diff --git a/cmd/omegaup-runner/main.go b/cmd/omegaup-runner/main.go
index 72200f0..313ae51 100644
--- a/cmd/omegaup-runner/main.go
+++ b/cmd/omegaup-runner/main.go
@@ -474,7 +474,9 @@ func runOneshotCI(ctx *common.Context, sandbox runner.Sandbox) *ci.Report {
 				"grade",
 				strconv.FormatUint(run.AttemptID, 10),
 			)
-			defer os.RemoveAll(runRoot)
+			if !ctx.Config.Runner.PreserveFiles {
+				defer os.RemoveAll(runRoot)
+			}
 
 			result, err := runner.Grade(ctx, nil, &run, inputRef.Input, sandbox)
 			if err != nil {
@@ -491,10 +493,18 @@ func runOneshotCI(ctx *common.Context, sandbox runner.Sandbox) *ci.Report {
 				ctx.Log.Error(
 					"Error generating outputs",
 					map[string]any{
-						"config": runConfig.OutGeneratorConfig,
-						"err":    err,
+						"config":       runConfig.OutGeneratorConfig,
+						"compileError": result.CompileError,
+						"err":          err,
 					},
 				)
+				if result.CompileError != nil {
+					return errors.Errorf(
+						"expecting a verdict of {AC, PA, WA}; got %s:\n%q",
+						result.Verdict,
+						*result.CompileError,
+					)
+				}
 				return errors.Errorf(
 					"expecting a verdict of {AC, PA, WA}; got %s",
 					result.Verdict,
@@ -675,7 +685,9 @@ func runOneshotCI(ctx *common.Context, sandbox runner.Sandbox) *ci.Report {
 							},
 						)
 					}
-					os.RemoveAll(runRoot)
+					if !ctx.Config.Runner.PreserveFiles {
+						os.RemoveAll(runRoot)
+					}
 				}()
 			}
 
@@ -747,7 +759,7 @@ func main() {
 			)
 			os.Exit(1)
 		}
-		if os.Getenv("PRESERVE") != "" {
+		if os.Getenv("PRESERVE") != "" || *oneshot == "ci" {
 			ctx.Config.Runner.PreserveFiles = true
 		}
 		if !ctx.Config.Runner.PreserveFiles {
@@ -801,7 +813,7 @@ func main() {
 			}
 			if *resultsOutputDirectory != "" {
 				{
-					f, err := os.Create(path.Join(*resultsOutputDirectory, "ci.log"))
+					err := os.WriteFile(path.Join(*resultsOutputDirectory, "ci.log"), ctx.LogBuffer(), 0o644)
 					if err != nil {
 						ctx.Log.Error(
 							"Failed to create log file",
@@ -809,17 +821,6 @@ func main() {
 								"err": err,
 							},
 						)
-					} else {
-						_, err = f.Write(ctx.LogBuffer())
-						f.Close()
-						if err != nil {
-							ctx.Log.Error(
-								"Failed to write log file",
-								map[string]any{
-									"err": err,
-								},
-							)
-						}
 					}
 				}
 				{
diff --git a/runner/sandbox.go b/runner/sandbox.go
index a5de671..af9332e 100644
--- a/runner/sandbox.go
+++ b/runner/sandbox.go
@@ -399,10 +399,24 @@ func (o *OmegajailSandbox) invokeOmegajail(ctx *common.Context, omegajailParams
 		cmd.Stderr = omegajailErrorFd
 	}
 	if err := cmd.Run(); err != nil {
+		var output string
+		if omegajailErrorFd != nil {
+			b, err := os.ReadFile(omegajailErrorFile)
+			if err == nil {
+				output = string(b)
+			}
+		}
+		if output == "" {
+			b, err := os.ReadFile(errorFile)
+			if err == nil {
+				output = string(b)
+			}
+		}
 		ctx.Log.Error(
 			"Omegajail execution failed",
 			map[string]any{
 				"err": err,
+				"out": output,
 			},
 		)
 	}