diff --git a/src/console/PhutilConsoleFormatter.php b/src/console/PhutilConsoleFormatter.php
--- a/src/console/PhutilConsoleFormatter.php
+++ b/src/console/PhutilConsoleFormatter.php
@@ -22,23 +22,38 @@
 
   public static function getDisableANSI() {
     if (self::$disableANSI === null) {
-      $term = phutil_utf8_strtolower(getenv('TERM'));
-      // ansicon enables ANSI support on Windows
-      if (!$term && getenv('ANSICON')) {
-        $term = 'ansi';
+      self::$disableANSI = self::newShouldDisableAnsi();
+    }
+    return self::$disableANSI;
+  }
+
+  private static function newShouldDisableANSI() {
+    $term = phutil_utf8_strtolower(getenv('TERM'));
+
+    // ansicon enables ANSI support on Windows
+    if (!$term && getenv('ANSICON')) {
+      $term = 'ansi';
+    }
+
+
+    if (phutil_is_windows()) {
+      if ($term !== 'cygwin' && $term !== 'ansi') {
+        return true;
       }
+    }
+
+    $stdout = PhutilSystem::getStdoutHandle();
+    if ($stdout === null) {
+      return true;
+    }
 
-      if (phutil_is_windows() && $term !== 'cygwin' && $term !== 'ansi') {
-        self::$disableANSI = true;
-      } else if (!defined('STDOUT')) {
-        self::$disableANSI = true;
-      } else if (function_exists('posix_isatty') && !posix_isatty(STDOUT)) {
-        self::$disableANSI = true;
-      } else {
-        self::$disableANSI = false;
+    if (function_exists('posix_isatty')) {
+      if (!posix_isatty($stdout)) {
+        return true;
       }
     }
-    return self::$disableANSI;
+
+    return false;
   }
 
   public static function formatString($format /* ... */) {
diff --git a/src/filesystem/PhutilErrorLog.php b/src/filesystem/PhutilErrorLog.php
--- a/src/filesystem/PhutilErrorLog.php
+++ b/src/filesystem/PhutilErrorLog.php
@@ -94,7 +94,7 @@
 
     if (strlen($message)) {
       $message = tsprintf("%B\n", $message);
-      @fwrite(STDERR, $message);
+      PhutilSystem::writeStderr($message);
     }
   }
 
diff --git a/src/future/exec/PhutilExecPassthru.php b/src/future/exec/PhutilExecPassthru.php
--- a/src/future/exec/PhutilExecPassthru.php
+++ b/src/future/exec/PhutilExecPassthru.php
@@ -53,10 +53,14 @@
     if ($is_write) {
       $stdin_spec = array('pipe', 'r');
     } else {
-      $stdin_spec = STDIN;
+      $stdin_spec = PhutilSystem::getStdinHandle();
     }
 
-    $spec = array($stdin_spec, STDOUT, STDERR);
+    $spec = array(
+      $stdin_spec,
+      PhutilSystem::getStdoutHandle(),
+      PhutilSystem::getStderrHandle(),
+    );
     $pipes = array();
 
     $unmasked_command = $command->getUnmaskedString();
diff --git a/src/log/ArcanistLogEngine.php b/src/log/ArcanistLogEngine.php
--- a/src/log/ArcanistLogEngine.php
+++ b/src/log/ArcanistLogEngine.php
@@ -19,7 +19,7 @@
   }
 
   private function writeBytes($bytes) {
-    fprintf(STDERR, '%s', $bytes);
+    PhutilSystem::writeStderr($bytes);
     return $this;
   }
 
diff --git a/src/parser/ArcanistBaseCommitParser.php b/src/parser/ArcanistBaseCommitParser.php
--- a/src/parser/ArcanistBaseCommitParser.php
+++ b/src/parser/ArcanistBaseCommitParser.php
@@ -33,7 +33,7 @@
 
   private function log($message) {
     if ($this->verbose) {
-      fwrite(STDERR, $message."\n");
+      PhutilSystem::writeStderr($message."\n");
     }
   }
 
diff --git a/src/parser/argument/PhutilArgumentParser.php b/src/parser/argument/PhutilArgumentParser.php
--- a/src/parser/argument/PhutilArgumentParser.php
+++ b/src/parser/argument/PhutilArgumentParser.php
@@ -805,7 +805,7 @@
 
 
   private function logMessage($message) {
-    fwrite(STDERR, $message);
+    PhutilSystem::writeStderr($message);
   }
 
