diff --git a/src/core/http.ts b/src/core/http.ts
index 9685aff..34817e9 100644
--- a/src/core/http.ts
+++ b/src/core/http.ts
@@ -29,19 +29,19 @@ export class HttpHandler {
         this.#baseUrl = props.urlEndpoint ?? DefaultEndpoint
     }
 
-    async get<T = unknown>(path: string, data?: unknown): Promise<T> {
+    async get<T = unknown>(path: string, data?: unknown): Promise<T | undefined> {
         return this.#request<T>('GET', path, data)
     }
 
-    async post<T = unknown>(path: string, data?: unknown): Promise<T> {
+    async post<T = unknown>(path: string, data?: unknown): Promise<T | undefined> {
         return this.#request<T>('POST', path, data)
     }
 
-    async delete<T = unknown>(path: string, data?: unknown): Promise<T> {
+    async delete<T = unknown>(path: string, data?: unknown): Promise<T | undefined> {
         return this.#request<T>('DELETE', path, data)
     }
 
-    async #request<T>(method: HttpMethod, path: string, data?: unknown): Promise<T> {
+    async #request<T>(method: HttpMethod, path: string, data?: unknown): Promise<T | undefined> {
         const url = `${this.#baseUrl}/client/${path}`
 
         try {
@@ -65,17 +65,22 @@ export class HttpHandler {
         }
     }
 
-    async #handleResponse<T>(response: Response): Promise<T> {
+    async #handleResponse<T>(response: Response): Promise<T | undefined> {
         if (!response.ok) {
             throw await this.#mapError(response)
         }
 
+        const contentLength = response.headers.get('content-length')
+        if (contentLength === '0') {
+            return undefined
+        }
+
         const contentType = response.headers.get('content-type')
         if (!contentType || !contentType.includes('application/json')) {
-            return undefined as T
+            return undefined
         }
 
-        return response.json() as Promise<T>
+        return response.json()
     }
 
     async #mapError(response: Response): Promise<LunogramError> {
diff --git a/src/core/resources/base.ts b/src/core/resources/base.ts
index 5f418bf..d1c05df 100644
--- a/src/core/resources/base.ts
+++ b/src/core/resources/base.ts
@@ -9,15 +9,15 @@ export abstract class BaseResource {
 
     protected abstract readonly endpoint: string
 
-    protected async get<T = unknown>(data?: unknown): Promise<T> {
+    protected async get<T = unknown>(data?: unknown): Promise<T | undefined> {
         return this.#http.get<T>(this.endpoint, data)
     }
 
-    protected async post<T = unknown>(data?: unknown, pathOverride?: string): Promise<T> {
+    protected async post<T = unknown>(data?: unknown, pathOverride?: string): Promise<T | undefined> {
         return this.#http.post<T>(pathOverride ?? this.endpoint, data)
     }
 
-    protected async remove<T = unknown>(data?: unknown, pathOverride?: string): Promise<T> {
+    protected async remove<T = unknown>(data?: unknown, pathOverride?: string): Promise<T | undefined> {
         return this.#http.delete<T>(pathOverride ?? this.endpoint, data)
     }
 }
diff --git a/src/core/resources/organizations/events.ts b/src/core/resources/organizations/events.ts
index 8e7face..6a70c85 100644
--- a/src/core/resources/organizations/events.ts
+++ b/src/core/resources/organizations/events.ts
@@ -8,7 +8,7 @@ export class OrganizationEventsResource extends BaseResource {
      * Posts organization events for asynchronous processing.
      * @param data - Array of organization events
      */
-    async post<T = unknown>(data: OrganizationEvent[]): Promise<T> {
-        return super.post(data)
+    async post<T = unknown>(data: OrganizationEvent[]): Promise<T | undefined> {
+        return super.post<T>(data)
     }
 }
diff --git a/src/core/resources/organizations/organization.ts b/src/core/resources/organizations/organization.ts
index 19b291a..10c370b 100644
--- a/src/core/resources/organizations/organization.ts
+++ b/src/core/resources/organizations/organization.ts
@@ -26,8 +26,8 @@ export class OrganizationResource extends BaseResource {
      * @param data - Organization data including identifier, name, data, etc.
      * @returns Promise resolving to the created/updated organization
      */
-    async upsert(data: OrganizationRequest): Promise<OrganizationResponse> {
-        return this.post(data)
+    async upsert(data: OrganizationRequest): Promise<OrganizationResponse | undefined> {
+        return this.post<OrganizationResponse>(data)
     }
 
     /**
@@ -36,7 +36,7 @@ export class OrganizationResource extends BaseResource {
      * @returns Promise resolving when organization is deleted
      */
     async delete(data: DeleteOrganizationRequest): Promise<void> {
-        return this.remove(data)
+        return this.remove<void>(data)
     }
 
     /**
@@ -45,7 +45,7 @@ export class OrganizationResource extends BaseResource {
      * @returns Promise resolving when user is added
      */
     async addUser(data: OrganizationUserRequest): Promise<void> {
-        return this.post(data, 'organizations/users')
+        return this.post<void>(data, 'organizations/users')
     }
 
