diff --git a/stub/src/main/java/com/google/net/stubby/stub/AbstractServiceDescriptor.java b/stub/src/main/java/com/google/net/stubby/stub/AbstractServiceDescriptor.java
new file mode 100644
index 0000000000..c5e0d7544c
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/AbstractServiceDescriptor.java
@@ -0,0 +1,21 @@
+package com.google.net.stubby.stub;
+
+import com.google.common.collect.ImmutableList;
+
+import java.util.Map;
+
+/**
+ * Base class for all stub configurations.
+ */
+public abstract class AbstractServiceDescriptor<T extends AbstractServiceDescriptor> {
+
+  /**
+   * Returns the list of operations defined in the stub configuration.
+   */
+  public abstract ImmutableList<MethodDescriptor> methods();
+
+  /**
+   * Returns a new stub configuration for the provided method configurations.
+   */
+  protected abstract T build(Map<String, MethodDescriptor> methodMap);
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/AbstractStub.java b/stub/src/main/java/com/google/net/stubby/stub/AbstractStub.java
new file mode 100644
index 0000000000..81024aea5c
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/AbstractStub.java
@@ -0,0 +1,80 @@
+package com.google.net.stubby.stub;
+
+import com.google.common.collect.Maps;
+
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Common base type for stub implementations. Allows for reconfiguration.
+ */
+// TODO(user): Move into 3rd party when tidy
+// TOOD(lryan/kevinb): Excessive parameterization can be a pain, try to eliminate once the generated
+// code is more tangible.
+public abstract class AbstractStub<S extends AbstractStub, C extends AbstractServiceDescriptor<C>> {
+  protected final Channel channel;
+  protected final C config;
+
+  /**
+   * Constructor for use by subclasses.
+   */
+  protected AbstractStub(Channel channel, C config) {
+    this.channel = channel;
+    this.config = config;
+  }
+
+  protected C getServiceDescriptor() {
+    return config;
+  }
+
+  public StubConfigBuilder configureNewStub() {
+    return new StubConfigBuilder();
+  }
+
+  /**
+   * Returns a new stub configuration for the provided method configurations.
+   */
+  protected abstract S build(Channel channel, C config);
+
+  /**
+   * Utility class for (re) configuring the operations in a stub.
+   */
+  public class StubConfigBuilder {
+
+    private final Map<String, MethodDescriptor> methodMap;
+
+    private StubConfigBuilder() {
+      methodMap = Maps.newHashMapWithExpectedSize(config.methods().size());
+      for (MethodDescriptor method : AbstractStub.this.config.methods()) {
+        methodMap.put(method.getName(), method);
+      }
+    }
+
+    /**
+     * Set a timeout for all methods in the stub.
+     */
+    public StubConfigBuilder setTimeout(long timeout, TimeUnit unit) {
+      for (MethodDescriptor methodDescriptor : methodMap.values()) {
+        setTimeout(methodDescriptor, timeout, unit);
+      }
+      return this;
+    }
+
+    /**
+     * Set the timeout for the specified method in microseconds.
+     */
+    private StubConfigBuilder setTimeout(MethodDescriptor method, long timeout, TimeUnit unit) {
+      // This is the pattern we would use for per-method configuration but currently
+      // no strong use-cases for it, hence private here
+      methodMap.put(method.getName(), method.withTimeout(timeout, unit));
+      return this;
+    }
+
+    /**
+     * Create a new stub configuration
+     */
+    public S build() {
+      return AbstractStub.this.build(channel, config.build(methodMap));
+    }
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/Call.java b/stub/src/main/java/com/google/net/stubby/stub/Call.java
new file mode 100644
index 0000000000..598ae5d356
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/Call.java
@@ -0,0 +1,17 @@
+package com.google.net.stubby.stub;
+
+/**
+ * Encapsulates the producer and consumer aspects of a call. A Call is a deferred execution context
+ * that does not dispatch data to the remote implementation until 'start' is called.
+ * <p>
+ * Call and it's sub-classes are used by the stub code generators to produced typed stubs.
+ * </p>
+ */
+// TODO(user): Implement context support
+public interface Call<RequestT, ResponseT> extends StreamObserver<RequestT>  {
+  /**
+   * Start a call passing it the response {@link StreamObserver}.