 
diff --git a/src/progress/PhutilConsoleProgressSink.php b/src/progress/PhutilConsoleProgressSink.php
--- a/src/progress/PhutilConsoleProgressSink.php
+++ b/src/progress/PhutilConsoleProgressSink.php
@@ -110,6 +110,6 @@
   }
 
   private function printLine($line) {
-    fprintf(STDERR, '%s', $line);
+    PhutilSystem::writeStderr($line);
   }
 }
diff --git a/src/symbols/PhutilSymbolLoader.php b/src/symbols/PhutilSymbolLoader.php
--- a/src/symbols/PhutilSymbolLoader.php
+++ b/src/symbols/PhutilSymbolLoader.php
@@ -296,11 +296,12 @@
         // library without breaking library startup.
         if ($should_continue) {
           // We may not have `pht()` yet.
-          fprintf(
-            STDERR,
+          $message = sprintf(
             "%s: %s\n",
             'IGNORING CLASS LOAD FAILURE',
             $caught->getMessage());
+
+          @file_put_contents('php://stderr', $message);
         } else {
           throw $caught;
         }
diff --git a/src/upload/ArcanistFileUploader.php b/src/upload/ArcanistFileUploader.php
--- a/src/upload/ArcanistFileUploader.php
+++ b/src/upload/ArcanistFileUploader.php
@@ -313,7 +313,7 @@
    * @task internal
    */
   private function writeStatus($message) {
-    fwrite(STDERR, $message."\n");
+    PhutilSystem::writeStderr($message."\n");
   }
 
 }
diff --git a/src/utils/PhutilSystem.php b/src/utils/PhutilSystem.php
--- a/src/utils/PhutilSystem.php
+++ b/src/utils/PhutilSystem.php
@@ -3,10 +3,76 @@
 /**
  * Interact with the operating system.
  *
+ * @task stdio Interacting with Standard I/O
  * @task memory Interacting with System Memory
  */
 final class PhutilSystem extends Phobject {
 
+  private static $stdin = false;
+  private static $stderr = false;
+  private static $stdout = false;
+
+  /**
+   * @task stdio
+   */
+  public static function getStdinHandle() {
+    if (self::$stdin === false) {
+      self::$stdin = self::newStdioHandle('php://stdin');
+    }
+
+    return self::$stdin;
+  }
+
+  /**
+   * @task stdio
+   */
+  public static function getStdoutHandle() {
+    if (self::$stdout === false) {
+      self::$stdout = self::newStdioHandle('php://stdout');
+    }
+
+    return self::$stdout;
+  }
+
+  /**
+   * @task stdio
+   */
+  public static function getStderrHandle() {
+    if (self::$stderr === false) {
+      self::$stderr = self::newStdioHandle('php://stderr');
+    }
+
+    return self::$stderr;
+  }
+
+  /**
+   * @task stdio
+   */
+  public static function writeStderr($message) {
+    $stderr = self::getStderrHandle();
+
+    if ($stderr === null) {
+      return;
+    }
+
+    $message = phutil_string_cast($message);
+    @fwrite($stderr, $message);
+  }
+
+
+  /**
+   * @task stdio
+   */
+  private static function newStdioHandle($ref) {
+    $ignored_mode = '';
+
+    $handle = @fopen($ref, $ignored_mode);
+    if ($handle === false) {
+      return null;
+    }
+
+    return $handle;
+  }
 
   /**
    * Get information about total and free memory on the system.
diff --git a/src/workflow/ArcanistDiffWorkflow.php b/src/workflow/ArcanistDiffWorkflow.php
--- a/src/workflow/ArcanistDiffWorkflow.php
+++ b/src/workflow/ArcanistDiffWorkflow.php
@@ -806,7 +806,10 @@
     if ($is_raw) {
 
       if ($this->getArgument('raw')) {
-        fwrite(STDERR, pht('Reading diff from stdin...')."\n");
+        PhutilSystem::writeStderr(
+          tsprintf(
+            "%s\n",
+            pht('Reading diff from stdin...')));
         $raw_diff = file_get_contents('php://stdin');
       } else if ($this->getArgument('raw-command')) {
         list($raw_diff) = execx('%C', $this->getArgument('raw-command'));
diff --git a/src/workflow/ArcanistWorkflow.php b/src/workflow/ArcanistWorkflow.php
--- a/src/workflow/ArcanistWorkflow.php
+++ b/src/workflow/ArcanistWorkflow.php
@@ -1565,7 +1565,7 @@
    * @return void
    */
   final protected function writeStatusMessage($msg) {
-    fwrite(STDERR, $msg);
+    PhutilSystem::writeStderr($msg);
   }
 
   final public function writeInfo($title, $message) {