diff --git a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/ModuleDebug.aidl b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/ModuleDebug.aidl
index 80ee185..467d37b 100644
--- a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/ModuleDebug.aidl
+++ b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/ModuleDebug.aidl
@@ -35,4 +35,5 @@
 @JavaDerive(equals=true, toString=true) @VintfStability
 parcelable ModuleDebug {
   boolean simulateDeviceConnections;
+  int streamTransientStateDelayMs;
 }
diff --git a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/StreamDescriptor.aidl b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/StreamDescriptor.aidl
index 3a77ad1..84a1fe7 100644
--- a/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/StreamDescriptor.aidl
+++ b/audio/aidl/aidl_api/android.hardware.audio.core/current/android/hardware/audio/core/StreamDescriptor.aidl
@@ -57,7 +57,8 @@
   }
   @FixedSize @VintfStability
   union Command {
-    int hal_reserved_exit;
+    int halReservedExit;
+    android.media.audio.common.Void getStatus;
     android.media.audio.common.Void start;
     int burst;
     android.media.audio.common.Void drain;
diff --git a/audio/aidl/android/hardware/audio/core/IModule.aidl b/audio/aidl/android/hardware/audio/core/IModule.aidl
index be40051..1bc2ccc 100644
--- a/audio/aidl/android/hardware/audio/core/IModule.aidl
+++ b/audio/aidl/android/hardware/audio/core/IModule.aidl
@@ -53,9 +53,13 @@
      * the HAL module behavior that would otherwise require human intervention.
      *
      * The HAL module must throw an error if there is an attempt to change
-     * the debug behavior for the aspect which is currently in use.
+     * the debug behavior for the aspect which is currently in use, or when
+     * the value of any of the debug flags is invalid. See 'ModuleDebug' for
+     * the full list of constraints.
      *
      * @param debug The debug options.
+     * @throws EX_ILLEGAL_ARGUMENT If some of the configuration parameters are
+     *                             invalid.
      * @throws EX_ILLEGAL_STATE If the flag(s) being changed affect functionality
      *                          which is currently in use.
      */
diff --git a/audio/aidl/android/hardware/audio/core/ModuleDebug.aidl b/audio/aidl/android/hardware/audio/core/ModuleDebug.aidl
index 858a9bd..86a9b22 100644
--- a/audio/aidl/android/hardware/audio/core/ModuleDebug.aidl
+++ b/audio/aidl/android/hardware/audio/core/ModuleDebug.aidl
@@ -35,4 +35,13 @@
      *    profiles.
      */
     boolean simulateDeviceConnections;
+    /**
+     * Must be non-negative. When set to non-zero, HAL module must delay
+     * transition from "transient" stream states (see StreamDescriptor.aidl)
+     * by the specified amount of milliseconds. The purpose of this delay
+     * is to allow VTS to test sending of stream commands while the stream is
+     * in a transient state. The delay must apply to newly created streams,
+     * it is not required to apply the delay to already opened streams.
+     */
+    int streamTransientStateDelayMs;
 }
diff --git a/audio/aidl/android/hardware/audio/core/StreamDescriptor.aidl b/audio/aidl/android/hardware/audio/core/StreamDescriptor.aidl
index 2b1fc99..92d131a 100644
--- a/audio/aidl/android/hardware/audio/core/StreamDescriptor.aidl
+++ b/audio/aidl/android/hardware/audio/core/StreamDescriptor.aidl
@@ -84,13 +84,13 @@
  *     are different.
  *
  * State machines of both input and output streams start from the 'STANDBY'
- * state.  Transitions between states happen naturally with changes in the
+ * state. Transitions between states happen naturally with changes in the
  * states of the model elements. For simplicity, we restrict the change to one
  * element only, for example, in the 'STANDBY' state, either the producer or the
  * consumer can become active, but not both at the same time. States 'STANDBY',
  * 'IDLE', 'READY', and '*PAUSED' are "stable"—they require an external event,
  * whereas a change from the 'DRAINING' state can happen with time as the buffer
- * gets empty.
+ * gets empty, thus it's a "transient" state.
  *
  * The state machine for input streams is defined in the `stream-in-sm.gv` file,
  * for output streams—in the `stream-out-sm.gv` file. State machines define how
@@ -198,7 +198,14 @@
          * implementation must pass a random cookie as the command argument,
          * which is only known to the implementation.
