diff --git a/mobile/examples/swift/hello_world/AppDelegate.swift b/mobile/examples/swift/hello_world/AppDelegate.swift
index 6b0f9da8a90c..14c5ec6a10b4 100644
--- a/mobile/examples/swift/hello_world/AppDelegate.swift
+++ b/mobile/examples/swift/hello_world/AppDelegate.swift
@@ -1,7 +1,7 @@
 import Envoy
 import UIKit
 
-private enum ConfigLoadError: Error {
+private enum ConfigLoadError: Swift.Error {
   case noFileAtPath
 }
 
diff --git a/mobile/library/swift/src/BUILD b/mobile/library/swift/src/BUILD
index 6d9f7655fe54..573233318d01 100644
--- a/mobile/library/swift/src/BUILD
+++ b/mobile/library/swift/src/BUILD
@@ -5,12 +5,16 @@ load("//bazel:swift_static_framework.bzl", "swift_static_framework")
 swift_static_framework(
     name = "ios_framework",
     srcs = [
+        "Client.swift",
         "Envoy.swift",
+        "Error.swift",
         "LogLevel.swift",
         "Request.swift",
         "RequestBuilder.swift",
         "RequestMethod.swift",
+        "ResponseHandler.swift",
         "RetryPolicy.swift",
+        "StreamEmitter.swift",
     ],
     module_name = "Envoy",
     objc_includes = ["//library/objective-c:EnvoyEngine.h"],
diff --git a/mobile/library/swift/src/Client.swift b/mobile/library/swift/src/Client.swift
new file mode 100644
index 000000000000..65e4e986fb50
--- /dev/null
+++ b/mobile/library/swift/src/Client.swift
@@ -0,0 +1,12 @@
+/// Client that is able to send and receive requests through Envoy.
+@objc
+public protocol Client {
+  /// Start a new stream.
+  ///
+  /// - parameter request: The request for opening a stream.
+  /// - parameter handler: Handler for receiving stream events.
+  ///
+  /// - returns: Emitter for sending streaming data outward.
+  func startStream(request: Request, handler: ResponseHandler)
+    -> StreamEmitter
+}
diff --git a/mobile/library/swift/src/Error.swift b/mobile/library/swift/src/Error.swift
new file mode 100644
index 000000000000..d56f2c9e1541
--- /dev/null
+++ b/mobile/library/swift/src/Error.swift
@@ -0,0 +1,17 @@
+import Foundation
+
+@objcMembers
+public final class Error: NSObject, Swift.Error {
+  /// Error code associated with the exception that occurred.
+  public let errorCode: Int
+  /// A description of what exception that occurred.
+  public let message: String
+  /// Optional cause for the error.
+  public let cause: Swift.Error?
+
+  init(errorCode: Int, message: String, cause: Swift.Error?) {
+    self.errorCode = errorCode
+    self.message = message
+    self.cause = cause
+  }
+}
diff --git a/mobile/library/swift/src/ResponseHandler.swift b/mobile/library/swift/src/ResponseHandler.swift
new file mode 100644
index 000000000000..bd3a8a01d7ec
--- /dev/null
+++ b/mobile/library/swift/src/ResponseHandler.swift
@@ -0,0 +1,39 @@
+import Foundation
+
+/// Callback interface for receiving stream events.
+@objc
+public protocol ResponseHandler {
+  /// Called when response headers are received by the stream.
+  ///
+  /// - parameter headers:    The headers of the response.
+  /// - parameter statusCode: The status code of the response.
+  func onHeaders(_ headers: [String: [String]], statusCode: Int)
+
+  /// Called when a data frame is received by the stream.
+  ///
+  /// - parameter data:      Bytes in the response.
+  /// - parameter endStream: True if the stream is complete.
+  func onData(_ data: Data, endStream: Bool)
+
+  /// Called when response metadata is received by the stream.
+  ///
+  /// - parameter metadata:  The metadata of the response.
+  /// - parameter endStream: True if the stream is complete.
+  func onMetadata(_ metadata: [String: [String]], endStream: Bool)
+
+  /// Called when response trailers are received by the stream.
+  ///
+  /// - parameter trailers: The trailers of the response.
+  func onTrailers(_ trailers: [String: [String]])
+
+  /// Called when an internal Envoy exception occurs with the stream.
+  ///
+  /// - parameter error: The error that occurred with the stream.
+  func onError(_ error: Error)
+
+  /// Called when the stream is canceled.
+  func onCanceled()
+
+  /// Called when the stream has been completed.
+  func onCompletion()
+}
diff --git a/mobile/library/swift/src/StreamEmitter.swift b/mobile/library/swift/src/StreamEmitter.swift
new file mode 100644
index 000000000000..0f99baf9a00d
--- /dev/null
+++ b/mobile/library/swift/src/StreamEmitter.swift
@@ -0,0 +1,50 @@
+import Foundation
+
+/// Interface allowing for sending/emitting data on an Envoy stream.
+@objc
+public protocol StreamEmitter {
+  /// Returns whether the emitter is still active and can
+  /// perform communications with the associated stream.
+  ///
+  /// - returns: True if the stream is active.
+  func isActive() -> Bool
+
+  /// Send data over the associated stream.
+  ///
+  /// - parameter data: Data to send over the stream.
+  ///
+  /// - throws: `Envoy.Error` when the stream is inactive or data can't be sent.
+  ///
+  /// - returns: The stream emitter, for chaining syntax.
+  func sendData(_ data: Data) throws -> StreamEmitter
+
+  /// Sent metadata over the associated stream.
+  ///
+  /// - parameter metadata: Metadata to send over the stream.
+  ///
+  /// - throws: `Envoy.Error` when the stream is inactive or data can't be sent.
+  ///
+  /// - returns: The stream emitter, for chaining syntax.
+  func sendMetadata(_ metadata: [String: [String]]) throws -> StreamEmitter
+
+  /// End the stream after sending any provided trailers.
+  ///
+  /// - parameter trailers: Trailers to send over the stream.
+  ///
+  /// - throws: `Envoy.Error` when the stream is inactive or data can't be sent.
+  func close(trailers: [String: [String]]) throws
+
+  /// Cancel and end the associated stream.
+  ///
+  /// - throws: `Envoy.Error` when the stream is inactive or data can't be sent.
+  func cancel() throws
+}
+
+extension StreamEmitter {
+  /// Convenience function for ending the stream without sending any trailers.
+  ///
+  /// - throws: `Envoy.Error` when the stream is inactive or data can't be sent.
+  public func close() throws {
+    try self.close(trailers: [:])
+  }
+}