Merge changes from topic "remove-biometrics-aidl-cookie" into sc-dev

* changes:
  Remove SessionState from IFace VTS
  Remove SessionState from IFace example
  Remove SessionState from IFace
  Remove SessionState from IFingerprint example
  Remove SessionState from IFingerprint VTS
  Remove SessionState from IFingerprint

21 files changed, 350 insertions, 756 deletions

diff --git a/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISession.aidl b/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISession.aidl
index 205429bd7a..9033989563 100644
--- a/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISession.aidl
+++ b/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISession.aidl
@@ -34,17 +34,17 @@
 package android.hardware.biometrics.face;
 @VintfStability
 interface ISession {
-  void generateChallenge(in int cookie);
-  void revokeChallenge(in int cookie, in long challenge);
-  android.hardware.biometrics.common.ICancellationSignal enroll(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat, in android.hardware.biometrics.face.EnrollmentType type, in android.hardware.biometrics.face.Feature[] features, in android.hardware.common.NativeHandle previewSurface);
-  android.hardware.biometrics.common.ICancellationSignal authenticate(in int cookie, in long operationId);
-  android.hardware.biometrics.common.ICancellationSignal detectInteraction(in int cookie);
-  void enumerateEnrollments(in int cookie);
-  void removeEnrollments(in int cookie, in int[] enrollmentIds);
-  void getFeatures(in int cookie, in int enrollmentId);
-  void setFeature(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat, in int enrollmentId, in android.hardware.biometrics.face.Feature feature, boolean enabled);
-  void getAuthenticatorId(in int cookie);
-  void invalidateAuthenticatorId(in int cookie);
-  void resetLockout(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat);
-  void close(in int cookie);
+  void generateChallenge();
+  void revokeChallenge(in long challenge);
+  android.hardware.biometrics.common.ICancellationSignal enroll(in android.hardware.keymaster.HardwareAuthToken hat, in android.hardware.biometrics.face.EnrollmentType type, in android.hardware.biometrics.face.Feature[] features, in android.hardware.common.NativeHandle previewSurface);
+  android.hardware.biometrics.common.ICancellationSignal authenticate(in long operationId);
+  android.hardware.biometrics.common.ICancellationSignal detectInteraction();
+  void enumerateEnrollments();
+  void removeEnrollments(in int[] enrollmentIds);
+  void getFeatures(in int enrollmentId);
+  void setFeature(in android.hardware.keymaster.HardwareAuthToken hat, in int enrollmentId, in android.hardware.biometrics.face.Feature feature, boolean enabled);
+  void getAuthenticatorId();
+  void invalidateAuthenticatorId();
+  void resetLockout(in android.hardware.keymaster.HardwareAuthToken hat);
+  void close();
 }
diff --git a/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISessionCallback.aidl b/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISessionCallback.aidl
index b0bfa3084e..2bb053a31c 100644
--- a/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISessionCallback.aidl
+++ b/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/ISessionCallback.aidl
@@ -34,7 +34,6 @@
 package android.hardware.biometrics.face;
 @VintfStability
 interface ISessionCallback {
-  void onStateChanged(in int cookie, in android.hardware.biometrics.face.SessionState state);
   void onChallengeGenerated(in long challenge);
   void onChallengeRevoked(in long challenge);
   void onAuthenticationFrame(in android.hardware.biometrics.face.AuthenticationFrame frame);
diff --git a/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/SessionState.aidl b/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/SessionState.aidl
deleted file mode 100644
index 4db47c9c67..0000000000
--- a/biometrics/face/aidl/aidl_api/android.hardware.biometrics.face/current/android/hardware/biometrics/face/SessionState.aidl
+++ /dev/null
@@ -1,51 +0,0 @@
-/*
- * Copyright (C) 2021 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-///////////////////////////////////////////////////////////////////////////////
-// THIS FILE IS IMMUTABLE. DO NOT EDIT IN ANY CASE.                          //
-///////////////////////////////////////////////////////////////////////////////
-
-// This file is a snapshot of an AIDL file. Do not edit it manually. There are
-// two cases:
-// 1). this is a frozen version file - do not edit this in any case.
-// 2). this is a 'current' file. If you make a backwards compatible change to
-//     the interface (from the latest frozen version), the build system will
-//     prompt you to update this file with `m <name>-update-api`.
-//
-// You must not make a backward incompatible change to any AIDL file built
-// with the aidl_interface module type with versions property set. The module
-// type is used to build AIDL files in a way that they can be used across
-// independently updatable components of the system. If a device is shipped
-// with such a backward incompatible change, it has a high risk of breaking
-// later when a module using the interface is updated, e.g., Mainline modules.
-
-package android.hardware.biometrics.face;
-@Backing(type="byte") @VintfStability
-enum SessionState {
-  IDLING = 0,
-  CLOSED = 1,
-  GENERATING_CHALLENGE = 2,
-  REVOKING_CHALLENGE = 3,
-  ENROLLING = 4,
-  AUTHENTICATING = 5,
-  DETECTING_INTERACTION = 6,
-  ENUMERATING_ENROLLMENTS = 7,
-  REMOVING_ENROLLMENTS = 8,
-  GETTING_FEATURES = 9,
-  SETTING_FEATURE = 10,
-  GETTING_AUTHENTICATOR_ID = 11,
-  INVALIDATING_AUTHENTICATOR_ID = 12,
-  RESETTING_LOCKOUT = 13,
-}
diff --git a/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl b/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl
index 66c7c38710..75025157a7 100644
--- a/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl
+++ b/biometrics/face/aidl/android/hardware/biometrics/face/ISession.aidl
@@ -23,11 +23,25 @@ import android.hardware.common.NativeHandle;
 import android.hardware.keymaster.HardwareAuthToken;
 
 /**
- * A session is a collection of immutable state (sensorId, userId), mutable state (SessionState),
- * methods available for the framework to call, and a callback (ISessionCallback) to notify the
- * framework about the events and results. A session is used to establish communication between
- * the framework and the HAL.
+ * Operations that can be performed for unique sessions retrieved via IFace#createSession.
+ * Operations defined within this interface can be divided into the following categories:
+ * 1) Cancellable operations. These are usually the operations that can execute for several
+ *     minutes. To allow for cancellation, they return an instance of ICancellationSignal that
+ *     lets the framework cancel them by calling ICancellationSignal#cancel. If such an operation
+ *     is cancelled, it must notify the framework by calling ISessionCallback#onError with
+ *     Error::CANCELED.
+ * 2) Non-cancellable operations. Such operations cannot be cancelled once started.
+ *
+ * The lifecycle of an operation ends when one of its terminal callbacks is called. For example,
+ * ISession#authenticate is considered completed when any of the following callbacks is called:
+ * ISessionCallback#onError, ISessionCallback#onAuthenticationSucceeded,
+ * ISessionCallback#onAuthenticationFailed.
+ *
+ * ISession only supports execution of one operation at a time, regardless of whether it's
+ * cancellable or not. The framework must wait for a corresponding callback indicating the end of
+ * the current operation before a new operation can be started.
  */
+
 @VintfStability
 interface ISession {
     /**
@@ -68,9 +82,8 @@ interface ISession {
      * | 0        | 10     | <Time4>    | <Random4> |
      * ----------------------------------------------
      *
-     * @param cookie A unique number identifying this operation
      */
-    void generateChallenge(in int cookie);
+    void generateChallenge();
 
     /**
      * revokeChallenge:
@@ -79,10 +92,9 @@ interface ISession {
      * parameters is requested, the implementation must still notify the framework using the
      * provided callback.
      *
-     * @param cookie A unique number identifying this operation
      * @param challenge Challenge that should be revoked.
      */
-    void revokeChallenge(in int cookie, in long challenge);
+    void revokeChallenge(in long challenge);
 
     /**
      * getEnrollmentConfig:
@@ -101,19 +113,13 @@ interface ISession {
      *
      * A request to add a face enrollment.
      *
-     * Once the HAL is able to start processing the enrollment request, it must notify the framework
-     * via ISessionCallback#onStateChanged with SessionState::ENROLLING.
-     *
      * At any point during enrollment, if a non-recoverable error occurs, the HAL must notify the
-     * framework via ISessionCallback#onError with the applicable enrollment-specific error, and
-     * then send ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no subsequent
-     * operation is in the queue.
+     * framework via ISessionCallback#onError with the applicable enrollment-specific error.
      *
      * Before capturing face data, the implementation must first verify the authenticity and
      * integrity of the provided HardwareAuthToken. In addition, it must check that the challenge
      * within the provided HardwareAuthToken is valid. See ISession#generateChallenge. If any of
-     * the above checks fail, the framework must be notified via ISessionCallback#onError and the
-     * HAL must notify the framework when it returns to the idle state. See
+     * the above checks fail, the framework must be notified using ISessionCallback#onError with
      * Error::UNABLE_TO_PROCESS.
      *
      * During enrollment, the implementation may notify the framework via
@@ -121,15 +127,12 @@ interface ISession {
      * can be invoked multiple times if necessary. Similarly, the framework may be notified of
      * enrollment progress changes via ISessionCallback#onEnrollmentProgress. Once the framework is
      * notified that there are 0 "remaining" steps, the framework may cache the "enrollmentId". See
-     * ISessionCallback#onEnrollmentProgress for more info. The HAL must notify the framework once
-     * it returns to the idle state.
+     * ISessionCallback#onEnrollmentProgress for more info.
      *
-     * When a finger is successfully added and before the framework is notified of remaining=0, the
-     * implementation MUST update and associate this (sensorId, userId) pair with a new new
+     * When a face is successfully added and before the framework is notified of remaining=0, the
+     * implementation MUST update and associate this (sensorId, userId) pair with a new
      * entropy-encoded random identifier. See ISession#getAuthenticatorId for more information.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat See above documentation.
      * @param enrollmentType See the EnrollmentType enum.
      * @param features See the Feature enum.
@@ -139,7 +142,7 @@ interface ISession {
      * @return ICancellationSignal An object that can be used by the framework to cancel this
      * operation.
      */
-    ICancellationSignal enroll(in int cookie, in HardwareAuthToken hat, in EnrollmentType type,
+    ICancellationSignal enroll(in HardwareAuthToken hat, in EnrollmentType type,
             in Feature[] features, in NativeHandle previewSurface);
 
     /**
@@ -147,13 +150,8 @@ interface ISession {
      *
      * A request to start looking for faces to authenticate.
      *
-     * Once the HAL is able to start processing the authentication request, it must notify framework
-     * via ISessionCallback#onStateChanged with SessionState::AUTHENTICATING.
-     *
      * At any point during authentication, if a non-recoverable error occurs, the HAL must notify
-     * the framework via ISessionCallback#onError with the applicable authentication-specific error,
-     * and then send ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no
-     * subsequent operation is in the queue.
+     * the framework via ISessionCallback#onError with the applicable authentication-specific error.
      *
      * During authentication, the implementation may notify the framework via
      * ISessionCallback#onAcquired with messages that may be used to guide the user. This callback
@@ -175,8 +173,6 @@ interface ISession {
      * must be set with the operationId passed in during #authenticate. If the sensor is NOT
      * SensorStrength::STRONG, the HardwareAuthToken MUST be null.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param operationId For sensors configured as SensorStrength::STRONG, this must be used ONLY
      *                    upon successful authentication and wrapped in the HardwareAuthToken's
      *                    "challenge" field and sent to the framework via
@@ -190,7 +186,7 @@ interface ISession {
      * @return ICancellationSignal An object that can be used by the framework to cancel this
      * operation.
      */
-    ICancellationSignal authenticate(in int cookie, in long operationId);
+    ICancellationSignal authenticate(in long operationId);
 