          */
-        int hal_reserved_exit;
+        int halReservedExit;
+        /**
+         * Retrieve the current state of the stream. This command must be
+         * processed by the stream in any state. The stream must provide current
+         * positions, counters, and its state in the reply. This command must be
+         * handled by the HAL module without any observable side effects.
+         */
+        Void getStatus;
         /**
          * See the state machines on the applicability of this command to
          * different states.
@@ -215,15 +222,14 @@
          *    read from the hardware into the 'audio.fmq' queue.
          *
          * In both cases it is allowed for this field to contain any
-         * non-negative number. The value 0 can be used if the client only needs
-         * to retrieve current positions and latency. Any sufficiently big value
-         * which exceeds the size of the queue's area which is currently
-         * available for reading or writing by the HAL module must be trimmed by
-         * the HAL module to the available size. Note that the HAL module is
-         * allowed to consume or provide less data than requested, and it must
-         * return the amount of actually read or written data via the
-         * 'Reply.fmqByteCount' field. Thus, only attempts to pass a negative
-         * number must be constituted as a client's error.
+         * non-negative number. Any sufficiently big value which exceeds the
+         * size of the queue's area which is currently available for reading or
+         * writing by the HAL module must be trimmed by the HAL module to the
+         * available size. Note that the HAL module is allowed to consume or
+         * provide less data than requested, and it must return the amount of
+         * actually read or written data via the 'Reply.fmqByteCount'
+         * field. Thus, only attempts to pass a negative number must be
+         * constituted as a client's error.
          *
          * Differences for the MMap No IRQ mode:
          *
@@ -233,6 +239,9 @@
          *    with sending of this command.
          *
          *  - the value must always be set to 0.
+         *
+         * See the state machines on the applicability of this command to
+         * different states.
          */
         int burst;
         /**
diff --git a/audio/aidl/default/Module.cpp b/audio/aidl/default/Module.cpp
index 6863fe3..a8f3b9b 100644
--- a/audio/aidl/default/Module.cpp
+++ b/audio/aidl/default/Module.cpp
@@ -135,8 +135,8 @@
         StreamContext temp(
                 std::make_unique<StreamContext::CommandMQ>(1, true /*configureEventFlagWord*/),
                 std::make_unique<StreamContext::ReplyMQ>(1, true /*configureEventFlagWord*/),
-                frameSize,
-                std::make_unique<StreamContext::DataMQ>(frameSize * in_bufferSizeFrames));
+                frameSize, std::make_unique<StreamContext::DataMQ>(frameSize * in_bufferSizeFrames),
+                mDebug.streamTransientStateDelayMs);
         if (temp.isValid()) {
             *out_context = std::move(temp);
         } else {
@@ -242,6 +242,11 @@
                    << "while having external devices connected";
         return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_STATE);
     }
+    if (in_debug.streamTransientStateDelayMs < 0) {
+        LOG(ERROR) << __func__ << ": streamTransientStateDelayMs is negative: "
+                   << in_debug.streamTransientStateDelayMs;
+        return ndk::ScopedAStatus::fromExceptionCode(EX_ILLEGAL_ARGUMENT);
+    }
     mDebug = in_debug;
     return ndk::ScopedAStatus::ok();
 }
diff --git a/audio/aidl/default/Stream.cpp b/audio/aidl/default/Stream.cpp
index 21dc4b6..c5d00a2 100644
--- a/audio/aidl/default/Stream.cpp
+++ b/audio/aidl/default/Stream.cpp
@@ -96,23 +96,36 @@
     }
 }
 
+void StreamWorkerCommonLogic::populateReplyWrongState(
+        StreamDescriptor::Reply* reply, const StreamDescriptor::Command& command) const {
+    LOG(WARNING) << "command '" << toString(command.getTag())
+                 << "' can not be handled in the state " << toString(mState);
+    reply->status = STATUS_INVALID_OPERATION;
+}
+
 const std::string StreamInWorkerLogic::kThreadName = "reader";
 
 StreamInWorkerLogic::Status StreamInWorkerLogic::cycle() {
+    // Note: for input streams, draining is driven by the client, thus
+    // "empty buffer" condition can only happen while handling the 'burst'
+    // command. Thus, unlike for output streams, it does not make sense to
+    // delay the 'DRAINING' state here by 'mTransientStateDelayMs'.
+    // TODO: Add a delay for transitions of async operations when/if they added.
