diff --git a/content/manuals/ai/sandboxes/customize/templates.md b/content/manuals/ai/sandboxes/customize/templates.md
index 72bcade5d94..3006bc19b91 100644
--- a/content/manuals/ai/sandboxes/customize/templates.md
+++ b/content/manuals/ai/sandboxes/customize/templates.md
@@ -61,16 +61,19 @@ default.
 The agent containers created from the `-docker` templates run in privileged
 mode inside the microVM (not on your host), with a dedicated block volume at
 `/var/lib/docker`, and `dockerd` starts automatically inside the sandbox. The
-block volume defaults to 50 GB and uses a sparse file, so it only consumes
+block volume defaults to 10 GB and uses a sparse file, so it only consumes
 disk space as Docker writes to it.
 
-To override the volume size, set the `DOCKER_SANDBOXES_DOCKER_SIZE`
-environment variable to a size string before starting the sandbox:
+To change the volume size for a sandbox, set
+`DOCKER_SANDBOXES_DOCKER_SIZE` when you create it:
 
 ```console
-$ DOCKER_SANDBOXES_DOCKER_SIZE=10g sbx run claude
+$ DOCKER_SANDBOXES_DOCKER_SIZE=20g sbx run claude
 ```
 
+The volume size must be at least 512 MiB. The environment variable doesn't
+resize existing volumes.
+
 Use the non-Docker variant if you don't need to build or run containers
 inside the sandbox and want a lighter, non-privileged environment. Specify
 it explicitly with `--template`:
diff --git a/content/manuals/ai/sandboxes/troubleshooting.md b/content/manuals/ai/sandboxes/troubleshooting.md
index fc518e40ebf..b3dc1f16140 100644
--- a/content/manuals/ai/sandboxes/troubleshooting.md
+++ b/content/manuals/ai/sandboxes/troubleshooting.md
@@ -204,15 +204,24 @@ the egress path in the **PROXY** column:
 
 ## Sandbox runs out of disk space
 
-The sandbox root (`/`) filesystem defaults to 20 GB. To increase it, set `DOCKER_SANDBOXES_ROOT_SIZE`
-before creating the sandbox:
+The sandbox root (`/`) filesystem defaults to 20 GB. To increase it, set
+`DOCKER_SANDBOXES_ROOT_SIZE` before creating the sandbox:
 
 ```console
 $ DOCKER_SANDBOXES_ROOT_SIZE=40g sbx run claude
 ```
 
-`DOCKER_SANDBOXES_ROOT_SIZE` controls the root filesystem size. `DOCKER_SANDBOXES_DOCKER_SIZE`
-controls the Docker data disk (`/var/lib/docker`) size. The two are independent — set both if needed.
+`DOCKER_SANDBOXES_ROOT_SIZE` controls the root filesystem size. The Docker data
+disk at `/var/lib/docker` is independent and defaults to 10 GB. To change the
+Docker data disk size for a sandbox, set `DOCKER_SANDBOXES_DOCKER_SIZE` when you
+create it:
+
+```console
+$ DOCKER_SANDBOXES_DOCKER_SIZE=20g sbx run claude
+```
+
+The Docker data disk must be at least 512 MiB. The environment variable doesn't
+resize existing volumes.
 
 For a [clone-mode sandbox](usage.md#clone-mode), set
 `DOCKER_SANDBOXES_CLONED_WORKSPACE_SIZE` before creating the sandbox to