diff --git a/include/llbuild/BuildSystem/BuildFile.h b/include/llbuild/BuildSystem/BuildFile.h
index 39ad02c3..90748e39 100644
--- a/include/llbuild/BuildSystem/BuildFile.h
+++ b/include/llbuild/BuildSystem/BuildFile.h
@@ -138,7 +138,7 @@ class BuildFileDelegate {
   ///
   /// \param isImplicit Whether the node is an implicit one (created as a side
   /// effect of being declared by a command).
-  virtual std::unique_ptr<Node> lookupNode(StringRef name,
+  virtual std::unique_ptr<Node> createNode(StringRef name,
                                            bool isImplicit=false) = 0;
 };
 
diff --git a/include/llbuild/BuildSystem/BuildSystem.h b/include/llbuild/BuildSystem/BuildSystem.h
index bc372fee..c4c18b7a 100644
--- a/include/llbuild/BuildSystem/BuildSystem.h
+++ b/include/llbuild/BuildSystem/BuildSystem.h
@@ -36,6 +36,7 @@ namespace buildsystem {
 
 class BuildDescription;
 class BuildKey;
+class BuildNode;
 class BuildValue;
 class Command;
 class Node;
@@ -312,6 +313,8 @@ class BuildSystem {
   /// @}
 
   ShellCommandHandler* resolveShellCommandHandler(ShellCommand* command);
+  
+  BuildNode *lookupNode(StringRef name);
 };
 
 }
diff --git a/lib/BuildSystem/BuildFile.cpp b/lib/BuildSystem/BuildFile.cpp
index f13ee327..1f725460 100644
--- a/lib/BuildSystem/BuildFile.cpp
+++ b/lib/BuildSystem/BuildFile.cpp
@@ -368,7 +368,7 @@ class BuildFileImpl {
       return it->second.get();
     
     // Otherwise, ask the delegate to create the node.
-    auto node = delegate.lookupNode(name, isImplicit);
+    auto node = delegate.createNode(name, isImplicit);
     assert(node);
     auto result = node.get();
     nodes[name] = std::move(node);
diff --git a/lib/BuildSystem/BuildSystem.cpp b/lib/BuildSystem/BuildSystem.cpp
index 46175ad0..ba99987a 100644
--- a/lib/BuildSystem/BuildSystem.cpp
+++ b/lib/BuildSystem/BuildSystem.cpp
@@ -125,7 +125,7 @@ class BuildSystemFileDelegate : public BuildFileDelegate {
   virtual void loadedCommand(StringRef name,
                              const Command& target) override;
 
-  virtual std::unique_ptr<Node> lookupNode(StringRef name,
+  virtual std::unique_ptr<Node> createNode(StringRef name,
                                            bool isImplicit=false) override;
 
   /// @}
@@ -162,6 +162,8 @@ class BuildSystemEngineDelegate : public BuildEngineDelegate {
   BuildSystemImpl& getBuildSystem() {
     return system;
   }
+  
+  BuildNode *lookupNode(StringRef name);
 };
 
 class BuildSystemImpl {
@@ -274,8 +276,10 @@ class BuildSystemImpl {
              const Twine& message) {
     getDelegate().error(filename, at, message);
   }
+  
+  BuildNode* lookupNode(StringRef name);
 
-  std::unique_ptr<BuildNode> lookupNode(StringRef name,
+  std::unique_ptr<BuildNode> createNode(StringRef name,
                                         bool isImplicit);
 
   uint32_t getMergedSchemaVersion() {
@@ -1695,7 +1699,26 @@ class BuildSystemRule : public Rule {
 
 
 
-
+BuildNode *BuildSystemEngineDelegate::lookupNode(StringRef name) {
+  // Find the node.
+  auto it = getBuildDescription().getNodes().find(name);
+  BuildNode* node;
+  if (it != getBuildDescription().getNodes().end()) {
+    node = static_cast<BuildNode*>(it->second.get());
+  } else {
+    auto it = dynamicNodes.find(name);
+    if (it != dynamicNodes.end()) {
+      node = it->second.get();
+    } else {
+      // Create nodes on the fly for any unknown ones.
+      auto nodeOwner = system.createNode(
+                                         name, /*isImplicit=*/true);
+      node = nodeOwner.get();
+      dynamicNodes[name] = std::move(nodeOwner);
+    }
+  }
+  return node;
+}
 