+   * @param responseObserver Which receive response messages.
+   */
+  public void start(StreamObserver<ResponseT> responseObserver);
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/CallContext.java b/stub/src/main/java/com/google/net/stubby/stub/CallContext.java
new file mode 100644
index 0000000000..81ac4ebbee
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/CallContext.java
@@ -0,0 +1,14 @@
+package com.google.net.stubby.stub;
+
+import java.io.InputStream;
+
+/**
+ * Common handling for context data
+ */
+// TODO(user): Implement
+public class CallContext {
+
+  void addResponseContext(String name, InputStream value) {
+
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/Calls.java b/stub/src/main/java/com/google/net/stubby/stub/Calls.java
new file mode 100644
index 0000000000..c8b90c7557
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/Calls.java
@@ -0,0 +1,243 @@
+package com.google.net.stubby.stub;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Throwables;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import com.google.net.stubby.Status;
+import com.google.net.stubby.transport.Transport;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.LinkedBlockingQueue;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * Utility functions for processing different call idioms. We have one-to-one correspondence
+ * between utilities in this class and the potential signatures in a generated stub class so
+ * that the runtime can vary behavior without requiring regeneration of the stub.
+ */
+public class Calls {
+
+  /**
+   * Execute a unary call and return a {@link ListenableFuture} to the response.
+   * @return a future for the single response message.
+   */
+  public static <ReqT, RespT> ListenableFuture<RespT> unaryFutureCall(
+      Call<ReqT, RespT> call,
+      ReqT param) {
+    SettableFuture<RespT> responseFuture = SettableFuture.create();
+    asyncServerStreamingCall(call, param, new UnaryStreamToFuture<RespT>(responseFuture));
+    return responseFuture;
+  }
+
+  /**
+   * Execute a unary call and block on the response.
+   * @return the single response message.
+   */
+  public static <ReqT, RespT> RespT blockingUnaryCall(Call<ReqT, RespT> call, ReqT param) {
+    return Futures.getUnchecked(unaryFutureCall(call, param));
+  }
+
+  /**
+   * Execute a unary call with a response {@link StreamObserver}.
+   */
+  public static <ReqT, RespT> void asyncUnaryCall(
+      Call<ReqT, RespT> call,
+      ReqT param,
+      StreamObserver<RespT> observer) {
+    asyncServerStreamingCall(call, param, observer);
+  }
+
+  /**
+   * Execute a server-streaming call returning a blocking {@link Iterator} over the
+   * response stream.
+   * @return an iterator over the response stream.
+   */
+  // TODO(user): Not clear if we want to use this idiom for 'simple' stubs.
+  public static <ReqT, RespT> Iterator<RespT> blockingServerStreamingCall(
+      Call<ReqT, RespT> call, ReqT param) {
+    // This is an interesting scenario for flow control...
+    // TODO(user): Capacity restriction is entirely arbitrary, need to parameterize.
+    BlockingResponseStream<RespT> result = new BlockingResponseStream<>(4096);
+    asyncServerStreamingCall(call, param, result);
+    return result;
+  }
+
+  /**
+   * Execute a server-streaming call with a response {@link StreamObserver}.
+   */
+  public static <ReqT, RespT> void asyncServerStreamingCall(
+      Call<ReqT, RespT> call,
+      ReqT param,
+      StreamObserver<RespT> responseObserver) {
+    call.start(responseObserver);
+    try {
+      call.onValue(param);
+      call.onCompleted();
+    } catch (Throwable t) {
+      call.onError(t);
+    }
+  }
+
+  /**
+   * Execute a client-streaming call with a blocking {@link Iterator} of request messages.
+   * @return the single response value.
+   */
+  public static <ReqT, RespT> RespT blockingClientStreamingCall(
+      Call<ReqT, RespT> call,
+      Iterator<ReqT> clientStream) {
+    SettableFuture<RespT> responseFuture = SettableFuture.create();
+    call.start(new UnaryStreamToFuture<RespT>(responseFuture));
+    try {
+      while (clientStream.hasNext()) {
+        call.onValue(clientStream.next());
+      }
+      call.onCompleted();
+    } catch (Throwable t) {
+      // Notify runtime of the error which will cancel the call
+      call.onError(t);
+      throw Throwables.propagate(t);
+    }
+    return Futures.getUnchecked(responseFuture);
+  }
+
+  /**
+   * Execute a client-streaming call returning a {@link StreamObserver} for the request messages.
