diff --git a/src/applications/almanac/typeahead/AlmanacInterfaceDatasource.php b/src/applications/almanac/typeahead/AlmanacInterfaceDatasource.php
index 3609cb06f6..73ae32938b 100644
--- a/src/applications/almanac/typeahead/AlmanacInterfaceDatasource.php
+++ b/src/applications/almanac/typeahead/AlmanacInterfaceDatasource.php
@@ -3,6 +3,12 @@
 final class AlmanacInterfaceDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: We should make this browsable, but need to make the result set
+    // orderable by device name.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type an interface name...');
   }
diff --git a/src/applications/diffusion/typeahead/DiffusionArcanistProjectDatasource.php b/src/applications/diffusion/typeahead/DiffusionArcanistProjectDatasource.php
index 963c0b2ca9..ce77b56f9b 100644
--- a/src/applications/diffusion/typeahead/DiffusionArcanistProjectDatasource.php
+++ b/src/applications/diffusion/typeahead/DiffusionArcanistProjectDatasource.php
@@ -3,6 +3,11 @@
 final class DiffusionArcanistProjectDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: We should probably make this browsable, or maybe remove it.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type an arcanist project name...');
   }
diff --git a/src/applications/diffusion/typeahead/DiffusionSymbolDatasource.php b/src/applications/diffusion/typeahead/DiffusionSymbolDatasource.php
index 97ab83f44d..0203ff2971 100644
--- a/src/applications/diffusion/typeahead/DiffusionSymbolDatasource.php
+++ b/src/applications/diffusion/typeahead/DiffusionSymbolDatasource.php
@@ -3,6 +3,12 @@
 final class DiffusionSymbolDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // This is slightly involved to make browsable, and browsing symbols
+    // does not seem likely to be very useful in any real software project.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type a symbol name...');
   }
diff --git a/src/applications/harbormaster/typeahead/HarbormasterBuildDependencyDatasource.php b/src/applications/harbormaster/typeahead/HarbormasterBuildDependencyDatasource.php
index c1228c9446..997e129bb3 100644
--- a/src/applications/harbormaster/typeahead/HarbormasterBuildDependencyDatasource.php
+++ b/src/applications/harbormaster/typeahead/HarbormasterBuildDependencyDatasource.php
@@ -3,6 +3,11 @@
 final class HarbormasterBuildDependencyDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: This should be browsable, but fixing it is involved.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type another build step name...');
   }
diff --git a/src/applications/legalpad/typeahead/LegalpadDocumentDatasource.php b/src/applications/legalpad/typeahead/LegalpadDocumentDatasource.php
index 853d775184..a536843d0b 100644
--- a/src/applications/legalpad/typeahead/LegalpadDocumentDatasource.php
+++ b/src/applications/legalpad/typeahead/LegalpadDocumentDatasource.php
@@ -2,6 +2,11 @@
 
 final class LegalpadDocumentDatasource extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: This should be made browsable.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type a document name...');
   }
diff --git a/src/applications/macro/typeahead/PhabricatorMacroDatasource.php b/src/applications/macro/typeahead/PhabricatorMacroDatasource.php
index 339be08fa7..4b8d52b4d4 100644
--- a/src/applications/macro/typeahead/PhabricatorMacroDatasource.php
+++ b/src/applications/macro/typeahead/PhabricatorMacroDatasource.php
@@ -2,6 +2,11 @@
 
 final class PhabricatorMacroDatasource extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: This should be made browsable.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type a macro name...');
   }
diff --git a/src/applications/mailinglists/typeahead/PhabricatorMailingListDatasource.php b/src/applications/mailinglists/typeahead/PhabricatorMailingListDatasource.php
index 53f7d82e0e..c08da2a30d 100644
--- a/src/applications/mailinglists/typeahead/PhabricatorMailingListDatasource.php
+++ b/src/applications/mailinglists/typeahead/PhabricatorMailingListDatasource.php
@@ -3,6 +3,11 @@
 final class PhabricatorMailingListDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: Make this browsable if we don't delete it before then.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type a mailing list name...');
   }
diff --git a/src/applications/maniphest/typeahead/ManiphestTaskPriorityDatasource.php b/src/applications/maniphest/typeahead/ManiphestTaskPriorityDatasource.php
index 172caea1a6..568aa0636d 100644
--- a/src/applications/maniphest/typeahead/ManiphestTaskPriorityDatasource.php
+++ b/src/applications/maniphest/typeahead/ManiphestTaskPriorityDatasource.php
@@ -25,7 +25,7 @@ final class ManiphestTaskPriorityDatasource
         ->setName($name);
     }
 