     /**
      * detectInteraction:
@@ -199,17 +195,12 @@ interface ISession {
      * SensorProps#supportsDetectInteraction is true. If invoked on implementations that do not
      * support this functionality, the HAL must respond with ISession#onError(UNABLE_TO_PROCESS, 0).
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::DETECTING_INTERACTION.
-     *
      * The framework will use this method in cases where determing user presence is required, but
      * identifying/authentication is not. For example, when the device is encrypted (first boot) or
      * in lockdown mode.
      *
      * At any point during detectInteraction, if a non-recoverable error occurs, the HAL must notify
-     * the framework via ISessionCallback#onError with the applicable error, and then send
-     * ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no subsequent operation is
-     * in the queue.
+     * the framework via ISessionCallback#onError with the applicable error.
      *
      * The implementation must only check for a face-like image was detected (e.g. to
      * minimize interactions due to non-face objects), and the lockout counter must not
@@ -222,17 +213,14 @@ interface ISession {
      * 1) Any face is detected and the framework is notified via
      *    ISessionCallback#onInteractiondetected
      * 2) The operation was cancelled by the framework (see ICancellationSignal)
-     * 3) The HAL ends the operation, for example when a subsequent operation pre-empts this one.
      *
      * Note that if the operation is canceled, the implementation must notify the framework via
      * ISessionCallback#onError with Error::CANCELED.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      * @return ICancellationSignal An object that can be used by the framework to cancel this
      * operation.
      */
-    ICancellationSignal detectInteraction(in int cookie);
+    ICancellationSignal detectInteraction();
 
     /*
      * enumerateEnrollments:
@@ -240,32 +228,22 @@ interface ISession {
      * A request to enumerate (list) the enrollments for this (sensorId, userId) pair. The
      * framework typically uses this to ensure that its cache is in sync with the HAL.
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::ENUMERATING_ENROLLMENTS.
-     *
      * The implementation must then notify the framework with a list of enrollments applicable
      * for the current session via ISessionCallback#onEnrollmentsEnumerated.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    void enumerateEnrollments(in int cookie);
+    void enumerateEnrollments();
 
     /**
      * removeEnrollments:
      *
      * A request to remove the enrollments for this (sensorId, userId) pair.
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::REMOVING_ENROLLMENTS.
-     *
      * After removing the enrollmentIds from everywhere necessary (filesystem, secure subsystems,
      * etc), the implementation must notify the framework via ISessionCallback#onEnrollmentsRemoved.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    void removeEnrollments(in int cookie, in int[] enrollmentIds);
+    void removeEnrollments(in int[] enrollmentIds);
 
     /**
      * getFeatures:
@@ -273,20 +251,14 @@ interface ISession {
      * Returns a list of currently enabled features for the provided enrollmentId.
      *
      * If the enrollmentId is invalid, the HAL must invoke ISessionCallback#onError with
-     * Error::UNABLE_TO_PROCESS and return to SessionState::IDLING if no subsequent work is in the
-     * queue.
-     *
-     * Once the HAL is able to start processing this request, it must notify the framework by using
-     * ISessionCallback#onStateChanged with SessionState::GETTING_FEATURES.
+     * Error::UNABLE_TO_PROCESS.
      *
      * The HAL must notify the framework about the result by calling
      * ISessionCallback#onFeaturesRetrieved.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param enrollmentId the ID of the enrollment for which the features are requested.
      */
-    void getFeatures(in int cookie, in int enrollmentId);
+    void getFeatures(in int enrollmentId);
 
     /**
      * setFeature:
@@ -296,24 +268,18 @@ interface ISession {
      * (see @param hat). The HAL must verify the hat before changing any feature state.
      *
      * If either the hat or enrollmentId is invalid, the HAL must invoke ISessionCallback#onError
-     * with Error::UNABLE_TO_PROCESS and return to SessionState::IDLING if no subsequent work is in
-     * the queue.
-     *
-     * Once the HAL is able to start processing this request, it must notify the framework by using
-     * ISessionCallback#onStateChanged with SessionState::SETTING_FEATURE.
+     * with Error::UNABLE_TO_PROCESS.
      *
      * After the feature is successfully set, the HAL must notify the framework by calling
      * ISessionCallback#onFeatureSet.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat HardwareAuthToken See above documentation.
      * @param enrollmentId the ID of the enrollment for which the feature update is requested.
      * @param feature The feature to be enabled or disabled.
      * @param enabled Whether the provided features should be enabled or disabled.
      */
-    void setFeature(in int cookie, in HardwareAuthToken hat, in int enrollmentId,
-            in Feature feature, boolean enabled);
+    void setFeature(
+            in HardwareAuthToken hat, in int enrollmentId, in Feature feature, boolean enabled);
 
     /**
      * getAuthenticatorId:
@@ -341,10 +307,8 @@ interface ISession {
      *   3) MUST not change if a face is deleted.
      *   4) MUST be an entropy-encoded random number
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void getAuthenticatorId(in int cookie);
+    void getAuthenticatorId();
 
     /**
      * invalidateAuthenticatorId:
@@ -368,10 +332,8 @@ interface ISession {
      * for more details). As such, the framework would coordinate invalidation across multiple
      * biometric HALs as necessary.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void invalidateAuthenticatorId(in int cookie);
+    void invalidateAuthenticatorId();
 
     /**
      * resetLockout:
@@ -382,8 +344,7 @@ interface ISession {
      *   2) Verify that the timestamp provided within the HAT is relatively recent (e.g. on the
      *      order of minutes, not hours).
      * If either of the checks fail, the HAL must invoke ISessionCallback#onError with
-     * Error::UNABLE_TO_PROCESS and return to SessionState::IDLING if no subsequent work is in the
-     * queue.
+     * Error::UNABLE_TO_PROCESS.
      *
      * Upon successful verification, the HAL must clear the lockout counter and notify the framework
      * via ISessionCallback#onLockoutCleared.
@@ -414,27 +375,20 @@ interface ISession {
      * See the Android CDD section 7.3.10 for the full set of lockout and rate-limiting
      * requirements.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat HardwareAuthToken See above documentation.
      */
-    void resetLockout(in int cookie, in HardwareAuthToken hat);
+    void resetLockout(in HardwareAuthToken hat);
 
     /*
      * Close this session and allow the HAL to release the resources associated with this session.
      *
-     * A session can only be closed when it's in SessionState::IDLING. Closing a session will
-     * result in a ISessionCallback#onStateChanged call with SessionState::CLOSED.
-     *
-     * If a session is unresponsive or stuck in a state other than SessionState::CLOSED,
-     * IFace#reset could be used as a last resort to terminate the session and recover the HAL
-     * from a bad state.
+     * A session can only be closed when the HAL is idling, i.e. not performing any operations.
+     * If the HAL is busy performing a cancellable operation, the operation must be explicitly
+     * cancelled with a call to ICancellationSignal#cancel before the session can be closed.
      *
      * All sessions must be explicitly closed. Calling IFace#createSession while there is an active
      * session is considered an error.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void close(in int cookie);
+    void close();
 }
diff --git a/biometrics/face/aidl/android/hardware/biometrics/face/ISessionCallback.aidl b/biometrics/face/aidl/android/hardware/biometrics/face/ISessionCallback.aidl
index c1aa3fcf80..a2601e7360 100644
--- a/biometrics/face/aidl/android/hardware/biometrics/face/ISessionCallback.aidl
+++ b/biometrics/face/aidl/android/hardware/biometrics/face/ISessionCallback.aidl
@@ -21,17 +21,11 @@ import android.hardware.biometrics.face.AuthenticationFrame;
 import android.hardware.biometrics.face.EnrollmentFrame;
 import android.hardware.biometrics.face.Error;
 import android.hardware.biometrics.face.Feature;
-import android.hardware.biometrics.face.SessionState;
 import android.hardware.keymaster.HardwareAuthToken;
 
 @VintfStability
 interface ISessionCallback {
     /**
-     * Used to notify the framework of session state changes. See ISession for more information.
-     */
-    void onStateChanged(in int cookie, in SessionState state);
-
-    /**
      * Notifies the framework when a challenge is successfully generated.
      */
     void onChallengeGenerated(in long challenge);
@@ -42,9 +36,9 @@ interface ISessionCallback {
     void onChallengeRevoked(in long challenge);
 
     /**
-     * This method must only be used to notify the framework during the following states:
-     *   1) SessionState::AUTHENTICATING
-     *   2) SessionState::DETECTING_INTERACTION
+     * This method must only be used to notify the framework during the following operations:
+     *   1) ISession#authenticate
+     *   2) ISession#detectInteraction
      *
      * These messages may be used to provide user guidance multiple times if necessary per
      * operation.
@@ -54,8 +48,8 @@ interface ISessionCallback {
     void onAuthenticationFrame(in AuthenticationFrame frame);
 
     /**
-     * This method must only be used to notify the framework during the SessionState::ENROLLING
-     * state.
+     * This method must only be used to notify the framework during the ISession#enroll
+     * operation.
      *
      * These messages may be used to provide user guidance multiple times if necessary per
      * operation.
@@ -65,18 +59,18 @@ interface ISessionCallback {
     void onEnrollmentFrame(in EnrollmentFrame frame);
 
     /**
-     * This method must only be used to notify the framework during the following states:
-     *   1) SessionState::ENROLLING
-     *   2) SessionState::AUTHENTICATING
-     *   3) SessionState::DETECTING_INTERACTION
-     *   4) SessionState::INVALIDATING_AUTHENTICATOR_ID
-     *   5) SessionState::RESETTING_LOCKOUT
+     * This method must only be used to notify the framework during the following operations:
+     *   1) ISession#enroll
+     *   2) ISession#authenticate
+     *   3) ISession#detectInteraction
+     *   4) ISession#invalidateAuthenticatorId
+     *   5) ISession#resetLockout
      *
      * These messages may be used to notify the framework or user that a non-recoverable error
      * has occurred. The operation is finished, and the HAL must proceed with the next operation
-     * or return to SessionState::IDLING if the queue is empty.
+     * or return to the idling state.
      *
-     * Note that cancellation (see common::ICancellationSignal) and preemption most be followed with
+     * Note that cancellation (see common::ICancellationSignal) and preemption must be followed with
      * an Error::CANCELED message.
      *
      * @param error See the Error enum.
@@ -88,8 +82,7 @@ interface ISessionCallback {
     void onError(in Error error, in int vendorCode);
 
