diff --git a/src/gateway/server-methods/chat.ts b/src/gateway/server-methods/chat.ts
index 353e7d74771..b8e99447929 100644
--- a/src/gateway/server-methods/chat.ts
+++ b/src/gateway/server-methods/chat.ts
@@ -700,6 +700,17 @@ function sanitizeChatHistoryContentBlock(
     entry.bytes = bytes;
     changed = true;
   }
+  if (type === "audio" && entry.source && typeof entry.source === "object") {
+    const source = { ...(entry.source as Record<string, unknown>) };
+    if (source.type === "base64" && typeof source.data === "string") {
+      const bytes = Buffer.byteLength(source.data, "utf8");
+      delete source.data;
+      source.omitted = true;
+      source.bytes = bytes;
+      entry.source = source;
+      changed = true;
+    }
+  }
   return { block: changed ? entry : block, changed };
 }
 
diff --git a/src/gateway/server-methods/server-methods.test.ts b/src/gateway/server-methods/server-methods.test.ts
index fc3a6c8eda8..46bd9aad86b 100644
--- a/src/gateway/server-methods/server-methods.test.ts
+++ b/src/gateway/server-methods/server-methods.test.ts
@@ -263,6 +263,46 @@ describe("injectTimestamp", () => {
 });
 
 describe("sanitizeChatHistoryMessages", () => {
+  it("redacts base64 audio content blocks from chat history", () => {
+    const data = Buffer.from("voice-bytes").toString("base64");
+    const result = sanitizeChatHistoryMessages([
+      {
+        role: "assistant",
+        content: [
+          { type: "text", text: "Audio reply" },
+          {
+            type: "audio",
+            source: {
+              type: "base64",
+              media_type: "audio/mp3",
+              data,
+            },
+          },
+        ],
+        timestamp: 1,
+      },
+    ]);
+
+    expect(result).toEqual([
+      {
+        role: "assistant",
+        content: [
+          { type: "text", text: "Audio reply" },
+          {
+            type: "audio",
+            source: {
+              type: "base64",
+              media_type: "audio/mp3",
+              omitted: true,
+              bytes: Buffer.byteLength(data, "utf8"),
+            },
+          },
+        ],
+        timestamp: 1,
+      },
+    ]);
+  });
+
   it("drops commentary-only assistant entries when phase exists only in textSignature", () => {
     const result = sanitizeChatHistoryMessages([
       {