+   * @return request stream observer.
+   */
+  public static <ReqT, RespT> StreamObserver<ReqT> asyncClientStreamingCall(
+      Call<ReqT, RespT> call,
+      StreamObserver<RespT> responseObserver) {
+    return duplexStreamingCall(call, responseObserver);
+  }
+
+
+  /**
+   * Execute a duplex-streaming call.
+   * @return request stream observer.
+   */
+  public static <ReqT, RespT> StreamObserver<ReqT> duplexStreamingCall(
+      Call<ReqT, RespT> call, StreamObserver<RespT> responseObserver) {
+    call.start(responseObserver);
+    return call;
+  }
+
+  /**
+   * Complete a SettableFuture using {@link StreamObserver} events.
+   */
+  private static class UnaryStreamToFuture<RespT> implements StreamObserver<RespT> {
+    private final SettableFuture<RespT> responseFuture;
+    private RespT value;
+
+    public UnaryStreamToFuture(SettableFuture<RespT> responseFuture) {
+      this.responseFuture = responseFuture;
+    }
+
+    @Override
+    public void onValue(RespT value) {
+      if (this.value != null) {
+        throw new Status(Transport.Code.INTERNAL, "More than one value received for unary call")
+            .asRuntimeException();
+      }
+      this.value = value;
+    }
+
+    @Override
+    public void onError(Throwable t) {
+      responseFuture.setException(t);
+    }
+
+    @Override
+    public void onCompleted() {
+      if (value == null) {
+        // No value received so mark the future as an error
+        responseFuture.setException(
+            new Status(Transport.Code.INTERNAL, "No value received for unary call")
+                .asRuntimeException().fillInStackTrace());
+      }
+      responseFuture.set(value);
+    }
+  }
+
+  /**
+   * Convert events on a {@link StreamObserver} into a blocking {@link Iterator}
+   */
+  @ThreadSafe
+  private static class BlockingResponseStream<T> implements Iterator<T>, StreamObserver<T> {
+
+    private final LinkedBlockingQueue<Object> buffer;
+    private final int maxBufferSize;
+    private Object last;
+    private boolean done = false;
+
+    /**
+     * Construct a buffering iterator so that blocking clients can consume the response stream.
+     * @param maxBufferSize limit on number of messages in the buffer before the stream is
+     * terminated.
+     */
+    private BlockingResponseStream(int maxBufferSize) {
+      buffer = new LinkedBlockingQueue<Object>();
+      this.maxBufferSize = maxBufferSize;
+    }
+
+    @Override
+    public synchronized void onValue(T value) {
+      Preconditions.checkState(!done, "Call to onValue afer onError/onCompleted");
+      if (buffer.size() >= maxBufferSize) {
+        // Throw the exception as observables are required to propagate it to onError
+        throw new CancellationException("Buffer size exceeded");
+      } else {
+        buffer.offer(value);
+      }
+    }
+
+    @Override
+    public synchronized void onError(Throwable t) {
+      Preconditions.checkState(!done, "Call to onError after call to onError/onCompleted");
+      buffer.offer(t);
+      done = true;
+    }
+
+    @Override
+    public synchronized void onCompleted() {
+      Preconditions.checkState(!done, "Call to onCompleted after call to onError/onCompleted");
+      buffer.offer(this);
+      done = true;
+    }
+
+    @Override
+    public synchronized boolean hasNext() {
+      // Will block here indefinitely waiting for content, RPC timeouts defend against
+      // permanent hangs here as onError will be reported.
