diff --git a/frontend/scripts/research/consult-biography-backtest.mts b/frontend/scripts/research/consult-biography-backtest.mts
index 47b2ad4b..fd565c0f 100644
--- a/frontend/scripts/research/consult-biography-backtest.mts
+++ b/frontend/scripts/research/consult-biography-backtest.mts
@@ -291,7 +291,9 @@ async function runJob(job: Job, resolved: ResolvedLanguageModel) {
   const runId = ctx.requestId;
   // route.ts consultationBaseMessages: stored history as plain messages, then this turn.
   const baseMessages = [
-    ...historyOf(job.followUp).map((message) => ({ role: message.role, content: message.text })),
+    ...historyOf(job.followUp).map((message) => (message.role === "user"
+      ? { role: "user" as const, content: message.text }
+      : { role: "assistant" as const, content: message.text })),
     { role: "user" as const, content: userTurn(job.question, job.followUp) },
   ];
   const streamOptions = {