diff --git a/docs/implementation-plan.v1.md b/docs/implementation-plan.v1.md
index 0821097..2f8ac5b 100644
--- a/docs/implementation-plan.v1.md
+++ b/docs/implementation-plan.v1.md
@@ -893,6 +893,14 @@ watchdog/tunnel is bound
 only to the helper's private Docker gateway. Stop the helper before the normal
 `test-host reset`. It is a recovery interface, not a product component or a
 replacement for Guest Control/native test automation.
+Because Windows can power off the virtual monitor while the VM remains
+running, `test-host prepare` must also reapply the disposable display/sleep
+keepalive and record `prepare-display-keepalive`. A zero-bpp VRDE framebuffer
+otherwise leaves an otherwise authenticated Guacamole browser at “Waiting for
+response”. If the public browser hostname has an AAAA record, `rdp-access up
+--bind 0.0.0.0` must own a tracked IPv6-to-IPv4 forward and expose its
+`ipv6_forward` status; this prevents a browser selecting IPv6 for the WebSocket
+from silently taking a different, refused path.
 
 For this provisioned lane, the approved host-only credential-file location is
 `/home/cabbage/.local/share/rvbox-secrets/rvbox-win10-test.password`. It must
diff --git a/docs/testing-vm.md b/docs/testing-vm.md
index 6c54079..ca9e197 100644
--- a/docs/testing-vm.md
+++ b/docs/testing-vm.md
@@ -91,6 +91,9 @@ self-signed HTTPS Guacamole gateway while retaining VRDE on Helium loopback and
 the reconnecting SSH watchdog/tunnel on a private Docker gateway. Follow its
 full lease/prepare/up/
 down/reset lifecycle; it is not an alternative to the native test controller.
+In public-bind mode the helper also owns a tracked IPv6-to-IPv4 `socat` forward
+when the browser hostname has an AAAA record; check `ipv6_forward=active` in
+`rdp-access status` before diagnosing a browser-side “Waiting for response”.
 
 ## Snapshots and reset contract
 
@@ -112,10 +115,14 @@ stateful run must:
 1. Acquire the run lease and verify the VM name, UUID, and snapshot UUID.
 2. Restore `baseline-clean-administrator` if the current state is not the baseline.
 3. Start headless and wait for `VMState=running` plus Guest Additions readiness.
-4. Run the bounded test, collect redacted artifacts, and close every Guest
+4. Apply the disposable display/sleep keepalive (`monitor-timeout`, standby,
+   and hibernate timers set to zero) so VirtualBox VRDE cannot expose a
+   zero-bpp framebuffer after Windows idle timeout. This is recorded as
+   `prepare-display-keepalive` and is reapplied after every snapshot restore.
+5. Run the bounded test, collect redacted artifacts, and close every Guest
    Control process that was opened by the run.
-5. Request a graceful guest shutdown and wait for `VMState=poweroff`.
-6. Restore `baseline-clean-administrator` again and leave the VM powered off.
+6. Request a graceful guest shutdown and wait for `VMState=poweroff`.
+7. Restore `baseline-clean-administrator` again and leave the VM powered off.
 
 Use `controlvm ... poweroff` only for a hung, disposable test; it can lose
 guest state. Never delete any clean snapshot, unregister the VM, or alter
diff --git a/docs/testing.md b/docs/testing.md
index ad44ef4..8e7f2c1 100644
--- a/docs/testing.md
+++ b/docs/testing.md
@@ -208,6 +208,9 @@ Interactive browser access is a deliberately temporary recovery path only. See
 [`test/rdp-access`](../test/rdp-access/README.md) for the Docker-only,
 self-signed HTTPS Guacamole lifecycle; it must be started only after the native
 fixture controller has prepared and leased the VM, and stopped before reset.
