diff --git a/src/main/Notification/WindmillNotificationClient.java b/src/main/Notification/WindmillNotificationClient.java
new file mode 100644
index 00000000..aeb9182f
--- /dev/null
+++ b/src/main/Notification/WindmillNotificationClient.java
@@ -0,0 +1,112 @@
+package Notification;
+
+import okhttp3.*;
+import com.google.gson.Gson;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+import java.util.regex.Pattern;
+
+import lombok.extern.slf4j.Slf4j;
+import org.jetbrains.annotations.NotNull;
+
+@Slf4j
+public class WindmillNotificationClient {
+    private final OkHttpClient client;
+    private final Gson gson;
+    private final String WINDMILL_URL;
+    private final String WINDMILL_TOKEN;
+    private final String TWILIO_PHONE_NUMBER;
+    private final Map<String, String> twilioResource;
+    private final Pattern PHONE_PATTERN = Pattern.compile("\\+1\\d{10}"); // +1 followed by 10 digits
+
+    public WindmillNotificationClient() {
+        this.client = new OkHttpClient.Builder()
+                .connectTimeout(30, TimeUnit.SECONDS)
+                .readTimeout(30, TimeUnit.SECONDS)
+                .writeTimeout(30, TimeUnit.SECONDS)
+                .build();
+        this.gson = new Gson();
+        this.WINDMILL_URL = System.getenv("WINDMILL_URL");
+        this.WINDMILL_TOKEN = System.getenv("WINDMILL_TOKEN");
+        this.TWILIO_PHONE_NUMBER = System.getenv("TWILIO_PHONE_NUMBER");
+        this.twilioResource = new HashMap<>();
+        String TWILIO_ACCOUNT_SID = System.getenv("ACCOUNT_SID");
+        String TWILIO_AUTH_TOKEN = System.getenv("AUTH_TOKEN_TWILIO");
+        this.twilioResource.put("accountSid", TWILIO_ACCOUNT_SID);
+        this.twilioResource.put("token", TWILIO_AUTH_TOKEN);
+    }
+
+    // Constructor for testing
+    public WindmillNotificationClient(String windmillUrl, String windmillToken, String twilioPhoneNumber,
+                                      String twilioAccountSid, String twilioAuthToken) {
+        this.client = new OkHttpClient();
+        this.gson = new Gson();
+        this.WINDMILL_URL = windmillUrl;
+        this.WINDMILL_TOKEN = windmillToken;
+        this.TWILIO_PHONE_NUMBER = twilioPhoneNumber;
+        this.twilioResource = new HashMap<>();
+        this.twilioResource.put("accountSid", twilioAccountSid);
+        this.twilioResource.put("token", twilioAuthToken);
+    }
+
+    public boolean isValidPhoneNumber(String phoneNumber) {
+        return phoneNumber != null && this.PHONE_PATTERN.matcher(phoneNumber).matches();
+    }
+
+    public void executeRequest(Request request, Callback callback) {
+        client.newCall(request).enqueue(callback);
+    }
+
+    public void sendSms(String to, String message) {
+        if (!isValidPhoneNumber(to)) {
+            log.error("sendSms failed: invalid phone number provided: {}", to);
+            return;
+        }
+        if (message == null || message.isBlank()) {
+            log.error("sendSms failed: empty message provided: {}", message);
+            return;
+        }
+
+        Map<String, Object> payload = Map.of(
+                "method", "sms",
+                "message", message,
+                "sms_config", Map.of(
+                        "twilio_auth", twilioResource,
+                        "to_phone_number", to,
+                        "from_phone_number", this.TWILIO_PHONE_NUMBER
+                ),
+                "email_config", Map.of()
+        );
+
+        Request request = new Request.Builder()
+                .url(this.WINDMILL_URL)
+                .post(RequestBody.create(gson.toJson(payload), MediaType.parse("application/json")))
+                .addHeader("Authorization", "Bearer " + this.WINDMILL_TOKEN)
+                .build();
+
+        log.info("Sending SMS to {} with message: {}", to, message);
+
+        Callback callback = new Callback() {
+            public void onFailure(@NotNull Call call, @NotNull IOException e) {
