diff --git a/slack-base/src/main/java/com/hubspot/slack/client/methods/SlackMethods.java b/slack-base/src/main/java/com/hubspot/slack/client/methods/SlackMethods.java
index ecddefd4..98504b67 100644
--- a/slack-base/src/main/java/com/hubspot/slack/client/methods/SlackMethods.java
+++ b/slack-base/src/main/java/com/hubspot/slack/client/methods/SlackMethods.java
@@ -275,7 +275,11 @@ public enum SlackMethods implements SlackMethod {
     RateLimitingTiers.TIER_2,
     JsonStatus.ACCEPTS_JSON
   ),
-
+  files_completeUploadExternal(
+    MethodWriteMode.WRITE,
+    RateLimitingTiers.TIER_4,
+    JsonStatus.ACCEPTS_JSON
+  ),
   files_delete(MethodWriteMode.WRITE, RateLimitingTiers.TIER_3, JsonStatus.ACCEPTS_JSON),
   files_getUploadURLExternal(
     MethodWriteMode.WRITE,
diff --git a/slack-base/src/main/java/com/hubspot/slack/client/methods/params/files/CompleteUploadExternalParamsIF.java b/slack-base/src/main/java/com/hubspot/slack/client/methods/params/files/CompleteUploadExternalParamsIF.java
new file mode 100644
index 00000000..44b68055
--- /dev/null
+++ b/slack-base/src/main/java/com/hubspot/slack/client/methods/params/files/CompleteUploadExternalParamsIF.java
@@ -0,0 +1,20 @@
+package com.hubspot.slack.client.methods.params.files;
+
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import com.hubspot.immutables.style.HubSpotStyle;
+import java.util.List;
+import java.util.Optional;
+import org.immutables.value.Value.Immutable;
+
+@Immutable
+@HubSpotStyle
+@JsonNaming(SnakeCaseStrategy.class)
+@JsonInclude(JsonInclude.Include.NON_EMPTY)
+public interface CompleteUploadExternalParamsIF {
+  List<FileInfo> getFiles();
+  Optional<String> getChannelId();
+  Optional<String> getThreadTs();
+  Optional<String> getInitialComment();
+}
diff --git a/slack-base/src/main/java/com/hubspot/slack/client/methods/params/files/FileInfoIF.java b/slack-base/src/main/java/com/hubspot/slack/client/methods/params/files/FileInfoIF.java
new file mode 100644
index 00000000..6c4beeef
--- /dev/null
+++ b/slack-base/src/main/java/com/hubspot/slack/client/methods/params/files/FileInfoIF.java
@@ -0,0 +1,14 @@
+package com.hubspot.slack.client.methods.params.files;
+
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import com.hubspot.immutables.style.HubSpotStyle;
+import org.immutables.value.Value.Immutable;
+
+@Immutable
+@HubSpotStyle
+@JsonNaming(SnakeCaseStrategy.class)
+public interface FileInfoIF {
+  String getId();
+  String getTitle();
+}
diff --git a/slack-base/src/main/java/com/hubspot/slack/client/models/response/files/CompleteUploadExternalResponseIF.java b/slack-base/src/main/java/com/hubspot/slack/client/models/response/files/CompleteUploadExternalResponseIF.java
new file mode 100644
index 00000000..1a4f8854
--- /dev/null
+++ b/slack-base/src/main/java/com/hubspot/slack/client/models/response/files/CompleteUploadExternalResponseIF.java
@@ -0,0 +1,16 @@
+package com.hubspot.slack.client.models.response.files;
+
+import com.fasterxml.jackson.databind.PropertyNamingStrategies.SnakeCaseStrategy;
+import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import com.hubspot.immutables.style.HubSpotStyle;
+import com.hubspot.slack.client.models.files.SlackFile;
+import com.hubspot.slack.client.models.response.SlackResponse;
+import java.util.List;
+import org.immutables.value.Value.Immutable;
+
+@Immutable
+@HubSpotStyle
+@JsonNaming(SnakeCaseStrategy.class)
+public interface CompleteUploadExternalResponseIF extends SlackResponse {
+  List<SlackFile> getFiles();
+}
diff --git a/slack-java-client/src/main/java/com/hubspot/slack/client/SlackClient.java b/slack-java-client/src/main/java/com/hubspot/slack/client/SlackClient.java
index 8ea43b76..c898c9fd 100644
--- a/slack-java-client/src/main/java/com/hubspot/slack/client/SlackClient.java
