diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -2223,6 +2223,7 @@
     'PhabricatorEventListener' => 'infrastructure/events/PhabricatorEventListener.php',
     'PhabricatorEventType' => 'infrastructure/events/constant/PhabricatorEventType.php',
     'PhabricatorExampleEventListener' => 'infrastructure/events/PhabricatorExampleEventListener.php',
+    'PhabricatorExecFutureFileUploadSource' => 'applications/files/uploadsource/PhabricatorExecFutureFileUploadSource.php',
     'PhabricatorExtendedPolicyInterface' => 'applications/policy/interface/PhabricatorExtendedPolicyInterface.php',
     'PhabricatorExtendingPhabricatorConfigOptions' => 'applications/config/option/PhabricatorExtendingPhabricatorConfigOptions.php',
     'PhabricatorExtensionsSetupCheck' => 'applications/config/check/PhabricatorExtensionsSetupCheck.php',
@@ -2312,6 +2313,7 @@
     'PhabricatorFileUploadController' => 'applications/files/controller/PhabricatorFileUploadController.php',
     'PhabricatorFileUploadDialogController' => 'applications/files/controller/PhabricatorFileUploadDialogController.php',
     'PhabricatorFileUploadException' => 'applications/files/exception/PhabricatorFileUploadException.php',
+    'PhabricatorFileUploadSource' => 'applications/files/uploadsource/PhabricatorFileUploadSource.php',
     'PhabricatorFileinfoSetupCheck' => 'applications/config/check/PhabricatorFileinfoSetupCheck.php',
     'PhabricatorFilesApplication' => 'applications/files/application/PhabricatorFilesApplication.php',
     'PhabricatorFilesApplicationStorageEnginePanel' => 'applications/files/applicationpanel/PhabricatorFilesApplicationStorageEnginePanel.php',
@@ -6504,6 +6506,7 @@
     'PhabricatorEventListener' => 'PhutilEventListener',
     'PhabricatorEventType' => 'PhutilEventType',
     'PhabricatorExampleEventListener' => 'PhabricatorEventListener',
+    'PhabricatorExecFutureFileUploadSource' => 'PhabricatorFileUploadSource',
     'PhabricatorExtendingPhabricatorConfigOptions' => 'PhabricatorApplicationConfigOptions',
     'PhabricatorExtensionsSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorExternalAccount' => array(
@@ -6621,6 +6624,7 @@
     'PhabricatorFileUploadController' => 'PhabricatorFileController',
     'PhabricatorFileUploadDialogController' => 'PhabricatorFileController',
     'PhabricatorFileUploadException' => 'Exception',
+    'PhabricatorFileUploadSource' => 'Phobject',
     'PhabricatorFileinfoSetupCheck' => 'PhabricatorSetupCheck',
     'PhabricatorFilesApplication' => 'PhabricatorApplication',
     'PhabricatorFilesApplicationStorageEnginePanel' => 'PhabricatorApplicationConfigurationPanel',
diff --git a/src/applications/diffusion/conduit/DiffusionFileContentQueryConduitAPIMethod.php b/src/applications/diffusion/conduit/DiffusionFileContentQueryConduitAPIMethod.php
--- a/src/applications/diffusion/conduit/DiffusionFileContentQueryConduitAPIMethod.php
+++ b/src/applications/diffusion/conduit/DiffusionFileContentQueryConduitAPIMethod.php
@@ -39,14 +39,20 @@
       $file_query->setByteLimit($byte_limit);
     }
 
-    $content = $file_query->execute();
+    $file = $file_query->execute();
 
     $too_slow = (bool)$file_query->getExceededTimeLimit();
     $too_huge = (bool)$file_query->getExceededByteLimit();
 
     $file_phid = null;
     if (!$too_slow && !$too_huge) {
-      $file = $this->newFile($drequest, $content);
+      $repository = $drequest->getRepository();
+      $repository_phid = $repository->getPHID();
+
+      $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
+        $file->attachToObject($repository_phid);
+      unset($unguarded);
+
       $file_phid = $file->getPHID();
     }
 
