diff --git a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
index 10e340d7f8f..d760bba414c 100644
--- a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
@@ -1841,8 +1841,9 @@ function Question(props: ToolProps<typeof QuestionTool>) {
   const { theme } = useTheme()
   const count = createMemo(() => props.input.questions?.length ?? 0)
 
-  function format(answer?: string[]) {
+  function format(answer?: string[] | string) {
     if (!answer?.length) return "(no answer)"
+    if (!Array.isArray(answer)) return String(answer)
     return answer.join(", ")
   }
 
diff --git a/packages/opencode/src/tool/question.ts b/packages/opencode/src/tool/question.ts
index c6f0b91599b..9e680b42258 100644
--- a/packages/opencode/src/tool/question.ts
+++ b/packages/opencode/src/tool/question.ts
@@ -15,8 +15,9 @@ export const QuestionTool = Tool.define("question", {
       tool: ctx.callID ? { messageID: ctx.messageID, callID: ctx.callID } : undefined,
     })
 
-    function format(answer: Question.Answer | undefined) {
+    function format(answer: Question.Answer | string | undefined) {
       if (!answer?.length) return "Unanswered"
+      if (!Array.isArray(answer)) return String(answer)
       return answer.join(", ")
     }