Bastion Review (2026): Pricing, Features & Honest Verdict

TLDR

Bastion deploys isolated Linux VMs so each background coding agent runs sandboxed. Instead of a shared container, every agent gets its own KVM virtual machine, defined by JSON templates, running on your workstation or a cloud instance. It is a brand-new Show HN entrant in a crowded space, promising but unproven. Best for: developers running parallel coding agents who want real isolation. Price: Custom, self-hosted on your own hardware. Rating: 6.2/10.

What is Bastion?

Bastion is a developer tool that gives each coding agent its own isolated Linux virtual machine. The problem it targets is specific: when you let background AI coding agents run autonomously, you do not want them touching your real file system, your cloud credentials or your production database, and you do not want two agents working in parallel to step on each other. Bastion’s answer is a separate VM per agent, so each one has full control of its own environment, from the file system to background processes, without affecting anything outside.

It uses KVM, the Linux kernel’s virtualization layer, which means it runs on any Linux system with KVM support, from a local workstation up to a cloud instance like AWS EC2. Environments are not configured by hand; you define them with schema-validated JSON templates, so an agent’s setup is reproducible and version-controllable. You interface with the running VMs through OpenCode or plain SSH. Bastion launched recently as a Show HN, so it is early, and it enters a category that already includes well-funded players. We verified it is a real, shipping tool rather than a waitlist, but it is young.

Why this matters now comes down to how coding agents have changed in the last year. Developers increasingly run agents in the background, sometimes several at once, each grinding through a task with little supervision. That autonomy is useful, but it raises the stakes of a bad command. By early 2026 the whole industry had noticed: Cloudflare, Vercel and Modal all shipped sandbox features, and dedicated providers like E2B and Daytona built entire businesses around the problem. Bastion is one developer’s take on the same need, betting that a full VM per agent is the right level of isolation and that some people would rather run it themselves than rent it.

What Are Bastion’s Key Features?

One Isolated VM Per Agent

This is the core idea. Rather than running agents in shared containers, Bastion spins up a full virtual machine for each one. That gives stronger isolation: an agent gets complete control of its dev environment, and if it makes a destructive mistake, the blast radius is its own disposable VM. For anyone nervous about handing autonomy to a coding agent, VM-level separation is a meaningfully harder wall than a container, and it is the main reason to pick Bastion over lighter sandboxes.

Parallel Execution Without Conflicts

Because each agent runs in its own machine, you can run many at once with no runtime conflicts between them. One agent installing a system package or holding a port does not interfere with another. For developers experimenting with fleets of background agents, each tackling a different task, this clean separation is the practical payoff. It removes the class of bugs that come from agents sharing one environment.

JSON-Templated Environments

Bastion environments are initialized from schema-validated JSON templates instead of manual configuration. You declare what the agent’s environment should contain, and Bastion builds it the same way every time. Schema validation catches mistakes before a VM spins up. This makes environments reproducible and easy to keep in version control, which is the right approach for a workflow where you may launch and tear down many machines.

Runs Anywhere With KVM

Bastion is not locked to one cloud. Because it builds on KVM, it runs on a local Linux workstation for development and the same setup scales to cloud instances like AWS EC2 for heavier work. You connect through OpenCode or SSH, both of which fit existing developer habits. The trade-off is the KVM requirement: you need a Linux host with hardware virtualization, so it will not run natively on a Mac or Windows machine.

How Much Does Bastion Cost?

Bastion does not publish public pricing, which is normal for a brand-new Show HN project. Because it is self-hosted and runs on your own KVM-capable hardware, your real cost is the underlying compute rather than a subscription. Running it on a Linux workstation you already own is effectively free beyond electricity; running it on AWS EC2 means you pay for the instances that host the VMs.

That is a different model from the hosted sandbox services it competes with, which charge for the managed convenience. E2B, the popular hosted option, has a free Hobby tier with a one-time credit and a Pro plan around $150 per month, billing roughly $0.05 per vCPU-hour. Daytona prices sandboxes usage-based from about $0.09 per hour for a small configuration. Modal offers serverless sandboxes with around $30 per month in free credits and usage-based pricing after.

So the cost comparison is really self-hosting versus managed. With Bastion you trade the convenience of a hosted API for control and potentially lower spend if you already have the hardware. With the funded alternatives you pay for someone else to run the infrastructure and keep it fast. Which is cheaper depends entirely on your scale and whether you have a Linux box to run it on. A solo developer with a spare Linux workstation could run a handful of agent VMs for essentially the cost of power. A team spinning up dozens of short-lived agents per day across cloud instances might find a usage-based hosted service simpler to reason about, since they only pay while an agent is actually running rather than for an always-on host.

Who is Bastion Best For?

Use Bastion if you run multiple background coding agents and you want each one genuinely isolated in its own VM rather than a shared container. It suits developers and small teams who are comfortable with Linux, KVM and SSH, and who would rather self-host on their own workstation or cloud instance than pay for a managed service. If your worry is an autonomous agent doing damage, the VM boundary is the feature you came for.

Skip Bastion if you want a polished, managed sandbox with an API, dashboards and support, in which case a funded platform like E2B or Daytona will be smoother today. Skip it too if your host is macOS or Windows without a Linux KVM environment, since that is a hard requirement. And if you are running production-critical workloads, the youth of the project is a real consideration; this is an early tool, not a proven platform.

Best Bastion Alternatives

E2B

E2B is the best-known hosted sandbox for AI agents, offering a managed API where agents get a sandboxed environment with a terminal and tools. It has a free Hobby tier with a starting credit and a Pro plan around $150 per month, billing about $0.05 per vCPU-hour. Choose E2B if you want a mature, hosted service and would rather not run your own infrastructure.

Daytona

Daytona provides fast, usage-based sandboxes for agents, priced from roughly $0.09 per hour for a small configuration. It focuses on quick startup times and pay-as-you-go economics, which suits bursty agent workloads. Pick Daytona if you want managed sandboxes with granular hourly billing rather than self-hosting on your own hardware.

Modal

Modal is a serverless compute platform that offers agent sandboxes alongside general workloads, with around $30 per month in free credits and usage-based pricing after. It uniquely supports GPU access inside sandboxes, which matters if your agents need it. Choose Modal if you want serverless flexibility and possible GPU compute in one platform.

Final Verdict: Is Bastion Worth It?

Bastion’s core idea is sound. Giving each coding agent a real KVM virtual machine, defined by reproducible JSON templates and runnable on your own hardware, is a genuinely stronger isolation model than shared containers for autonomous, parallel agent work. For a developer who wants control and a hard security boundary without paying a hosted service, it is an appealing self-hosted option, and the OpenCode and SSH access fit existing workflows. We rate it 6.2 out of 10.

The rating reflects how early it is. This is a recent Show HN in a crowded field where E2B, Daytona and Modal already ship polished, funded platforms. The Linux and KVM requirement narrows who can run it, there is no public pricing, and the track record is thin. If you are an experienced developer who wants to self-host isolated agent VMs and you enjoy being early, Bastion is worth trying today. If you need a proven, managed solution, watch it mature and reach for a hosted alternative for now.