+For a public hostname with an AAAA record, its `up --bind 0.0.0.0` mode also
+tracks an IPv6-to-IPv4 forward; verify `ipv6_forward=active` before debugging
+a browser stuck at “Waiting for response”.
 
 The Linux production Compose asset has a separate, loopback-only smoke lane. It
 uses a disposable self-signed key only under the ignored `.test-runs` tree,
diff --git a/scripts/windows/test-host b/scripts/windows/test-host
index 3ae1095..48ed497 100755
--- a/scripts/windows/test-host
+++ b/scripts/windows/test-host
@@ -316,6 +316,18 @@ wait_guest_additions() {
     fail "Guest Additions did not publish version and Windows OS-release properties"
 }
 
+configure_display_keepalive() {
+    # VirtualBox VRDE reports a zero-bpp framebuffer when Windows powers off
+    # the virtual monitor.  That leaves an authenticated Guacamole tunnel in
+    # its "Waiting for response" state even though RDP negotiation succeeded.
+    # Keep the disposable diagnostic fixture awake; this is deliberately
+    # applied after every snapshot restore because power-plan state belongs to
+    # the guest snapshot, not to the controller.
+    provisioner_run --exe 'C:\Windows\System32\cmd.exe' --wait-stdout --wait-stderr --unquoted-args -- \
+        /d /s /c '(powercfg /change monitor-timeout-ac 0 && powercfg /change monitor-timeout-dc 0 && powercfg /change standby-timeout-ac 0 && powercfg /change standby-timeout-dc 0 && powercfg /change hibernate-timeout-ac 0 && powercfg /change hibernate-timeout-dc 0 && echo RVBOX_GUEST_OK)' >/dev/null || \
+        fail "fixture provisioner could not disable disposable display/sleep timers"
+}
+
 wait_service() {
     wanted=$1
     attempt=0
@@ -366,6 +378,8 @@ case "$action" in
         step prepare-vm-started
         wait_guest_additions
         step prepare-guest-additions-ready
+        configure_display_keepalive
+        step prepare-display-keepalive
         assert_clean_guest
         step prepare-clean-baseline-verified
         ;;
diff --git a/test/rdp-access/README.md b/test/rdp-access/README.md
index 8c1594f..36c3dd7 100644
--- a/test/rdp-access/README.md
+++ b/test/rdp-access/README.md
@@ -9,6 +9,7 @@ The helper builds this private path:
 
 ```text
 browser -- HTTPS/self-signed --> nginx + Guacamole containers
+       (IPv4 and, in public mode, a tracked IPv6 forward)
                                       |
                                  private Docker gateway
                                       |
@@ -69,9 +70,23 @@ port (`54001`). They can be overridden without editing tracked files through
 `RVBOX_TEST_VBOX_HOST`, `RDP_ACCESS_VRDE_HOST`, `RDP_ACCESS_VRDE_PORT`,
 `RDP_ACCESS_WEB_USER`, `RDP_ACCESS_RDP_USER`, `RDP_ACCESS_BIND`,
 `RDP_ACCESS_HTTP_PORT`, `RDP_ACCESS_TUNNEL_PORT`, and
-`RDP_ACCESS_PUBLIC_HOST`. The helper deliberately limits the VRDE host to
+`RDP_ACCESS_PUBLIC_HOST`, `RDP_ACCESS_IPV6_BIND`, and
+`RDP_ACCESS_IPV6_FORWARD`. The helper deliberately limits the VRDE host to
 Helium loopback (`127.0.0.1` or `localhost`) so an override cannot accidentally
 turn the diagnostic server into a remote target.
+Set `RDP_ACCESS_GUACD_LOG_LEVEL=debug` temporarily when collecting detailed
+guacd/RDP negotiation diagnostics; the default is `info`.
