diff --git a/mettle/worker/BUILD b/mettle/worker/BUILD
index e538b31a..0c32265c 100644
--- a/mettle/worker/BUILD
+++ b/mettle/worker/BUILD
@@ -1,6 +1,9 @@
 go_library(
     name = "worker",
-    srcs = glob(["*.go"]),
+    srcs = glob(
+        ["*.go"],
+        exclude = ["*_test.go"],
+    ),
     visibility = ["//mettle/..."],
     deps = [
         "///third_party/go/cloud.google.com_go_pubsub//apiv1",
@@ -43,3 +46,12 @@ go_library(
         "//third_party/proto/resourceusage",
     ],
 )
+
+go_test(
+    name = "worker_test",
+    srcs = glob(["*_test.go"]),
+    deps = [
+        ":worker",
+        "///third_party/go/github.com_stretchr_testify//assert",
+    ],
+)
diff --git a/mettle/worker/worker.go b/mettle/worker/worker.go
index 1150b8cd..d314975b 100644
--- a/mettle/worker/worker.go
+++ b/mettle/worker/worker.go
@@ -14,6 +14,7 @@ import (
 	"path"
 	"path/filepath"
 	"runtime"
+	"sort"
 	"strconv"
 	"strings"
 	"syscall"
@@ -438,6 +439,7 @@ type worker struct {
 	fileDownload    time.Duration
 	lastURL         string // This is reset somewhat lazily.
 	stdout, stderr  bytes.Buffer
+	platformProps   map[string]string
 
 	// For limiting parallelism during download / write actions
 	limiter, iolimiter chan struct{}
@@ -477,6 +479,7 @@ func (w *worker) RunTask(ctx context.Context) (*pb.ExecuteResponse, error) {
 	}
 	w.currentMsg = nil
 	w.actionDigest = nil
+	w.platformProps = nil
 	return response, err
 }
 
@@ -517,6 +520,7 @@ func (w *worker) runTask(msg *pubsub.Message) *pb.ExecuteResponse {
 			Status: status(err, codes.FailedPrecondition, "Badly serialised request: %s", err),
 		}
 	}
+	w.platformProps = copyPlatformProperties(msg.Metadata)
 	return w.runTaskRequest(req)
 }
 
@@ -534,6 +538,7 @@ func (w *worker) runTaskRequest(req *pb.ExecuteRequest) *pb.ExecuteResponse {
 	logr.WithFields(logrus.Fields{
 		"hash": w.actionDigest.Hash,
 	}).Debug("Received task for action digest")
+	w.logPlatformProperties()
 	w.lastURL = w.actionURL()
 
 	action, command, status := w.fetchRequestBlobs(req)
@@ -562,6 +567,43 @@ func (w *worker) runTaskRequest(req *pb.ExecuteRequest) *pb.ExecuteResponse {
 	return w.execute(req, action, command)
 }
 
+func copyPlatformProperties(metadata map[string]string) map[string]string {
+	if len(metadata) == 0 {
+		return nil
+	}
+	ret := make(map[string]string, len(metadata))
+	for k, v := range metadata {
+		ret[k] = v
+	}
+	return ret
+}
+
+func formatPlatformProperties(props map[string]string) string {
+	if len(props) == 0 {
+		return ""
+	}
+	keys := make([]string, 0, len(props))
+	for key := range props {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	formatted := make([]string, 0, len(keys))
+	for _, key := range keys {
+		formatted = append(formatted, key+"="+props[key])
+	}
+	return strings.Join(formatted, ", ")
+}
+
+func (w *worker) logPlatformProperties() {
+	if len(w.platformProps) == 0 {
+		return
+	}
+	logr.WithFields(logrus.Fields{
+		"hash":               w.actionDigest.Hash,
+		"platformProperties": formatPlatformProperties(w.platformProps),
+	}).Info("Action specifies platform properties; would use them to select sandbox filesystem")
+}
+
 // forceShutdown sends any shutdown reports and calls log.Fatal() to shut down the worker
 func (w *worker) forceShutdown(shutdownMsg string) {
 	w.Report(false, false, false, "%s", shutdownMsg)
diff --git a/mettle/worker/worker_platform_test.go b/mettle/worker/worker_platform_test.go
new file mode 100644
index 00000000..eb145bac
--- /dev/null
+++ b/mettle/worker/worker_platform_test.go
@@ -0,0 +1,39 @@
+package worker
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCopyPlatformProperties(t *testing.T) {
+	original := map[string]string{
+		"filesystem":  "disk",
+		"worker_pool": "large",
+	}
+	copied := copyPlatformProperties(original)
+
+	assert.Equal(t, original, copied)
+
+	original["filesystem"] = "tmpfs"
+	assert.Equal(t, "disk", copied["filesystem"])
+}
+
+func TestCopyPlatformPropertiesNilWhenEmpty(t *testing.T) {
+	assert.Nil(t, copyPlatformProperties(nil))
+	assert.Nil(t, copyPlatformProperties(map[string]string{}))
+}
+
+func TestFormatPlatformProperties(t *testing.T) {
+	props := map[string]string{
+		"worker_pool": "large",
+		"filesystem":  "disk",
+	}
+
+	assert.Equal(t, "filesystem=disk, worker_pool=large", formatPlatformProperties(props))
+}
+
+func TestFormatPlatformPropertiesEmpty(t *testing.T) {
+	assert.Equal(t, "", formatPlatformProperties(nil))
+	assert.Equal(t, "", formatPlatformProperties(map[string]string{}))
+}