 std::unique_ptr<Rule> BuildSystemEngineDelegate::lookupRule(const KeyType& keyData) {
   // Decode the key.
@@ -1858,22 +1881,7 @@ std::unique_ptr<Rule> BuildSystemEngineDelegate::lookupRule(const KeyType& keyDa
     
   case BuildKey::Kind::Node: {
     // Find the node.
-    auto it = getBuildDescription().getNodes().find(key.getNodeName());
-    BuildNode* node;
-    if (it != getBuildDescription().getNodes().end()) {
-      node = static_cast<BuildNode*>(it->second.get());
-    } else {
-      auto it = dynamicNodes.find(key.getNodeName());
-      if (it != dynamicNodes.end()) {
-        node = it->second.get();
-      } else {
-        // Create nodes on the fly for any unknown ones.
-        auto nodeOwner = system.lookupNode(
-            key.getNodeName(), /*isImplicit=*/true);
-        node = nodeOwner.get();
-        dynamicNodes[key.getNodeName()] = std::move(nodeOwner);
-      }
-    }
+    BuildNode* node = lookupNode(key.getNodeName());
 
     // Create the rule used to construct this node.
     //
@@ -2051,8 +2059,12 @@ void BuildSystemEngineDelegate::error(const Twine& message) {
 
 #pragma mark - BuildSystemImpl implementation
 
+BuildNode *BuildSystemImpl::lookupNode(StringRef name) {
+  return engineDelegate.lookupNode(name);
+}
+
 std::unique_ptr<BuildNode>
-BuildSystemImpl::lookupNode(StringRef name, bool isImplicit) {
+BuildSystemImpl::createNode(StringRef name, bool isImplicit) {
   if (name.endswith("/")) {
     return BuildNode::makeDirectory(name);
   }
@@ -4084,9 +4096,9 @@ void BuildSystemFileDelegate::loadedCommand(StringRef name,
 }
 
 std::unique_ptr<Node>
-BuildSystemFileDelegate::lookupNode(StringRef name,
+BuildSystemFileDelegate::createNode(StringRef name,
                                     bool isImplicit) {
-  return system.lookupNode(name, isImplicit);
+  return system.createNode(name, isImplicit);
 }
 
 }
@@ -4169,6 +4181,10 @@ BuildSystem::resolveShellCommandHandler(ShellCommand* command) {
   return static_cast<BuildSystemImpl*>(impl)->resolveShellCommandHandler(command);
 }
 
+BuildNode* BuildSystem::lookupNode(StringRef name) {
+  return static_cast<BuildSystemImpl*>(impl)->lookupNode(name);
+}
+
 // This function checks if the given path is prefixed by another path.
 bool llbuild::buildsystem::pathIsPrefixedByPath(std::string path,
                                                 std::string prefixPath) {
diff --git a/lib/Commands/BuildSystemCommand.cpp b/lib/Commands/BuildSystemCommand.cpp
index 96f28808..46a4cd96 100644
--- a/lib/Commands/BuildSystemCommand.cpp
+++ b/lib/Commands/BuildSystemCommand.cpp
@@ -92,7 +92,7 @@ class ParseBuildFileDelegate : public BuildFileDelegate {
 
   virtual void loadedDefaultTarget(StringRef target) override;
 
-  virtual std::unique_ptr<Node> lookupNode(StringRef name,
+  virtual std::unique_ptr<Node> createNode(StringRef name,
                                            bool isImplicit) override;
 
   virtual void loadedCommand(StringRef name,
@@ -368,7 +368,7 @@ void ParseBuildFileDelegate::loadedDefaultTarget(StringRef target) {
 }
 
 std::unique_ptr<Node>
-ParseBuildFileDelegate::lookupNode(StringRef name,
+ParseBuildFileDelegate::createNode(StringRef name,
                                    bool isImplicit) {
   if (!isImplicit) {
     if (showOutput) {
diff --git a/products/libllbuild/BuildSystem-C-API.cpp b/products/libllbuild/BuildSystem-C-API.cpp
index d755a0ff..25d42992 100644
--- a/products/libllbuild/BuildSystem-C-API.cpp
+++ b/products/libllbuild/BuildSystem-C-API.cpp
@@ -719,6 +719,9 @@ class CAPIExternalCommand : public ExternalCommand {
   
   /// The paths to the dependency output files, if used.
   SmallVector<std::string, 1> depsPaths{};
+  
+  /// Names of output nodes of this command.
+  SmallVector<std::string, 1> outputNodeNames{};
 
