diff --git a/src/daemon/judge/index.ts b/src/daemon/judge/index.ts
index 7ded701..68dc924 100644
--- a/src/daemon/judge/index.ts
+++ b/src/daemon/judge/index.ts
@@ -32,6 +32,7 @@ export async function judge(
     }
 
     let judger: JudgerBase;
+    console.log("Task typ: " + task.type);
     if (task.type === ProblemType.Standard) {
         judger = new StandardJudger(testData, task.param as StandardJudgeParameter, task.priority);
     } else if (task.type === ProblemType.AnswerSubmission) {
diff --git a/src/daemon/judge/interaction.ts b/src/daemon/judge/interaction.ts
index 4ba14b1..627b4d3 100644
--- a/src/daemon/judge/interaction.ts
+++ b/src/daemon/judge/interaction.ts
@@ -26,7 +26,7 @@ export class InteractionJudger extends JudgerBase {
 
     async preprocessTestData(): Promise<void> {
         if (this.testData.interactor != null) {
-            winston.verbose("Compiling special judge.");
+            winston.verbose("Compiling interactor.");
             const [interactorExecutableName, interactorResult] = await compile(this.testData.interactor.sourceCode,
                 this.testData.interactor.language, null, this.priority);
             if (interactorResult.status !== TaskStatus.Done) {
@@ -69,9 +69,9 @@ export class InteractionJudger extends JudgerBase {
 
         // We do not have to create a InteractionRunResult
         const [inputContent, outputContent, runResult]: [string, string, StandardRunResult] = await Promise.all([
-            readFileLength(pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.input), Cfg.dataDisplayLimit),
-            readFileLength(pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.output), Cfg.dataDisplayLimit),
-            runTask({ type: RPCTaskType.RunStandard, task: task }, this.priority, started)
+            readFileLength(curCase.input ? pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.input) : null, Cfg.dataDisplayLimit),
+            readFileLength(curCase.output ? pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.output) : null, Cfg.dataDisplayLimit),
+            runTask({ type: RPCTaskType.RunInteraction, task: task }, this.priority, started)
         ]) as any;
 
         return {
diff --git a/src/daemon/judge/standard.ts b/src/daemon/judge/standard.ts
index a48dd52..9db7646 100644
--- a/src/daemon/judge/standard.ts
+++ b/src/daemon/judge/standard.ts
@@ -70,8 +70,8 @@ export class StandardJudger extends JudgerBase {
         };
 
         const [inputContent, outputContent, runResult]: [string, string, StandardRunResult] = await Promise.all([
-            readFileLength(pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.input), Cfg.dataDisplayLimit),
-            readFileLength(pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.output), Cfg.dataDisplayLimit),
+            readFileLength(curCase.input ? pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.input) : null, Cfg.dataDisplayLimit),
+            readFileLength(curCase.output ? pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.output) : null, Cfg.dataDisplayLimit),
             runTask({ type: RPCTaskType.RunStandard, task: task }, this.priority, started)
         ]) as any;
 
diff --git a/src/daemon/judge/submit-answer.ts b/src/daemon/judge/submit-answer.ts
index 4f65f34..986347f 100644
--- a/src/daemon/judge/submit-answer.ts
+++ b/src/daemon/judge/submit-answer.ts
@@ -77,8 +77,8 @@ export class AnswerSubmissionJudger extends JudgerBase {
         }
 
         const [inputContent, outputContent, runResult]: [string, string, AnswerSubmissionRunResult] = await Promise.all([
-            readFileLength(pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.input), Cfg.dataDisplayLimit),
-            readFileLength(pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.output), Cfg.dataDisplayLimit),
+            readFileLength(curCase.input ? pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.input) : null, Cfg.dataDisplayLimit),
+            readFileLength(curCase.output ? pathLib.join(Cfg.testDataDirectory, this.testData.name, curCase.output) : null, Cfg.dataDisplayLimit),
             runTask({ type: RPCTaskType.RunSubmitAnswer, task: task }, this.priority, started)
         ]) as any;
 