+
     StreamDescriptor::Command command{};
     if (!mCommandMQ->readBlocking(&command, 1)) {
         LOG(ERROR) << __func__ << ": reading of command from MQ failed";
         mState = StreamDescriptor::State::ERROR;
         return Status::ABORT;
     }
+    LOG(DEBUG) << __func__ << ": received command " << command.toString() << " in " << kThreadName;
     StreamDescriptor::Reply reply{};
     reply.status = STATUS_BAD_VALUE;
     using Tag = StreamDescriptor::Command::Tag;
     switch (command.getTag()) {
-        case Tag::hal_reserved_exit:
-            if (const int32_t cookie = command.get<Tag::hal_reserved_exit>();
+        case Tag::halReservedExit:
+            if (const int32_t cookie = command.get<Tag::halReservedExit>();
                 cookie == mInternalCommandCookie) {
-                LOG(DEBUG) << __func__ << ": received EXIT command";
                 setClosed();
                 // This is an internal command, no need to reply.
                 return Status::EXIT;
@@ -120,8 +133,10 @@
                 LOG(WARNING) << __func__ << ": EXIT command has a bad cookie: " << cookie;
             }
             break;
+        case Tag::getStatus:
+            populateReply(&reply, mIsConnected);
+            break;
         case Tag::start:
-            LOG(DEBUG) << __func__ << ": received START read command";
             if (mState == StreamDescriptor::State::STANDBY ||
                 mState == StreamDescriptor::State::DRAINING) {
                 populateReply(&reply, mIsConnected);
@@ -129,15 +144,13 @@
                                  ? StreamDescriptor::State::IDLE
                                  : StreamDescriptor::State::ACTIVE;
             } else {
-                LOG(WARNING) << __func__ << ": START command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::burst:
             if (const int32_t fmqByteCount = command.get<Tag::burst>(); fmqByteCount >= 0) {
-                LOG(DEBUG) << __func__ << ": received BURST read command for " << fmqByteCount
-                           << " bytes";
+                LOG(DEBUG) << __func__ << ": '" << toString(command.getTag()) << "' command for "
+                           << fmqByteCount << " bytes";
                 if (mState == StreamDescriptor::State::IDLE ||
                     mState == StreamDescriptor::State::ACTIVE ||
                     mState == StreamDescriptor::State::PAUSED ||
@@ -151,69 +164,56 @@
                     } else if (mState == StreamDescriptor::State::DRAINING) {
                         // To simplify the reference code, we assume that the read operation
                         // has consumed all the data remaining in the hardware buffer.
-                        // TODO: Provide parametrization on the duration of draining to test
-                        //       handling of commands during the 'DRAINING' state.
+                        // In a real implementation, here we would either remain in
+                        // the 'DRAINING' state, or transfer to 'STANDBY' depending on the
+                        // buffer state.
                         mState = StreamDescriptor::State::STANDBY;
                     }
                 } else {
-                    LOG(WARNING) << __func__ << ": BURST command can not be handled in the state "
-                                 << toString(mState);
-                    reply.status = STATUS_INVALID_OPERATION;
+                    populateReplyWrongState(&reply, command);
                 }
             } else {
                 LOG(WARNING) << __func__ << ": invalid burst byte count: " << fmqByteCount;
             }
             break;
         case Tag::drain:
-            LOG(DEBUG) << __func__ << ": received DRAIN read command";
             if (mState == StreamDescriptor::State::ACTIVE) {
                 usleep(1000);  // Simulate a blocking call into the driver.
                 populateReply(&reply, mIsConnected);
                 // Can switch the state to ERROR if a driver error occurs.
                 mState = StreamDescriptor::State::DRAINING;
             } else {
-                LOG(WARNING) << __func__ << ": DRAIN command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::standby:
-            LOG(DEBUG) << __func__ << ": received STANDBY read command";
             if (mState == StreamDescriptor::State::IDLE) {
                 usleep(1000);  // Simulate a blocking call into the driver.
                 populateReply(&reply, mIsConnected);
                 // Can switch the state to ERROR if a driver error occurs.
                 mState = StreamDescriptor::State::STANDBY;
             } else {
-                LOG(WARNING) << __func__ << ": FLUSH command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::pause:
-            LOG(DEBUG) << __func__ << ": received PAUSE read command";
             if (mState == StreamDescriptor::State::ACTIVE) {
                 usleep(1000);  // Simulate a blocking call into the driver.
