diff --git a/api/spec/src/cloud/main.tsp b/api/spec/src/cloud/main.tsp
index df1797b8a..aa6cccd2a 100644
--- a/api/spec/src/cloud/main.tsp
+++ b/api/spec/src/cloud/main.tsp
@@ -142,3 +142,7 @@ namespace OpenMeterCloud.Entitlements {
   @tag("Entitlements (Experimental)")
   interface Subjects extends OpenMeter.Entitlements.Subjects {}
 }
+
+@route("/api/v1/customers")
+@tag("Customers")
+interface Customers extends OpenMeter.Customers {}
diff --git a/api/spec/src/cloud/subjects.tsp b/api/spec/src/cloud/subjects.tsp
index cc4a30a44..74989bc02 100644
--- a/api/spec/src/cloud/subjects.tsp
+++ b/api/spec/src/cloud/subjects.tsp
@@ -32,8 +32,15 @@ interface Subjects {
    * If the subject exists, it will be partially updated with the provided fields.
    */
   @post
-  @operationId("listSubjects")
+  @operationId("upsertSubject")
   upsert(@body subject: Subject[]): Subject[] | OpenMeter.CommonErrors;
+
+  /**
+   * Delete subject by ID or key.
+   */
+  @delete
+  @operationId("deleteSubject")
+  delete(@path subjectIdOrKey: string): void | OpenMeter.CommonErrors;
 }
 
 /**
diff --git a/api/spec/src/entitlements/subjects.tsp b/api/spec/src/entitlements/subjects.tsp
index b0d3c9fb6..7f5991502 100644
--- a/api/spec/src/entitlements/subjects.tsp
+++ b/api/spec/src/entitlements/subjects.tsp
@@ -155,7 +155,7 @@ interface Subjects {
     /**
      * Windowsize
      */
-    @query windowSize?: OpenMeter.WindowSize,
+    @query windowSize: OpenMeter.WindowSize,
 
     /**
      * The timezone used when calculating the windows.
diff --git a/api/spec/src/events.tsp b/api/spec/src/events.tsp
index d335ab0de..89eabfeeb 100644
--- a/api/spec/src/events.tsp
+++ b/api/spec/src/events.tsp
@@ -27,7 +27,7 @@ interface Events {
      */
     @query
     @example(utcDateTime.fromISO("2023-01-01T00:00:00Z"))
-    ingestedAtFrom: utcDateTime,
+    ingestedAtFrom?: utcDateTime,
 
     /**
      * End date-time in RFC 3339 format.
@@ -36,7 +36,7 @@ interface Events {
      */
     @query
     @example(utcDateTime.fromISO("2023-01-01T00:00:00Z"))
-    ingestedAtTo: utcDateTime,
+    ingestedAtTo?: utcDateTime,
 
     /**
      * If not provided lists all events.
@@ -47,7 +47,7 @@ interface Events {
      */
     @query
     @example(false)
-    hasError: boolean,
+    hasError?: boolean,
 
     /**
      * The event ID.
@@ -56,7 +56,7 @@ interface Events {
      */
     @query
     @example("my-event-id")
-    id: string,
+    id?: string,
 
     /**
      * The event subject.
@@ -65,7 +65,7 @@ interface Events {
      */
     @query
     @example("customer-1")
-    subject: string,
+    subject?: string,
 
     /**
      * Start date-time in RFC 3339 format.
@@ -74,7 +74,7 @@ interface Events {
      */
     @query
     @example(utcDateTime.fromISO("2023-01-01T00:00:00Z"))
-    from: utcDateTime,
+    from?: utcDateTime,
 
     /**
      * End date-time in RFC 3339 format.
@@ -83,7 +83,7 @@ interface Events {
      */
     @query
     @example(utcDateTime.fromISO("2023-01-01T00:00:00Z"))
-    to: utcDateTime,
+    to?: utcDateTime,
 
     /**
      * Number of events to return.
@@ -92,7 +92,7 @@ interface Events {
     @minValue(1)
     @maxValue(100)
     @example(100)
-    limit: integer = 100,
+    limit?: integer = 100,
   ): IngestedEvent[] | CommonErrors;
 
   @post
diff --git a/api/spec/src/notification/rule.tsp b/api/spec/src/notification/rule.tsp
index cd11dcf72..90faa6449 100644
--- a/api/spec/src/notification/rule.tsp
+++ b/api/spec/src/notification/rule.tsp
@@ -223,7 +223,7 @@ interface Rules {
      */
     @query
     @example(true)
-    includeDeleted?: boolean,
+    includeDeleted?: boolean = false,
 
     /**
      * Include disabled notification rules in response.
@@ -232,7 +232,7 @@ interface Rules {
      */
     @query
     @example(false)
-    includeDisabled?: boolean,
+    includeDisabled?: boolean = false,
 
     // TODO(chrisgacsal): figure out if there is a way to use union type for attribute like this
     // where the code generation results a less complicated/more idiomatic code.
diff --git a/api/spec/src/portal.tsp b/api/spec/src/portal.tsp
index 652c8fd38..9b0ea90f1 100644
--- a/api/spec/src/portal.tsp
+++ b/api/spec/src/portal.tsp
@@ -77,7 +77,11 @@ interface Meters {
   @route("/{meterSlug}/query")
   @operationId("queryPortalMeter")
   @sharedRoute
-  queryJson(@path meterSlug: Key, ...OpenMeter.MeterQuery, @header accept?: "application/json" = "application/json"): {
+  queryJson(
+    @path meterSlug: Key,
+    ...OmitProperties<OpenMeter.MeterQuery, "subject">,
+    @header accept?: "application/json" = "application/json",
+  ): {
     @header contentType: "application/json";
     @body _: MeterQueryResult;
   } | NotFoundError | CommonErrors;
@@ -89,7 +93,7 @@ interface Meters {
   @route("/{meterSlug}/query")
   @operationId("queryPortalMeter")
   @sharedRoute
-  queryCsv(@path meterSlug: Key, ...OpenMeter.MeterQuery, @header accept?: "text/csv"): {
+  queryCsv(@path meterSlug: Key, ...OmitProperties<OpenMeter.MeterQuery, "subject">, @header accept?: "text/csv"): {
     @header contentType: "text/csv";
 
     @body