Add structured Error in HarnessEnd

Makefile

@@ -21,6 +21,7 @@ proto:
 		protoc --go_out=. --go_opt=paths=source_relative \
 		       --go-grpc_out=. --go-grpc_opt=paths=source_relative \
 		       proto/ax.proto proto/content.proto
+	@python3 -m grpc_tools.protoc -I. --python_out=python --grpc_python_out=python proto/ax.proto proto/content.proto
 	@echo "Protobuf generation complete!"
 
 # Run tests

cmd/ax/harnessclient.go

@@ -116,7 +116,12 @@ func runHarnessClient(cmd *cobra.Command, args []string) error {
 				fmt.Printf("Server > message[%d] (%s): %s\n", i, m.Role, text)
 			}
 		case *proto.HarnessResponse_End:
-			fmt.Printf("Server > [end] state=%s %s\n", payload.End.GetState(), payload.End.GetErrorMessage())
+			if errDetail := payload.End.GetError(); errDetail != nil {
+				fmt.Printf("Server > [end] state=%s error=(code=%d description=%q)\n",
+					payload.End.GetState(), errDetail.GetCode(), errDetail.GetDescription())
+			} else {
+				fmt.Printf("Server > [end] state=%s\n", payload.End.GetState())
+			}
 		}
 	}
 

internal/harness/antigravity.go

@@ -155,7 +155,10 @@ func (e *antigravityExecution) Run(ctx context.Context, handler Handler) error {
 			}
 		case *proto.HarnessResponse_End:
 			if payload.End.GetState() == proto.State_STATE_FAILED {
-				return fmt.Errorf("harness failed: %s", payload.End.GetErrorMessage())
+				if errDetail := payload.End.GetError(); errDetail != nil {
+					return fmt.Errorf("harness failed: [%d] %s", errDetail.GetCode(), errDetail.GetDescription())
+				}
+				return fmt.Errorf("harness failed with no error details")
 			}
 			return handler.OnComplete(ctx, e.id)
 		}

internal/harness/mocks_test.go

@@ -100,6 +100,8 @@ type mockHarnessServer struct {
 	failConnect bool
 	// failFrame makes Connect terminate the turn with HarnessEnd{STATE_FAILED}.
 	failFrame bool
+	// errCode is the error code used by failFrame.
+	errCode int32
 	// errMessage is the error text used by failConnect/failFrame.
 	errMessage string
 
@@ -138,7 +140,13 @@ func (s *mockHarnessServer) Connect(stream proto.HarnessService_ConnectServer) e
 		return stream.Send(&proto.HarnessResponse{
 			ConversationId: convID,
 			Type: &proto.HarnessResponse_End{
-				End: &proto.HarnessEnd{State: proto.State_STATE_FAILED, ErrorMessage: s.errMessage},
+				End: &proto.HarnessEnd{
+					State: proto.State_STATE_FAILED,
+					Error: &proto.Error{
+						Code:        s.errCode,
+						Description: s.errMessage,
+					},
+				},
 			},
 		})
 	}

internal/harness/substrate.go

@@ -232,7 +232,10 @@ func (e *substrateExecution) Run(ctx context.Context, handler Handler) error {
 			}
 		case *proto.HarnessResponse_End:
 			if payload.End.GetState() == proto.State_STATE_FAILED {
-				return fmt.Errorf("harness failed: %s", payload.End.GetErrorMessage())
+				if errDetail := payload.End.GetError(); errDetail != nil {
+					return fmt.Errorf("harness failed: [%d] %s", errDetail.GetCode(), errDetail.GetDescription())
+				}
+				return fmt.Errorf("harness failed with no error details")
 			}
 			return handler.OnComplete(ctx, e.execID)
 		}

internal/harness/substrate_test.go

@@ -269,7 +269,7 @@ func TestSubstrateHarness_ResumeNilActor(t *testing.T) {
 
 func TestSubstrateHarness_HarnessFailedFrame(t *testing.T) {
 	ctrl := &mockControlServer{resumeIP: "127.0.0.1"}
-	srv := &mockHarnessServer{failFrame: true, errMessage: "boom"}
+	srv := &mockHarnessServer{failFrame: true, errCode: 13, errMessage: "boom"}
 	h := newTestSubstrateHarness(t, startControlServer(t, ctrl), startHarnessServer(t, srv))
 
 	ctx := context.Background()