     /**
-     * This method must only be used to notify the framework during the following state:
-     *   1) SessionState::ENROLLING
+     * This method must only be used to notify the framework during the ISession#enroll operation.
      *
      * @param enrollmentId Unique stable identifier for the enrollment that's being added by this
      *                     ISession#enroll invocation.
@@ -98,7 +91,7 @@ interface ISessionCallback {
     void onEnrollmentProgress(in int enrollmentId, int remaining);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Used to notify the framework about a successful authentication. This ends the authentication
      * lifecycle.
@@ -112,7 +105,7 @@ interface ISessionCallback {
     void onAuthenticationSucceeded(in int enrollmentId, in HardwareAuthToken hat);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Used to notify the framework about a failed authentication. This ends the authentication
      * lifecycle.
@@ -120,7 +113,7 @@ interface ISessionCallback {
     void onAuthenticationFailed();
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Authentication is locked out due to too many unsuccessful attempts. This is a rate-limiting
      * lockout, and authentication can be restarted after a period of time. See
@@ -133,7 +126,7 @@ interface ISessionCallback {
     void onLockoutTimed(in long durationMillis);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Authentication is disabled until the user unlocks with their device credential
      * (PIN/Pattern/Password). See ISession#resetLockout.
@@ -160,7 +153,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::DETECTING_INTERACTION
+     * ISession#detectInteraction
      *
      * Notifies the framework that user interaction occurred. See ISession#detectInteraction.
      */
@@ -168,7 +161,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::ENUMERATING_ENROLLMENTS.
+     * ISession#enumerateEnrollments.
      *
      * Notifies the framework of the current enrollments. See ISession#enumerateEnrollments.
      *
@@ -177,7 +170,7 @@ interface ISessionCallback {
     void onEnrollmentsEnumerated(in int[] enrollmentIds);
 
     /**
-     * This method must only be used to notify the framework during SessionState::GETTING_FEATURES.
+     * This method must only be used to notify the framework during ISession#getFeatures.
      *
      * Provides a list of features that are currently enabled for the given enrollmentId.
      *
@@ -187,7 +180,7 @@ interface ISessionCallback {
     void onFeaturesRetrieved(in Feature[] features, in int enrollmentId);
 
     /**
-     * This method must only be used to notify the framework during SessionState::SETTING_FEATURE.
+     * This method must only be used to notify the framework during ISession#setFeature.
      *
      * Notifies the framework that ISession#setFeature has completed.
      *
@@ -198,7 +191,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::REMOVING_ENROLLMENTS.
+     * ISession#removeEnrollments.
      *
      * Notifies the framework that the specified enrollments are removed.
      *
@@ -208,7 +201,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::GETTING_AUTHENTICATOR_ID.
+     * ISession#getAuthenticatorId.
      *
      * Notifies the framework with the authenticatorId corresponding to this session's
      * (userId, sensorId) pair.
@@ -219,7 +212,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::INVALIDATING_AUTHENTICATOR_ID.
+     * ISession#invalidateAuthenticatorId.
      *
      * See ISession#invalidateAuthenticatorId for more information.
      *
diff --git a/biometrics/face/aidl/android/hardware/biometrics/face/SessionState.aidl b/biometrics/face/aidl/android/hardware/biometrics/face/SessionState.aidl
deleted file mode 100644
index afde4eb2d5..0000000000
--- a/biometrics/face/aidl/android/hardware/biometrics/face/SessionState.aidl
+++ /dev/null
@@ -1,91 +0,0 @@
-/*
- * Copyright (C) 2021 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package android.hardware.biometrics.face;
-
-@VintfStability
-@Backing(type="byte")
-enum SessionState {
-    /**
-     * The HAL is not processing any session requests.
-     */
-    IDLING,
-
-    /**
-     * The session has been closed by the client.
-     */
-    CLOSED,
-
-    /**
-     * The HAL is processing the ISession#generateChallenge request.
-     */
-    GENERATING_CHALLENGE,
-
-    /**
-     * The HAL is processing the ISession#revokeChallenge request.
-     */
-    REVOKING_CHALLENGE,
-
-    /**
-     * The HAL is processing the ISession#enroll request.
-     */
-    ENROLLING,
-
-    /**
-     * The HAL is processing the ISession#authenticate request.
-     */
-    AUTHENTICATING,
-
-    /**
-     * The HAL is processing the ISession#detectInteraction request.
-     */
-    DETECTING_INTERACTION,
-
-    /**
-     * The HAL is processing the ISession#enumerateEnrollments request.
-     */
-    ENUMERATING_ENROLLMENTS,
-
-    /**
-     * The HAL is processing the ISession#removeEnrollments request.
-     */
-    REMOVING_ENROLLMENTS,
-
-    /**
-     * The HAL is processing the ISession#getFeatures request.
-     */
-    GETTING_FEATURES,
-
-    /**
-     * The HAL is processing the ISession#setFeature request.
-     */
-    SETTING_FEATURE,
-
-    /**
-     * The HAL is processing the ISession#getAuthenticatorId request.
-     */
-    GETTING_AUTHENTICATOR_ID,
-
-    /**
-     * The HAL is processing the ISession#invalidateAuthenticatorId request.
-     */
-    INVALIDATING_AUTHENTICATOR_ID,
-
-    /**
-     * The HAL is processing the ISession#resetLockout request.
-     */
-    RESETTING_LOCKOUT
-}
diff --git a/biometrics/face/aidl/default/Session.cpp b/biometrics/face/aidl/default/Session.cpp
index ce6c5572e6..b5eb717351 100644
--- a/biometrics/face/aidl/default/Session.cpp
+++ b/biometrics/face/aidl/default/Session.cpp
@@ -30,119 +30,105 @@ class CancellationSignal : public common::BnCancellationSignal {
 
     ndk::ScopedAStatus cancel() override {
         cb_->onError(Error::CANCELED, 0 /* vendorCode */);
-        cb_->onStateChanged(0, SessionState::IDLING);
         return ndk::ScopedAStatus::ok();
     }
 };
 
 Session::Session(std::shared_ptr<ISessionCallback> cb) : cb_(std::move(cb)) {}
 
-ndk::ScopedAStatus Session::generateChallenge(int32_t /*cookie*/) {
+ndk::ScopedAStatus Session::generateChallenge() {
     LOG(INFO) << "generateChallenge";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::GENERATING_CHALLENGE);
         cb_->onChallengeGenerated(0);
-        cb_->onStateChanged(0, SessionState::IDLING);
     }
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::revokeChallenge(int32_t /*cookie*/, int64_t challenge) {
+ndk::ScopedAStatus Session::revokeChallenge(int64_t challenge) {
     LOG(INFO) << "revokeChallenge";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::REVOKING_CHALLENGE);
         cb_->onChallengeRevoked(challenge);
-        cb_->onStateChanged(0, SessionState::IDLING);
     }
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::enroll(
-        int32_t /*cookie*/, const keymaster::HardwareAuthToken& /*hat*/,
-        EnrollmentType /*enrollmentType*/, const std::vector<Feature>& /*features*/,
-        const NativeHandle& /*previewSurface*/,
+        const keymaster::HardwareAuthToken& /*hat*/, EnrollmentType /*enrollmentType*/,
+        const std::vector<Feature>& /*features*/, const NativeHandle& /*previewSurface*/,
         std::shared_ptr<biometrics::common::ICancellationSignal>* /*return_val*/) {
     LOG(INFO) << "enroll";
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::authenticate(int32_t /*cookie*/, int64_t /*keystoreOperationId*/,
+ndk::ScopedAStatus Session::authenticate(int64_t /*keystoreOperationId*/,
                                          std::shared_ptr<common::ICancellationSignal>* return_val) {
     LOG(INFO) << "authenticate";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::AUTHENTICATING);
+        cb_->onError(Error::UNABLE_TO_PROCESS, 0 /* vendorCode */);
     }
     *return_val = SharedRefBase::make<CancellationSignal>(cb_);
     return ndk::ScopedAStatus::ok();
 }
 
 ndk::ScopedAStatus Session::detectInteraction(
-        int32_t /*cookie*/, std::shared_ptr<common::ICancellationSignal>* /*return_val*/) {
+        std::shared_ptr<common::ICancellationSignal>* /*return_val*/) {
     LOG(INFO) << "detectInteraction";
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::enumerateEnrollments(int32_t /*cookie*/) {
+ndk::ScopedAStatus Session::enumerateEnrollments() {
     LOG(INFO) << "enumerateEnrollments";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::ENUMERATING_ENROLLMENTS);
         cb_->onEnrollmentsEnumerated(std::vector<int32_t>());
-        cb_->onStateChanged(0, SessionState::IDLING);
     }
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::removeEnrollments(int32_t /*cookie*/,
-                                              const std::vector<int32_t>& /*enrollmentIds*/) {
+ndk::ScopedAStatus Session::removeEnrollments(const std::vector<int32_t>& /*enrollmentIds*/) {
     LOG(INFO) << "removeEnrollments";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::REMOVING_ENROLLMENTS);
         cb_->onEnrollmentsRemoved(std::vector<int32_t>());
-        cb_->onStateChanged(0, SessionState::IDLING);
     }
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::getFeatures(int32_t /*cookie*/, int32_t /*enrollmentId*/) {
+ndk::ScopedAStatus Session::getFeatures(int32_t /*enrollmentId*/) {
     LOG(INFO) << "getFeatures";
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::setFeature(int32_t /*cookie*/,
-                                       const keymaster::HardwareAuthToken& /*hat*/,
+ndk::ScopedAStatus Session::setFeature(const keymaster::HardwareAuthToken& /*hat*/,
                                        int32_t /*enrollmentId*/, Feature /*feature*/,
                                        bool /*enabled*/) {
     LOG(INFO) << "setFeature";
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::getAuthenticatorId(int32_t /*cookie*/) {
+ndk::ScopedAStatus Session::getAuthenticatorId() {
     LOG(INFO) << "getAuthenticatorId";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::GETTING_AUTHENTICATOR_ID);
         cb_->onAuthenticatorIdRetrieved(0 /* authenticatorId */);
-        cb_->onStateChanged(0, SessionState::IDLING);
     }
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::invalidateAuthenticatorId(int32_t /*cookie*/) {
+ndk::ScopedAStatus Session::invalidateAuthenticatorId() {
     LOG(INFO) << "invalidateAuthenticatorId";
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::resetLockout(int32_t /*cookie*/,
-                                         const keymaster::HardwareAuthToken& /*hat*/) {
+ndk::ScopedAStatus Session::resetLockout(const keymaster::HardwareAuthToken& /*hat*/) {
     LOG(INFO) << "resetLockout";
     if (cb_) {
-        cb_->onStateChanged(0, SessionState::RESETTING_LOCKOUT);
         cb_->onLockoutCleared();
-        cb_->onStateChanged(0, SessionState::IDLING);
     }
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::close(int32_t /*cookie*/) {
+ndk::ScopedAStatus Session::close() {
+    if (cb_) {
+        cb_->onSessionClosed();
+    }
     return ndk::ScopedAStatus::ok();
 }
 
diff --git a/biometrics/face/aidl/default/Session.h b/biometrics/face/aidl/default/Session.h
index eb9ae83342..73cdf08625 100644
--- a/biometrics/face/aidl/default/Session.h
+++ b/biometrics/face/aidl/default/Session.h
@@ -30,40 +30,38 @@ class Session : public BnSession {
   public:
     explicit Session(std::shared_ptr<ISessionCallback> cb);
 
-    ndk::ScopedAStatus generateChallenge(int32_t cookie) override;
+    ndk::ScopedAStatus generateChallenge() override;
 
-    ndk::ScopedAStatus revokeChallenge(int32_t cookie, int64_t challenge) override;
+    ndk::ScopedAStatus revokeChallenge(int64_t challenge) override;
 