@@ -57,26 +63,4 @@
     );
   }
 
-  private function newFile(DiffusionRequest $drequest, $content) {
-    $path = $drequest->getPath();
-    $name = basename($path);
-
-    $repository = $drequest->getRepository();
-    $repository_phid = $repository->getPHID();
-
-    $file = PhabricatorFile::buildFromFileDataOrHash(
-      $content,
-      array(
-        'name' => $name,
-        'ttl' => time() + phutil_units('48 hours in seconds'),
-        'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
-      ));
-
-    $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
-      $file->attachToObject($repository_phid);
-    unset($unguarded);
-
-    return $file;
-  }
-
 }
diff --git a/src/applications/diffusion/query/filecontent/DiffusionFileContentQuery.php b/src/applications/diffusion/query/filecontent/DiffusionFileContentQuery.php
--- a/src/applications/diffusion/query/filecontent/DiffusionFileContentQuery.php
+++ b/src/applications/diffusion/query/filecontent/DiffusionFileContentQuery.php
@@ -54,23 +54,46 @@
       $future->setStdoutSizeLimit($byte_limit + 1);
     }
 
+    $drequest = $this->getRequest();
+
+    $name = basename($drequest->getPath());
+    $ttl = PhabricatorTime::getNow() + phutil_units('48 hours in seconds');
+
     try {
-      $file_content = $this->resolveFileContentFuture($future);
+      $threshold = PhabricatorFileStorageEngine::getChunkThreshold();
+      $future->setReadBufferSize($threshold);
+
+      $source = id(new PhabricatorExecFutureFileUploadSource())
+        ->setName($name)
+        ->setTTL($ttl)
+        ->setViewPolicy(PhabricatorPolicies::POLICY_NOONE)
+        ->setExecFuture($future);
+
+      $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
+        $file = $source->uploadFile();
+      unset($unguarded);
+
     } catch (CommandException $ex) {
       if (!$future->getWasKilledByTimeout()) {
         throw $ex;
       }
 
       $this->didHitTimeLimit = true;
-      $file_content = null;
+      $file = null;
     }
 
-    if ($byte_limit && (strlen($file_content) > $byte_limit)) {
+    if ($byte_limit && ($file->getByteSize() > $byte_limit)) {
       $this->didHitByteLimit = true;
-      $file_content = null;
+
+      $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
+        id(new PhabricatorDestructionEngine())
+          ->destroyObject($file);
+      unset($unguarded);
+
+      $file = null;
     }
 
-    return $file_content;
+    return $file;
   }
 
 }
diff --git a/src/applications/files/applicationpanel/PhabricatorFilesApplicationStorageEnginePanel.php b/src/applications/files/applicationpanel/PhabricatorFilesApplicationStorageEnginePanel.php
--- a/src/applications/files/applicationpanel/PhabricatorFilesApplicationStorageEnginePanel.php
+++ b/src/applications/files/applicationpanel/PhabricatorFilesApplicationStorageEnginePanel.php
@@ -26,11 +26,15 @@
     $rows = array();
     $rowc = array();
     foreach ($engines as $key => $engine) {
-      $limited = $no;
+      if ($engine->isTestEngine()) {
+        continue;
+      }
+
       $limit = null;
       if ($engine->hasFilesizeLimit()) {
-        $limited = $yes;
         $limit = phutil_format_bytes($engine->getFilesizeLimit());
+      } else {
+        $limit = pht('Unlimited');
       }
 
       if ($engine->canWriteFiles()) {
@@ -39,12 +43,6 @@
         $writable = $no;
       }
 
