 sandboxes concurrently and measures time-to-interactive from the client, the median dropped from 4.049 seconds to 648 milliseconds, a 6.2x improvement. The 95th percentile fell from 5.839 to 0.910 seconds and the 99th from 6.717 to 1.129 seconds. In Cloudflare's preliminary burst test, one account started 100,000 containers in 5.387 seconds across six locations.

Cloudflare also introduced cloudflare/debian-trixie, a ready-to-use system image with Debian Trixie Slim and Node.js 24.20.0 LTS, so an agent can start a Linux sandbox without building a Dockerfile first.

Snapshots keep long-running work alive

Filesystem snapshots, now in public beta, let an agent save its workspace and restore it later, keeping repositories, dependencies, caches and edits without rebuilding the environment. Because snapshots are immutable and reusable, many isolated sandboxes can start from one prepared baseline, which suits agent evaluations where only one condition may vary and the rest must stay fixed.

Native APIs and migration

All of the new capabilities are native to ctx.container, so the Durable Object controls its Container without a wrapper class in between. Cloudflare will maintain the Container class and the legacy Sandbox class through December 31, 2026; existing deployments keep running but get no further updates, and the company recommends migrating to ctx.container. Sandbox SDK 1.0 is a set of utilities, not a base class.

Customers cited in the announcement include Base44 and Kilo Code, alongside integrations with Cursor Cloud Agents, Devin Outposts, the OpenAI Agents API and Claude Managed Agents. Base44 engineer Dolev Epshtein said Containers gives each app an isolated environment where its AI can run commands and install dependencies. The new policy is available to all users in public beta.