-    ndk::ScopedAStatus enroll(int32_t cookie, const keymaster::HardwareAuthToken& hat,
+    ndk::ScopedAStatus enroll(const keymaster::HardwareAuthToken& hat,
                               EnrollmentType enrollmentType, const std::vector<Feature>& features,
                               const NativeHandle& previewSurface,
                               std::shared_ptr<common::ICancellationSignal>* return_val) override;
 
     ndk::ScopedAStatus authenticate(
-            int32_t cookie, int64_t keystoreOperationId,
+            int64_t keystoreOperationId,
             std::shared_ptr<common::ICancellationSignal>* returnVal) override;
 
     ndk::ScopedAStatus detectInteraction(
-            int32_t cookie, std::shared_ptr<common::ICancellationSignal>* returnVal) override;
+            std::shared_ptr<common::ICancellationSignal>* returnVal) override;
 
-    ndk::ScopedAStatus enumerateEnrollments(int32_t cookie) override;
+    ndk::ScopedAStatus enumerateEnrollments() override;
 
-    ndk::ScopedAStatus removeEnrollments(int32_t cookie,
-                                         const std::vector<int32_t>& enrollmentIds) override;
+    ndk::ScopedAStatus removeEnrollments(const std::vector<int32_t>& enrollmentIds) override;
 
-    ndk::ScopedAStatus getFeatures(int32_t cookie, int32_t enrollmentId) override;
+    ndk::ScopedAStatus getFeatures(int32_t enrollmentId) override;
 
-    ndk::ScopedAStatus setFeature(int32_t cookie, const keymaster::HardwareAuthToken& hat,
-                                  int32_t enrollmentId, Feature feature, bool enabled) override;
+    ndk::ScopedAStatus setFeature(const keymaster::HardwareAuthToken& hat, int32_t enrollmentId,
+                                  Feature feature, bool enabled) override;
 
-    ndk::ScopedAStatus getAuthenticatorId(int32_t cookie) override;
+    ndk::ScopedAStatus getAuthenticatorId() override;
 
-    ndk::ScopedAStatus invalidateAuthenticatorId(int32_t cookie) override;
+    ndk::ScopedAStatus invalidateAuthenticatorId() override;
 
-    ndk::ScopedAStatus resetLockout(int32_t cookie,
-                                    const keymaster::HardwareAuthToken& hat) override;
+    ndk::ScopedAStatus resetLockout(const keymaster::HardwareAuthToken& hat) override;
 
-    ndk::ScopedAStatus close(int32_t cookie) override;
+    ndk::ScopedAStatus close() override;
 
   private:
     std::shared_ptr<ISessionCallback> cb_;
diff --git a/biometrics/face/aidl/vts/VtsHalBiometricsFaceTargetTest.cpp b/biometrics/face/aidl/vts/VtsHalBiometricsFaceTargetTest.cpp
index 936fcc69e5..60e0a2a41f 100644
--- a/biometrics/face/aidl/vts/VtsHalBiometricsFaceTargetTest.cpp
+++ b/biometrics/face/aidl/vts/VtsHalBiometricsFaceTargetTest.cpp
@@ -21,35 +21,31 @@
 #include <android/binder_manager.h>
 #include <android/binder_process.h>
 
+#include <chrono>
 #include <future>
 
 namespace aidl::android::hardware::biometrics::face {
 namespace {
 
+using namespace std::literals::chrono_literals;
+
 constexpr int kSensorId = 0;
 constexpr int kUserId = 0;
-constexpr auto kCallbackTimeout = std::chrono::seconds(1);
 
-enum class SessionCallbackMethodName {
-    kOnStateChanged,
+enum class MethodName {
+    kOnError,
+    kOnSessionClosed,
 };
 
-struct SessionCallbackInvocation {
-    SessionCallbackMethodName method_name;
-    SessionState state;
+struct Invocation {
+    MethodName methodName;
+    Error error;
+    int32_t vendorCode;
 };
 
 class SessionCallback : public BnSessionCallback {
   public:
-    explicit SessionCallback(std::promise<SessionCallbackInvocation> invocation_promise)
-        : invocation_promise_(std::move(invocation_promise)) {}
-    ndk::ScopedAStatus onStateChanged(int32_t /*cookie*/, SessionState state) override {
-        SessionCallbackInvocation invocation = {};
-        invocation.method_name = SessionCallbackMethodName::kOnStateChanged;
-        invocation.state = state;
-        invocation_promise_.set_value(invocation);
-        return ndk::ScopedAStatus::ok();
-    }
+    explicit SessionCallback(Invocation* inv) : mInv(inv) {}
 
     ndk::ScopedAStatus onChallengeGenerated(int64_t /*challenge*/) override {
         return ndk::ScopedAStatus::ok();
@@ -67,7 +63,12 @@ class SessionCallback : public BnSessionCallback {
         return ndk::ScopedAStatus::ok();
     }
 
-    ndk::ScopedAStatus onError(Error /*error*/, int32_t /*vendorCode*/) override {
+    ndk::ScopedAStatus onError(Error error, int32_t vendorCode) override {
+        *mInv = {};
+        mInv->methodName = MethodName::kOnError;
+        mInv->error = error;
+        mInv->vendorCode = vendorCode;
+
         return ndk::ScopedAStatus::ok();
     }
 
@@ -120,10 +121,15 @@ class SessionCallback : public BnSessionCallback {
         return ndk::ScopedAStatus::ok();
     }
 
-    ndk::ScopedAStatus onSessionClosed() override { return ndk::ScopedAStatus::ok(); }
+    ndk::ScopedAStatus onSessionClosed() override {
+        *mInv = {};
+        mInv->methodName = MethodName::kOnSessionClosed;
+
+        return ndk::ScopedAStatus::ok();
+    }
 
   private:
-    std::promise<SessionCallbackInvocation> invocation_promise_;
+    Invocation* mInv;
 };
 
 class Face : public testing::TestWithParam<std::string> {
@@ -131,28 +137,34 @@ class Face : public testing::TestWithParam<std::string> {
     void SetUp() override {
         AIBinder* binder = AServiceManager_waitForService(GetParam().c_str());
         ASSERT_NE(binder, nullptr);
-        hal_ = IFace::fromBinder(ndk::SpAIBinder(binder));
+        mHal = IFace::fromBinder(ndk::SpAIBinder(binder));
     }
 
-    std::shared_ptr<IFace> hal_;
+    std::shared_ptr<IFace> mHal;
+    Invocation mInv;
 };
 
 TEST_P(Face, AuthenticateTest) {
-    std::promise<SessionCallbackInvocation> invocation_promise;
-    std::future<SessionCallbackInvocation> invocation_future = invocation_promise.get_future();
-    std::shared_ptr<SessionCallback> session_cb =
-            ndk::SharedRefBase::make<SessionCallback>(std::move(invocation_promise));
+    // Prepare the callback.
+    auto cb = ndk::SharedRefBase::make<SessionCallback>(&mInv);
 
+    // Create a session
     std::shared_ptr<ISession> session;
-    ASSERT_TRUE(hal_->createSession(kSensorId, kUserId, session_cb, &session).isOk());
+    ASSERT_TRUE(mHal->createSession(kSensorId, kUserId, cb, &session).isOk());
+
+    // Call authenticate
+    std::shared_ptr<common::ICancellationSignal> cancellationSignal;
+    ASSERT_TRUE(session->authenticate(0 /* operationId */, &cancellationSignal).isOk());
+
+    // Get the results
+    EXPECT_EQ(mInv.methodName, MethodName::kOnError);
+    EXPECT_EQ(mInv.error, Error::UNABLE_TO_PROCESS);
+    EXPECT_EQ(mInv.vendorCode, 0);
 
-    std::shared_ptr<common::ICancellationSignal> cancel_cb;
-    ASSERT_TRUE(session->authenticate(0, 0, &cancel_cb).isOk());
-    ASSERT_EQ(invocation_future.wait_for(kCallbackTimeout), std::future_status::ready);
+    // Close the session
+    ASSERT_TRUE(session->close().isOk());
 
-    SessionCallbackInvocation invocation = invocation_future.get();
-    EXPECT_EQ(invocation.method_name, SessionCallbackMethodName::kOnStateChanged);
-    EXPECT_EQ(invocation.state, SessionState::AUTHENTICATING);
+    EXPECT_EQ(mInv.methodName, MethodName::kOnSessionClosed);
 }
 
 GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(Face);
@@ -161,6 +173,7 @@ INSTANTIATE_TEST_SUITE_P(IFace, Face,
                          ::android::PrintInstanceNameToString);
 
 }  // namespace
+}  // namespace aidl::android::hardware::biometrics::face
 
 int main(int argc, char** argv) {
     ::testing::InitGoogleTest(&argc, argv);
@@ -169,4 +182,3 @@ int main(int argc, char** argv) {
     return RUN_ALL_TESTS();
 }
 
