diff --git a/GUIDE.md b/GUIDE.md
index a1c9401..d5779cb 100644
--- a/GUIDE.md
+++ b/GUIDE.md
@@ -1,5 +1,3 @@
-**English** | [简体中文](./GUIDE.zh-CN.md)
-
 # DingTalk Channel SDK Integration Guide
 
 Connect your Agent to DingTalk for real-time conversations in **group chats and direct messages**. The SDK handles event ingestion, message parsing and deduplication, reply sending, streaming output (typewriter effect), media upload/download, and card interactions—you just need to tell it "what the user said and what the bot should respond with."
diff --git a/OVERVIEW.md b/OVERVIEW.md
index 9f45fee..b1c33fa 100644
--- a/OVERVIEW.md
+++ b/OVERVIEW.md
@@ -1,5 +1,3 @@
-**English** | [简体中文](./OVERVIEW.zh-CN.md)
-
 # DingTalk Channel SDK Family · Project Overview
 
 > Origin issue: [DingTalk-Real-AI/dingtalk-workspace-cli#796](https://github.com/DingTalk-Real-AI/dingtalk-workspace-cli/issues/796)—"Will DingTalk offer a Channel-like integration SDK in the future?"
diff --git a/SPEC.md b/SPEC.md
index 1ec2b1d..15c24ae 100644
--- a/SPEC.md
+++ b/SPEC.md
@@ -1,5 +1,3 @@
-**English** | [简体中文](./SPEC.zh-CN.md)
-
 # DingTalk Channel SDK — Four-Language Unified Contract (SPEC v0.1)
 
 > Positioning: **A conversation access layer decoupled from Agent runtime**. The SDK handles the dirty work of the "channel",
diff --git a/src/main/java/com/dingtalk/channel/DingTalkChannel.java b/src/main/java/com/dingtalk/channel/DingTalkChannel.java
index 63ce332..5ec3450 100644
--- a/src/main/java/com/dingtalk/channel/DingTalkChannel.java
+++ b/src/main/java/com/dingtalk/channel/DingTalkChannel.java
@@ -198,7 +198,7 @@ public byte[] downloadFile(String downloadCode, String msgId, String mediaType)
         try {
             java.net.HttpURLConnection conn = openMediaConnection(downloadUrl);
             try (java.io.InputStream in = conn.getInputStream()) {
-                return in.readAllBytes();
+                return readAll(in);
             } finally {
                 conn.disconnect();
             }
@@ -278,7 +278,7 @@ private java.net.HttpURLConnection openMediaConnection(String initialUrl) throws
             if (status != 200) {
                 try (java.io.InputStream err = conn.getErrorStream()) {
                     if (err != null) {
-                        err.readAllBytes();
+                        readAll(err);
                     }
                 } finally {
                     conn.disconnect();
@@ -290,6 +290,16 @@ private java.net.HttpURLConnection openMediaConnection(String initialUrl) throws
         throw new java.io.IOException("too many redirects");
     }
 
+    private static byte[] readAll(java.io.InputStream in) throws java.io.IOException {
+        java.io.ByteArrayOutputStream buf = new java.io.ByteArrayOutputStream();
+        byte[] chunk = new byte[8192];
+        int n;
+        while ((n = in.read(chunk)) != -1) {
+            buf.write(chunk, 0, n);
+        }
+        return buf.toByteArray();
+    }
+
     /** 换取媒体下载 URL（downloadCode → downloadUrl）。 */
     private String resolveDownloadUrl(String downloadCode, String msgId) {
         if (downloadCode == null || downloadCode.isEmpty()) {
diff --git a/src/test/java/com/dingtalk/channel/safety/PolicyOverrideTest.java b/src/test/java/com/dingtalk/channel/safety/PolicyOverrideTest.java
index 1e1def0..b8a1d8a 100644
--- a/src/test/java/com/dingtalk/channel/safety/PolicyOverrideTest.java
+++ b/src/test/java/com/dingtalk/channel/safety/PolicyOverrideTest.java
@@ -4,8 +4,8 @@
 import com.dingtalk.channel.IncomingMessage;
 import org.junit.Test;
 
+import java.util.Arrays;
 import java.util.HashMap;
-import java.util.List;
 import java.util.Map;
 
 import static org.junit.Assert.assertEquals;
@@ -29,7 +29,7 @@ public void overrideAdmitsGroupInAllowlistMode() {
         Map<String, PolicyConfig.GroupOverride> ov = new HashMap<>();
         ov.put("cid-other", new PolicyConfig.GroupOverride());
         PolicyGate gate = new PolicyGate(new PolicyConfig()
-                .groupAllowlist(List.of("cid-allowed"))
+                .groupAllowlist(Arrays.asList("cid-allowed"))
                 .groupOverrides(ov));
         assertTrue(gate.evaluate(msg("cid-other", "staff-1", true)).allowed);
         assertEquals(RejectReason.GROUP_NOT_ALLOWED, gate.evaluate(msg("cid-unknown", "staff-1", true)).reason);
@@ -40,7 +40,7 @@ public void blocklistNeverOverridden() {
         Map<String, PolicyConfig.GroupOverride> ov = new HashMap<>();
         ov.put("cid-bad", new PolicyConfig.GroupOverride().enabled(true));
         PolicyGate gate = new PolicyGate(new PolicyConfig()
-                .groupBlocklist(List.of("cid-bad"))
+                .groupBlocklist(Arrays.asList("cid-bad"))
                 .groupOverrides(ov));
         assertEquals(RejectReason.GROUP_BLOCKED, gate.evaluate(msg("cid-bad", "staff-1", true)).reason);
     }
@@ -66,8 +66,8 @@ public void overrideDisableAndRequireMention() {
     public void overrideAllowFromAndBlockFrom() {
         Map<String, PolicyConfig.GroupOverride> ov = new HashMap<>();
         ov.put("cid-1", new PolicyConfig.GroupOverride()
-                .allowFrom(List.of("staff-1", "staff-2"))
-                .blockFrom(List.of("staff-2")));
+                .allowFrom(Arrays.asList("staff-1", "staff-2"))
+                .blockFrom(Arrays.asList("staff-2")));
         PolicyGate gate = new PolicyGate(new PolicyConfig().groupOverrides(ov));
         assertTrue(gate.evaluate(msg("cid-1", "staff-1", true)).allowed);
         assertEquals(RejectReason.SENDER_NOT_ALLOWED, gate.evaluate(msg("cid-1", "staff-9", true)).reason);