diff --git a/scripts/arcanist.php b/scripts/arcanist.php
index dfd7309e..c3ec4308 100755
--- a/scripts/arcanist.php
+++ b/scripts/arcanist.php
@@ -82,10 +82,13 @@ try {
       if ($config_trace_mode) {
         echo "Loading phutil library '{$name}' from '{$location}'...\n";
       }
-      $library_root = Filesystem::resolvePath(
+      $resolved_location = Filesystem::resolvePath(
         $location,
         $working_copy->getProjectRoot());
-      phutil_load_library($library_root);
+      if (Filesystem::pathExists($resolved_location)) {
+        $location = $resolved_location;
+      }
+      phutil_load_library($location);
     }
   }
 
diff --git a/src/lint/patcher/ArcanistLintPatcher.php b/src/lint/patcher/ArcanistLintPatcher.php
index eefb8ad6..de687147 100644
--- a/src/lint/patcher/ArcanistLintPatcher.php
+++ b/src/lint/patcher/ArcanistLintPatcher.php
@@ -106,7 +106,12 @@ final class ArcanistLintPatcher {
       $new_str = $lint->getReplacementText();
       $new_len = strlen($new_str);
 
-      $data = substr_replace($data, $new_str, $working_offset, $old_len);
+      if ($working_offset == strlen($data)) {
+        // Temporary hack to work around a destructive hphpi issue, see #451031.
+        $data .= $new_str;
+      } else {
+        $data = substr_replace($data, $new_str, $working_offset, $old_len);
+      }
 
       $this->changeCharacterDelta($new_len - $old_len);
       $this->setDirtyCharacterOffset($orig_offset + $old_len);
diff --git a/src/repository/api/subversion/ArcanistSubversionAPI.php b/src/repository/api/subversion/ArcanistSubversionAPI.php
index 7d4cef26..4dd7fa7e 100644
--- a/src/repository/api/subversion/ArcanistSubversionAPI.php
+++ b/src/repository/api/subversion/ArcanistSubversionAPI.php
@@ -29,7 +29,7 @@ class ArcanistSubversionAPI extends ArcanistRepositoryAPI {
 
   protected $svnInfoRaw = array();
   protected $svnDiffRaw = array();
-  
+
   private $svnBaseRevisionNumber;
 
   public function getSourceControlSystemName() {
@@ -165,7 +165,7 @@ class ArcanistSubversionAPI extends ArcanistRepositoryAPI {
     $info = $this->getSVNInfo('/');
     return $info['URL'].'@'.$this->getSVNBaseRevisionNumber();
   }
-  
+
   public function getSVNBaseRevisionNumber() {
     if ($this->svnBaseRevisionNumber) {
       return $this->svnBaseRevisionNumber;
@@ -173,7 +173,7 @@ class ArcanistSubversionAPI extends ArcanistRepositoryAPI {
     $info = $this->getSVNInfo('/');
     return $info['Revision'];
   }
-  
+
   public function overrideSVNBaseRevisionNumber($effective_base_revision) {
     $this->svnBaseRevisionNumber = $effective_base_revision;
     return $this;
diff --git a/src/workflow/diff/ArcanistDiffWorkflow.php b/src/workflow/diff/ArcanistDiffWorkflow.php
index a1d75ef5..3eb23bb1 100644
--- a/src/workflow/diff/ArcanistDiffWorkflow.php
+++ b/src/workflow/diff/ArcanistDiffWorkflow.php
@@ -522,7 +522,7 @@ EOTEXT
               $revlist);
           }
         }
-        
+
         // If you have a change which affects several files, all of which are
         // at a consistent base revision, treat that revision as the effective
         // base revision. The use case here is that you made a change to some
diff --git a/src/workflow/svn-hook-pre-commit/ArcanistSvnHookPreCommitWorkflow.php b/src/workflow/svn-hook-pre-commit/ArcanistSvnHookPreCommitWorkflow.php
index 68620928..f0caaefb 100644
--- a/src/workflow/svn-hook-pre-commit/ArcanistSvnHookPreCommitWorkflow.php
+++ b/src/workflow/svn-hook-pre-commit/ArcanistSvnHookPreCommitWorkflow.php
@@ -190,7 +190,8 @@ EOTEXT
 
     $working_copy = ArcanistWorkingCopyIdentity::newFromRootAndConfigFile(
       $project_root,
-      $config);
+      $config,
+      $config_file." (svnlook: {$transaction} {$repository})");
 
     $lint_engine = $working_copy->getConfig('lint_engine');
     if (!$lint_engine) {
diff --git a/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php b/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
index 76992e9c..7763ac9a 100644
--- a/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
+++ b/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
@@ -36,24 +36,30 @@ class ArcanistWorkingCopyIdentity {
         continue;
       }
       $proj_raw = Filesystem::readFile($config_file);
-      $config = self::parseRawConfigFile($proj_raw);
+      $config = self::parseRawConfigFile($proj_raw, $config_file);
       $project_root = $dir;
       break;
     }
     return new ArcanistWorkingCopyIdentity($project_root, $config);
   }
 
-  public static function newFromRootAndConfigFile($root, $config_raw) {
-    $config = self::parseRawConfigFile($config_raw);
+  public static function newFromRootAndConfigFile(
+    $root,
+    $config_raw,
+    $from_where) {
+
+    $config = self::parseRawConfigFile($config_raw, $from_where);
     return new ArcanistWorkingCopyIdentity($root, $config);
   }
 
-  private static function parseRawConfigFile($raw_config) {
+  private static function parseRawConfigFile($raw_config, $from_where) {
     $proj = json_decode($raw_config, true);
     if (!is_array($proj)) {
       throw new Exception(
-        "Unable to parse '.arcconfig' file in '{$dir}'. The file contents ".
-        "should be valid JSON.");
+        "Unable to parse '.arcconfig' file '{$from_where}'. The file contents ".
+        "should be valid JSON.\n\n".
+        "FILE CONTENTS\n".
+        substr($raw_config, 0, 2048));
     }
     $required_keys = array(
       'project_id',
@@ -61,8 +67,8 @@ class ArcanistWorkingCopyIdentity {
     foreach ($required_keys as $key) {
       if (!array_key_exists($key, $proj)) {
         throw new Exception(
-          "Required key '{$key}' is missing from '.arcconfig' file in ".
-          "'{$dir}'.");
+          "Required key '{$key}' is missing from '.arcconfig' file ".
+          "'{$from_where}'.");
       }
     }
     return $proj;