diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index bfba62e253..465108ac7c 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -528,6 +528,8 @@ phutil_register_library_map(array(
     'DiffusionAuditorsAddAuditorsHeraldAction' => 'applications/diffusion/herald/DiffusionAuditorsAddAuditorsHeraldAction.php',
     'DiffusionAuditorsAddSelfHeraldAction' => 'applications/diffusion/herald/DiffusionAuditorsAddSelfHeraldAction.php',
     'DiffusionAuditorsHeraldAction' => 'applications/diffusion/herald/DiffusionAuditorsHeraldAction.php',
+    'DiffusionBlameConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionBlameConduitAPIMethod.php',
+    'DiffusionBlameQuery' => 'applications/diffusion/query/blame/DiffusionBlameQuery.php',
     'DiffusionBlockHeraldAction' => 'applications/diffusion/herald/DiffusionBlockHeraldAction.php',
     'DiffusionBranchQueryConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionBranchQueryConduitAPIMethod.php',
     'DiffusionBranchTableController' => 'applications/diffusion/controller/DiffusionBranchTableController.php',
@@ -601,6 +603,7 @@ phutil_register_library_map(array(
     'DiffusionFindSymbolsConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionFindSymbolsConduitAPIMethod.php',
     'DiffusionGetLintMessagesConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionGetLintMessagesConduitAPIMethod.php',
     'DiffusionGetRecentCommitsByPathConduitAPIMethod' => 'applications/diffusion/conduit/DiffusionGetRecentCommitsByPathConduitAPIMethod.php',
+    'DiffusionGitBlameQuery' => 'applications/diffusion/query/blame/DiffusionGitBlameQuery.php',
     'DiffusionGitBranch' => 'applications/diffusion/data/DiffusionGitBranch.php',
     'DiffusionGitBranchTestCase' => 'applications/diffusion/data/__tests__/DiffusionGitBranchTestCase.php',
     'DiffusionGitFileContentQuery' => 'applications/diffusion/query/filecontent/DiffusionGitFileContentQuery.php',
@@ -632,6 +635,7 @@ phutil_register_library_map(array(
     'DiffusionLowLevelParentsQuery' => 'applications/diffusion/query/lowlevel/DiffusionLowLevelParentsQuery.php',
     'DiffusionLowLevelQuery' => 'applications/diffusion/query/lowlevel/DiffusionLowLevelQuery.php',
     'DiffusionLowLevelResolveRefsQuery' => 'applications/diffusion/query/lowlevel/DiffusionLowLevelResolveRefsQuery.php',
+    'DiffusionMercurialBlameQuery' => 'applications/diffusion/query/blame/DiffusionMercurialBlameQuery.php',
     'DiffusionMercurialFileContentQuery' => 'applications/diffusion/query/filecontent/DiffusionMercurialFileContentQuery.php',
     'DiffusionMercurialRawDiffQuery' => 'applications/diffusion/query/rawdiff/DiffusionMercurialRawDiffQuery.php',
     'DiffusionMercurialRequest' => 'applications/diffusion/request/DiffusionMercurialRequest.php',
@@ -743,6 +747,7 @@ phutil_register_library_map(array(
     'DiffusionSubversionServeSSHWorkflow' => 'applications/diffusion/ssh/DiffusionSubversionServeSSHWorkflow.php',
     'DiffusionSubversionWireProtocol' => 'applications/diffusion/protocol/DiffusionSubversionWireProtocol.php',
     'DiffusionSubversionWireProtocolTestCase' => 'applications/diffusion/protocol/__tests__/DiffusionSubversionWireProtocolTestCase.php',
+    'DiffusionSvnBlameQuery' => 'applications/diffusion/query/blame/DiffusionSvnBlameQuery.php',
     'DiffusionSvnFileContentQuery' => 'applications/diffusion/query/filecontent/DiffusionSvnFileContentQuery.php',
     'DiffusionSvnRawDiffQuery' => 'applications/diffusion/query/rawdiff/DiffusionSvnRawDiffQuery.php',
     'DiffusionSvnRequest' => 'applications/diffusion/request/DiffusionSvnRequest.php',
@@ -4493,6 +4498,8 @@ phutil_register_library_map(array(
     'DiffusionAuditorsAddAuditorsHeraldAction' => 'DiffusionAuditorsHeraldAction',
     'DiffusionAuditorsAddSelfHeraldAction' => 'DiffusionAuditorsHeraldAction',
     'DiffusionAuditorsHeraldAction' => 'HeraldAction',