-}  // namespace aidl::android::hardware::biometrics::face
diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
index 87eaf96a41..9934a763e7 100644
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
+++ b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
@@ -34,17 +34,17 @@
 package android.hardware.biometrics.fingerprint;
 @VintfStability
 interface ISession {
-  void generateChallenge(in int cookie);
-  void revokeChallenge(in int cookie, in long challenge);
-  android.hardware.biometrics.common.ICancellationSignal enroll(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat);
-  android.hardware.biometrics.common.ICancellationSignal authenticate(in int cookie, in long operationId);
-  android.hardware.biometrics.common.ICancellationSignal detectInteraction(in int cookie);
-  void enumerateEnrollments(in int cookie);
-  void removeEnrollments(in int cookie, in int[] enrollmentIds);
-  void getAuthenticatorId(in int cookie);
-  void invalidateAuthenticatorId(in int cookie);
-  void resetLockout(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat);
-  void close(in int cookie);
+  void generateChallenge();
+  void revokeChallenge(in long challenge);
+  android.hardware.biometrics.common.ICancellationSignal enroll(in android.hardware.keymaster.HardwareAuthToken hat);
+  android.hardware.biometrics.common.ICancellationSignal authenticate(in long operationId);
+  android.hardware.biometrics.common.ICancellationSignal detectInteraction();
+  void enumerateEnrollments();
+  void removeEnrollments(in int[] enrollmentIds);
+  void getAuthenticatorId();
+  void invalidateAuthenticatorId();
+  void resetLockout(in android.hardware.keymaster.HardwareAuthToken hat);
+  void close();
   void onPointerDown(in int pointerId, in int x, in int y, in float minor, in float major);
   void onPointerUp(in int pointerId);
   void onUiReady();
diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
index 3a977178ff..3c40ad63bf 100644
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
+++ b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
@@ -34,7 +34,6 @@
 package android.hardware.biometrics.fingerprint;
 @VintfStability
 interface ISessionCallback {
-  void onStateChanged(in int cookie, in android.hardware.biometrics.fingerprint.SessionState state);
   void onChallengeGenerated(in long challenge);
   void onChallengeRevoked(in long challenge);
   void onAcquired(in android.hardware.biometrics.fingerprint.AcquiredInfo info, in int vendorCode);
diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/SessionState.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/SessionState.aidl
deleted file mode 100644
index 9b0b6f6a77..0000000000
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/SessionState.aidl
+++ /dev/null
@@ -1,49 +0,0 @@
-/*
- * Copyright (C) 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-///////////////////////////////////////////////////////////////////////////////
-// THIS FILE IS IMMUTABLE. DO NOT EDIT IN ANY CASE.                          //
-///////////////////////////////////////////////////////////////////////////////
-
-// This file is a snapshot of an AIDL file. Do not edit it manually. There are
-// two cases:
-// 1). this is a frozen version file - do not edit this in any case.
-// 2). this is a 'current' file. If you make a backwards compatible change to
-//     the interface (from the latest frozen version), the build system will
-//     prompt you to update this file with `m <name>-update-api`.
-//
-// You must not make a backward incompatible change to any AIDL file built
-// with the aidl_interface module type with versions property set. The module
-// type is used to build AIDL files in a way that they can be used across
-// independently updatable components of the system. If a device is shipped
-// with such a backward incompatible change, it has a high risk of breaking
-// later when a module using the interface is updated, e.g., Mainline modules.
-
-package android.hardware.biometrics.fingerprint;
-@Backing(type="byte") @VintfStability
-enum SessionState {
-  IDLING = 0,
-  CLOSED = 1,
-  GENERATING_CHALLENGE = 2,
-  REVOKING_CHALLENGE = 3,
-  ENROLLING = 4,
-  AUTHENTICATING = 5,
-  DETECTING_INTERACTION = 6,
-  ENUMERATING_ENROLLMENTS = 7,
-  REMOVING_ENROLLMENTS = 8,
-  GETTING_AUTHENTICATOR_ID = 9,
-  INVALIDATING_AUTHENTICATOR_ID = 10,
-  RESETTING_LOCKOUT = 11,
-}
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl
index 98a45307b9..271a9bf1cf 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/IFingerprint.aidl
@@ -32,27 +32,14 @@ interface IFingerprint {
     /**
      * createSession:
      *
-     * Creates a session which can then be used by the framework to perform operations such as
-     * enroll, authenticate, etc for the given sensorId and userId.
+     * Creates a instance of ISession which can be used by the framework to perform operations
+     * such as ISession#enroll, ISession#authenticate, etc. for the given sensorId and userId.
      *
-     * Calling this method while there is an active session is considered an error. If the
-     * framework is in a bad state and for some reason cannot close its session, it should use
-     * the reset method below.
-     *
-     * A physical sensor identified by sensorId typically supports only a single in-flight session
-     * at a time. As such, if a session is currently in a state other than SessionState::IDLING, the
-     * HAL MUST finish or cancel the current operation and return to SessionState::IDLING before the
-     * new session is created. For example:
-     *   1) If a session for sensorId=0, userId=0 is currently in a cancellable state (see
-     *      ICancellationSignal) such as SessionState::AUTHENTICATING and the framework requests a
-     *      new session for sensorId=0, userId=10, the HAL must end the current session with
-     *      Error::CANCELED, invoke ISessionCallback#onStateChanged with SessionState::IDLING, and
-     *      then return a new session for sensorId=0, userId=10.
-     *   2) If a session for sensorId=0, userId=0 is currently in a non-cancellable state such as
-     *      SessionState::REMOVING_ENROLLMENTS, and the framework requests a new session for
-     *      sensorId=0, userId=10, the HAL must finish the current operation before invoking
-     *      ISessionCallback#onStateChanged with SessionState::IDLING, and return a new session for
-     *      sensorId=0, userId=10.
+     * Calling this method while there is an active session is considered an error. If the framework
+     * wants to create a new session when it already has an active session, it must first cancel the
+     * current operation if it's cancellable, or wait until it completes. Then, the framework must
+     * explicitly close the session with ISession#close. Once the framework receives
+     * ISessionCallback#onSessionClosed, a new session can be created.
      *
      * Implementations must store user-specific state or metadata in /data/vendor_de/<user>/fpdata
      * as specified by the SeLinux policy. This directory is created/removed by vold (see
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
index ef2e6fc499..940548ba88 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
@@ -22,23 +22,28 @@ import android.hardware.keymaster.HardwareAuthToken;
 /**
  * Operations that can be performed for unique sessions retrieved via IFingerprint#createSession.
  * Methods defined within this interface can be split into the following categories:
- *   1) Methods associated with a state (see the SessionState enum). State-based operations are
- *      handled by the HAL in FIFO order.
- *   1a) Cancellable state-based operations. If a cancellable operation is in-progress and the
- *       framework requests a subsequent state-based operation, the implementation should finish
- *       the operation via ISessionCallback#onError with Error::CANCELED.
- *   1b) Non-cancellable state-based operations. These operations should fully complete before the
- *       next state-based operation can be started.
- *   2) Methods without a state. These methods may be invoked by the framework depending on its
- *      use case. For example on devices with sensors of FingerprintSensorType::UNDER_DISPLAY_*,
- *      ISession#onFingerDown may be invoked while the HAL is in SessionState::ENROLLING,
- *      SessionState::AUTHENTICATING, or SessionState::DETECTING_INTERACTION.
+ *   1) Non-interrupting operations. These operations are handled by the HAL in FIFO order.
+ *   1a) Cancellable operations. These are usually the operations that can execute for several
+ *       minutes. To allow for cancellation, they return an instance of ICancellationSignal that
+ *       lets the framework cancel them by calling ICancellationSignal#cancel. If such an operation
+ *       is cancelled, it must notify the framework by calling ISessionCallback#onError with
+ *       Error::CANCELED.
+ *   1b) Non-cancellable operations. Such operations cannot be cancelled once started.
+ *   2) Interrupting operations. These operations may be invoked by the framework immediately,
+ *      regardless of whether another operation is executing. For example, on devices with sensors
+ *      of FingerprintSensorType::UNDER_DISPLAY_*, ISession#onFingerDown may be invoked while the
+ *      HAL is executing ISession#enroll, ISession#authenticate or ISession#detectInteraction.
  *
- * If the HAL has multiple operations in its queue, it is not required to notify the framework
- * of SessionState::IDLING between each operation. However, it must notify the framework when all
- * work is completed. See ISessionCallback#onStateChanged. For example, the following is a valid
- * sequence of ISessionCallback#onStateChanged invocations: SessionState::IDLING -->
- * SessionState::ENROLLING --> SessionState::ENUMERATING_ENROLLMENTS --> SessionState::IDLING.
+ * The lifecycle of a non-interrupting operation ends when one of its terminal callbacks is called.
+ * For example, ISession#authenticate is considered completed when either of the following callbacks
+ * is called: ISessionCallback#onError or ISessionCallback#onAuthenticationSucceeded.
+ *
+ * The lifecycle of an interrupting operation ends when it returns. Interrupting operations do not
+ * have callbacks.
+ *
+ * ISession only supports execution of one non-interrupting operation at a time, regardless of
+ * whether it's cancellable. The framework must wait for a corresponding callback indicating the end of
+ * the current non-interrupting operation before a new non-interrupting operation can be started.
  */
 @VintfStability
 interface ISession {
@@ -84,9 +89,8 @@ interface ISession {
      * | 0        | 10     | <Time4>    | <Random4> |
      * ----------------------------------------------
      *
-     * @param cookie A unique number identifying this operation
      */
-    void generateChallenge(in int cookie);
+    void generateChallenge();
 
     /**
      * revokeChallenge:
@@ -95,23 +99,17 @@ interface ISession {
      * parameters is requested, the implementation must still notify the framework using the
      * provided callback.
      *
-     * @param cookie A unique number identifying this operation
      * @param challenge Challenge that should be revoked.
      */
-    void revokeChallenge(in int cookie, in long challenge);
+    void revokeChallenge(in long challenge);
 
     /**
      * enroll:
      *
      * A request to add a fingerprint enrollment.
      *
-     * Once the HAL is able to start processing the enrollment request, it must notify the framework
-     * via ISessionCallback#onStateChanged with SessionState::ENROLLING.
-     *
      * At any point during enrollment, if a non-recoverable error occurs, the HAL must notify the
-     * framework via ISessionCallback#onError with the applicable enrollment-specific error, and
-     * then send ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no subsequent
-     * operation is in the queue.
+     * framework via ISessionCallback#onError with the applicable enrollment-specific error.
      *
      * Before capturing fingerprint data, the implementation must first verify the authenticity and
      * integrity of the provided HardwareAuthToken. In addition, it must check that the challenge
@@ -132,24 +130,17 @@ interface ISession {
      * implementation MUST update and associate this (sensorId, userId) pair with a new new
      * entropy-encoded random identifier. See ISession#getAuthenticatorId for more information.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat See above documentation.
      */
-    ICancellationSignal enroll(in int cookie, in HardwareAuthToken hat);
+    ICancellationSignal enroll(in HardwareAuthToken hat);
 
     /**
      * authenticate:
      *
      * A request to start looking for fingerprints to authenticate.
      *
-     * Once the HAL is able to start processing the authentication request, it must notify framework
-     * via ISessionCallback#onStateChanged with SessionState::AUTHENTICATING.
-     *
      * At any point during authentication, if a non-recoverable error occurs, the HAL must notify
-     * the framework via ISessionCallback#onError with the applicable authentication-specific error,
-     * and then send ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no
-     * subsequent operation is in the queue.
+     * the framework via ISessionCallback#onError with the applicable authentication-specific error.
      *
      * During authentication, the implementation may notify the framework via
      * ISessionCallback#onAcquired with messages that may be used to guide the user. This callback
@@ -171,8 +162,6 @@ interface ISession {
      * must be set with the operationId passed in during #authenticate. If the sensor is NOT
      * SensorStrength::STRONG, the HardwareAuthToken MUST be null.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param operationId For sensors configured as SensorStrength::STRONG, this must be used ONLY
      *                    upon successful authentication and wrapped in the HardwareAuthToken's
      *                    "challenge" field and sent to the framework via
@@ -184,7 +173,7 @@ interface ISession {
      *                    setUserAuthenticationParameters in KeyGenParameterSpec.Builder and
      *                    KeyProtection.Builder.
      */
-    ICancellationSignal authenticate(in int cookie, in long operationId);
+    ICancellationSignal authenticate(in long operationId);
 
     /**
      * detectInteraction:
@@ -193,17 +182,12 @@ interface ISession {
      * if SensorProps#supportsDetectInteraction is true. If invoked on implementations that do not
      * support this functionality, the HAL must respond with ISession#onError(UNABLE_TO_PROCESS, 0).
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::DETECTING_INTERACTION.
-     *
      * The framework will use this method in cases where determing user presence is required, but
      * identifying/authentication is not. For example, when the device is encrypted (first boot) or
      * in lockdown mode.
      *
      * At any point during detectInteraction, if a non-recoverable error occurs, the HAL must notify
-     * the framework via ISessionCallback#onError with the applicable error, and then send
-     * ISessionCallback#onStateChanged(cookie, SessionState::IDLING) if no subsequent operation is
-     * in the queue.
+     * the framework via ISessionCallback#onError with the applicable error.
      *
      * The implementation must only check for a fingerprint-like image was detected (e.g. to
      * minimize interactions due to non-fingerprint objects), and the lockout counter must not
@@ -221,10 +205,8 @@ interface ISession {
      * Note that if the operation is canceled, the implementation must notify the framework via
      * ISessionCallback#onError with Error::CANCELED.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    ICancellationSignal detectInteraction(in int cookie);
+    ICancellationSignal detectInteraction();
 
