docs: document SSH agent forwarding settings

content/manuals/ai/sandboxes/configuration/credentials.md

@@ -274,11 +274,30 @@ interact with GitHub APIs on your behalf.
 
 ### SSH agent
 
-If your host has an SSH agent and `SSH_AUTH_SOCK` is set, Docker Sandboxes
-forwards the agent into the sandbox and sets `SSH_AUTH_SOCK` there. The
-private keys stay on your host. Processes inside the sandbox can request
-signatures from the forwarded agent, but they can't read or copy the private
-key.
+SSH agent forwarding is enabled by default. When `SSH_AUTH_SOCK` is set,
+Docker Sandboxes uses the value from the client that creates, starts, or joins
+each sandbox. It forwards that agent into the sandbox and sets `SSH_AUTH_SOCK`
+there.
+
+Run `sbx setup` to configure forwarding and choose which socket to use:
+
+```console
+$ sbx setup
+```
+
+In the SSH agent step, you can disable forwarding, use each client's current
+`SSH_AUTH_SOCK`, or set a fixed socket path for every sandbox. A fixed path is
+useful for agents that use a custom socket, such as the 1Password SSH agent.
+
+After changing forwarding or the socket selection, restart the daemon so
+existing sandboxes use the new configuration:
+
+```console
+$ sbx daemon restart
+```
+
+The private keys stay on your host. Processes inside the sandbox can request
+signatures from the forwarded agent, but they can't read or copy a private key.
 
 Use SSH agent forwarding for Git operations over SSH and SSH-based commit
 signing. The signing key must be loaded in the host SSH agent for sandboxed

content/manuals/ai/sandboxes/security/isolation.md

@@ -233,4 +233,10 @@ environment variables or files inside the sandbox unless you explicitly set
 them. This means a compromised sandbox cannot read API keys from the local
 environment.
 
+SSH agent forwarding is enabled by default. Private keys stay on the host, but
+any process inside the sandbox can ask the forwarded agent to authenticate or
+sign data. Docker Sandboxes forwards only sockets it recognizes as SSH agents.
+A sandbox receives no SSH agent when forwarding is disabled, the configuration
+is unavailable, or the selected socket can't be used.
+
 For how to store and manage credentials, see [Credentials](../configuration/credentials.md).

content/manuals/ai/sandboxes/troubleshooting.md

@@ -273,6 +273,18 @@ the command again:
 Docker Sandboxes can sign Git commits with SSH keys from your host agent.
 For setup steps, see [Commit signing](workflows/git.md#commit-signing).
 
+Forwarding is enabled by default. Run `sbx setup` and confirm that forwarding
+is enabled and the SSH agent row shows the intended socket mode:
+
+```console
+$ sbx setup
+```
+
+If you use each client's current `SSH_AUTH_SOCK`, reconnect from a shell where
+it points to the intended agent. If you use a fixed socket, confirm that the
+configured path points to an active host agent. After changing forwarding or
+the socket selection, run `sbx daemon restart`.
+
 If `ssh-add -L` prints `The agent has no identities.`, the sandbox can reach
 the forwarded agent, but the host agent doesn't have a loaded key. Load the
 signing key into your host SSH agent:

content/manuals/ai/sandboxes/workflows/git.md

@@ -183,11 +183,13 @@ yourself after reviewing the changes.
 
 ## Commit signing
 
-Sandboxes forward your host SSH agent into the sandbox, so the agent can
-sign commits with your SSH key without the private key ever leaving your
-host.
+SSH agent forwarding is enabled by default. When `SSH_AUTH_SOCK` is set,
+sandboxes forward your host SSH agent into the sandbox, so the agent can sign
+commits with your SSH key without the private key ever leaving your host. If
+you turned off forwarding or use a fixed SSH agent socket, see
+[SSH agent configuration](../configuration/credentials.md#ssh-agent).
 
-1. On your host, make sure the signing key is loaded in your SSH agent:
+1. Make sure the signing key is loaded in your host SSH agent:
 
    ```console
    $ ssh-add ~/.ssh/id_ed25519