fix(zero-style): correct timestep handling in episode continuation

web-ui/src/ZeroStyleApp.tsx

@@ -96,7 +96,7 @@ function getZeroStyleParams(): {
     assistantNoiseTopK,
   };
 }
-// TODO: inference_human timestep is currently incorrect
+
 function ZeroStyleApp() {
   const [problem, setProblem] = useState<Problem | null>(null);
   const [initCode, setInitCode] = useState("");

web-ui/src/app/api/episode-data/route.ts

@@ -52,14 +52,18 @@ export async function GET(request: NextRequest) {
       }
 
       // Get the specific timestep line
-      if (timestepNum > lines.length) {
+      // File structure: Line 0 = Header, Line 1 = timestep 0, Line 2 = timestep 1, etc.
+      // So timestep N is at line index N+1
+      const lineIndex = timestepNum + 1;
+
+      if (lineIndex >= lines.length) {
         return NextResponse.json(
-          { error: `Timestep ${timestepNum} exceeds available lines (${lines.length})` },
+          { error: `Timestep ${timestepNum} exceeds available data (max timestep: ${lines.length - 2})` },
           { status: 400 }
         );
       }
 
-      const timestepLine = lines[timestepNum]; // Timestep[i] is on line i+1
+      const timestepLine = lines[lineIndex];
       const timestepData = JSON.parse(timestepLine);
 
       const text = timestepData.text || '';

web-ui/src/simulation/simulators/StateServiceHumanSimulator.ts

@@ -119,8 +119,10 @@ export class StateServiceHumanSimulator implements HumanSimulator {
 
   setInitialTimestep(timestep: number): void {
     console.log("🎯 Setting initial timestep to:", timestep);
-    this.timestep = timestep;
-    console.log("🎯 Timestep after setting:", this.timestep);
+    // The provided timestep represents the last completed state in the attribution log.
+    // The next inference should start from timestep + 1.
+    this.timestep = timestep + 1;
+    console.log("🎯 Next inference will start at timestep:", this.timestep);
   }
 
   getStats(): SimulationStats {