diff --git a/cchat.go b/cchat.go
index f90cde0..5151cd2 100644
--- a/cchat.go
+++ b/cchat.go
@@ -252,15 +252,16 @@ type Backlogger interface {
 // are not in cchat through a very basic terminal interface.
 type Commander interface {
 	// Run executes the given command, with the slice being already split arguments,
-	// similar to os.Args. The function could return an output stream, in which the
-	// frontend must display it live and close it on EOF.
+	// similar to os.Args. The function can return both a []byte and an error value.
+	// The frontend should render the byte slice's value first, then display the
+	// error.
 	//
-	// The function can do IO, and outputs should be written to the given io.Writer.
+	// This function can do IO.
 	//
 	// The client should make guarantees that an empty string (and thus a
 	// zero-length string slice) should be ignored. The backend should be able to
 	// assume that the argument slice is always length 1 or more.
-	Run([]string, io.Writer) error // Blocking
+	Run(words []string) ([]byte, error) // Blocking
 
 	// Asserters.
 
diff --git a/repository/main.go b/repository/main.go
index 4ebe050..b93c6e2 100644
--- a/repository/main.go
+++ b/repository/main.go
@@ -851,23 +851,23 @@ var Main = Packages{
 						Comment: Comment{`
 							Run executes the given command, with the slice being
 							already split arguments, similar to os.Args. The
-							function could return an output stream, in which the
-							frontend must display it live and close it on EOF.
+							function can return both a []byte and an error
+							value. The frontend should render the byte slice's
+							value first, then display the error.
 
-							The function can do IO, and outputs should be
-							written to the given io.Writer.
+							This function can do IO.
 
 							The client should make guarantees that an empty
 							string (and thus a zero-length string slice) should
-							be ignored.  The backend should be able to assume
+							be ignored. The backend should be able to assume
 							that the argument slice is always length 1 or more.
 						`},
 						Name: "Run",
 					},
 					Parameters: []NamedType{
-						{Type: "[]string"},
-						{Type: "io.Writer"},
+						{Name: "words", Type: "[]string"},
 					},
+					ReturnValue: NamedType{Type: "[]byte"},
 					ReturnError: true,
 				},
 				AsserterMethod{ChildType: "Completer"},