                 populateReply(&reply, mIsConnected);
                 // Can switch the state to ERROR if a driver error occurs.
                 mState = StreamDescriptor::State::PAUSED;
             } else {
-                LOG(WARNING) << __func__ << ": PAUSE command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::flush:
-            LOG(DEBUG) << __func__ << ": received FLUSH read command";
             if (mState == StreamDescriptor::State::PAUSED) {
                 usleep(1000);  // Simulate a blocking call into the driver.
                 populateReply(&reply, mIsConnected);
                 // Can switch the state to ERROR if a driver error occurs.
                 mState = StreamDescriptor::State::STANDBY;
             } else {
-                LOG(WARNING) << __func__ << ": FLUSH command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
     }
@@ -261,20 +261,32 @@
 const std::string StreamOutWorkerLogic::kThreadName = "writer";
 
 StreamOutWorkerLogic::Status StreamOutWorkerLogic::cycle() {
+    if (mState == StreamDescriptor::State::DRAINING) {
+        if (auto stateDurationMs = std::chrono::duration_cast<std::chrono::milliseconds>(
+                    std::chrono::steady_clock::now() - mTransientStateStart);
+            stateDurationMs >= mTransientStateDelayMs) {
+            mState = StreamDescriptor::State::IDLE;
+            if (mTransientStateDelayMs.count() != 0) {
+                LOG(DEBUG) << __func__ << ": switched to state " << toString(mState)
+                           << " after a timeout";
+            }
+        }
+    }
+
     StreamDescriptor::Command command{};
     if (!mCommandMQ->readBlocking(&command, 1)) {
         LOG(ERROR) << __func__ << ": reading of command from MQ failed";
         mState = StreamDescriptor::State::ERROR;
         return Status::ABORT;
     }
+    LOG(DEBUG) << __func__ << ": received command " << command.toString() << " in " << kThreadName;
     StreamDescriptor::Reply reply{};
     reply.status = STATUS_BAD_VALUE;
     using Tag = StreamDescriptor::Command::Tag;
     switch (command.getTag()) {
-        case Tag::hal_reserved_exit:
-            if (const int32_t cookie = command.get<Tag::hal_reserved_exit>();
+        case Tag::halReservedExit:
+            if (const int32_t cookie = command.get<Tag::halReservedExit>();
                 cookie == mInternalCommandCookie) {
-                LOG(DEBUG) << __func__ << ": received EXIT command";
                 setClosed();
                 // This is an internal command, no need to reply.
                 return Status::EXIT;
@@ -282,31 +294,31 @@
                 LOG(WARNING) << __func__ << ": EXIT command has a bad cookie: " << cookie;
             }
             break;
+        case Tag::getStatus:
+            populateReply(&reply, mIsConnected);
+            break;
         case Tag::start:
-            LOG(DEBUG) << __func__ << ": received START write command";
             switch (mState) {
                 case StreamDescriptor::State::STANDBY:
                     mState = StreamDescriptor::State::IDLE;
+                    populateReply(&reply, mIsConnected);
                     break;
                 case StreamDescriptor::State::PAUSED:
                     mState = StreamDescriptor::State::ACTIVE;
+                    populateReply(&reply, mIsConnected);
                     break;
                 case StreamDescriptor::State::DRAIN_PAUSED:
-                    mState = StreamDescriptor::State::PAUSED;
+                    switchToTransientState(StreamDescriptor::State::DRAINING);
+                    populateReply(&reply, mIsConnected);
                     break;
                 default:
-                    LOG(WARNING) << __func__ << ": START command can not be handled in the state "
-                                 << toString(mState);
-                    reply.status = STATUS_INVALID_OPERATION;
-            }
-            if (reply.status != STATUS_INVALID_OPERATION) {
-                populateReply(&reply, mIsConnected);
+                    populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::burst:
             if (const int32_t fmqByteCount = command.get<Tag::burst>(); fmqByteCount >= 0) {
-                LOG(DEBUG) << __func__ << ": received BURST write command for " << fmqByteCount
-                           << " bytes";
+                LOG(DEBUG) << __func__ << ": '" << toString(command.getTag()) << "' command for "
+                           << fmqByteCount << " bytes";
                 if (mState !=
                     StreamDescriptor::State::ERROR) {  // BURST can be handled in all valid states
                     if (!write(fmqByteCount, &reply)) {
@@ -320,47 +332,33 @@
                         mState = StreamDescriptor::State::ACTIVE;
                     }  // When in 'ACTIVE' and 'PAUSED' do not need to change the state.
