fix: 40GB disk for docker Spot instances (monorepo + Docker layers)

orchestrator/dispatch/main.go

@@ -309,6 +309,12 @@ func startSpotRunner(ctx context.Context, c cfg, label, runID string) (string, e
 
 	client := ec2.NewFromConfig(awsCfg)
 
+	// Docker builds need more disk (monorepo + layers)
+	diskSize := int32(20)
+	if label == "docker" {
+		diskSize = 40
+	}
+
 	out, err := client.RunInstances(ctx, &ec2.RunInstancesInput{
 		ImageId:      aws.String(c.AMI),
 		InstanceType: ec2types.InstanceType(spot.InstanceType),
@@ -316,6 +322,16 @@ func startSpotRunner(ctx context.Context, c cfg, label, runID string) (string, e
 		MaxCount:     aws.Int32(1),
 		UserData:     aws.String(userData),
 
+		// Root volume — bigger for Docker builds
+		BlockDeviceMappings: []ec2types.BlockDeviceMapping{{
+			DeviceName: aws.String("/dev/xvda"),
+			Ebs: &ec2types.EbsBlockDevice{
+				VolumeSize:          aws.Int32(diskSize),
+				VolumeType:          ec2types.VolumeTypeGp3,
+				DeleteOnTermination: aws.Bool(true),
+			},
+		}},
+
 		// Spot request
 		InstanceMarketOptions: &ec2types.InstanceMarketOptionsRequest{
 			MarketType: ec2types.MarketTypeSpot,