-    return $results;
+    return $this->filterResultsAgainstTokens($results);
   }
 
 }
diff --git a/src/applications/maniphest/typeahead/ManiphestTaskStatusDatasource.php b/src/applications/maniphest/typeahead/ManiphestTaskStatusDatasource.php
index e7eba2923c..27b3f90386 100644
--- a/src/applications/maniphest/typeahead/ManiphestTaskStatusDatasource.php
+++ b/src/applications/maniphest/typeahead/ManiphestTaskStatusDatasource.php
@@ -25,6 +25,6 @@ final class ManiphestTaskStatusDatasource
         ->setName($name);
     }
 
-    return $results;
+    return $this->filterResultsAgainstTokens($results);
   }
 }
diff --git a/src/applications/meta/typeahead/PhabricatorApplicationDatasource.php b/src/applications/meta/typeahead/PhabricatorApplicationDatasource.php
index 19b40f727a..18b6683dfc 100644
--- a/src/applications/meta/typeahead/PhabricatorApplicationDatasource.php
+++ b/src/applications/meta/typeahead/PhabricatorApplicationDatasource.php
@@ -37,7 +37,7 @@ final class PhabricatorApplicationDatasource
         ->setImageSprite('phabricator-search-icon '.$img);
     }
 
-    return $results;
+    return $this->filterResultsAgainstTokens($results);
   }
 
 }
diff --git a/src/applications/metamta/typeahead/PhabricatorMetaMTAApplicationEmailDatasource.php b/src/applications/metamta/typeahead/PhabricatorMetaMTAApplicationEmailDatasource.php
index bbe5e0d8f6..887aecfd80 100644
--- a/src/applications/metamta/typeahead/PhabricatorMetaMTAApplicationEmailDatasource.php
+++ b/src/applications/metamta/typeahead/PhabricatorMetaMTAApplicationEmailDatasource.php
@@ -3,6 +3,11 @@
 final class PhabricatorMetaMTAApplicationEmailDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: Make this browsable.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type an application email address...');
   }
diff --git a/src/applications/owners/typeahead/PhabricatorOwnersPackageDatasource.php b/src/applications/owners/typeahead/PhabricatorOwnersPackageDatasource.php
index c0a6c92589..a8658549ec 100644
--- a/src/applications/owners/typeahead/PhabricatorOwnersPackageDatasource.php
+++ b/src/applications/owners/typeahead/PhabricatorOwnersPackageDatasource.php
@@ -3,6 +3,11 @@
 final class PhabricatorOwnersPackageDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // TODO: Make this browsable.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type a package name...');
   }
diff --git a/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php b/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php
index e2a6de0e43..2672e7d79a 100644
--- a/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php
+++ b/src/applications/typeahead/controller/PhabricatorTypeaheadModularDatasourceController.php
@@ -25,6 +25,7 @@ final class PhabricatorTypeaheadModularDatasourceController
     if (isset($sources[$class])) {
       $source = $sources[$class];
       $source->setParameters($request->getRequestData());
+      $source->setViewer($viewer);
 
       // NOTE: Wrapping the source in a Composite datasource ensures we perform
       // application visibility checks for the viewer, so we do not need to do
@@ -40,6 +41,10 @@ final class PhabricatorTypeaheadModularDatasourceController
       $hard_limit = 1000;
 
       if ($is_browse) {
+        if (!$composite->isBrowsable()) {
+          return new Aphront404Response();
+        }
+
         $limit = 10;
         $offset = $request->getInt('offset');
 
diff --git a/src/applications/typeahead/datasource/PhabricatorTypeaheadCompositeDatasource.php b/src/applications/typeahead/datasource/PhabricatorTypeaheadCompositeDatasource.php
index b1f55190c9..334d9354de 100644
--- a/src/applications/typeahead/datasource/PhabricatorTypeaheadCompositeDatasource.php
+++ b/src/applications/typeahead/datasource/PhabricatorTypeaheadCompositeDatasource.php
@@ -3,8 +3,20 @@
 abstract class PhabricatorTypeaheadCompositeDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  private $usable;
+
   abstract public function getComponentDatasources();
 