+
+When `--bind 0.0.0.0` is used, `up` also starts a tracked `socat` listener on
+`[::]:$RDP_ACCESS_HTTP_PORT` and forwards it to the IPv4 gateway listener. This
+matters when the public hostname has an AAAA record: some browsers choose IPv6
+for the WebSocket even if the initial page used IPv4. The listener is recorded
+under `.runtime/ipv6-forward.pid` and is removed by `down` and `clean`. Its
+default bind is `::` (`RDP_ACCESS_IPV6_BIND`); set
+`RDP_ACCESS_IPV6_FORWARD=never` to deliberately use IPv4 only, `always` to make
+IPv6 startup a hard requirement, or leave the default `auto` for a warning and
+an IPv4-only fallback when `socat` is unavailable. `status` reports
+`ipv6_forward=active`, `active_external`, `inactive`, or `disabled`.
 
 If `up` is run again while the Compose services are still running, it is
 idempotent: an existing healthy tunnel is reused, and a missing tunnel is
@@ -123,7 +138,9 @@ test/rdp-access/rdp-access url
 
 If the browser reaches Guacamole but stays on “Waiting for response”, run
 `status` first. Confirm `private_tunnel=active` (or
-`active_external`), then check the VM state and the last lines of
+`active_external`) and, for a public dual-stack hostname,
+`ipv6_forward=active` (or a known-good external forward). Then check the VM
+state and the last lines of
 `.runtime/tunnel.log`. A tunnel can be recreated without losing the Compose
 stack by running `up` again. This helper already uses `security=rdp` and
 disables Guacamole's GFX extension, which are required by the fixture's legacy
@@ -132,9 +149,11 @@ VRDE server. Do not switch the helper to native Windows RDP:
 unusable, stop this helper and use Guest Control for the deterministic portion
 of the work; record the blocked interactive step in the native test report.
 
-The helper requires Docker/Docker Compose, SSH access through the existing
-`helium-remote` alias, and the fixture password file documented in
+The helper requires Docker/Docker Compose, `socat` for the optional public
+dual-stack forward, SSH access through the existing `helium-remote` alias, and
+the fixture password file documented in
 [`docs/testing-vm.md`](../../docs/testing-vm.md). It does not install host
-packages, write credentials into Git, or alter VM settings. The tracked files
-are Docker-only configuration and the controller script; all generated content
-is ignored beneath `.runtime/`.
+packages, write credentials into Git, or alter VM identity/settings. The
+authoritative `test-host prepare` step applies only the disposable
+display/sleep keepalive needed by VirtualBox VRDE; all generated content is
+ignored beneath `.runtime/`.
diff --git a/test/rdp-access/compose.yaml b/test/rdp-access/compose.yaml
index c7f19a1..b2dbc27 100644
--- a/test/rdp-access/compose.yaml
+++ b/test/rdp-access/compose.yaml
@@ -1,6 +1,8 @@
 services:
   guacd:
     image: guacamole/guacd:1.6.0
+    environment:
+      LOG_LEVEL: ${RDP_ACCESS_GUACD_LOG_LEVEL:-info}
 
   guacamole:
     image: guacamole/guacamole:1.6.0
