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 205429b..9033989 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 b0bfa30..2bb053a 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 4db47c9..0000000
--- 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 66c7c38..7502515 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.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 @@
      * | 0        | 10     | <Time4>    | <Random4> |
      * ----------------------------------------------
      *
-     * @param cookie A unique number identifying this operation
      */
-    void generateChallenge(in int cookie);
+    void generateChallenge();
 
     /**
      * revokeChallenge:
@@ -79,10 +92,9 @@
      * 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 @@
      *
      * 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 @@
      * 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 @@
      * @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 @@
      *
      * 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 @@
      * 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 @@
      * @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 @@
      * 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 @@
      * 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 @@
      * 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 @@
      * 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 @@
      * (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 @@
      *   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 @@
      * 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 @@
      *   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 @@
      * 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 c1aa3fc..a2601e7 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.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 @@
     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 @@
     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 @@
     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 @@
     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 @@
     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 @@
     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 @@
     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 @@
     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 @@
 
     /**
      * 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 @@
 
     /**
      * 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 @@
     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 @@
     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 @@
 
     /**
      * 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 @@
 
     /**
      * 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 @@
 
     /**
      * 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 afde4eb..0000000
--- 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
-}