     /*
      * enumerateEnrollments:
@@ -232,32 +214,22 @@ interface ISession {
      * A request to enumerate (list) the enrollments for this (sensorId, userId) pair. The
      * framework typically uses this to ensure that its cache is in sync with the HAL.
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::ENUMERATING_ENROLLMENTS.
-     *
      * The implementation must then notify the framework with a list of enrollments applicable
      * for the current session via ISessionCallback#onEnrollmentsEnumerated.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    void enumerateEnrollments(in int cookie);
+    void enumerateEnrollments();
 
     /**
      * removeEnrollments:
      *
      * A request to remove the enrollments for this (sensorId, userId) pair.
      *
-     * Once the HAL is able to start processing this request, it must notify the framework via
-     * ISessionCallback#onStateChanged with SessionState::REMOVING_ENROLLMENTS.
-     *
      * After removing the enrollmentIds from everywhere necessary (filesystem, secure subsystems,
      * etc), the implementation must notify the framework via ISessionCallback#onEnrollmentsRemoved.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path.
-     *               The framework will guarantee that it is unique per ISession.
      */
-    void removeEnrollments(in int cookie, in int[] enrollmentIds);
+    void removeEnrollments(in int[] enrollmentIds);
 
     /**
      * getAuthenticatorId:
@@ -285,10 +257,8 @@ interface ISession {
      *   3) MUST not change if a fingerprint is deleted.
      *   4) MUST be an entropy-encoded random number
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void getAuthenticatorId(in int cookie);
+    void getAuthenticatorId();
 
     /**
      * invalidateAuthenticatorId:
@@ -312,10 +282,8 @@ interface ISession {
      * for more details). As such, the framework would coordinate invalidation across multiple
      * biometric HALs as necessary.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void invalidateAuthenticatorId(in int cookie);
+    void invalidateAuthenticatorId();
 
     /**
      * resetLockout:
@@ -326,8 +294,7 @@ interface ISession {
      *   2) Verify that the timestamp provided within the HAT is relatively recent (e.g. on the
      *      order of minutes, not hours).
      * If either of the checks fail, the HAL must invoke ISessionCallback#onError with
-     * Error::UNABLE_TO_PROCESS and return to SessionState::IDLING if no subsequent work is in the
-     * queue.
+     * Error::UNABLE_TO_PROCESS and return to the idling state.
      *
      * Upon successful verification, the HAL must clear the lockout counter and notify the framework
      * via ISessionCallback#onLockoutCleared.
@@ -358,29 +325,26 @@ interface ISession {
      * See the Android CDD section 7.3.10 for the full set of lockout and rate-limiting
      * requirements.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      * @param hat HardwareAuthToken See above documentation.
      */
-    void resetLockout(in int cookie, in HardwareAuthToken hat);
+    void resetLockout(in HardwareAuthToken hat);
 
     /*
      * Close this session and allow the HAL to release the resources associated with this session.
      *
-     * A session can only be closed when it's in SessionState::IDLING. Closing a session will
-     * result in a ISessionCallback#onStateChanged call with SessionState::CLOSED.
+     * A session can only be closed when the HAL is idling, i.e. not performing any of the
+     * non-interruptable operations. If the HAL is busy performing a cancellable operation, the
+     * operation must be explicitly cancelled with a call to ICancellationSignal#cancel before
+     * the session can be closed.
      *
-     * If a session is unresponsive or stuck in a state other than SessionState::CLOSED,
-     * IFingerprint#reset could be used as a last resort to terminate the session and recover the
-     * HAL from a bad state.
+     * After a session is closed, the HAL must notify the framework by calling
+     * ISessionCallback#onSessionClosed.
      *
      * All sessions must be explicitly closed. Calling IFingerprint#createSession while there is an
      * active session is considered an error.
      *
-     * @param cookie An identifier used to track subsystem operations related to this call path. The
-     *               client must guarantee that it is unique per ISession.
      */
-    void close(in int cookie);
+    void close();
 
     /**
      * Methods for notifying the under-display fingerprint sensor about external events.
@@ -394,9 +358,8 @@ interface ISession {
      * of other types, the HAL must treat this as a no-op and return immediately.
      *
      * For sensors of type FingerprintSensorType::UNDER_DISPLAY_*, this method is used to notify the
-     * HAL of display touches. This method can be invoked when the session is in one of the
-     * following states: SessionState::ENROLLING, SessionState::AUTHENTICATING, or
-     * SessionState::DETECTING_INTERACTION.
+     * HAL of display touches. This method can be invoked when the HAL is performing any one of:
+     * ISession#authenticate, ISession#enroll, ISession#detectInteraction.
      *
      * Note that the framework will only invoke this method if the event occurred on the display on
      * which this sensor is located.
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
index cf3a271ef6..95657b3d7b 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISessionCallback.aidl
@@ -18,17 +18,11 @@ package android.hardware.biometrics.fingerprint;
 
 import android.hardware.biometrics.fingerprint.AcquiredInfo;
 import android.hardware.biometrics.fingerprint.Error;
-import android.hardware.biometrics.fingerprint.SessionState;
 import android.hardware.keymaster.HardwareAuthToken;
 
 @VintfStability
 interface ISessionCallback {
     /**
-     * Used to notify the framework of session state changes. See ISession for more information.
-     */
-    void onStateChanged(in int cookie, in SessionState state);
-
-    /**
      * Notifies the framework when a challenge is successfully generated.
      */
     void onChallengeGenerated(in long challenge);
@@ -39,10 +33,10 @@ interface ISessionCallback {
     void onChallengeRevoked(in long challenge);
 
     /**
-     * This method must only be used to notify the framework during the following states:
-     *   1) SessionState::ENROLLING
-     *   2) SessionState::AUTHENTICATING
-     *   3) SessionState::DETECTING_INTERACTION
+     * This method must only be used to notify the framework during the following operations:
+     *   1) ISession#enroll
+     *   2) ISession#authenticate
+     *   3) ISession#detectInteraction
      *
      * These messages may be used to provide user guidance multiple times if necessary per
      * operation.
@@ -56,18 +50,18 @@ interface ISessionCallback {
     void onAcquired(in AcquiredInfo info, in int vendorCode);
 
     /**
-     * This method must only be used to notify the framework during the following states:
-     *   1) SessionState::ENROLLING
-     *   2) SessionState::AUTHENTICATING
-     *   3) SessionState::DETECTING_INTERACTION
-     *   4) SessionState::INVALIDATING_AUTHENTICATOR_ID
-     *   5) SessionState::RESETTING_LOCKOUT
+     * This method must only be used to notify the framework during the following operations:
+     *   1) ISession#enroll
+     *   2) ISession#authenticate
+     *   3) ISession#detectInteraction
+     *   4) ISession#invalidateAuthenticatorId
+     *   5) ISession#resetLockout
      *
      * These messages may be used to notify the framework or user that a non-recoverable error
-     * has occurred. The operation is finished, and the HAL must proceed with the next operation
-     * or return to SessionState::IDLING if the queue is empty.
+     * has occurred. The operation is finished, and the HAL can proceed with the next operation
+     * or return to the idling state.
      *
-     * Note that cancellation (see common::ICancellationSignal) and preemption most be followed with
+     * Note that cancellation (see common::ICancellationSignal) and preemption must be followed with
      * an Error::CANCELED message.
      *
      * @param error See the Error enum.
@@ -79,8 +73,7 @@ interface ISessionCallback {
     void onError(in Error error, in int vendorCode);
 
     /**
-     * This method must only be used to notify the framework during the following state:
-     *   1) SessionState::ENROLLING
+     * This method must only be used to notify the framework during the ISession#enroll operation.
      *
      * @param enrollmentId Unique stable identifier for the enrollment that's being added by this
      *                     ISession#enroll invocation.
@@ -89,7 +82,7 @@ interface ISessionCallback {
     void onEnrollmentProgress(in int enrollmentId, int remaining);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Used to notify the framework upon successful authentication. Note that the authentication
      * lifecycle ends when either 1) a fingerprint is accepted, or 2) an error occurred. The
@@ -104,7 +97,7 @@ interface ISessionCallback {
     void onAuthenticationSucceeded(in int enrollmentId, in HardwareAuthToken hat);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Used to notify the framework upon rejected attempts. Note that the authentication
      * lifecycle ends when either 1) a fingerprint is accepted, or 2) an occurred. The
@@ -113,7 +106,7 @@ interface ISessionCallback {
     void onAuthenticationFailed();
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Authentication is locked out due to too many unsuccessful attempts. This is a rate-limiting
      * lockout, and authentication can be restarted after a period of time. See
@@ -126,7 +119,7 @@ interface ISessionCallback {
     void onLockoutTimed(in long durationMillis);
 
     /**
-     * This method must only be used to notify the framework during SessionState::AUTHENTICATING.
+     * This method must only be used to notify the framework during ISession#authenticate.
      *
      * Authentication is disabled until the user unlocks with their device credential
      * (PIN/Pattern/Password). See ISession#resetLockout.
@@ -153,7 +146,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::DETECTING_INTERACTION
+     * ISession#detectInteraction
      *
      * Notifies the framework that user interaction occurred. See ISession#detectInteraction.
      */
@@ -161,7 +154,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::ENUMERATING_ENROLLMENTS.
+     * ISession#enumerateEnrollments.
      *
      * Notifies the framework of the current enrollments. See ISession#enumerateEnrollments.
      *
@@ -171,7 +164,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::REMOVING_ENROLLMENTS.
+     * ISession#removeEnrollments.
      *
      * Notifies the framework that the specified enrollments are removed.
      *
@@ -181,7 +174,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::GETTING_AUTHENTICATOR_ID.
+     * ISession#getAuthenticatorId.
      *
      * Notifies the framework with the authenticatorId corresponding to this session's
      * (userId, sensorId) pair.
@@ -192,7 +185,7 @@ interface ISessionCallback {
 