+      try {
+        last = (last == null) ? buffer.take() : last;
+        if (last instanceof Throwable) {
+          throw Throwables.propagate((Throwable) last);
+        }
+        return last != this;
+      } catch (InterruptedException ie) {
+        Thread.interrupted();
+        throw Status.fromThrowable(ie).asRuntimeException();
+      }
+    }
+
+    @Override
+    public synchronized T next() {
+      if (!hasNext()) {
+        throw new NoSuchElementException();
+      }
+      T tmp = (T) last;
+      last = null;
+      return tmp;
+    }
+
+    @Override
+    public void remove() {
+      throw new UnsupportedOperationException();
+    }
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/Channel.java b/stub/src/main/java/com/google/net/stubby/stub/Channel.java
new file mode 100644
index 0000000000..843406708b
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/Channel.java
@@ -0,0 +1,17 @@
+package com.google.net.stubby.stub;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * An abstraction layer between stubs and the transport details. Channels are responsible for
+ * call initiation and tracking. Channels can be decorated to provide cross-cutting behaviors
+ * across all operations in a stub.
+ */
+@ThreadSafe
+public interface Channel {
+
+  /**
+   * Prepare a call to the given service method.
+   */
+  public <ReqT, RespT> Call<ReqT, RespT> prepare(MethodDescriptor<ReqT, RespT> method);
+}
\ No newline at end of file
diff --git a/stub/src/main/java/com/google/net/stubby/stub/Marshaller.java b/stub/src/main/java/com/google/net/stubby/stub/Marshaller.java
new file mode 100644
index 0000000000..44c46b84e2
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/Marshaller.java
@@ -0,0 +1,20 @@
+package com.google.net.stubby.stub;
+
+import java.io.InputStream;
+
+/**
+ * An typed abstraction over message serialization.
+ */
+public interface Marshaller<T> {
+
+  /**
+   * Given a message produce an {@link InputStream} for it.
+   */
+  // TODO(user): Switch to ByteSource equivalent when ready
+  public InputStream stream(T value);
+
+  /**
+   * Given an {@link InputStream} parse it into an instance of the declared type.
+   */
+  public T parse(InputStream stream);
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/Marshallers.java b/stub/src/main/java/com/google/net/stubby/stub/Marshallers.java
new file mode 100644
index 0000000000..13a7c14aad
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/Marshallers.java
@@ -0,0 +1,37 @@
+package com.google.net.stubby.stub;
+
+import com.google.net.stubby.DeferredProtoInputStream;
+import com.google.net.stubby.Status;
+import com.google.net.stubby.transport.Transport;
+import com.google.protobuf.InvalidProtocolBufferException;
+import com.google.protobuf.MessageLite;
+import com.google.protobuf.Parser;
+
+import java.io.InputStream;
+
+/**
+ * Utility functions for working with Marshallers.
+ */
+public class Marshallers {
+
+  private Marshallers() {}
+
+  public static <T extends MessageLite> Marshaller<T> forProto(final Parser<T> parser) {
+    return new Marshaller<T>() {
+      @Override
+      public InputStream stream(T value) {
+        return new DeferredProtoInputStream(value);
+      }
+
+      @Override
+      public T parse(InputStream stream) {
+        try {
+          return parser.parseFrom(stream);
+        } catch (InvalidProtocolBufferException ipbe) {
+          throw new Status(Transport.Code.INTERNAL, "Invalid protobuf byte sequence", ipbe)
+              .asRuntimeException();
+        }
+      }
+    };
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/MessageSink.java b/stub/src/main/java/com/google/net/stubby/stub/MessageSink.java
new file mode 100644
index 0000000000..e401cd09f0
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/MessageSink.java
@@ -0,0 +1,8 @@
+package com.google.net.stubby.stub;
+
+public interface MessageSink<E> {
+
+  public void receive(E message, boolean last);
+
+  public void close();
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/MessageSource.java b/stub/src/main/java/com/google/net/stubby/stub/MessageSource.java
new file mode 100644
index 0000000000..8b899c221e
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/MessageSource.java
@@ -0,0 +1,6 @@
+package com.google.net.stubby.stub;
+
+public interface MessageSource<E> {
+
+  public void produceToSink(MessageSink<E> sink);
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/MethodDescriptor.java b/stub/src/main/java/com/google/net/stubby/stub/MethodDescriptor.java
new file mode 100644
index 0000000000..f569721185
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/MethodDescriptor.java
@@ -0,0 +1,74 @@
+package com.google.net.stubby.stub;
+
+import com.google.common.base.Preconditions;
+
+import java.io.InputStream;
+import java.util.concurrent.TimeUnit;
+
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Descriptor for a single operation, used by Channel to execute a call.