                 } else {
-                    LOG(WARNING) << __func__ << ": BURST command can not be handled in the state "
-                                 << toString(mState);
-                    reply.status = STATUS_INVALID_OPERATION;
+                    populateReplyWrongState(&reply, command);
                 }
             } else {
                 LOG(WARNING) << __func__ << ": invalid burst byte count: " << fmqByteCount;
             }
             break;
         case Tag::drain:
-            LOG(DEBUG) << __func__ << ": received DRAIN write command";
             if (mState == StreamDescriptor::State::ACTIVE) {
                 usleep(1000);  // Simulate a blocking call into the driver.
                 populateReply(&reply, mIsConnected);
                 // Can switch the state to ERROR if a driver error occurs.
-                mState = StreamDescriptor::State::IDLE;
-                // Since there is no actual hardware that would be draining the buffer,
-                // in order to simplify the reference code, we assume that draining
-                // happens instantly, thus skipping the 'DRAINING' state.
-                // TODO: Provide parametrization on the duration of draining to test
-                //       handling of commands during the 'DRAINING' state.
+                switchToTransientState(StreamDescriptor::State::DRAINING);
             } else {
-                LOG(WARNING) << __func__ << ": DRAIN command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::standby:
-            LOG(DEBUG) << __func__ << ": received STANDBY write command";
             if (mState == StreamDescriptor::State::IDLE) {
                 usleep(1000);  // Simulate a blocking call into the driver.
                 populateReply(&reply, mIsConnected);
                 // Can switch the state to ERROR if a driver error occurs.
                 mState = StreamDescriptor::State::STANDBY;
             } else {
-                LOG(WARNING) << __func__ << ": STANDBY command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::pause:
-            LOG(DEBUG) << __func__ << ": received PAUSE write command";
             if (mState == StreamDescriptor::State::ACTIVE ||
                 mState == StreamDescriptor::State::DRAINING) {
                 populateReply(&reply, mIsConnected);
@@ -368,21 +366,16 @@
                                  ? StreamDescriptor::State::PAUSED
                                  : StreamDescriptor::State::DRAIN_PAUSED;
             } else {
-                LOG(WARNING) << __func__ << ": PAUSE command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
         case Tag::flush:
-            LOG(DEBUG) << __func__ << ": received FLUSH write command";
             if (mState == StreamDescriptor::State::PAUSED ||
                 mState == StreamDescriptor::State::DRAIN_PAUSED) {
                 populateReply(&reply, mIsConnected);
                 mState = StreamDescriptor::State::IDLE;
             } else {
-                LOG(WARNING) << __func__ << ": FLUSH command can not be handled in the state "
-                             << toString(mState);
-                reply.status = STATUS_INVALID_OPERATION;
+                populateReplyWrongState(&reply, command);
             }
             break;
     }
@@ -450,9 +443,8 @@
 void StreamCommon<Metadata, StreamWorker>::stopWorker() {
     if (auto commandMQ = mContext.getCommandMQ(); commandMQ != nullptr) {
         LOG(DEBUG) << __func__ << ": asking the worker to exit...";
-        auto cmd =
-                StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::hal_reserved_exit>(
-                        mContext.getInternalCommandCookie());
+        auto cmd = StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::halReservedExit>(
+                mContext.getInternalCommandCookie());
         // Note: never call 'pause' and 'resume' methods of StreamWorker
         // in the HAL implementation. These methods are to be used by
         // the client side only. Preventing the worker loop from running
diff --git a/audio/aidl/default/include/core-impl/Stream.h b/audio/aidl/default/include/core-impl/Stream.h
index 5ee0f82..bcbabad 100644
--- a/audio/aidl/default/include/core-impl/Stream.h