     /**
      * This method must only be used to notify the framework during
-     * SessionState::INVALIDATING_AUTHENTICATOR_ID.
+     * ISession#invalidateAuthenticatorId.
      *
      * See ISession#invalidateAuthenticatorId for more information.
      *
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/SessionState.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/SessionState.aidl
deleted file mode 100644
index 19a6ce3682..0000000000
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/SessionState.aidl
+++ /dev/null
@@ -1,81 +0,0 @@
-/*
- * Copyright (C) 2020 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package android.hardware.biometrics.fingerprint;
-
-@VintfStability
-@Backing(type="byte")
-enum SessionState {
-    /**
-     * The HAL is not processing any session requests.
-     */
-    IDLING,
-
-    /**
-     * The session has been closed by the client.
-     */
-    CLOSED,
-
-    /**
-     * The HAL is processing the ISession#generateChallenge request.
-     */
-    GENERATING_CHALLENGE,
-
-    /**
-     * The HAL is processing the ISession#revokeChallenge request.
-     */
-    REVOKING_CHALLENGE,
-
-    /**
-     * The HAL is processing the ISession#enroll request.
-     */
-    ENROLLING,
-
-    /**
-     * The HAL is processing the ISession#authenticate request.
-     */
-    AUTHENTICATING,
-
-    /**
-     * The HAL is processing the ISession#detectInteraction request.
-     */
-    DETECTING_INTERACTION,
-
-    /**
-     * The HAL is processing the ISession#enumerateEnrollments request.
-     */
-    ENUMERATING_ENROLLMENTS,
-
-    /**
-     * The HAL is processing the ISession#removeEnrollments request.
-     */
-    REMOVING_ENROLLMENTS,
-
-    /**
-     * The HAL is processing the ISession#getAuthenticatorId request.
-     */
-    GETTING_AUTHENTICATOR_ID,
-
-    /**
-     * The HAL is processing the ISession#invalidateAuthenticatorId request.
-     */
-    INVALIDATING_AUTHENTICATOR_ID,
-
-    /**
-     * The HAL is processing the ISession#resetLockout request.
-     */
-    RESETTING_LOCKOUT
-}
diff --git a/biometrics/fingerprint/aidl/default/Fingerprint.cpp b/biometrics/fingerprint/aidl/default/Fingerprint.cpp
index fbfa52f0e7..734ff600b7 100644
--- a/biometrics/fingerprint/aidl/default/Fingerprint.cpp
+++ b/biometrics/fingerprint/aidl/default/Fingerprint.cpp
@@ -22,7 +22,7 @@ namespace aidl::android::hardware::biometrics::fingerprint {
 namespace {
 constexpr size_t MAX_WORKER_QUEUE_SIZE = 5;
 constexpr int SENSOR_ID = 1;
-constexpr common::SensorStrength SENSOR_STRENGTH = common::SensorStrength::STRONG;
+constexpr common::SensorStrength SENSOR_STRENGTH = common::SensorStrength::WEAK;
 constexpr int MAX_ENROLLMENTS_PER_USER = 5;
 constexpr FingerprintSensorType SENSOR_TYPE = FingerprintSensorType::REAR;
 constexpr bool SUPPORTS_NAVIGATION_GESTURES = true;
diff --git a/biometrics/fingerprint/aidl/default/Session.cpp b/biometrics/fingerprint/aidl/default/Session.cpp
index f030f138f5..ca481e7cf0 100644
--- a/biometrics/fingerprint/aidl/default/Session.cpp
+++ b/biometrics/fingerprint/aidl/default/Session.cpp
@@ -39,54 +39,56 @@ Session::Session(int sensorId, int userId, std::shared_ptr<ISessionCallback> cb,
 }
 
 void Session::scheduleStateOrCrash(SessionState state) {
-    CHECK(mScheduledState == SessionState::IDLING);
-    CHECK(mCurrentState == SessionState::IDLING);
+    // TODO(b/166800618): call enterIdling from the terminal callbacks and restore these checks.
+    // CHECK(mScheduledState == SessionState::IDLING);
+    // CHECK(mCurrentState == SessionState::IDLING);
     mScheduledState = state;
 }
 
-void Session::enterStateOrCrash(int cookie, SessionState state) {
+void Session::enterStateOrCrash(SessionState state) {
     CHECK(mScheduledState == state);
     mCurrentState = state;
     mScheduledState = SessionState::IDLING;
-    mCb->onStateChanged(cookie, mCurrentState);
 }
 
-void Session::enterIdling(int cookie) {
-    mCurrentState = SessionState::IDLING;
-    mCb->onStateChanged(cookie, mCurrentState);
+void Session::enterIdling() {
+    // TODO(b/166800618): call enterIdling from the terminal callbacks and rethink this conditional.
+    if (mCurrentState != SessionState::CLOSED) {
+        mCurrentState = SessionState::IDLING;
+    }
 }
 
 bool Session::isClosed() {
     return mCurrentState == SessionState::CLOSED;
 }
 
-ndk::ScopedAStatus Session::generateChallenge(int32_t cookie) {
+ndk::ScopedAStatus Session::generateChallenge() {
     LOG(INFO) << "generateChallenge";
     scheduleStateOrCrash(SessionState::GENERATING_CHALLENGE);
 
-    mWorker->schedule(Callable::from([this, cookie] {
-        enterStateOrCrash(cookie, SessionState::GENERATING_CHALLENGE);
+    mWorker->schedule(Callable::from([this] {
+        enterStateOrCrash(SessionState::GENERATING_CHALLENGE);
         mEngine->generateChallengeImpl(mCb.get());
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::revokeChallenge(int32_t cookie, int64_t challenge) {
+ndk::ScopedAStatus Session::revokeChallenge(int64_t challenge) {
     LOG(INFO) << "revokeChallenge";
     scheduleStateOrCrash(SessionState::REVOKING_CHALLENGE);
 
-    mWorker->schedule(Callable::from([this, cookie, challenge] {
-        enterStateOrCrash(cookie, SessionState::REVOKING_CHALLENGE);
+    mWorker->schedule(Callable::from([this, challenge] {
+        enterStateOrCrash(SessionState::REVOKING_CHALLENGE);
         mEngine->revokeChallengeImpl(mCb.get(), challenge);
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::enroll(int32_t cookie, const keymaster::HardwareAuthToken& hat,
+ndk::ScopedAStatus Session::enroll(const keymaster::HardwareAuthToken& hat,
                                    std::shared_ptr<common::ICancellationSignal>* out) {
     LOG(INFO) << "enroll";
     scheduleStateOrCrash(SessionState::ENROLLING);
@@ -94,21 +96,21 @@ ndk::ScopedAStatus Session::enroll(int32_t cookie, const keymaster::HardwareAuth
     std::promise<void> cancellationPromise;
     auto cancFuture = cancellationPromise.get_future();
 
-    mWorker->schedule(Callable::from([this, cookie, hat, cancFuture = std::move(cancFuture)] {
-        enterStateOrCrash(cookie, SessionState::ENROLLING);
+    mWorker->schedule(Callable::from([this, hat, cancFuture = std::move(cancFuture)] {
+        enterStateOrCrash(SessionState::ENROLLING);
         if (shouldCancel(cancFuture)) {
             mCb->onError(Error::CANCELED, 0 /* vendorCode */);
         } else {
             mEngine->enrollImpl(mCb.get(), hat);
         }
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     *out = SharedRefBase::make<CancellationSignal>(std::move(cancellationPromise));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::authenticate(int32_t cookie, int64_t operationId,
+ndk::ScopedAStatus Session::authenticate(int64_t operationId,
                                          std::shared_ptr<common::ICancellationSignal>* out) {
     LOG(INFO) << "authenticate";
     scheduleStateOrCrash(SessionState::AUTHENTICATING);
@@ -116,112 +118,111 @@ ndk::ScopedAStatus Session::authenticate(int32_t cookie, int64_t operationId,
     std::promise<void> cancPromise;
     auto cancFuture = cancPromise.get_future();
 
-    mWorker->schedule(
-            Callable::from([this, cookie, operationId, cancFuture = std::move(cancFuture)] {
-                enterStateOrCrash(cookie, SessionState::AUTHENTICATING);
-                if (shouldCancel(cancFuture)) {
-                    mCb->onError(Error::CANCELED, 0 /* vendorCode */);
-                } else {
-                    mEngine->authenticateImpl(mCb.get(), operationId);
-                }
-                enterIdling(cookie);
-            }));
+    mWorker->schedule(Callable::from([this, operationId, cancFuture = std::move(cancFuture)] {
+        enterStateOrCrash(SessionState::AUTHENTICATING);
+        if (shouldCancel(cancFuture)) {
+            mCb->onError(Error::CANCELED, 0 /* vendorCode */);
+        } else {
+            mEngine->authenticateImpl(mCb.get(), operationId);
+        }
+        enterIdling();
+    }));
 
     *out = SharedRefBase::make<CancellationSignal>(std::move(cancPromise));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::detectInteraction(int32_t cookie,
-                                              std::shared_ptr<common::ICancellationSignal>* out) {
+ndk::ScopedAStatus Session::detectInteraction(std::shared_ptr<common::ICancellationSignal>* out) {
     LOG(INFO) << "detectInteraction";
     scheduleStateOrCrash(SessionState::DETECTING_INTERACTION);
 
     std::promise<void> cancellationPromise;
     auto cancFuture = cancellationPromise.get_future();
 
-    mWorker->schedule(Callable::from([this, cookie, cancFuture = std::move(cancFuture)] {
-        enterStateOrCrash(cookie, SessionState::DETECTING_INTERACTION);
+    mWorker->schedule(Callable::from([this, cancFuture = std::move(cancFuture)] {
+        enterStateOrCrash(SessionState::DETECTING_INTERACTION);
         if (shouldCancel(cancFuture)) {
             mCb->onError(Error::CANCELED, 0 /* vendorCode */);
         } else {
             mEngine->detectInteractionImpl(mCb.get());
         }
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     *out = SharedRefBase::make<CancellationSignal>(std::move(cancellationPromise));
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::enumerateEnrollments(int32_t cookie) {
+ndk::ScopedAStatus Session::enumerateEnrollments() {
     LOG(INFO) << "enumerateEnrollments";
     scheduleStateOrCrash(SessionState::ENUMERATING_ENROLLMENTS);
 
-    mWorker->schedule(Callable::from([this, cookie] {
-        enterStateOrCrash(cookie, SessionState::ENUMERATING_ENROLLMENTS);
+    mWorker->schedule(Callable::from([this] {
+        enterStateOrCrash(SessionState::ENUMERATING_ENROLLMENTS);
         mEngine->enumerateEnrollmentsImpl(mCb.get());
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::removeEnrollments(int32_t cookie,
-                                              const std::vector<int32_t>& enrollmentIds) {
+ndk::ScopedAStatus Session::removeEnrollments(const std::vector<int32_t>& enrollmentIds) {
     LOG(INFO) << "removeEnrollments";
     scheduleStateOrCrash(SessionState::REMOVING_ENROLLMENTS);
 
-    mWorker->schedule(Callable::from([this, cookie, enrollmentIds] {
-        enterStateOrCrash(cookie, SessionState::REMOVING_ENROLLMENTS);
+    mWorker->schedule(Callable::from([this, enrollmentIds] {
+        enterStateOrCrash(SessionState::REMOVING_ENROLLMENTS);
         mEngine->removeEnrollmentsImpl(mCb.get(), enrollmentIds);
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::getAuthenticatorId(int32_t cookie) {
+ndk::ScopedAStatus Session::getAuthenticatorId() {
     LOG(INFO) << "getAuthenticatorId";
     scheduleStateOrCrash(SessionState::GETTING_AUTHENTICATOR_ID);
 
-    mWorker->schedule(Callable::from([this, cookie] {
-        enterStateOrCrash(cookie, SessionState::GETTING_AUTHENTICATOR_ID);
+    mWorker->schedule(Callable::from([this] {
+        enterStateOrCrash(SessionState::GETTING_AUTHENTICATOR_ID);
         mEngine->getAuthenticatorIdImpl(mCb.get());
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::invalidateAuthenticatorId(int32_t cookie) {
+ndk::ScopedAStatus Session::invalidateAuthenticatorId() {
     LOG(INFO) << "invalidateAuthenticatorId";
     scheduleStateOrCrash(SessionState::INVALIDATING_AUTHENTICATOR_ID);
 