+  public function isBrowsable() {
+    foreach ($this->getUsableDatasources() as $datasource) {
+      if (!$datasource->isBrowsable()) {
+        return false;
+      }
+    }
+
+    return parent::isBrowsable();
+  }
+
   public function getDatasourceApplicationClass() {
     return null;
   }
@@ -43,26 +55,29 @@ abstract class PhabricatorTypeaheadCompositeDatasource
   }
 
   private function getUsableDatasources() {
-    $sources = $this->getComponentDatasources();
+    if ($this->usable === null) {
+      $sources = $this->getComponentDatasources();
 
-    $usable = array();
-    foreach ($sources as $source) {
-      $application_class = $source->getDatasourceApplicationClass();
+      $usable = array();
+      foreach ($sources as $source) {
+        $application_class = $source->getDatasourceApplicationClass();
 
-      if ($application_class) {
-        $result = id(new PhabricatorApplicationQuery())
-          ->setViewer($this->getViewer())
-          ->withClasses(array($application_class))
-          ->execute();
-        if (!$result) {
-          continue;
+        if ($application_class) {
+          $result = id(new PhabricatorApplicationQuery())
+            ->setViewer($this->getViewer())
+            ->withClasses(array($application_class))
+            ->execute();
+          if (!$result) {
+            continue;
+          }
         }
-      }
 
-      $usable[] = $source;
+        $usable[] = $source;
+      }
+      $this->usable = $usable;
     }
 
-    return $usable;
+    return $this->usable;
   }
 
 }
diff --git a/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php b/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php
index 3d6d2b75f2..a15a248e23 100644
--- a/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php
+++ b/src/applications/typeahead/datasource/PhabricatorTypeaheadDatasource.php
@@ -102,4 +102,75 @@ abstract class PhabricatorTypeaheadDatasource extends Phobject {
       ->execute();
   }
 
+
+  /**
+   * Can the user browse through results from this datasource?
+   *
+   * Browsable datasources allow the user to switch from typeahead mode to
+   * a browse mode where they can scroll through all results.
+   *
+   * By default, datasources are browsable, but some datasources can not
+   * generate a meaningful result set or can't filter results on the server.
+   *
+   * @return bool
+   */
+  public function isBrowsable() {
+    return true;
+  }
+
+
+  /**
+   * Filter a list of results, removing items which don't match the query
+   * tokens.
+   *
+   * This is useful for datasources which return a static list of hard-coded
+   * or configured results and can't easily do query filtering in a real
+   * query class. Instead, they can just build the entire result set and use
+   * this method to filter it.
+   *
+   * For datasources backed by database objects, this is often much less
+   * efficient than filtering at the query level.
+   *
+   * @param list<PhabricatorTypeaheadResult> List of typeahead results.
+   * @return list<PhabricatorTypeaheadResult> Filtered results.
+   */
+  protected function filterResultsAgainstTokens(array $results) {
+    $tokens = $this->getTokens();
+    if (!$tokens) {
+      return $results;
+    }
+
+    $map = array();
+    foreach ($tokens as $token) {
+      $map[$token] = strlen($token);
+    }
+
+    foreach ($results as $key => $result) {
+      $rtokens = self::tokenizeString($result->getName());
+
+      // For each token in the query, we need to find a match somewhere
+      // in the result name.
+      foreach ($map as $token => $length) {
+        // Look for a match.
+        $match = false;
+        foreach ($rtokens as $rtoken) {
+          if (!strncmp($rtoken, $token, $length)) {
+            // This part of the result name has the query token as a prefix.
+            $match = true;
+            break;
+          }
+        }
+
+        if (!$match) {
+          // We didn't find a match for this query token, so throw the result
+          // away. Try with the next result.
+          unset($results[$key]);
+          break;
+        }
+      }
+    }
+
+    return $results;
+  }
+
 }
diff --git a/src/applications/typeahead/datasource/PhabricatorTypeaheadMonogramDatasource.php b/src/applications/typeahead/datasource/PhabricatorTypeaheadMonogramDatasource.php
index 267976b773..ebaf3d39d8 100644
--- a/src/applications/typeahead/datasource/PhabricatorTypeaheadMonogramDatasource.php
+++ b/src/applications/typeahead/datasource/PhabricatorTypeaheadMonogramDatasource.php
@@ -3,6 +3,13 @@
 final class PhabricatorTypeaheadMonogramDatasource
   extends PhabricatorTypeaheadDatasource {
 
+  public function isBrowsable() {
+    // This source isn't meaningfully browsable. Although it's technically
+    // possible to let users browse through every object on an install, there
+    // is no use case for it and it doesn't seem worth building.
+    return false;
+  }
+
   public function getPlaceholderText() {
     return pht('Type an object name...');
   }