diff --git a/test/rdp-access/nginx.conf b/test/rdp-access/nginx.conf
index 16f0fc2..2896ea5 100644
--- a/test/rdp-access/nginx.conf
+++ b/test/rdp-access/nginx.conf
@@ -15,5 +15,8 @@ server {
         proxy_set_header Upgrade $http_upgrade;
         proxy_set_header Connection "upgrade";
         proxy_buffering off;
+        proxy_read_timeout 1h;
+        proxy_send_timeout 1h;
+        proxy_set_header X-Accel-Buffering no;
     }
 }
diff --git a/test/rdp-access/rdp-access b/test/rdp-access/rdp-access
index 3b5b634..56a5296 100755
--- a/test/rdp-access/rdp-access
+++ b/test/rdp-access/rdp-access
@@ -16,6 +16,9 @@ project=rvbox-rdp-access
 : "${RDP_ACCESS_PUBLIC_HOST:=localhost}"
 : "${RDP_ACCESS_WEB_USER:=rvboxtest}"
 : "${RDP_ACCESS_RDP_USER:=rvboxtest}"
+: "${RDP_ACCESS_GUACD_LOG_LEVEL:=info}"
+: "${RDP_ACCESS_IPV6_BIND:=::}"
+: "${RDP_ACCESS_IPV6_FORWARD:=auto}"
 : "${RVBOX_TEST_VBOX_HOST:=helium-remote}"
 : "${RDP_ACCESS_VRDE_HOST:=127.0.0.1}"
 : "${RDP_ACCESS_VRDE_PORT:=3389}"
@@ -46,7 +49,10 @@ up options:
 Environment equivalents: RDP_ACCESS_BIND, RDP_ACCESS_HTTP_PORT,
 RDP_ACCESS_TUNNEL_PORT, RDP_ACCESS_PUBLIC_HOST, RDP_ACCESS_WEB_USER,
 RDP_ACCESS_RDP_USER, RVBOX_TEST_VBOX_HOST, RDP_ACCESS_VRDE_HOST, and
-RDP_ACCESS_VRDE_PORT.
+RDP_ACCESS_VRDE_PORT. In public mode, RDP_ACCESS_IPV6_BIND and
+RDP_ACCESS_IPV6_FORWARD (auto, always, or never) control the reversible
+IPv6-to-IPv4 listener for dual-stack hostnames. Set
+RDP_ACCESS_GUACD_LOG_LEVEL=debug for temporary protocol diagnostics.
 EOF
 }
 
@@ -69,6 +75,7 @@ compose() {
     RDP_ACCESS_RUNTIME_DIR=$runtime_dir \
     RDP_ACCESS_BIND=$RDP_ACCESS_BIND \
     RDP_ACCESS_HTTP_PORT=$RDP_ACCESS_HTTP_PORT \
+    RDP_ACCESS_GUACD_LOG_LEVEL=$RDP_ACCESS_GUACD_LOG_LEVEL \
     RDP_ACCESS_CERT_NAME=$RDP_ACCESS_PUBLIC_HOST \
     RDP_ACCESS_CERT_SAN=$cert_san \
     RDP_ACCESS_HOST_UID=$(id -u) \
@@ -100,6 +107,8 @@ cert_name_file=$runtime_dir/cert-name
 tunnel_stop_file=$runtime_dir/tunnel.stop
 tunnel_pid_file=$runtime_dir/tunnel-watchdog.pid
 tunnel_log_file=$runtime_dir/tunnel.log
+ipv6_pid_file=$runtime_dir/ipv6-forward.pid
+ipv6_log_file=$runtime_dir/ipv6-forward.log
 
 stop_tunnel() {
     mkdir -p "$runtime_dir"
@@ -135,6 +144,102 @@ stop_tunnel() {
     rm -f "$tunnel_pid_file" "$tunnel_stop_file"
 }
 
+ipv6_process_matches() {
+    ipv6_pid=$1
+    ipv6_cmd=$(ps -p "$ipv6_pid" -o args= 2>/dev/null || true)
+    case $ipv6_cmd in
+        *"TCP6-LISTEN:$RDP_ACCESS_HTTP_PORT"*"TCP4:127.0.0.1:$RDP_ACCESS_HTTP_PORT"*) return 0 ;;
+        *) return 1 ;;
+    esac
+}
+
+ipv6_listener_active() {
+    command -v ss >/dev/null 2>&1 || return 1
+    ss -H -ltn6 2>/dev/null | awk -v port=":$RDP_ACCESS_HTTP_PORT" \
+        '{ if ($4 ~ (port "$")) found=1 } END { exit !found }'
+}
+
+stop_ipv6_forward() {
+    [ -f "$ipv6_pid_file" ] || return 0
+    ipv6_pid=$(cat "$ipv6_pid_file" 2>/dev/null || true)
+    case $ipv6_pid in
+        ''|*[!0-9]*) ;;
+        *)
+            if ipv6_process_matches "$ipv6_pid"; then