diff --git a/src/runner/judge.ts b/src/runner/judge.ts
index 840dbaa..1a06c71 100644
--- a/src/runner/judge.ts
+++ b/src/runner/judge.ts
@@ -1,8 +1,9 @@
 import pathLib = require('path');
 import randomString = require('randomstring');
+import util = require('util');
 import fse = require('fs-extra');
 import winston = require('winston');
-import syspipe = require('syspipe');
+const syspipe = require('syspipe');
 
 import { SandboxStatus } from 'simple-sandbox/lib/interfaces';
 import { TestcaseResultType, StandardRunTask, StandardRunResult, InteractionRunTask, AnswerSubmissionRunTask, AnswerSubmissionRunResult } from '../interfaces';
@@ -285,7 +286,7 @@ export async function judgeInteraction(task: InteractionRunTask)
         winston.debug("Fetching user binary...");
         const [userBinaryDirectory, userLanguage, userCode] = await fetchBinary(task.userExecutableName);
         winston.debug("Fetching interactor binary...");
-        const [interactorBinaryDirectory, interactorLanguage] = await fetchBinary(task.userExecutableName);
+        const [interactorBinaryDirectory, interactorLanguage] = await fetchBinary(task.interactorExecutableName);
 
         pipe1 = syspipe.pipe(),
             pipe2 = syspipe.pipe();
@@ -311,8 +312,6 @@ export async function judgeInteraction(task: InteractionRunTask)
         const [interactorResult, runResult] = await Promise.all([interactorTaskPromise
             .then((result) => { stopUser(); return result; }, (err) => { stopUser(); return Promise.reject(err); }), userProgramTaskPromise]);
 
-        const userError = await readFileLength(pathLib.join(workingDir, tempErrFile), Cfg.stderrDisplayLimit);
-
         const time = Math.round(runResult.result.time / 1e6),
             memory = runResult.result.memory / 1024;
 
@@ -327,6 +326,7 @@ export async function judgeInteraction(task: InteractionRunTask)
             message = `Killed: ${signals[runResult.result.code]}`;
             status = TestcaseResultType.RuntimeError;
         } else if (runResult.result.status !== SandboxStatus.OK) {
+            message = "Warning: corrupt sandbox result " + util.inspect(runResult.result);
             status = TestcaseResultType.RuntimeError;
         } else {
             message = `Exited with return code ${runResult.result.code}`;
@@ -344,7 +344,7 @@ export async function judgeInteraction(task: InteractionRunTask)
             time: time,
             memory: time,
             userOutput: null,
-            userError: userError,
+            userError: await readFileLength(pathLib.join(workingDir, tempErrFile), Cfg.stderrDisplayLimit),
             spjMessage: await readFileLength(pathLib.join(spjWorkingDir, tempErrFile), Cfg.stderrDisplayLimit)
         };
 
@@ -352,21 +352,23 @@ export async function judgeInteraction(task: InteractionRunTask)
         let score = 0;
         if (status == null) {
             const scoreString = await tryReadFile(spjWorkingDir + '/score.txt');
-            let score = Number(scoreString);
-            if ((!scoreString) || isNaN(score)) {
+            const rawScore = Number(scoreString);
+            if ((!scoreString) || isNaN(rawScore)) {
+                score = null;
                 status = TestcaseResultType.JudgementFailed;
                 message = `Interactor returned a non-number score ${scoreString}`;
             } else if (score === -1) {
-                score = 0;
                 status = TestcaseResultType.InvalidInteraction;
             } else {
-                score = score;
-                status = getStatusByScore(score);
+                score = rawScore;
+                status = getStatusByScore(rawScore);
             }
         }
+        winston.debug(`Interaction problem judge succeeded, score = ${score}`);
         return Object.assign(partialResult, {
             result: status,
-            scoringRate: score / spjFullScore
+            scoringRate: score / spjFullScore,
+            systemMessage: message
         });
     } finally {
         const closePipe = async (p) => {