+++ b/slack-java-client/src/main/java/com/hubspot/slack/client/SlackClient.java
@@ -48,6 +48,7 @@
 import com.hubspot.slack.client.methods.params.dialog.DialogOpenParams;
 import com.hubspot.slack.client.methods.params.dnd.DndInfoParams;
 import com.hubspot.slack.client.methods.params.dnd.DndSetSnoozeParams;
+import com.hubspot.slack.client.methods.params.files.CompleteUploadExternalParams;
 import com.hubspot.slack.client.methods.params.files.FilesSharedPublicUrlParams;
 import com.hubspot.slack.client.methods.params.files.FilesUploadParams;
 import com.hubspot.slack.client.methods.params.files.GetUploadUrlExternalParams;
@@ -118,6 +119,8 @@
 import com.hubspot.slack.client.models.response.dnd.DndInfoResponse;
 import com.hubspot.slack.client.models.response.dnd.DndSnoozeResponse;
 import com.hubspot.slack.client.models.response.emoji.EmojiListResponse;
+import com.hubspot.slack.client.models.response.files.CompleteUploadExternalResponse;
+import com.hubspot.slack.client.models.response.files.CompleteUploadExternalResponseIF;
 import com.hubspot.slack.client.models.response.files.FilesSharedPublicUrlResponse;
 import com.hubspot.slack.client.models.response.files.FilesUploadResponse;
 import com.hubspot.slack.client.models.response.files.GetUploadUrlExternalResponse;
@@ -392,10 +395,12 @@ CompletableFuture<Result<AddReactionResponse, SlackError>> addReaction(
   CompletableFuture<Result<FilesUploadResponse, SlackError>> uploadFile(
     FilesUploadParams params
   );
-
   CompletableFuture<Result<GetUploadUrlExternalResponse, SlackError>> getUploadURLExternal(
     GetUploadUrlExternalParams params
   );
+  CompletableFuture<Result<CompleteUploadExternalResponse, SlackError>> completeUploadExternal(
+    CompleteUploadExternalParams params
+  );
   CompletableFuture<Result<FilesSharedPublicUrlResponse, SlackError>> shareFilePublically(
     FilesSharedPublicUrlParams params
   );
diff --git a/slack-java-client/src/main/java/com/hubspot/slack/client/SlackWebClient.java b/slack-java-client/src/main/java/com/hubspot/slack/client/SlackWebClient.java
index e259e55e..c4a90b80 100644
--- a/slack-java-client/src/main/java/com/hubspot/slack/client/SlackWebClient.java
+++ b/slack-java-client/src/main/java/com/hubspot/slack/client/SlackWebClient.java
@@ -79,6 +79,7 @@
 import com.hubspot.slack.client.methods.params.dialog.DialogOpenParams;
 import com.hubspot.slack.client.methods.params.dnd.DndInfoParams;
 import com.hubspot.slack.client.methods.params.dnd.DndSetSnoozeParams;
+import com.hubspot.slack.client.methods.params.files.CompleteUploadExternalParams;
 import com.hubspot.slack.client.methods.params.files.FilesSharedPublicUrlParams;
 import com.hubspot.slack.client.methods.params.files.FilesUploadParams;
 import com.hubspot.slack.client.methods.params.files.GetUploadUrlExternalParams;
@@ -155,6 +156,7 @@
 import com.hubspot.slack.client.models.response.dnd.DndInfoResponse;
 import com.hubspot.slack.client.models.response.dnd.DndSnoozeResponse;
 import com.hubspot.slack.client.models.response.emoji.EmojiListResponse;
+import com.hubspot.slack.client.models.response.files.CompleteUploadExternalResponse;
 import com.hubspot.slack.client.models.response.files.FilesSharedPublicUrlResponse;
 import com.hubspot.slack.client.models.response.files.FilesUploadResponse;
 import com.hubspot.slack.client.models.response.files.GetUploadUrlExternalResponse;
@@ -596,7 +598,7 @@ protected LazyLoadingPage<Result<List<LiteMessage>, SlackError>, Long> getPage(
         ChannelsHistoryParams.Builder requestBuilder = ChannelsHistoryParams
           .builder()
           .from(params);
-        if (!params.getCount().isPresent()) {
+        if (params.getCount().isEmpty()) {
           requestBuilder.setCount(config.getChannelsHistoryMessageBatchSize().get());
         }
 