+++ b/audio/aidl/default/include/core-impl/Stream.h
@@ -17,6 +17,7 @@
 #pragma once
 
 #include <atomic>
+#include <chrono>
 #include <cstdlib>
 #include <map>
 #include <memory>
@@ -59,24 +60,27 @@
 
     StreamContext() = default;
     StreamContext(std::unique_ptr<CommandMQ> commandMQ, std::unique_ptr<ReplyMQ> replyMQ,
-                  size_t frameSize, std::unique_ptr<DataMQ> dataMQ)
+                  size_t frameSize, std::unique_ptr<DataMQ> dataMQ, int transientStateDelayMs)
         : mCommandMQ(std::move(commandMQ)),
           mInternalCommandCookie(std::rand()),
           mReplyMQ(std::move(replyMQ)),
           mFrameSize(frameSize),
-          mDataMQ(std::move(dataMQ)) {}
+          mDataMQ(std::move(dataMQ)),
+          mTransientStateDelayMs(transientStateDelayMs) {}
     StreamContext(StreamContext&& other)
         : mCommandMQ(std::move(other.mCommandMQ)),
           mInternalCommandCookie(other.mInternalCommandCookie),
           mReplyMQ(std::move(other.mReplyMQ)),
           mFrameSize(other.mFrameSize),
-          mDataMQ(std::move(other.mDataMQ)) {}
+          mDataMQ(std::move(other.mDataMQ)),
+          mTransientStateDelayMs(other.mTransientStateDelayMs) {}
     StreamContext& operator=(StreamContext&& other) {
         mCommandMQ = std::move(other.mCommandMQ);
         mInternalCommandCookie = other.mInternalCommandCookie;
         mReplyMQ = std::move(other.mReplyMQ);
         mFrameSize = other.mFrameSize;
         mDataMQ = std::move(other.mDataMQ);
+        mTransientStateDelayMs = other.mTransientStateDelayMs;
         return *this;
     }
 
@@ -86,6 +90,7 @@
     size_t getFrameSize() const { return mFrameSize; }
     int getInternalCommandCookie() const { return mInternalCommandCookie; }
     ReplyMQ* getReplyMQ() const { return mReplyMQ.get(); }
+    int getTransientStateDelayMs() const { return mTransientStateDelayMs; }
     bool isValid() const;
     void reset();
 
@@ -95,6 +100,7 @@
     std::unique_ptr<ReplyMQ> mReplyMQ;
     size_t mFrameSize;
     std::unique_ptr<DataMQ> mDataMQ;
+    int mTransientStateDelayMs;
 };
 
 class StreamWorkerCommonLogic : public ::android::hardware::audio::common::StreamLogic {
@@ -111,9 +117,16 @@
           mFrameSize(context.getFrameSize()),
           mCommandMQ(context.getCommandMQ()),
           mReplyMQ(context.getReplyMQ()),
-          mDataMQ(context.getDataMQ()) {}
+          mDataMQ(context.getDataMQ()),
+          mTransientStateDelayMs(context.getTransientStateDelayMs()) {}
     std::string init() override;
     void populateReply(StreamDescriptor::Reply* reply, bool isConnected) const;
+    void populateReplyWrongState(StreamDescriptor::Reply* reply,
+                                 const StreamDescriptor::Command& command) const;
+    void switchToTransientState(StreamDescriptor::State state) {
+        mState = state;
+        mTransientStateStart = std::chrono::steady_clock::now();
+    }
 
     // Atomic fields are used both by the main and worker threads.
     std::atomic<bool> mIsConnected = false;
@@ -125,6 +138,8 @@
     StreamContext::CommandMQ* mCommandMQ;
     StreamContext::ReplyMQ* mReplyMQ;
     StreamContext::DataMQ* mDataMQ;
+    const std::chrono::duration<int, std::milli> mTransientStateDelayMs;
+    std::chrono::time_point<std::chrono::steady_clock> mTransientStateStart;
     // We use an array and the "size" field instead of a vector to be able to detect
     // memory allocation issues.
     std::unique_ptr<int8_t[]> mDataBuffer;
diff --git a/audio/aidl/vts/VtsHalAudioCoreTargetTest.cpp b/audio/aidl/vts/VtsHalAudioCoreTargetTest.cpp
index 2f72bb0..a058069 100644
--- a/audio/aidl/vts/VtsHalAudioCoreTargetTest.cpp
+++ b/audio/aidl/vts/VtsHalAudioCoreTargetTest.cpp
@@ -1557,8 +1557,7 @@
 
     void SendInvalidCommandImpl(const AudioPortConfig& portConfig) {
         std::vector<StreamDescriptor::Command> commands = {
-                StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::hal_reserved_exit>(
-                        0),
+                StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::halReservedExit>(0),
                 // TODO: For proper testing of input streams, need to put the stream into
                 // a state which accepts BURST commands.