+                log.error("sendSms failed: " + e.getMessage());
+            }
+
+            public void onResponse(@NotNull Call call, @NotNull Response response) {
+                try (response) {
+                    if (response.isSuccessful()) {
+                        log.info("sent SMS successfully. Status: {}", response.code());
+                    } else {
+                        log.warn("SMS request completed but failed. Status: {}, Body: {}",
+                                response.code(), response.body() != null ? response.body().string() : "");
+                    }
+                } catch (IOException e) {
+                    log.error("caught error reading SMS response: " + e.getMessage());
+                }
+            }
+        };
+        executeRequest(request, callback);
+    }
+}
diff --git a/src/test/NotificationTest/WindmillNotificationClientTest.java b/src/test/NotificationTest/WindmillNotificationClientTest.java
new file mode 100644
index 00000000..ee9ebb87
--- /dev/null
+++ b/src/test/NotificationTest/WindmillNotificationClientTest.java
@@ -0,0 +1,48 @@
+package NotificationTest;
+
+import Notification.WindmillNotificationClient;
+import lombok.extern.slf4j.Slf4j;
+import okhttp3.Callback;
+import okhttp3.Request;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+@Slf4j
+public class WindmillNotificationClientTest {
+
+    WindmillNotificationClient client = new WindmillNotificationClient("http://localhost",
+            "test_windmill_token", "test_twilio_phone_number",
+            "test_twilio_account_sid", "test_twilio_auth_token");
+    @Test
+    public void sendSMSSuccess() {
+        var testClient = new WindmillNotificationClient("http://localhost",
+                "test_windmill_token", "test_twilio_phone_number",
+                "test_twilio_account_sid", "test_twilio_auth_token") {
+            @Override
+            public void executeRequest(Request request, Callback callback) {
+                // Don't actually send, just verify the request looks right
+                assertNotNull(request);
+                assertEquals("POST", request.method());
+            }
+        };
+
+        assertDoesNotThrow(() -> testClient.sendSms("+12025551234", "Test"));
+    }
+
+    @Test
+    public void testValidPhoneNumbers() {
+        assertTrue(client.isValidPhoneNumber("+12025551234"));
+        assertTrue(client.isValidPhoneNumber("+19999999999"));
+    }
+
+    @Test
+    public void testInvalidPhoneNumbers() {
+        assertFalse(client.isValidPhoneNumber("12025551234")); // missing +
+        assertFalse(client.isValidPhoneNumber("+44123456789")); // wrong country code
+        assertFalse(client.isValidPhoneNumber("+1202555123")); // too few digits
+        assertFalse(client.isValidPhoneNumber("+120255512345")); // too many digits
+        assertFalse(client.isValidPhoneNumber(null));
+    }
+}
diff --git a/src/test/NotificationTest/WindmillWebhookManualTest.java b/src/test/NotificationTest/WindmillWebhookManualTest.java
new file mode 100644
index 00000000..6caf821c
--- /dev/null
+++ b/src/test/NotificationTest/WindmillWebhookManualTest.java
@@ -0,0 +1,25 @@
+package NotificationTest;
+
+import Notification.WindmillNotificationClient;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+// Sends actual webhooks to windmill
+// Need to set environment variables in run configuration in Intellij (look at WindmillNotificationClient.java)
+class WindmillWebhookManualTest {
+
+    @Test
+    void sendSms() throws InterruptedException {
+        WindmillNotificationClient client = new WindmillNotificationClient();
+
+        System.out.println("Sending webhook...");
+        assertDoesNotThrow(() -> {
+            client.sendSms("TEST_PHONE_NUMBER_HERE", "Test payload");
+        });
+        System.out.println("Done! Check the webhook dashboard to verify receipt.");
+
+        // wait for callback
+        Thread.sleep(10000);
+    }
+}