+ */
+@Immutable
+public class MethodDescriptor<RequestT, ResponseT> {
+  private final String name;
+  // TODO(user): Make more generic than just proto? Use Function?
+  private final Marshaller<RequestT> requestMarshaller;
+  private final Marshaller<ResponseT> responseMarshaller;
+  private final long timeoutMicros;
+
+  public static <RequestT, ResponseT> MethodDescriptor<RequestT, ResponseT> create(
+      String name, long timeout, TimeUnit timeoutUnit,
+      Marshaller<RequestT> requestMarshaller,
+      Marshaller<ResponseT> responseMarshaller) {
+    return new MethodDescriptor<RequestT, ResponseT>(
+        name, timeoutUnit.toMicros(timeout), requestMarshaller, responseMarshaller);
+  }
+
+  private MethodDescriptor(String name, long timeoutMicros,
+                           Marshaller<RequestT> requestMarshaller,
+                           Marshaller<ResponseT> responseMarshaller) {
+    this.name = name;
+    Preconditions.checkArgument(timeoutMicros > 0);
+    this.timeoutMicros = timeoutMicros;
+    this.requestMarshaller = requestMarshaller;
+    this.responseMarshaller = responseMarshaller;
+  }
+
+  /**
+   * The fully qualified name of the method
+   */
+  public String getName() {
+    return name;
+  }
+
+  /**
+   * Timeout for the operation in microseconds
+   */
+  public long getTimeout() {
+    return timeoutMicros;
+  }
+
+  /**
+   * Parse a response payload from the given {@link InputStream}
+   */
+  public ResponseT parseResponse(InputStream input) {
+    return responseMarshaller.parse(input);
+  }
+
+  /**
+   * Convert a request message to an {@link InputStream}
+   */
+  public InputStream streamRequest(RequestT requestMessage) {
+    return requestMarshaller.stream(requestMessage);
+  }
+
+  /**
+   * Create a new descriptor with a different timeout
+   */
+  public MethodDescriptor withTimeout(long timeout, TimeUnit unit) {
+    return new MethodDescriptor(name , unit.toMicros(timeout),
+        requestMarshaller, responseMarshaller);
+  }
+}
\ No newline at end of file
diff --git a/stub/src/main/java/com/google/net/stubby/stub/SessionCall.java b/stub/src/main/java/com/google/net/stubby/stub/SessionCall.java
new file mode 100644
index 0000000000..1f6962c2e7
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/SessionCall.java
@@ -0,0 +1,123 @@
+package com.google.net.stubby.stub;
+
+import com.google.net.stubby.AbstractResponse;
+import com.google.net.stubby.Operation;
+import com.google.net.stubby.Request;
+import com.google.net.stubby.Response;
+import com.google.net.stubby.Session;
+import com.google.net.stubby.Status;
+
+import java.io.InputStream;
+
+/**
+ * A temporary shim layer between the new (Channel) and the old (Session). Will go away when the
+ * new transport layer is created.
+ */
+// TODO(user): Delete this class when new transport interfaces are introduced
+public class SessionCall<RequestT, ResponseT>
+    extends CallContext implements Call<RequestT, ResponseT> {
+
+  /**
+   * The {@link Request} used by the stub to dispatch the call
+   */
+  private Request request;
+
+  private StreamObserver<ResponseT> responseObserver;
+
+  private final MethodDescriptor<RequestT, ResponseT> methodDescriptor;
+  private final Session session;
+
+  protected SessionCall(MethodDescriptor<RequestT, ResponseT> methodDescriptor, Session session) {
+    // This will go away when we introduce new transport API.... nothing to see here
+    this.methodDescriptor = methodDescriptor;
+    this.session = session;
+  }
+
+  @Override
+  public void start(StreamObserver<ResponseT> responseObserver) {
+    request = session.startRequest(methodDescriptor.getName(), new Response.ResponseBuilder() {
+      @Override
+      public Response build(int id) {
+        return new CallResponse(id);
+      }
+
+      @Override
+      public Response build() {
+        return new CallResponse(-1);
+      }
+    });
+    this.responseObserver = responseObserver;
+  }
+
+  @Override
+  public void onValue(RequestT value) {
+    request.addPayload(methodDescriptor.streamRequest(value), Operation.Phase.PAYLOAD);
+  }
+
+  /**
+   * An error occurred while producing the request output. Cancel the request
+   * and close the response stream.