-    mWorker->schedule(Callable::from([this, cookie] {
-        enterStateOrCrash(cookie, SessionState::INVALIDATING_AUTHENTICATOR_ID);
+    mWorker->schedule(Callable::from([this] {
+        enterStateOrCrash(SessionState::INVALIDATING_AUTHENTICATOR_ID);
         mEngine->invalidateAuthenticatorIdImpl(mCb.get());
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::resetLockout(int32_t cookie, const keymaster::HardwareAuthToken& hat) {
+ndk::ScopedAStatus Session::resetLockout(const keymaster::HardwareAuthToken& hat) {
     LOG(INFO) << "resetLockout";
     scheduleStateOrCrash(SessionState::RESETTING_LOCKOUT);
 
-    mWorker->schedule(Callable::from([this, cookie, hat] {
-        enterStateOrCrash(cookie, SessionState::RESETTING_LOCKOUT);
+    mWorker->schedule(Callable::from([this, hat] {
+        enterStateOrCrash(SessionState::RESETTING_LOCKOUT);
         mEngine->resetLockoutImpl(mCb.get(), hat);
-        enterIdling(cookie);
+        enterIdling();
     }));
 
     return ndk::ScopedAStatus::ok();
 }
 
-ndk::ScopedAStatus Session::close(int32_t /*cookie*/) {
+ndk::ScopedAStatus Session::close() {
     LOG(INFO) << "close";
-    CHECK(mCurrentState == SessionState::IDLING) << "Can't close a non-idling session. Crashing.";
+    // TODO(b/166800618): call enterIdling from the terminal callbacks and restore this check.
+    // CHECK(mCurrentState == SessionState::IDLING) << "Can't close a non-idling session.
+    // Crashing.";
     mCurrentState = SessionState::CLOSED;
     mCb->onSessionClosed();
     return ndk::ScopedAStatus::ok();
diff --git a/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h b/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h
index 42e1aa5357..6667f7a7f0 100644
--- a/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h
+++ b/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h
@@ -37,7 +37,7 @@ class FakeFingerprintEngine {
         cb->onEnrollmentProgress(0 /* enrollmentId */, 0 /* remaining */);
     }
 
-    void authenticateImpl(ISessionCallback* cb, int64_t /*operationId*/) {
+    void authenticateImpl(ISessionCallback* cb, int64_t /* operationId */) {
         LOG(INFO) << "authenticateImpl";
         cb->onAuthenticationSucceeded(0 /* enrollmentId */, {} /* hat */);
     }
diff --git a/biometrics/fingerprint/aidl/default/include/Session.h b/biometrics/fingerprint/aidl/default/include/Session.h
index 97d5645c92..9e464229e1 100644
--- a/biometrics/fingerprint/aidl/default/include/Session.h
+++ b/biometrics/fingerprint/aidl/default/include/Session.h
@@ -27,37 +27,50 @@ namespace aidl::android::hardware::biometrics::fingerprint {
 namespace common = aidl::android::hardware::biometrics::common;
 namespace keymaster = aidl::android::hardware::keymaster;
 
+enum class SessionState {
+    IDLING,
+    CLOSED,
+    GENERATING_CHALLENGE,
+    REVOKING_CHALLENGE,
+    ENROLLING,
+    AUTHENTICATING,
+    DETECTING_INTERACTION,
+    ENUMERATING_ENROLLMENTS,
+    REMOVING_ENROLLMENTS,
+    GETTING_AUTHENTICATOR_ID,
+    INVALIDATING_AUTHENTICATOR_ID,
+    RESETTING_LOCKOUT,
+};
+
 class Session : public BnSession {
   public:
     Session(int sensorId, int userId, std::shared_ptr<ISessionCallback> cb,
             FakeFingerprintEngine* engine, WorkerThread* worker);
 
-    ndk::ScopedAStatus generateChallenge(int32_t cookie) override;
+    ndk::ScopedAStatus generateChallenge() override;
 
-    ndk::ScopedAStatus revokeChallenge(int32_t cookie, int64_t challenge) override;
+    ndk::ScopedAStatus revokeChallenge(int64_t challenge) override;
 
-    ndk::ScopedAStatus enroll(int32_t cookie, const keymaster::HardwareAuthToken& hat,
+    ndk::ScopedAStatus enroll(const keymaster::HardwareAuthToken& hat,
                               std::shared_ptr<common::ICancellationSignal>* out) override;
 
-    ndk::ScopedAStatus authenticate(int32_t cookie, int64_t operationId,
+    ndk::ScopedAStatus authenticate(int64_t operationId,
                                     std::shared_ptr<common::ICancellationSignal>* out) override;
 
     ndk::ScopedAStatus detectInteraction(
-            int32_t cookie, std::shared_ptr<common::ICancellationSignal>* out) override;
+            std::shared_ptr<common::ICancellationSignal>* out) override;
 
-    ndk::ScopedAStatus enumerateEnrollments(int32_t cookie) override;
+    ndk::ScopedAStatus enumerateEnrollments() override;
 
-    ndk::ScopedAStatus removeEnrollments(int32_t cookie,
-                                         const std::vector<int32_t>& enrollmentIds) override;
+    ndk::ScopedAStatus removeEnrollments(const std::vector<int32_t>& enrollmentIds) override;
 
-    ndk::ScopedAStatus getAuthenticatorId(int32_t cookie) override;
+    ndk::ScopedAStatus getAuthenticatorId() override;
 
-    ndk::ScopedAStatus invalidateAuthenticatorId(int32_t cookie) override;
+    ndk::ScopedAStatus invalidateAuthenticatorId() override;
 
-    ndk::ScopedAStatus resetLockout(int32_t cookie,
-                                    const keymaster::HardwareAuthToken& hat) override;
+    ndk::ScopedAStatus resetLockout(const keymaster::HardwareAuthToken& hat) override;
 
-    ndk::ScopedAStatus close(int32_t cookie) override;
+    ndk::ScopedAStatus close() override;
 
     ndk::ScopedAStatus onPointerDown(int32_t pointerId, int32_t x, int32_t y, float minor,
                                      float major) override;
@@ -76,11 +89,11 @@ class Session : public BnSession {
     // Crashes the HAL if the provided state doesn't match the previously scheduled state.
     // Otherwise, transitions into the provided state, clears the scheduled state, and notifies
     // the client about the transition by calling ISessionCallback#onStateChanged.
-    void enterStateOrCrash(int cookie, SessionState state);
+    void enterStateOrCrash(SessionState state);
 
     // Sets the current state to SessionState::IDLING and notifies the client about the transition
     // by calling ISessionCallback#onStateChanged.
-    void enterIdling(int cookie);
+    void enterIdling();
 
     // The sensor and user IDs for which this session was created.
     int32_t mSensorId;
diff --git a/biometrics/fingerprint/aidl/vts/VtsHalBiometricsFingerprintTargetTest.cpp b/biometrics/fingerprint/aidl/vts/VtsHalBiometricsFingerprintTargetTest.cpp
index 885f703d5b..f1cfb17837 100644
--- a/biometrics/fingerprint/aidl/vts/VtsHalBiometricsFingerprintTargetTest.cpp
+++ b/biometrics/fingerprint/aidl/vts/VtsHalBiometricsFingerprintTargetTest.cpp
@@ -22,46 +22,20 @@
 #include <android/binder_manager.h>
 #include <android/binder_process.h>
 
+#include <chrono>
 #include <future>
 
 namespace aidl::android::hardware::biometrics::fingerprint {
 namespace {
 
+using namespace std::literals::chrono_literals;
+
 constexpr int kSensorId = 0;
 constexpr int kUserId = 0;
-constexpr auto kCallbackTimeout = std::chrono::seconds(1);
-
-enum class MethodName {
-    kOnStateChanged,
-};
-
-struct Invocation {
-    MethodName methodName;
-    int32_t cookie;
-    SessionState state;
-};
 
 class SessionCallback : public BnSessionCallback {
   public:
-    explicit SessionCallback() : mIsPromiseValid(false) {}
-
-    void setPromise(std::promise<std::vector<Invocation>>&& promise) {
-        mPromise = std::move(promise);
-        mIsPromiseValid = true;
-    }
-
-    ndk::ScopedAStatus onStateChanged(int32_t cookie, SessionState state) override {
-        Invocation invocation = {};
-        invocation.methodName = MethodName::kOnStateChanged;
-        invocation.cookie = cookie;
-        invocation.state = state;
-        mInvocations.push_back(invocation);
-        if (state == SessionState::IDLING) {
-            assert(mIsPromiseValid);
-            mPromise.set_value(mInvocations);
-        }
-        return ndk::ScopedAStatus::ok();
-    }
+    explicit SessionCallback(std::promise<void>&& promise) : mPromise(std::move(promise)) {}
 
     ndk::ScopedAStatus onChallengeGenerated(int64_t /*challenge*/) override {
         return ndk::ScopedAStatus::ok();
@@ -119,12 +93,13 @@ class SessionCallback : public BnSessionCallback {
         return ndk::ScopedAStatus::ok();
     }
 
-    ndk::ScopedAStatus onSessionClosed() override { return ndk::ScopedAStatus::ok(); }
+    ndk::ScopedAStatus onSessionClosed() override {
+        mPromise.set_value();
+        return ndk::ScopedAStatus::ok();
+    }
 
   private:
-    bool mIsPromiseValid;
-    std::vector<Invocation> mInvocations;
-    std::promise<std::vector<Invocation>> mPromise;
+    std::promise<void> mPromise;
 };
 
 class Fingerprint : public testing::TestWithParam<std::string> {
@@ -139,33 +114,26 @@ class Fingerprint : public testing::TestWithParam<std::string> {
 };
 
 TEST_P(Fingerprint, AuthenticateTest) {
-    // Prepare the callback
-    std::promise<std::vector<Invocation>> promise;
+    auto promise = std::promise<void>{};
     auto future = promise.get_future();
-    std::shared_ptr<SessionCallback> cb = ndk::SharedRefBase::make<SessionCallback>();
-    cb->setPromise(std::move(promise));
+    // Prepare the callback.
+    auto cb = ndk::SharedRefBase::make<SessionCallback>(std::move(promise));
 
     // Create a session
     std::shared_ptr<ISession> session;
     ASSERT_TRUE(mHal->createSession(kSensorId, kUserId, cb, &session).isOk());
 
     // Call authenticate
-    int32_t cookie = 123;
     std::shared_ptr<common::ICancellationSignal> cancellationSignal;
-    ASSERT_TRUE(session->authenticate(cookie, 0, &cancellationSignal).isOk());
+    ASSERT_TRUE(session->authenticate(-1 /* operationId */, &cancellationSignal).isOk());
 
     // Get the results
-    ASSERT_TRUE(future.wait_for(kCallbackTimeout) == std::future_status::ready);
-    std::vector<Invocation> invocations = future.get();
+    // TODO(b/166799066): test authenticate.
 
     // Close the session
-    ASSERT_TRUE(session->close(0).isOk());
-
-    ASSERT_FALSE(invocations.empty());
-    EXPECT_EQ(invocations.front().methodName, MethodName::kOnStateChanged);
-    EXPECT_EQ(invocations.front().state, SessionState::AUTHENTICATING);
-    EXPECT_EQ(invocations.back().methodName, MethodName::kOnStateChanged);
-    EXPECT_EQ(invocations.back().state, SessionState::IDLING);
+    ASSERT_TRUE(session->close().isOk());
+    auto status = future.wait_for(1s);
+    ASSERT_EQ(status, std::future_status::ready);
 }
 
 GTEST_ALLOW_UNINSTANTIATED_PARAMETERIZED_TEST(Fingerprint);