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
@@ -269,11 +269,13 @@
     'ConduitAPI_user_query_Method' => 'applications/people/conduit/ConduitAPI_user_query_Method.php',
     'ConduitAPI_user_removestatus_Method' => 'applications/people/conduit/ConduitAPI_user_removestatus_Method.php',
     'ConduitAPI_user_whoami_Method' => 'applications/people/conduit/ConduitAPI_user_whoami_Method.php',
+    'ConduitApplicationNotInstalledException' => 'applications/conduit/protocol/exception/ConduitApplicationNotInstalledException.php',
     'ConduitCall' => 'applications/conduit/call/ConduitCall.php',
     'ConduitCallTestCase' => 'applications/conduit/call/__tests__/ConduitCallTestCase.php',
     'ConduitConnectionGarbageCollector' => 'applications/conduit/garbagecollector/ConduitConnectionGarbageCollector.php',
-    'ConduitException' => 'applications/conduit/protocol/ConduitException.php',
+    'ConduitException' => 'applications/conduit/protocol/exception/ConduitException.php',
     'ConduitLogGarbageCollector' => 'applications/conduit/garbagecollector/ConduitLogGarbageCollector.php',
+    'ConduitMethodNotFoundException' => 'applications/conduit/protocol/exception/ConduitMethodNotFoundException.php',
     'ConduitSSHWorkflow' => 'applications/conduit/ssh/ConduitSSHWorkflow.php',
     'ConpherenceActionMenuEventListener' => 'applications/conpherence/events/ConpherenceActionMenuEventListener.php',
     'ConpherenceConfigOptions' => 'applications/conpherence/config/ConpherenceConfigOptions.php',
@@ -2999,10 +3001,12 @@
     'ConduitAPI_user_query_Method' => 'ConduitAPI_user_Method',
     'ConduitAPI_user_removestatus_Method' => 'ConduitAPI_user_Method',
     'ConduitAPI_user_whoami_Method' => 'ConduitAPI_user_Method',
+    'ConduitApplicationNotInstalledException' => 'ConduitMethodNotFoundException',
     'ConduitCallTestCase' => 'PhabricatorTestCase',
     'ConduitConnectionGarbageCollector' => 'PhabricatorGarbageCollector',
     'ConduitException' => 'Exception',
     'ConduitLogGarbageCollector' => 'PhabricatorGarbageCollector',
+    'ConduitMethodNotFoundException' => 'ConduitException',
     'ConduitSSHWorkflow' => 'PhabricatorSSHWorkflow',
     'ConpherenceActionMenuEventListener' => 'PhabricatorEventListener',
     'ConpherenceConfigOptions' => 'PhabricatorApplicationConfigOptions',
diff --git a/src/applications/conduit/call/ConduitCall.php b/src/applications/conduit/call/ConduitCall.php
--- a/src/applications/conduit/call/ConduitCall.php
+++ b/src/applications/conduit/call/ConduitCall.php
@@ -179,8 +179,7 @@
       // Discard, we provide a more specific exception below.
     }
     if (!$ok) {
-      throw new ConduitException(
-        "Conduit method '{$method}' does not exist.");
+      throw new ConduitMethodNotFoundException($method);
     }
 
     $class_info = new ReflectionClass($method_class);
@@ -201,9 +200,7 @@
     $application = $method->getApplication();
     if ($application && !$application->isInstalled()) {
       $app_name = $application->getName();
-      throw new ConduitException(
-        "Method '{$method_class}' belongs to application '{$app_name}', ".
-        "which is not installed.");
+      throw new ConduitApplicationNotInstalledException($method, $app_name);
     }
 
     return $method;
diff --git a/src/applications/conduit/controller/PhabricatorConduitAPIController.php b/src/applications/conduit/controller/PhabricatorConduitAPIController.php
--- a/src/applications/conduit/controller/PhabricatorConduitAPIController.php
+++ b/src/applications/conduit/controller/PhabricatorConduitAPIController.php
@@ -104,7 +104,9 @@
         list($error_code, $error_info) = $auth_error;
       }
     } catch (Exception $ex) {
-      phlog($ex);
+      if (!($ex instanceof ConduitMethodNotFoundException)) {
+        phlog($ex);
+      }
       $result = null;
       $error_code = ($ex instanceof ConduitException
         ? 'ERR-CONDUIT-CALL'
diff --git a/src/applications/conduit/protocol/exception/ConduitApplicationNotInstalledException.php b/src/applications/conduit/protocol/exception/ConduitApplicationNotInstalledException.php
new file mode 100644
--- /dev/null
+++ b/src/applications/conduit/protocol/exception/ConduitApplicationNotInstalledException.php
@@ -0,0 +1,14 @@
+<?php
+
+final class ConduitApplicationNotInstalledException
+  extends ConduitMethodNotFoundException {
+
+  public function __construct($method, $application) {
+    parent::__construct(
+      pht(
+        "Method '%s' belongs to application '%s', which is not installed.",
+        $method,
+        $application));
+  }
+
+}
diff --git a/src/applications/conduit/protocol/ConduitException.php b/src/applications/conduit/protocol/exception/ConduitException.php
rename from src/applications/conduit/protocol/ConduitException.php
rename to src/applications/conduit/protocol/exception/ConduitException.php
--- a/src/applications/conduit/protocol/ConduitException.php
+++ b/src/applications/conduit/protocol/exception/ConduitException.php
@@ -1,6 +1,9 @@
 <?php
 
-final class ConduitException extends Exception {
+/**
+ * @concrete-extensible
+ */
+class ConduitException extends Exception {
 
   private $errorDescription;
 
@@ -12,7 +15,7 @@
    * @param string Detailed error description.
    * @return this
    */
-  public function setErrorDescription($error_description) {
+  final public function setErrorDescription($error_description) {
     $this->errorDescription = $error_description;
     return $this;
   }
@@ -22,7 +25,7 @@
    *
    * @return string|null Error description, if one is available.
    */
-  public function getErrorDescription() {
+  final public function getErrorDescription() {
     return $this->errorDescription;
   }
 
diff --git a/src/applications/conduit/protocol/exception/ConduitMethodNotFoundException.php b/src/applications/conduit/protocol/exception/ConduitMethodNotFoundException.php
new file mode 100644
--- /dev/null
+++ b/src/applications/conduit/protocol/exception/ConduitMethodNotFoundException.php
@@ -0,0 +1,12 @@
+<?php
+
+/**
+ * @concrete-extensible
+ */
+class ConduitMethodNotFoundException extends ConduitException {
+
+  public function __construct($method) {
+    parent::__construct(pht("Conduit method '%s' does not exist.", $method));
+  }
+
+}