@@ -633,7 +635,7 @@ protected LazyLoadingPage<Result<List<LiteMessage>, SlackError>, Long> getPage(
           );
 
         CompletableFuture<Boolean> hasMoreFuture = resultFuture.thenApply(result ->
-          result.match(err -> false, ok -> ok.hasMore())
+          result.match(err -> false, ChannelsHistoryResponse::hasMore)
         );
         CompletableFuture<Long> nextOffset = nextOffset(pagingDirection, pageFuture);
 
@@ -646,8 +648,8 @@ private CompletableFuture<Long> nextOffset(
     PagingDirection pagingDirection,
     CompletableFuture<Result<List<LiteMessage>, SlackError>> pageFuture
   ) {
-    return pageFuture.thenApply(page -> {
-      return page.match(
+    return pageFuture.thenApply(page ->
+      page.match(
         err -> null,
         messages -> {
           Set<String> timestamps = messages
@@ -670,8 +672,8 @@ private CompletableFuture<Long> nextOffset(
 
           return null;
         }
-      );
-    });
+      )
+    );
   }
 
   @Override
@@ -1037,7 +1039,7 @@ protected LazyLoadingPage<Result<List<LiteMessage>, SlackError>, Long> getPage(
         ConversationsHistoryParams.Builder requestBuilder = ConversationsHistoryParams
           .builder()
           .from(params);
-        if (!params.getLimit().isPresent()) {
+        if (params.getLimit().isEmpty()) {
           requestBuilder.setLimit(config.getConversationsHistoryMessageBatchSize().get());
         }
 
@@ -1074,7 +1076,7 @@ protected LazyLoadingPage<Result<List<LiteMessage>, SlackError>, Long> getPage(
           );
 
         CompletableFuture<Boolean> hasMoreFuture = resultFuture.thenApply(result ->
-          result.match(err -> false, ok -> ok.hasMore())
+          result.match(err -> false, ConversationsHistoryResponse::hasMore)
         );
         CompletableFuture<Long> nextOffset = nextOffset(pagingDirection, pageFuture);
 
@@ -1157,7 +1159,7 @@ protected LazyLoadingPage<Result<List<String>, SlackError>, String> getPage(
         ConversationMemberParams.Builder requestBuilder = ConversationMemberParams
           .builder()
           .from(params);
-        if (!params.getLimit().isPresent()) {
+        if (params.getLimit().isEmpty()) {
           requestBuilder.setLimit(config.getConversationMembersBatchSize().get());
         }
         Optional.ofNullable(offset).ifPresent(requestBuilder::setCursor);
@@ -1412,6 +1414,17 @@ public CompletableFuture<Result<GetUploadUrlExternalResponse, SlackError>> getUp
     );
   }
 
+  @Override
+  public CompletableFuture<Result<CompleteUploadExternalResponse, SlackError>> completeUploadExternal(
+    CompleteUploadExternalParams params
+  ) {
+    return postSlackCommand(
+      SlackMethods.files_completeUploadExternal,
+      params,
+      CompleteUploadExternalResponse.class
+    );
+  }
+
   @Override
   public CompletableFuture<Result<FilesSharedPublicUrlResponse, SlackError>> shareFilePublically(
     FilesSharedPublicUrlParams params