-      if ($engine->isTestEngine()) {
-        $test = $yes;
-      } else {
-        $test = $no;
-      }
-
       if (isset($writable_engines[$key]) || isset($chunk_engines[$key])) {
         $rowc[] = 'highlighted';
       } else {
@@ -54,9 +52,7 @@
       $rows[] = array(
         $key,
         get_class($engine),
-        $test,
         $writable,
-        $limited,
         $limit,
       );
     }
@@ -67,9 +63,7 @@
         array(
           pht('Key'),
           pht('Class'),
-          pht('Unit Test'),
           pht('Writable'),
-          pht('Has Limit'),
           pht('Limit'),
         ))
       ->setRowClasses($rowc)
@@ -78,8 +72,6 @@
           '',
           'wide',
           '',
-          '',
-          '',
           'n',
         ));
 
diff --git a/src/applications/files/uploadsource/PhabricatorExecFutureFileUploadSource.php b/src/applications/files/uploadsource/PhabricatorExecFutureFileUploadSource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/files/uploadsource/PhabricatorExecFutureFileUploadSource.php
@@ -0,0 +1,28 @@
+<?php
+
+final class PhabricatorExecFutureFileUploadSource
+  extends PhabricatorFileUploadSource {
+
+  private $future;
+
+  public function setExecFuture(ExecFuture $future) {
+    $this->future = $future;
+    return $this;
+  }
+
+  public function getExecFuture() {
+    return $this->future;
+  }
+
+  protected function newDataIterator() {
+    $future = $this->getExecFuture();
+
+    return id(new LinesOfALargeExecFuture($future))
+      ->setDelimiter(null);
+  }
+
+  protected function getDataLength() {
+    return null;
+  }
+
+}
diff --git a/src/applications/files/uploadsource/PhabricatorFileUploadSource.php b/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/files/uploadsource/PhabricatorFileUploadSource.php
@@ -0,0 +1,235 @@
+<?php
+
+abstract class PhabricatorFileUploadSource
+  extends Phobject {
+
+  private $name;
+  private $ttl;
+  private $viewPolicy;
+
+  private $rope;
+  private $data;
+  private $shouldChunk;
+  private $didRewind;
+  private $totalBytesWritten = 0;
+
+  public function setName($name) {
+    $this->name = $name;
+    return $this;
+  }
+
+  public function getName() {
+    return $this->name;
+  }
+
+  public function setTTL($ttl) {
+    $this->ttl = $ttl;
+    return $this;
+  }
+
+  public function getTTL() {
+    return $this->ttl;
+  }
+
+  public function setViewPolicy($view_policy) {
+    $this->viewPolicy = $view_policy;
+    return $this;
+  }
+
+  public function getViewPolicy() {
+    return $this->viewPolicy;
+  }
+
+  public function uploadFile() {
+    if (!$this->shouldChunkFile()) {
+      return $this->writeSingleFile();
+    } else {
+      return $this->writeChunkedFile();
+    }
+  }
+
+  private function getDataIterator() {
+    if (!$this->data) {
+      $this->data = $this->newDataIterator();
+    }
+    return $this->data;
+  }
+
+  private function getRope() {
+    if (!$this->rope) {
+      $this->rope = new PhutilRope();
+    }
+    return $this->rope;
+  }
+
+  abstract protected function newDataIterator();
+  abstract protected function getDataLength();
+
+  private function readFileData() {
+    $data = $this->getDataIterator();
+
+    if (!$this->didRewind) {
+      $data->rewind();
+      $this->didRewind = true;
+    } else {
+      $data->next();
+    }
+
+    if (!$data->valid()) {
+      return false;
+    }
+
+    $rope = $this->getRope();
+    $rope->append($data->current());
+
+    return true;
+  }
+
+  private function shouldChunkFile() {
+    if ($this->shouldChunk !== null) {
+      return $this->shouldChunk;
+    }
+
+    $threshold = PhabricatorFileStorageEngine::getChunkThreshold();
+
