diff --git a/internal/ateomnet/dns/relay.go b/internal/ateomnet/dns/relay.go
index 81e2854399..e7f421342e 100644
--- a/internal/ateomnet/dns/relay.go
+++ b/internal/ateomnet/dns/relay.go
@@ -20,10 +20,7 @@ import (
 	"log/slog"
 	"net"
 	"net/netip"
-	"strconv"
 	"time"
-
-	"github.com/agent-substrate/substrate/internal/ateomnet/netns"
 )
 
 const (
@@ -99,43 +96,6 @@ func NewRelayForUpstreams(upstreams []string) (*Relay, error) {
 	}, nil
 }
 
-// Serve serves UDP and TCP DNS in the sandbox's local gateway namespace.
-func (r *Relay) Serve(ctx context.Context, ns netns.Handle) (*Server, error) {
-	// Bind the wildcard because the microVM tap's gateway address is added later.
-	address := net.JoinHostPort("0.0.0.0", strconv.Itoa(dnsPort))
-
-	netC := netConn{
-		dialer: *r.dialer,
-	}
-
-	if err := netns.Do(ctx, ns, func(context.Context) error {
-		pc, err := net.ListenPacket("udp", address)
-		if err != nil {
-			return fmt.Errorf("while opening the actor DNS socket: %w", err)
-		}
-		netC.udp = pc
-		l, err := net.Listen("tcp", address)
-		if err != nil {
-			_ = pc.Close()
-			return fmt.Errorf("while opening the actor DNS listener: %w", err)
-		}
-		netC.tcpListener = l
-		return nil
-	}); err != nil {
-		return nil, err
-	}
-
-	egressUDP, err := net.ListenPacket("udp", ":0")
-	if err != nil {
-		_ = netC.udp.Close()
-		_ = netC.tcpListener.Close()
-		return nil, fmt.Errorf("while opening the worker DNS egress socket: %w", err)
-	}
-	netC.egressUDP = egressUDP
-
-	return r.serveOn(ctx, &netC)
-}
-
 // serveOn serves DNS on netC's sockets, which the caller has already bound,
 // and dials upstreams with netC's dialer.
 func (r *Relay) serveOn(ctx context.Context, netC *netConn) (*Server, error) {
diff --git a/internal/ateomnet/dns/relay_linux.go b/internal/ateomnet/dns/relay_linux.go
new file mode 100644
index 0000000000..53f0185b3f
--- /dev/null
+++ b/internal/ateomnet/dns/relay_linux.go
@@ -0,0 +1,63 @@
+//go:build linux
+
+// Copyright 2026 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package dns
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"strconv"
+
+	"github.com/agent-substrate/substrate/internal/ateomnet/netns"
+)
+
+// Serve serves UDP and TCP DNS in the sandbox's local gateway namespace.
+func (r *Relay) Serve(ctx context.Context, ns netns.Handle) (*Server, error) {
+	// Bind the wildcard because the microVM tap's gateway address is added later.
+	address := net.JoinHostPort("0.0.0.0", strconv.Itoa(dnsPort))
+
+	netC := netConn{
+		dialer: *r.dialer,
+	}
+
+	if err := netns.Do(ctx, ns, func(context.Context) error {
+		pc, err := net.ListenPacket("udp", address)
+		if err != nil {
+			return fmt.Errorf("while opening the actor DNS socket: %w", err)
+		}
+		netC.udp = pc
+		l, err := net.Listen("tcp", address)
+		if err != nil {
+			_ = pc.Close()
+			return fmt.Errorf("while opening the actor DNS listener: %w", err)
+		}
+		netC.tcpListener = l
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+
+	egressUDP, err := net.ListenPacket("udp", ":0")
+	if err != nil {
+		_ = netC.udp.Close()
+		_ = netC.tcpListener.Close()
+		return nil, fmt.Errorf("while opening the worker DNS egress socket: %w", err)
+	}
+	netC.egressUDP = egressUDP
+
+	return r.serveOn(ctx, &netC)
+}
diff --git a/pkg/objectstorage/env_test.go b/pkg/objectstorage/env_test.go
index 5b9b9e7e4e..ee02d368cc 100644
--- a/pkg/objectstorage/env_test.go
+++ b/pkg/objectstorage/env_test.go
@@ -41,6 +41,8 @@ func TestNewFromEnv(t *testing.T) {
 			missing := filepath.Join(t.TempDir(), "missing")
 			t.Setenv("AWS_CONFIG_FILE", missing)
 			t.Setenv("AWS_SHARED_CREDENTIALS_FILE", missing)
+			t.Setenv("AWS_PROFILE", "")
+			t.Setenv("AWS_DEFAULT_PROFILE", "")
 			t.Setenv("AWS_REGION", "us-east-1")
 			t.Setenv("ATE_STORAGE_BACKEND", tc.backend)
 			t.Setenv("AWS_S3_USE_PATH_STYLE", tc.pathStyle)