                 StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::burst>(-1),
@@ -1695,7 +1694,8 @@
     std::string mUnexpectedTransition;
 };
 
-using NamedCommandSequence = std::pair<std::string, std::vector<CommandAndState>>;
+enum { NAMED_CMD_NAME, NAMED_CMD_DELAY_MS, NAMED_CMD_CMDS };
+using NamedCommandSequence = std::tuple<std::string, int, std::vector<CommandAndState>>;
 enum { PARAM_MODULE_NAME, PARAM_CMD_SEQ, PARAM_SETUP_SEQ };
 using StreamIoTestParameters =
         std::tuple<std::string /*moduleName*/, NamedCommandSequence, bool /*useSetupSequence2*/>;
@@ -1716,7 +1716,12 @@
         }
         for (const auto& portConfig : allPortConfigs) {
             SCOPED_TRACE(portConfig.toString());
-            const auto& commandsAndStates = std::get<PARAM_CMD_SEQ>(GetParam()).second;
+            WithDebugFlags delayTransientStates = WithDebugFlags::createNested(debug);
+            delayTransientStates.flags().streamTransientStateDelayMs =
+                    std::get<NAMED_CMD_DELAY_MS>(std::get<PARAM_CMD_SEQ>(GetParam()));
+            ASSERT_NO_FATAL_FAILURE(delayTransientStates.SetUp(module.get()));
+            const auto& commandsAndStates =
+                    std::get<NAMED_CMD_CMDS>(std::get<PARAM_CMD_SEQ>(GetParam()));
             if (!std::get<PARAM_SETUP_SEQ>(GetParam())) {
                 ASSERT_NO_FATAL_FAILURE(RunStreamIoCommandsImplSeq1(portConfig, commandsAndStates));
             } else {
@@ -1974,6 +1979,11 @@
                          android::PrintInstanceNameToString);
 GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(AudioStreamOut);
 
+// This is the value used in test sequences for which the test needs to ensure
+// that the HAL stays in a transient state long enough to receive the next command.
+static const int kStreamTransientStateTransitionDelayMs = 3000;
+static const StreamDescriptor::Command kGetStatusCommand =
+        StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::getStatus>(Void{});
 static const StreamDescriptor::Command kStartCommand =
         StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::start>(Void{});
 static const StreamDescriptor::Command kBurstCommand =
@@ -1987,83 +1997,100 @@
 static const StreamDescriptor::Command kFlushCommand =
         StreamDescriptor::Command::make<StreamDescriptor::Command::Tag::flush>(Void{});
 static const NamedCommandSequence kReadOrWriteSeq =
-        std::make_pair(std::string("ReadOrWrite"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE)});
+        std::make_tuple(std::string("ReadOrWrite"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE)});
 static const NamedCommandSequence kDrainInSeq =
-        std::make_pair(std::string("Drain"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING),
-                               std::make_pair(kStartCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING),
-                               // TODO: This will need to be changed once DRAIN starts taking time.
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::STANDBY)});
+        std::make_tuple(std::string("Drain"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING),
+                                std::make_pair(kStartCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING)
+                                // TODO: Test that from DRAINING the stream goes either to DRAINING
+                                // or to STANDBY. Supporting this in a generic would complicate the
+                                // test code because after state bifurcation we probably need to use
+                                // different commands for each state, this way a sequence of
+                                // commands and states becomes a tree.
+                        });
 static const NamedCommandSequence kDrainOutSeq =
-        std::make_pair(std::string("Drain"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               // TODO: This will need to be changed once DRAIN starts taking time.
-                               std::make_pair(kDrainCommand, StreamDescriptor::State::IDLE)});
-// TODO: This will need to be changed once DRAIN starts taking time so we can pause it.
-static const NamedCommandSequence kDrainPauseOutSeq = std::make_pair(
-        std::string("DrainPause"),
-        std::vector<CommandAndState>{std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                                     std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                                     std::make_pair(kDrainCommand, StreamDescriptor::State::IDLE)});
+        std::make_tuple(std::string("Drain"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING),
+                                // Draining is synchronous, the stream switches to IDLE afterwards.