+    // If we don't know how large the file is, we're going to read some data
+    // from it until we know whether it's a small file or not. This will give
+    // us enough information to make a decision about chunking.
+    $length = $this->getDataLength();
+    if ($length === null) {
+      $rope = $this->getRope();
+      while ($this->readFileData()) {
+        $length = $rope->getByteLength();
+        if ($length > $threshold) {
+          break;
+        }
+      }
+    }
+
+    $this->shouldChunk = ($length > $threshold);
+
+    return $this->shouldChunk;
+  }
+
+  private function writeSingleFile() {
+    while ($this->readFileData()) {
+      // Read the entire file.
+    }
+
+    $rope = $this->getRope();
+    $data = $rope->getAsString();
+
+    $parameters = $this->getNewFileParameters();
+
+    return PhabricatorFile::newFromFileData($data, $parameters);
+  }
+
+  private function writeChunkedFile() {
+    $engine = $this->getChunkEngine();
+
+    $parameters = $this->getNewFileParameters();
+
+    $parameters = array(
+      'isPartial' => true,
+    ) + $parameters;
+
+    $data_length = $this->getDataLength();
+    if ($data_length !== null) {
+      $length = $data_length;
+    } else {
+      $length = 0;
+    }
+
+    $file = PhabricatorFile::newChunkedFile($engine, $length, $parameters);
+    $file->save();
+
+    $rope = $this->getRope();
+
+    // Read the source, writing chunks as we get enough data.
+    while ($this->readFileData()) {
+      while (true) {
+        $rope_length = $rope->getByteLength();
+        if ($rope_length < $engine->getChunkSize()) {
+          break;
+        }
+        $this->writeChunk($file, $engine);
+      }
+    }
+
+    // If we have extra bytes at the end, write them.
+    if ($rope->getByteLength()) {
+      $this->writeChunk($file, $engine);
+    }
+
+    $file->setIsPartial(0);
+    if ($data_length === null) {
+      $file->setByteSize($this->getTotalBytesWritten());
+    }
+    $file->save();
+
+    return $file;
+  }
+
+  private function writeChunk(
+    PhabricatorFile $file,
+    PhabricatorFileStorageEngine $engine) {
+
+    $offset = $this->getTotalBytesWritten();
+    $max_length = $engine->getChunkSize();
+    $rope = $this->getRope();
+
+    $data = $rope->getPrefixBytes($max_length);
+    $actual_length = strlen($data);
+    $rope->removeBytesFromHead($actual_length);
+
+    $chunk_data = PhabricatorFile::newFromFileData(
+      $data,
+      array(
+        'name' => $file->getMonogram().'.chunk-'.$offset,
+        'viewPolicy' => PhabricatorPolicies::POLICY_NOONE,
+      ));
+
+    $chunk = PhabricatorFileChunk::initializeNewChunk(
+      $file->getStorageHandle(),
+      $offset,
+      $offset + $actual_length);
+
+    $chunk
+      ->setDataFilePHID($chunk_data->getPHID())
+      ->save();
+
+    $this->setTotalBytesWritten($offset + $actual_length);
+
+    return $chunk;
+  }
+
+  private function getNewFileParameters() {
+    return array(
+      'name' => $this->getName(),
+      'ttl' => $this->getTTL(),
+      'viewPolicy' => $this->getViewPolicy(),
+    );
+  }
+
+  private function getChunkEngine() {
+    $chunk_engines = PhabricatorFileStorageEngine::loadWritableChunkEngines();
+    if (!$chunk_engines) {
+      throw new Exception(
+        pht(
+          'Unable to upload file: this server is not configured with any '.
+          'storage engine which can store large files.'));
+    }
+
+    return head($chunk_engines);
+  }
+
+  private function setTotalBytesWritten($total_bytes_written) {
+    $this->totalBytesWritten = $total_bytes_written;
+    return $this;
+  }
+
+  private function getTotalBytesWritten() {
+    return $this->totalBytesWritten;
+  }
+
+}