diff --git a/web/workspace/src/lib/workspace/memory/conversation-api.test.ts b/web/workspace/src/lib/workspace/memory/conversation-api.test.ts
index 76400b932..1e66b60f2 100644
--- a/web/workspace/src/lib/workspace/memory/conversation-api.test.ts
+++ b/web/workspace/src/lib/workspace/memory/conversation-api.test.ts
@@ -141,6 +141,29 @@ Deno.test("revisit uses the same account-scoped create input then reads authorit
   );
 });
 
+Deno.test("a full page of maximum-size JSON-escaped text fits the bounded public response reader", async () => {
+  const text = "x" + "\u0001".repeat(CHAT_LIMITS.maxTextBytes - 1);
+  const messages = Array.from(
+    { length: CHAT_LIMITS.maxPageLimit },
+    (_, index) => ({
+      ...message(index + 1),
+      text,
+    }),
+  );
+  const wire = JSON.stringify(page(messages));
+  assert(new TextEncoder().encode(wire).length > 2 * 1024 * 1024);
+  const fetchFn: typeof fetch = () => Promise.resolve(new Response(wire));
+  const result = await getConversationPage(
+    fetchFn,
+    scope,
+    conversation.id,
+    0,
+    new AbortController().signal,
+  );
+  assert(result.messages.length === CHAT_LIMITS.maxPageLimit);
+  assert(result.messages.at(-1)?.text === text);
+});
+
 Deno.test("ACK loss retains exact request bytes for explicit replay and accepted is not a reply", async () => {
   const saved = new Map<string, string>();
   const storage = {
diff --git a/web/workspace/src/lib/workspace/memory/conversation-api.ts b/web/workspace/src/lib/workspace/memory/conversation-api.ts
index fb6fcdf37..0361af55f 100644
--- a/web/workspace/src/lib/workspace/memory/conversation-api.ts
+++ b/web/workspace/src/lib/workspace/memory/conversation-api.ts
@@ -224,7 +224,8 @@ async function request(
     throw new ConversationApiError(response.status);
   }
   try {
-    return await readBoundedJson(response, 2 * 1024 * 1024);
+    // 100件×16KiBの有効な本文はJSON escapeで6倍になり得る。
+    return await readBoundedJson(response, 16 * 1024 * 1024);
   } catch {
     throw new ConversationApiError(null);
   }