diff --git a/cmd/sst/mosaic.go b/cmd/sst/mosaic.go
index c81c79b813..f1f5beb037 100644
--- a/cmd/sst/mosaic.go
+++ b/cmd/sst/mosaic.go
@@ -111,9 +111,12 @@ func CmdMosaic(c *cli.Cli) error {
 						<-processExited
 						fmt.Println("\n[restarting]")
 					}
-					fields, _ := shellquote.Split(nextEnv.Command)
-					if len(args) > 0 {
-						fields = args
+					fields := args
+					if len(fields) == 0 {
+						fields, err = parseCommand(nextEnv.Command)
+						if err != nil {
+							return err
+						}
 					}
 					cmd = process.Command(
 						fields[0],
@@ -330,9 +333,12 @@ func CmdMosaic(c *cli.Cli) error {
 					switch evt := unknown.(type) {
 					case *project.CompleteEvent:
 						for _, d := range evt.Devs {
-							if d.Command == "" {
+							if strings.TrimSpace(d.Command) == "" {
 								continue
 							}
+							if _, err := parseCommand(d.Command); err != nil {
+								return fmt.Errorf("invalid dev command for %q: %w", d.Name, err)
+							}
 							dir := filepath.Join(cwd, d.Directory)
 							title := d.Title
 							if title == "" {
@@ -448,11 +454,14 @@ func CmdMosaic(c *cli.Cli) error {
 					switch evt := unknown.(type) {
 					case *project.CompleteEvent:
 						for _, d := range evt.Devs {
-							if d.Command == "" {
+							if strings.TrimSpace(d.Command) == "" {
 								continue
 							}
+							words, err := parseCommand(d.Command)
+							if err != nil {
+								return fmt.Errorf("invalid dev command for %q: %w", d.Name, err)
+							}
 							dir := filepath.Join(cwd, d.Directory)
-							words, _ := shellquote.Split(d.Command)
 							title := d.Title
 							if title == "" {
 								title = d.Name
@@ -480,6 +489,21 @@ func CmdMosaic(c *cli.Cli) error {
 	return err
 }
 
+func parseCommand(command string) ([]string, error) {
+	if strings.TrimSpace(command) == "" {
+		return nil, fmt.Errorf("command is empty")
+	}
+
+	fields, err := shellquote.Split(command)
+	if err != nil {
+		return nil, err
+	}
+	if len(fields) == 0 {
+		return nil, fmt.Errorf("command is empty")
+	}
+	return fields, nil
+}
+
 func diff(a map[string]string, b map[string]string) bool {
 	if len(a) != len(b) {
 		return true
diff --git a/cmd/sst/mosaic_test.go b/cmd/sst/mosaic_test.go
new file mode 100644
index 0000000000..41281a54c3
--- /dev/null
+++ b/cmd/sst/mosaic_test.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestParseCommand(t *testing.T) {
+	tests := []struct {
+		name    string
+		command string
+		want    []string
+		wantErr bool
+	}{
+		{
+			name:    "splits shell arguments",
+			command: `npm run dev -- --name "my service"`,
+			want:    []string{"npm", "run", "dev", "--", "--name", "my service"},
+		},
+		{
+			name:    "rejects empty command",
+			command: "",
+			wantErr: true,
+		},
+		{
+			name:    "rejects whitespace command",
+			command: " \t ",
+			wantErr: true,
+		},
+		{
+			name:    "rejects malformed quoting",
+			command: `npm run "dev`,
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := parseCommand(tt.command)
+			if (err != nil) != tt.wantErr {
+				t.Fatalf("parseCommand(%q) error = %v, wantErr %t", tt.command, err, tt.wantErr)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("parseCommand(%q) = %q, want %q", tt.command, got, tt.want)
+			}
+		})
+	}
+}
diff --git a/platform/src/components/aws/service.ts b/platform/src/components/aws/service.ts
index 3ea034162a..1a3859c4b9 100644
--- a/platform/src/components/aws/service.ts
+++ b/platform/src/components/aws/service.ts
@@ -2803,8 +2803,29 @@ export class Service extends Component implements Link.Linkable {
     }
 
     function registerReceiver() {
+      if (
+        args.containers &&
+        args.dev &&
+        typeof args.dev === "object" &&
+        args.dev.command
+      ) {
+        new DevCommand(`${name}Dev`, {
+          link: args.link,
+          dev: args.dev,
+          aws: {
+            role: taskRole.arn,
+          },
+        });
+      }
+
       all([containers]).apply(([val]) => {
         for (const container of val) {
+          if (
+            !container.dev ||
+            typeof container.dev !== "object" ||
+            !container.dev.command
+          )
+            continue;
           const title = val.length == 1 ? name : `${name}${container.name}`;
           new DevCommand(`${title}Dev`, {
             link: args.link,
diff --git a/platform/test/components/service-alb.test.ts b/platform/test/components/service-alb.test.ts
index 2a08450708..88a5a4e7a8 100644
--- a/platform/test/components/service-alb.test.ts
+++ b/platform/test/components/service-alb.test.ts
@@ -270,6 +270,40 @@ describe("Service with external ALB", function () {
   });
 
   describe("multiple containers", () => {
+    it("registers dev commands only for containers with a dev command", async () => {
+      createdResources.length = 0;
+      // @ts-ignore — Service checks $dev to decide dev mode
+      global.$dev = true;
+
+      try {
+        new Service("DevMultiContainerService", {
+          cluster,
+          dev: { command: "npm run dev" },
+          containers: [
+            {
+              name: "api",
+              image: { context: "./api" },
+            },
+            {
+              name: "sidecar",
+              image: { context: "./worker" },
+            },
+          ],
+        });
+
+        await new Promise((resolve) => setTimeout(resolve, 0));
+      } finally {
+        // @ts-ignore — Restore the default used by the other tests
+        global.$dev = false;
+      }
+
+      const devCommands = createdResources.filter(
+        (resource) => resource.type === "sst:sst:DevCommand",
+      );
+      expect(devCommands).toHaveLength(1);
+      expect(devCommands[0].name).toBe("DevMultiContainerServiceDev");
+    });
+
     it("creates service with container field in rules", async () => {
       const service = new Service("MultiContainerService", {
         cluster,