+   */
+  @Override
+  public void onError(Throwable t) {
+    request.close(Status.fromThrowable(t));
+    this.responseObserver.onError(t);
+  }
+
+  @Override
+  public void onCompleted() {
+    request.close(Status.OK);
+  }
+
+  /**
+   * Adapts the transport layer response to calls on the response observer or
+   * recorded context state.
+   */
+  private class CallResponse extends AbstractResponse {
+
+    private CallResponse(int id) {
+      super(id);
+    }
+
+    @Override
+    public Operation addContext(String type, InputStream message, Phase nextPhase) {
+      try {
+        SessionCall.this.addResponseContext(type, message);
+        return super.addContext(type, message, nextPhase);
+      } finally {
+        if (getPhase() == Phase.CLOSED) {
+          propagateClosed();
+        }
+      }
+    }
+
+    @Override
+    public Operation addPayload(InputStream payload, Phase nextPhase) {
+      try {
+        SessionCall.this.responseObserver.onValue(methodDescriptor.parseResponse(payload));
+        return super.addPayload(payload, nextPhase);
+      } finally {
+        if (getPhase() == Phase.CLOSED) {
+          propagateClosed();
+        }
+      }
+    }
+
+    @Override
+    public Operation close(Status status) {
+      try {
+        return super.close(status);
+      } finally {
+        propagateClosed();
+      }
+    }
+
+    private void propagateClosed() {
+      if (Status.OK.getCode() == getStatus().getCode()) {
+        SessionCall.this.responseObserver.onCompleted();
+      } else {
+        SessionCall.this.responseObserver.onError(getStatus().asRuntimeException());
+      }
+    }
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/SessionChannel.java b/stub/src/main/java/com/google/net/stubby/stub/SessionChannel.java
new file mode 100644
index 0000000000..216e0e94e2
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/SessionChannel.java
@@ -0,0 +1,20 @@
+package com.google.net.stubby.stub;
+
+import com.google.net.stubby.Session;
+
+/**
+ * This class is a shim between Session & Channel. Will be removed when the new transport
+ * API is introduced.
+ */
+public class SessionChannel implements Channel {
+  private final Session session;
+
+  public SessionChannel(Session session) {
+    this.session = session;
+  }
+
+  @Override
+  public <ReqT, RespT> SessionCall<ReqT, RespT> prepare(MethodDescriptor<ReqT, RespT> method) {
+    return new SessionCall<ReqT, RespT>(method, session);
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/StreamObserver.java b/stub/src/main/java/com/google/net/stubby/stub/StreamObserver.java
new file mode 100644
index 0000000000..9cb502514c
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/StreamObserver.java
@@ -0,0 +1,41 @@
+package com.google.net.stubby.stub;
+
+/**
+ * Receives notifications from an observable stream of messages.
+ */
+// TODO(user): Consider whether we need to interact with flow-control at this layer. E.g.
+// public ListenableFuture<Void> onValue(V value). Do we layer it in here or as an additional
+// interface? Interaction with flow control can be done by blocking here.
+public interface StreamObserver<V>  {
+
+  /**
+   * Receive a value from the stream.
+   * <p>
+   * Can be called many times but is never called after onError or onCompleted are called.
+   * </p>
+   * <p>
+   * If an exception is thrown by an implementation the caller is expected to terminate the
+   * stream by calling {@linkplain #onError(Throwable)} with the caught exception prior to
+   * propagating it.
+   * </p>
+   */
+  public void onValue(V value);
+
+  /**
+   * Receive a terminating error from the stream.
+   * <p>
+   * May only be called once and is never called after onCompleted. In particular if an exception
+   * is thrown by an implementation of onError no further calls to any method are allowed.
+   * </p>
+   */
+  public void onError(Throwable t);
+
+  /**
+   * Notifies successful stream completion.