+                kill "$ipv6_pid" >/dev/null 2>&1 || true
+                sleep 1
+                if ipv6_process_matches "$ipv6_pid"; then
+                    kill -KILL "$ipv6_pid" >/dev/null 2>&1 || true
+                fi
+            fi
+            ;;
+    esac
+    rm -f "$ipv6_pid_file"
+}
+
+start_ipv6_forward() {
+    [ "$RDP_ACCESS_BIND" = 0.0.0.0 ] || return 0
+    case $RDP_ACCESS_IPV6_FORWARD in
+        never) stop_ipv6_forward; return 0 ;;
+        auto|always) ;;
+        *) fail "RDP_ACCESS_IPV6_FORWARD must be auto, always, or never" ;;
+    esac
+    if ! command -v socat >/dev/null 2>&1; then
+        if [ "$RDP_ACCESS_IPV6_FORWARD" = always ]; then
+            fail "socat is required for RDP_ACCESS_IPV6_FORWARD=always"
+        fi
+        printf 'rdp-access: warning: socat unavailable; IPv6 forwarding disabled (IPv4 remains active)\n' >&2
+        return 0
+    fi
+    if ipv6_listener_active; then
+        # Do not kill an unrelated listener.  The operator can inspect it via
+        # status; down only stops a PID that this helper started and verified.
+        printf 'rdp-access: IPv6 port %s is already occupied; retaining the existing listener\n' \
+            "$RDP_ACCESS_HTTP_PORT" >&2
+        return 0
+    fi
+    stop_ipv6_forward
+    umask 077
+    mkdir -p "$runtime_dir"
+    : >"$ipv6_log_file"
+    chmod 600 "$ipv6_log_file"
+    setsid nohup socat \
+        "TCP6-LISTEN:$RDP_ACCESS_HTTP_PORT,ipv6only=1,reuseaddr,fork,bind=$RDP_ACCESS_IPV6_BIND" \
+        "TCP4:127.0.0.1:$RDP_ACCESS_HTTP_PORT" \
+        </dev/null >>"$ipv6_log_file" 2>&1 &
+    ipv6_pid=$!
+    printf '%s\n' "$ipv6_pid" >"$ipv6_pid_file"
+    chmod 600 "$ipv6_pid_file"
+    attempts=0
+    while [ "$attempts" -lt 10 ]; do
+        if ipv6_process_matches "$ipv6_pid" && ipv6_listener_active; then
+            return 0
+        fi
+        attempts=$((attempts + 1))
+        sleep 1
+    done
+    stop_ipv6_forward
+    if [ "$RDP_ACCESS_IPV6_FORWARD" = always ]; then
+        fail "could not start IPv6 forwarding listener; inspect $ipv6_log_file"
+    fi
+    printf 'rdp-access: warning: IPv6 forwarding could not start (IPv4 remains active); inspect %s\n' \
+        "$ipv6_log_file" >&2
+}
+
+ipv6_forward_status() {
+    if [ -f "$ipv6_pid_file" ] && ipv6_process_matches "$(cat "$ipv6_pid_file" 2>/dev/null || true)" && ipv6_listener_active; then
+        printf 'ipv6_forward=active\n'
+        printf 'ipv6_forward_supervisor=helper\n'
+    elif ipv6_listener_active; then
+        printf 'ipv6_forward=active_external\n'
+        printf 'ipv6_forward_supervisor=external\n'
+    elif [ "$RDP_ACCESS_BIND" != 0.0.0.0 ] || [ "$RDP_ACCESS_IPV6_FORWARD" = never ]; then
+        printf 'ipv6_forward=disabled\n'
+    else
+        printf 'ipv6_forward=inactive\n'
+    fi
+}
+
 gateway_for_network() {
     docker network inspect --format '{{(index .IPAM.Config 0).Gateway}}' "${project}_default"
 }