   /// The working directory used to resolve relative paths in dependency files.
   std::string workingDirectory;
@@ -893,6 +896,9 @@ class CAPIExternalCommand : public ExternalCommand {
       SmallString<PATH_MAX> wd = value;
       llvm::sys::fs::make_absolute(wd);
       workingDirectory = StringRef(wd);
+    } else if (name == "outputs") {
+      outputNodeNames.clear();
+      outputNodeNames.emplace_back(value);
     } else {
       return false;
     }
@@ -904,6 +910,9 @@ class CAPIExternalCommand : public ExternalCommand {
     if (name == "deps") {
       depsPaths.clear();
       depsPaths.insert(depsPaths.begin(), values.begin(), values.end());
+    } else if (name == "outputs") {
+      outputNodeNames.clear();
+      outputNodeNames.insert(outputNodeNames.begin(), values.begin(), values.end());
     } else {
       return false;
     }
@@ -943,6 +952,10 @@ class CAPIExternalCommand : public ExternalCommand {
   
   virtual void startExternalCommand(BuildSystem& system,
                                     core::TaskInterface ti) override {
+    outputs.reserve(outputNodeNames.size());
+    for (auto name: outputNodeNames) {
+      outputs.push_back(system.lookupNode(name));
+    }
     cAPIDelegate.start(cAPIDelegate.context,
                        (llb_buildsystem_command_t*)this,
                        (llb_buildsystem_interface_t*)&system,
diff --git a/products/libllbuild/include/llbuild/llbuild-defines.h b/products/libllbuild/include/llbuild/llbuild-defines.h
index b095f0de..52a695dd 100644
--- a/products/libllbuild/include/llbuild/llbuild-defines.h
+++ b/products/libllbuild/include/llbuild/llbuild-defines.h
@@ -84,6 +84,7 @@
 /// compile for multiple versions of the API.
 ///
 /// Version History:
+/// 18: Added support for configuring outputs of dynamic tasks via the C API.
 ///
 /// 17: Added `llb_buildsystem_dependency_data_format_makefile_ignoring_subsequent_outputs`
 ///
@@ -120,6 +121,6 @@
 /// 1: Added `environment` parameter to llb_buildsystem_invocation_t.
 ///
 /// 0: Pre-history
-#define LLBUILD_C_API_VERSION 17
+#define LLBUILD_C_API_VERSION 18
 
 #endif
diff --git a/products/llbuildSwift/BuildSystemBindings.swift b/products/llbuildSwift/BuildSystemBindings.swift
index f85c60bc..140bf62d 100644
--- a/products/llbuildSwift/BuildSystemBindings.swift
+++ b/products/llbuildSwift/BuildSystemBindings.swift
@@ -239,6 +239,9 @@ public protocol ExternalCommand: AnyObject {
     /// This is checked to determine if the command needs to rebuild versus the last time it was run.
     func getSignature(_ command: Command) -> [UInt8]
     
+    /// Outputs nodes of the command.
+    var outputs: [String] { get }
+    
     /// Paths to files that contain discovered dependencies after command executed successfully for subsequent builds.
     var dependencyPaths: [String] { get }
     
@@ -300,6 +303,12 @@ public protocol ExternalCommand: AnyObject {
     func execute(_ command: Command, _ commandInterface: BuildSystemCommandInterface, _ jobContext: JobContext) -> CommandResult
 }
 
+public extension ExternalCommand {
+    var outputs: [String] {
+        []
+    }
+}
+
 public protocol ExternalDetachedCommand: AnyObject {
     /// Whether the command should run outside the execution lanes.
     /// If true the build system will call `executeDetached` and `cancelDetached`.
@@ -457,6 +466,24 @@ private final class CommandWrapper {
             }
             single(context, workingDirectoryKey, workingDirectoryValue)
         }
+        if !command.outputs.isEmpty {
+            var outputs: [llb_data_t] = []
+            for output in command.outputs {
+                outputs.append(copiedDataFromBytes(Array(output.utf8)))
+            }
+            var key = copiedDataFromBytes(Array("outputs".utf8))
+            defer {
+                llb_data_destroy(&key)
+                for index in outputs.indices {
+                    llb_data_destroy(&outputs[index])
+                }
+            }
+            if outputs.count == 1 {
+                single(context, key, outputs[0])
+            } else {
+                collection(context, key, &outputs, outputs.count)
+            }
+        }
     }
 
     func getSignature(_: OpaquePointer, _ data: UnsafeMutablePointer<llb_data_t>) {