+   * <p>
+   * May only be called once and is never called after onError. In particular if an exception is
+   * thrown by an implementation of onCompleted no further calls to any method are allowed.
+   * </p>
+   */
+  public void onCompleted();
+}
\ No newline at end of file
diff --git a/stub/src/main/java/com/google/net/stubby/stub/StreamRecorder.java b/stub/src/main/java/com/google/net/stubby/stub/StreamRecorder.java
new file mode 100644
index 0000000000..6b49af782e
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/StreamRecorder.java
@@ -0,0 +1,98 @@
+package com.google.net.stubby.stub;
+
+import com.google.common.collect.Lists;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import javax.annotation.Nullable;
+
+/**
+ * Utility implementation of {link StreamObserver} used in testing. Records all the observed
+ * values produced by the stream as well as any errors.
+ */
+public class StreamRecorder<T> implements StreamObserver<T> {
+
+  /**
+   * Create a new recorder.
+   */
+  public static <T> StreamRecorder<T> create() {
+    return new StreamRecorder<T>();
+  }
+
+  private final CountDownLatch latch;
+  private final List<T> results;
+  private Throwable error;
+  private final SettableFuture<T> firstValue;
+
+  private StreamRecorder() {
+    firstValue = SettableFuture.create();
+    latch = new CountDownLatch(1);
+    results = Collections.synchronizedList(Lists.<T>newArrayList());
+  }
+
+  @Override
+  public void onValue(T value) {
+    if (!firstValue.isDone()) {
+      firstValue.set(value);
+    }
+    results.add(value);
+  }
+
+  @Override
+  public void onError(Throwable t) {
+    if (!firstValue.isDone()) {
+      firstValue.setException(t);
+    }
+    error = t;
+    latch.countDown();
+  }
+
+  @Override
+  public void onCompleted() {
+    if (!firstValue.isDone()) {
+      firstValue.setException(new IllegalStateException("No first value provided"));
+    }
+    latch.countDown();
+  }
+
+  /**
+   * Wait for the stream to terminate.
+   */
+  public void awaitCompletion() throws Exception {
+    latch.await();
+  }
+
+  /**
+   * Wait a fixed timeout for the stream to terminate.
+   */
+  public boolean awaitCompletion(int timeout, TimeUnit unit) throws Exception {
+    return latch.await(timeout, unit);
+  }
+
+  /**
+   * Return the current set of received values.
+   */
+  public List<T> getValues() {
+    return Collections.unmodifiableList(results);
+  }
+
+  /**
+   * Return the stream terminating error.
+   */
+  @Nullable public Throwable getError() {
+    return error;
+  }
+
+  /**
+   * Return a {@link ListenableFuture} for the first value received from the stream. Useful
+   * for testing unary call patterns.
+   */
+  public ListenableFuture<T> firstValue() {
+    return firstValue;
+  }
+}
diff --git a/stub/src/main/java/com/google/net/stubby/stub/StubDescriptor.java b/stub/src/main/java/com/google/net/stubby/stub/StubDescriptor.java
new file mode 100644
index 0000000000..dc4380628e
--- /dev/null
+++ b/stub/src/main/java/com/google/net/stubby/stub/StubDescriptor.java
@@ -0,0 +1,38 @@
+package com.google.net.stubby.stub;
+
+import com.google.net.stubby.DeferredProtoInputStream;
+import com.google.protobuf.InvalidProtocolBufferException;
+import com.google.protobuf.MessageLite;
+
+import java.io.InputStream;
+
+/**
+ * StubDescriptor used by generated stubs
+ */
+// TODO(user): Should really be an interface
+public class StubDescriptor<I extends MessageLite, O extends MessageLite> {
+
+  private final String name;
+  private final O defaultO;
+
+  public StubDescriptor(String name, O defaultO) {
+    this.name = name;
+    this.defaultO = defaultO;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public O parseResponse(InputStream input) {
+    try {
+      return (O) defaultO.getParserForType().parseFrom(input);
+    } catch (InvalidProtocolBufferException ipbe) {
+      throw new RuntimeException(ipbe);
+    }
+  }
+
+  public InputStream streamRequest(I input) {
+    return new DeferredProtoInputStream(input);
+  }
+}