@@ -340,6 +445,8 @@ safe_name RDP_ACCESS_RDP_USER "$RDP_ACCESS_RDP_USER"
 safe_name RVBOX_TEST_VBOX_HOST "$RVBOX_TEST_VBOX_HOST"
 case $RDP_ACCESS_VRDE_HOST in 127.0.0.1|localhost) ;; *) fail "RDP_ACCESS_VRDE_HOST must be 127.0.0.1 or localhost" ;; esac
 safe_port RDP_ACCESS_VRDE_PORT "$RDP_ACCESS_VRDE_PORT"
+case $RDP_ACCESS_IPV6_BIND in ::|::1) ;; *) fail "RDP_ACCESS_IPV6_BIND must be :: or ::1" ;; esac
+case $RDP_ACCESS_IPV6_FORWARD in auto|always|never) ;; *) fail "RDP_ACCESS_IPV6_FORWARD must be auto, always, or never" ;; esac
 
 case $RDP_ACCESS_PUBLIC_HOST in
     *[!0-9.]* ) cert_san="DNS:$RDP_ACCESS_PUBLIC_HOST" ;;
@@ -375,6 +482,7 @@ case $action in
                 fail "existing Guacamole stack was found but the private VRDE tunnel could not be restored; inspect $tunnel_log_file"
             fi
             wait_for_gateway || fail "Guacamole stack is running but its HTTPS endpoint did not become ready; inspect Compose logs"
+            start_ipv6_forward
             if [ -f "$session_file" ]; then sed -n '1p' "$session_file"; fi
             exit 0
         fi
@@ -399,6 +507,7 @@ case $action in
         if ! wait_for_gateway; then
             fail "Guacamole gateway started but its HTTPS endpoint did not become ready; inspect Compose logs"
         fi
+        start_ipv6_forward
         printf 'Guacamole is ready at https://%s:%s/guacamole/\n' "$RDP_ACCESS_PUBLIC_HOST" "$RDP_ACCESS_HTTP_PORT"
         printf 'Accept the self-signed certificate warning, then sign in as %s with the fixture password.\n' "$RDP_ACCESS_WEB_USER"
         ;;
@@ -420,6 +529,7 @@ case $action in
         else
             printf 'private_tunnel=inactive\n'
         fi
+        ipv6_forward_status
         ;;
     url)
         [ "$#" -eq 0 ] || { usage >&2; fail "url accepts no options"; }
@@ -431,12 +541,14 @@ case $action in
         ;;
     down)
         [ "$#" -eq 0 ] || { usage >&2; fail "down accepts no options"; }
+        stop_ipv6_forward
         stop_tunnel
         compose down --remove-orphans || true
         printf 'Temporary gateway and private tunnel stopped; generated certificate and password hash retained in %s.\n' "$runtime_dir"
         ;;
     clean)
         [ "$#" -eq 0 ] || { usage >&2; fail "clean accepts only --images"; }
+        stop_ipv6_forward
         stop_tunnel
         compose down --remove-orphans || true
         case $runtime_dir in "$helper_dir"/.runtime) rm -rf "$runtime_dir" ;; *) fail "unsafe runtime path" ;; esac
diff --git a/test/rdp-access/user-mapping.xml.in b/test/rdp-access/user-mapping.xml.in
index 065ee97..060848d 100644
--- a/test/rdp-access/user-mapping.xml.in
+++ b/test/rdp-access/user-mapping.xml.in
@@ -15,6 +15,7 @@
             <param name="enable-wallpaper">false</param>
             <param name="enable-theming">false</param>
             <param name="enable-font-smoothing">false</param>
+            <param name="color-depth">24</param>
             <param name="disable-gfx">true</param>
         </connection>
     </authorize>