sbx: clarify prerequisites (kvm, macos version)

content/manuals/ai/sandboxes/get-started.md

@@ -19,25 +19,55 @@ cleaning up.
 
 ## Prerequisites
 
-- macOS (Apple silicon), Windows (x86_64, Windows 11 required), or Linux
-  (Ubuntu 22.04 or later, x86_64)
-- If you're on Windows, enable Windows Hypervisor Platform. Open an elevated
-  PowerShell prompt (Run as Administrator) and run:
+{{< tabs group="os" >}}
+{{< tab name="macOS" >}}
+
+- macOS Tahoe (26) or later
+- Apple silicon
+
+{{< /tab >}}
+{{< tab name="Windows" >}}
+
+- 64-bit Intel or AMD (x86_64)
+- Windows 11
+- Windows Hypervisor Platform enabled. Open an elevated PowerShell prompt (Run
+  as Administrator) and run:
   ```powershell
   Enable-WindowsOptionalFeature -Online -FeatureName HypervisorPlatform -All
   ```
-- If you're on Linux, your user must be in the `kvm` group for hardware
-  virtualization access.
-- An API key or authentication method for the agent you want to use. Most
-  agents require an API key for their model provider (Anthropic, OpenAI,
-  Google, and others). See the [agent pages](agents/) for provider-specific
-  instructions.
+
+{{< /tab >}}
+{{< tab name="Linux (Ubuntu)" >}}
+
+- Ubuntu 22.04 or later
+- 64-bit Intel or AMD (x86_64)
+- KVM hardware virtualization supported and enabled by the CPU. If you're
+  running inside a VM, nested virtualization must be turned on. Verify that KVM
+  is available:
+  ```console
+  $ lsmod | grep kvm
+  ```
+  A working setup shows `kvm_intel` or `kvm_amd` in the output. If the output
+  is empty, run `kvm-ok` for diagnostics. If KVM is unavailable, `sbx` will
+  not start.
+- Your user in the `kvm` group:
+  ```console
+  $ sudo usermod -aG kvm $USER
+  ```
+  Log out and back in (or run `newgrp kvm`) for the group change to take effect.
+
+{{< /tab >}}
+{{< /tabs >}}
+
+An API key or authentication method for the agent you want to use. Most agents
+require an API key for their model provider (Anthropic, OpenAI, Google, and
+others). See the [agent pages](agents/) for provider-specific instructions.
 
 Docker Desktop is not required to use `sbx`.
 
 ## Install and sign in
 
-{{< tabs >}}
+{{< tabs group="os" >}}
 {{< tab name="macOS" >}}
 
 ```console
@@ -59,15 +89,10 @@ $ sbx login
 ```console
 $ curl -fsSL https://get.docker.com | sudo REPO_ONLY=1 sh
 $ sudo apt-get install docker-sbx
-$ sudo usermod -aG kvm $USER
-$ newgrp kvm
 $ sbx login
 ```
 
-The first command adds Docker's `apt` repository to your system. The
-`usermod` command grants your user access to `/dev/kvm` for hardware
-virtualization. You need to log out and back in (or use `newgrp`) for the
-group change to take effect.
+The first command adds Docker's `apt` repository to your system.
 
 {{< /tab >}}
 {{< /tabs >}}