     /**
@@ -54,6 +54,6 @@ export class OrganizationResource extends BaseResource {
      * @returns Promise resolving when user is removed
      */
     async removeUser(data: RemoveOrganizationUserRequest): Promise<void> {
-        return this.remove(data, 'organizations/users')
+        return this.remove<void>(data, 'organizations/users')
     }
 }
diff --git a/src/core/resources/organizations/scheduled.ts b/src/core/resources/organizations/scheduled.ts
index af2f77d..97d7f1f 100644
--- a/src/core/resources/organizations/scheduled.ts
+++ b/src/core/resources/organizations/scheduled.ts
@@ -16,8 +16,8 @@ export class OrganizationScheduledResource extends BaseResource {
      * @param data - Scheduled resource data including name, identifier, scheduledAt, interval, etc.
      * @returns Promise resolving to the accepted scheduled resource
      */
-    async upsert(data: UpsertOrganizationScheduledRequest): Promise<ScheduledAcceptedResponse> {
-        return this.post(data)
+    async upsert(data: UpsertOrganizationScheduledRequest): Promise<ScheduledAcceptedResponse | undefined> {
+        return this.post<ScheduledAcceptedResponse>(data)
     }
 
     /**
@@ -26,6 +26,6 @@ export class OrganizationScheduledResource extends BaseResource {
      * @returns Promise resolving when scheduled resource is deleted
      */
     async delete(data: DeleteOrganizationScheduledRequest): Promise<void> {
-        return this.remove(data)
+        return this.remove<void>(data)
     }
 }
diff --git a/src/core/resources/users/events.ts b/src/core/resources/users/events.ts
index 39c3c48..31b0d65 100644
--- a/src/core/resources/users/events.ts
+++ b/src/core/resources/users/events.ts
@@ -8,7 +8,7 @@ export class UserEventsResource extends BaseResource {
      * Posts user events for asynchronous processing.
      * @param data - Array of user events
      */
-    async post<T = unknown>(data: UserEvent[]): Promise<T> {
-        return super.post(data)
+    async post<T = unknown>(data: UserEvent[]): Promise<T | undefined> {
+        return super.post<T>(data)
     }
 }
diff --git a/src/core/resources/users/scheduled.ts b/src/core/resources/users/scheduled.ts
index bc033af..a25a597 100644
--- a/src/core/resources/users/scheduled.ts
+++ b/src/core/resources/users/scheduled.ts
@@ -16,8 +16,8 @@ export class UserScheduledResource extends BaseResource {
      * @param data - Scheduled resource data including name, identifier, scheduledAt, interval, etc.
      * @returns Promise resolving to the accepted scheduled resource
      */
-    async upsert(data: UpsertUserScheduledRequest): Promise<ScheduledAcceptedResponse> {
-        return this.post(data)
+    async upsert(data: UpsertUserScheduledRequest): Promise<ScheduledAcceptedResponse | undefined> {
+        return this.post<ScheduledAcceptedResponse>(data)
     }
 
     /**
@@ -26,6 +26,6 @@ export class UserScheduledResource extends BaseResource {
      * @returns Promise resolving when scheduled resource is deleted
      */
     async delete(data: DeleteUserScheduledRequest): Promise<void> {
-        return this.remove(data)
+        return this.remove<void>(data)
     }
 }
diff --git a/src/core/resources/users/user.ts b/src/core/resources/users/user.ts
index 5af36fb..e72abc8 100644
--- a/src/core/resources/users/user.ts
+++ b/src/core/resources/users/user.ts
@@ -24,8 +24,8 @@ export class UserResource extends BaseResource {
      * @param data - User data including identifier, email, phone, etc.
      * @returns Promise resolving to the created/updated user
      */
-    async upsert(data: UpsertUserRequest): Promise<UserResponse> {
-        return this.post(data)
+    async upsert(data: UpsertUserRequest): Promise<UserResponse | undefined> {
+        return this.post<UserResponse>(data)
     }
 
     /**
@@ -34,6 +34,6 @@ export class UserResource extends BaseResource {
      * @returns Promise resolving when user is deleted
      */
     async delete(data: DeleteUserRequest): Promise<void> {
-        return this.remove(data)
+        return this.remove<void>(data)
     }
 }
diff --git a/src/platform/browser.ts b/src/platform/browser.ts
index 99e068c..91c11e0 100644
--- a/src/platform/browser.ts
+++ b/src/platform/browser.ts
@@ -24,14 +24,14 @@ class BrowserUserEventsResource extends UserEventsResource {
         this.#getIdentifier = getIdentifier
     }
 
-    async post<T = unknown>(data: UserEvent[]): Promise<T> {
+    async post<T = unknown>(data: UserEvent[]): Promise<T | undefined> {
         const identifier = this.#getIdentifier()
         const injected = data.map((event) => ({
             ...event,
             // Do not inject identifier when `match` is used (they are mutually exclusive)
             identifier: event.match ? event.identifier : (event.identifier ?? identifier),
         }))
-        return super.post(injected) as Promise<T>
+        return super.post<T>(injected)
     }
 }
 
@@ -43,7 +43,7 @@ class BrowserUserScheduledResource extends UserScheduledResource {
         this.#getIdentifier = getIdentifier
     }
 
-    async upsert(data: UpsertUserScheduledRequest): Promise<ScheduledAcceptedResponse> {
+    async upsert(data: UpsertUserScheduledRequest): Promise<ScheduledAcceptedResponse | undefined> {
         return super.upsert({
             ...data,
             identifier: data.identifier ?? this.#getIdentifier(),
@@ -113,7 +113,7 @@ class BrowserUserResource extends UserResource {
         return identifier
     }
 
-    async upsert(data: UpsertUserRequest): Promise<UserResponse> {
+    async upsert(data: UpsertUserRequest): Promise<UserResponse | undefined> {
         const identifier = this.#buildIdentifier(data.identifier)
         return super.upsert({ ...data, identifier })
     }