+    'DiffusionBlameConduitAPIMethod' => 'DiffusionQueryConduitAPIMethod',
+    'DiffusionBlameQuery' => 'DiffusionQuery',
     'DiffusionBlockHeraldAction' => 'HeraldAction',
     'DiffusionBranchQueryConduitAPIMethod' => 'DiffusionQueryConduitAPIMethod',
     'DiffusionBranchTableController' => 'DiffusionController',
@@ -4566,6 +4573,7 @@ phutil_register_library_map(array(
     'DiffusionFindSymbolsConduitAPIMethod' => 'DiffusionConduitAPIMethod',
     'DiffusionGetLintMessagesConduitAPIMethod' => 'DiffusionConduitAPIMethod',
     'DiffusionGetRecentCommitsByPathConduitAPIMethod' => 'DiffusionConduitAPIMethod',
+    'DiffusionGitBlameQuery' => 'DiffusionBlameQuery',
     'DiffusionGitBranch' => 'Phobject',
     'DiffusionGitBranchTestCase' => 'PhabricatorTestCase',
     'DiffusionGitFileContentQuery' => 'DiffusionFileContentQuery',
@@ -4597,6 +4605,7 @@ phutil_register_library_map(array(
     'DiffusionLowLevelParentsQuery' => 'DiffusionLowLevelQuery',
     'DiffusionLowLevelQuery' => 'Phobject',
     'DiffusionLowLevelResolveRefsQuery' => 'DiffusionLowLevelQuery',
+    'DiffusionMercurialBlameQuery' => 'DiffusionBlameQuery',
     'DiffusionMercurialFileContentQuery' => 'DiffusionFileContentQuery',
     'DiffusionMercurialRawDiffQuery' => 'DiffusionRawDiffQuery',
     'DiffusionMercurialRequest' => 'DiffusionRequest',
@@ -4708,6 +4717,7 @@ phutil_register_library_map(array(
     'DiffusionSubversionServeSSHWorkflow' => 'DiffusionSubversionSSHWorkflow',
     'DiffusionSubversionWireProtocol' => 'Phobject',
     'DiffusionSubversionWireProtocolTestCase' => 'PhabricatorTestCase',
+    'DiffusionSvnBlameQuery' => 'DiffusionBlameQuery',
     'DiffusionSvnFileContentQuery' => 'DiffusionFileContentQuery',
     'DiffusionSvnRawDiffQuery' => 'DiffusionRawDiffQuery',
     'DiffusionSvnRequest' => 'DiffusionRequest',
diff --git a/src/applications/diffusion/conduit/DiffusionBlameConduitAPIMethod.php b/src/applications/diffusion/conduit/DiffusionBlameConduitAPIMethod.php
new file mode 100644
index 0000000000..7cbb379039
--- /dev/null
+++ b/src/applications/diffusion/conduit/DiffusionBlameConduitAPIMethod.php
@@ -0,0 +1,44 @@
+<?php
+
+final class DiffusionBlameConduitAPIMethod
+  extends DiffusionQueryConduitAPIMethod {
+
+  public function getAPIMethodName() {
+    return 'diffusion.blame';
+  }
+
+  public function getMethodDescription() {
+    return pht('Get blame information for a list of paths.');
+  }
+
+  protected function defineReturnType() {
+    return 'map<string, wild>';
+  }
+
+  protected function defineCustomParamTypes() {
+    return array(
+      'paths' => 'required list<string>',
+      'commit' => 'required string',
+      'timeout' => 'optional int',
+    );
+  }
+
+  protected function getResult(ConduitAPIRequest $request) {
+    $drequest = $this->getDiffusionRequest();
+
+    $paths = $request->getValue('paths');
+
+    $blame_query = DiffusionBlameQuery::newFromDiffusionRequest($drequest)
+      ->setPaths($paths);
+
+    $timeout = $request->getValue('timeout');
+    if ($timeout) {
+      $blame_query->setTimeout($timeout);
+    }
+
+    $blame = $blame_query->execute();
+
+    return $blame;
+  }
+
+}
diff --git a/src/applications/diffusion/conduit/DiffusionQueryConduitAPIMethod.php b/src/applications/diffusion/conduit/DiffusionQueryConduitAPIMethod.php
index 4b3eb6721f..21e8da485f 100644
--- a/src/applications/diffusion/conduit/DiffusionQueryConduitAPIMethod.php
+++ b/src/applications/diffusion/conduit/DiffusionQueryConduitAPIMethod.php
@@ -110,6 +110,13 @@ abstract class DiffusionQueryConduitAPIMethod
         'commit' => $request->getValue('commit'),
       ));
 
+    if (!$drequest) {
+      throw new Exception(
+        pht(
+          'Repository "%s" is not a valid repository.',
+          $identifier));
+    }
+
     // Figure out whether we're going to handle this request on this device,
     // or proxy it to another node in the cluster.