+                                std::make_pair(kGetStatusCommand, StreamDescriptor::State::IDLE)});
+static const NamedCommandSequence kDrainPauseOutSeq = std::make_tuple(
+        std::string("DrainPause"), kStreamTransientStateTransitionDelayMs,
+        std::vector<CommandAndState>{
+                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING),
+                std::make_pair(kPauseCommand, StreamDescriptor::State::DRAIN_PAUSED),
+                std::make_pair(kStartCommand, StreamDescriptor::State::DRAINING),
+                std::make_pair(kPauseCommand, StreamDescriptor::State::DRAIN_PAUSED),
+                std::make_pair(kBurstCommand, StreamDescriptor::State::PAUSED)});
 static const NamedCommandSequence kStandbySeq =
-        std::make_pair(std::string("Standby"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kStandbyCommand, StreamDescriptor::State::STANDBY),
-                               // Perform a read or write in order to advance observable position
-                               // (this is verified by tests).
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE)});
+        std::make_tuple(std::string("Standby"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kStandbyCommand, StreamDescriptor::State::STANDBY),
+                                // Perform a read or write in order to advance observable position
+                                // (this is verified by tests).
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE)});
 static const NamedCommandSequence kPauseInSeq =
-        std::make_pair(std::string("Pause"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
-                               std::make_pair(kFlushCommand, StreamDescriptor::State::STANDBY)});
+        std::make_tuple(std::string("Pause"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
+                                std::make_pair(kFlushCommand, StreamDescriptor::State::STANDBY)});
 static const NamedCommandSequence kPauseOutSeq =
-        std::make_pair(std::string("Pause"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
-                               std::make_pair(kStartCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::PAUSED),
-                               std::make_pair(kStartCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED)});
+        std::make_tuple(std::string("Pause"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
+                                std::make_pair(kStartCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::PAUSED),
+                                std::make_pair(kStartCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED)});
 static const NamedCommandSequence kFlushInSeq =
-        std::make_pair(std::string("Flush"),
-                       std::vector<CommandAndState>{
-                               std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
-                               std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
-                               std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
-                               std::make_pair(kFlushCommand, StreamDescriptor::State::STANDBY)});
-static const NamedCommandSequence kFlushOutSeq = std::make_pair(
-        std::string("Flush"),
+        std::make_tuple(std::string("Flush"), 0,
+                        std::vector<CommandAndState>{
+                                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                                std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
+                                std::make_pair(kFlushCommand, StreamDescriptor::State::STANDBY)});
+static const NamedCommandSequence kFlushOutSeq = std::make_tuple(
+        std::string("Flush"), 0,
         std::vector<CommandAndState>{std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
                                      std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
                                      std::make_pair(kPauseCommand, StreamDescriptor::State::PAUSED),
                                      std::make_pair(kFlushCommand, StreamDescriptor::State::IDLE)});
+static const NamedCommandSequence kDrainPauseFlushOutSeq = std::make_tuple(
+        std::string("DrainPauseFlush"), kStreamTransientStateTransitionDelayMs,
+        std::vector<CommandAndState>{
+                std::make_pair(kStartCommand, StreamDescriptor::State::IDLE),
+                std::make_pair(kBurstCommand, StreamDescriptor::State::ACTIVE),
+                std::make_pair(kDrainCommand, StreamDescriptor::State::DRAINING),
+                std::make_pair(kPauseCommand, StreamDescriptor::State::DRAIN_PAUSED),
+                std::make_pair(kFlushCommand, StreamDescriptor::State::IDLE)});
 std::string GetStreamIoTestName(const testing::TestParamInfo<StreamIoTestParameters>& info) {
     return android::PrintInstanceNameToString(
                    testing::TestParamInfo<std::string>{std::get<PARAM_MODULE_NAME>(info.param),
                                                        info.index})
             .append("_")
-            .append(std::get<PARAM_CMD_SEQ>(info.param).first)
+            .append(std::get<NAMED_CMD_NAME>(std::get<PARAM_CMD_SEQ>(info.param)))
             .append("_SetupSeq")
             .append(std::get<PARAM_SETUP_SEQ>(info.param) ? "2" : "1");
 }
@@ -2079,7 +2106,8 @@
         AudioStreamIoOutTest, AudioStreamIoOut,
         testing::Combine(testing::ValuesIn(android::getAidlHalInstanceNames(IModule::descriptor)),
                          testing::Values(kReadOrWriteSeq, kDrainOutSeq, kDrainPauseOutSeq,
-                                         kStandbySeq, kPauseOutSeq, kFlushOutSeq),
+                                         kStandbySeq, kPauseOutSeq, kFlushOutSeq,
+                                         kDrainPauseFlushOutSeq),
                          testing::Values(false, true)),
         GetStreamIoTestName);
 GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(AudioStreamIoOut);