 
diff --git a/src/applications/diffusion/query/blame/DiffusionBlameQuery.php b/src/applications/diffusion/query/blame/DiffusionBlameQuery.php
new file mode 100644
index 0000000000..6d83020dd2
--- /dev/null
+++ b/src/applications/diffusion/query/blame/DiffusionBlameQuery.php
@@ -0,0 +1,69 @@
+<?php
+
+abstract class DiffusionBlameQuery extends DiffusionQuery {
+
+  private $timeout;
+  private $paths;
+
+  public function setTimeout($timeout) {
+    $this->timeout = $timeout;
+    return $this;
+  }
+
+  public function getTimeout() {
+    return $this->timeout;
+  }
+
+  public function setPaths(array $paths) {
+    $this->paths = $paths;
+    return $this;
+  }
+
+  public function getPaths() {
+    return $this->paths;
+  }
+
+  abstract protected function newBlameFuture(DiffusionRequest $request, $path);
+
+  abstract protected function resolveBlameFuture(ExecFuture $future);
+
+  final public static function newFromDiffusionRequest(
+    DiffusionRequest $request) {
+    return parent::newQueryObject(__CLASS__, $request);
+  }
+
+  final protected function executeQuery() {
+    $paths = $this->getPaths();
+    $request = $this->getRequest();
+    $timeout = $this->getTimeout();
+
+    $futures = array();
+    foreach ($paths as $path) {
+      $future = $this->newBlameFuture($request, $path);
+
+      if ($timeout) {
+        $future->setTimeout($timeout);
+      }
+
+      $futures[$path] = $future;
+    }
+
+
+    $blame = array();
+
+    if ($futures) {
+      $futures = id(new FutureIterator($futures))
+        ->limit(4);
+
+      foreach ($futures as $path => $future) {
+        $path_blame = $this->resolveBlameFuture($future);
+        if ($path_blame !== null) {
+          $blame[$path] = $path_blame;
+        }
+      }
+    }
+
+    return $blame;
+  }
+
+}
diff --git a/src/applications/diffusion/query/blame/DiffusionGitBlameQuery.php b/src/applications/diffusion/query/blame/DiffusionGitBlameQuery.php
new file mode 100644
index 0000000000..f98cc645a7
--- /dev/null
+++ b/src/applications/diffusion/query/blame/DiffusionGitBlameQuery.php
@@ -0,0 +1,34 @@
+<?php
+
+final class DiffusionGitBlameQuery extends DiffusionBlameQuery {
+
+  protected function newBlameFuture(DiffusionRequest $request, $path) {
+    $repository = $request->getRepository();
+
+    $commit = $request->getCommit();
+
+    return $repository->getLocalCommandFuture(
+      '--no-pager blame -s -l %s -- %s',
+      $commit,
+      $path);
+  }
+
+  protected function resolveBlameFuture(ExecFuture $future) {
+    list($err, $stdout) = $future->resolve();
+
+    if ($err) {
+      return null;
+    }
+
+    $result = array();
+
+    $lines = phutil_split_lines($stdout);
+    foreach ($lines as $line) {
+      list($commit) = explode(' ', $line, 2);
+      $result[] = $commit;
+    }
+
+    return $result;
+  }
+
+}
diff --git a/src/applications/diffusion/query/blame/DiffusionMercurialBlameQuery.php b/src/applications/diffusion/query/blame/DiffusionMercurialBlameQuery.php
new file mode 100644
index 0000000000..60eeb31c4f
--- /dev/null
+++ b/src/applications/diffusion/query/blame/DiffusionMercurialBlameQuery.php
@@ -0,0 +1,36 @@
+<?php
+
+final class DiffusionMercurialBlameQuery extends DiffusionBlameQuery {
+
+  protected function newBlameFuture(DiffusionRequest $request, $path) {
+    $repository = $request->getRepository();
+    $commit = $request->getCommit();
+
+    // NOTE: We're using "--debug" to make "--changeset" give us the full
+    // commit hashes.
+
+    return $repository->getLocalCommandFuture(
+      'annotate --debug --changeset --rev %s -- %s',
+      $commit,
+      $path);
+  }
+
+  protected function resolveBlameFuture(ExecFuture $future) {
+    list($err, $stdout) = $future->resolve();
+
+    if ($err) {
+      return null;
+    }
+
+    $result = array();
+
+    $lines = phutil_split_lines($stdout);
+    foreach ($lines as $line) {
+      list($commit) = explode(':', $line, 2);
+      $result[] = $commit;
+    }
+
+    return $result;
+  }
+
+}
diff --git a/src/applications/diffusion/query/blame/DiffusionSvnBlameQuery.php b/src/applications/diffusion/query/blame/DiffusionSvnBlameQuery.php
new file mode 100644
index 0000000000..afa99e2bb3
--- /dev/null
+++ b/src/applications/diffusion/query/blame/DiffusionSvnBlameQuery.php
@@ -0,0 +1,36 @@
+<?php
+
+final class DiffusionSvnBlameQuery extends DiffusionBlameQuery {
+
+  protected function newBlameFuture(DiffusionRequest $request, $path) {
+    $repository = $request->getRepository();
+    $commit = $request->getCommit();
+
+    return $repository->getRemoteCommandFuture(
+      'blame --force %s',
+      $repository->getSubversionPathURI($path, $commit));
+  }
+
+  protected function resolveBlameFuture(ExecFuture $future) {
+    list($err, $stdout) = $future->resolve();
+
+    if ($err) {
+      return null;
+    }
+
+    $result = array();
+    $matches = null;
+
+    $lines = phutil_split_lines($stdout);
+    foreach ($lines as $line) {
+      if (preg_match('/^\s*(\d+)/', $line, $matches)) {
+        $result[] = (int)$matches[1];
+      } else {
+        $result[] = null;
+      }
+    }
+
+    return $result;
+  }
+
+}