diff --git a/platforms/react-native/__mocks__/react-native.ts b/platforms/react-native/__mocks__/react-native.ts
index 594df9f4..09a916cf 100644
--- a/platforms/react-native/__mocks__/react-native.ts
+++ b/platforms/react-native/__mocks__/react-native.ts
@@ -56,7 +56,14 @@ const UIManager = {
     if (name === 'RCTAcceleratedCheckoutButtons') {
       return {
         Constants: {
-          checkoutProtocolEventTypes: ['ec.start'],
+          checkoutProtocolEventTypes: [
+            'ec.complete',
+            'ec.error',
+            'ec.line_items.change',
+            'ec.messages.change',
+            'ec.start',
+            'ec.totals.change',
+          ],
         },
       };
     }
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ProtocolRelay.kt b/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ProtocolRelay.kt
index 7562bf1e..968fe8dc 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ProtocolRelay.kt
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/main/java/com/shopify/reactnative/checkoutkit/ProtocolRelay.kt
@@ -38,11 +38,36 @@ object ProtocolRelay {
         var client = CheckoutProtocol.Client()
         for (method in subscribedMethods) {
             when (method) {
+                CheckoutProtocol.complete.method -> {
+                    client = client.on(CheckoutProtocol.complete) { checkout ->
+                        forwardEnvelope(method, checkout, dispatch)
+                    }
+                }
+                CheckoutProtocol.error.method -> {
+                    client = client.on(CheckoutProtocol.error) { error ->
+                        forwardEnvelope(method, error, dispatch)
+                    }
+                }
+                CheckoutProtocol.lineItemsChange.method -> {
+                    client = client.on(CheckoutProtocol.lineItemsChange) { checkout ->
+                        forwardEnvelope(method, checkout, dispatch)
+                    }
+                }
+                CheckoutProtocol.messagesChange.method -> {
+                    client = client.on(CheckoutProtocol.messagesChange) { checkout ->
+                        forwardEnvelope(method, checkout, dispatch)
+                    }
+                }
                 CheckoutProtocol.start.method -> {
                     client = client.on(CheckoutProtocol.start) { checkout ->
                         forwardEnvelope(method, checkout, dispatch)
                     }
                 }
+                CheckoutProtocol.totalsChange.method -> {
+                    client = client.on(CheckoutProtocol.totalsChange) { checkout ->
+                        forwardEnvelope(method, checkout, dispatch)
+                    }
+                }
             }
         }
         return client
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/test/java/com/shopify/reactnative/checkoutkit/ProtocolRelayTest.kt b/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/test/java/com/shopify/reactnative/checkoutkit/ProtocolRelayTest.kt
index c31e83b2..2a612bfa 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/test/java/com/shopify/reactnative/checkoutkit/ProtocolRelayTest.kt
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/android/src/test/java/com/shopify/reactnative/checkoutkit/ProtocolRelayTest.kt
@@ -81,6 +81,56 @@ class ProtocolRelayTest {
         assertThat(firstItem["imageUrl"]?.jsonPrimitive?.content).isEqualTo("https://example.com/image.png")
     }
 
+    @Test
+    fun `relay dispatches envelope for every public checkout state event`() {
+        val methods = listOf(
+            "ec.complete",
+            "ec.line_items.change",
+            "ec.messages.change",
+            "ec.start",
+            "ec.totals.change",
+        )
+
+        for (method in methods) {
+            var captured: String? = null
+            val client = ProtocolRelay.makeClient(
+                listOf(method),
+                DispatchCallback { json -> captured = json },
+            )
+
+            client.process(checkoutNotificationFixture(method))
+            shadowOf(Looper.getMainLooper()).runToEndOfTasks()
+
+            val json = captured
+            assertThat(json).isNotNull()
+            val parsed = Json.parseToJsonElement(json!!).jsonObject
+            assertThat(parsed["type"]?.jsonPrimitive?.content).isEqualTo(method)
+            assertThat(parsed["payload"]!!.jsonObject["id"]?.jsonPrimitive?.content).isEqualTo("checkout-123")
+        }
+    }
+
+    @Test
+    fun `relay dispatches envelope on ec error`() {
+        var captured: String? = null
+        val client = ProtocolRelay.makeClient(
+            listOf("ec.error"),
+            DispatchCallback { json -> captured = json },
+        )
+
+        client.process(ecErrorNotificationFixture)
+        shadowOf(Looper.getMainLooper()).runToEndOfTasks()
+
+        val json = captured
+        assertThat(json).isNotNull()
+        val parsed = Json.parseToJsonElement(json!!).jsonObject
+        assertThat(parsed["type"]?.jsonPrimitive?.content).isEqualTo("ec.error")
+
+        val payload = parsed["payload"]!!.jsonObject
+        assertThat(payload["messages"]!!.jsonArray[0].jsonObject["content"]?.jsonPrimitive?.content)
+            .isEqualTo("Something went wrong")
+        assertThat(payload["ucp"]!!.jsonObject["status"]?.jsonPrimitive?.content).isEqualTo("error")
+    }
+
     @Test
     fun `relay ignores methods not in subscribed list`() {
         var captured: String? = null
@@ -118,6 +168,11 @@ private data class SnakePayload(
     @SerialName("line_items") val lineItems: List<String>,
 )
 
+private fun checkoutNotificationFixture(method: String) = ecStartNotificationFixture.replace(
+    "\"method\": \"ec.start\"",
+    "\"method\": \"$method\"",
+)
+
 private val ecStartNotificationFixture = """
 {
   "jsonrpc": "2.0",
@@ -156,3 +211,25 @@ private val ecStartNotificationFixture = """
   }
 }
 """.trimIndent()
+
+private val ecErrorNotificationFixture = """
+{
+  "jsonrpc": "2.0",
+  "method": "ec.error",
+  "params": {
+    "error": {
+      "ucp": {
+        "version": "2026-04-08",
+        "status": "error"
+      },
+      "messages": [
+        {
+          "type": "error",
+          "content": "Something went wrong",
+          "severity": "recoverable"
+        }
+      ]
+    }
+  }
+}
+""".trimIndent()
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ProtocolRelay.swift b/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ProtocolRelay.swift
index 084cfe25..848c5554 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ProtocolRelay.swift
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/ProtocolRelay.swift
@@ -29,7 +29,12 @@ import Foundation
 #endif
 
 let supportedProtocolRelayMethods = [
-    CheckoutProtocol.start.method
+    CheckoutProtocol.complete.method,
+    CheckoutProtocol.error.method,
+    CheckoutProtocol.lineItemsChange.method,
+    CheckoutProtocol.messagesChange.method,
+    CheckoutProtocol.start.method,
+    CheckoutProtocol.totalsChange.method
 ]
 
 func makeRelayClient(
@@ -40,10 +45,30 @@ func makeRelayClient(
 
     for method in subscribedMethods {
         switch method {
+        case CheckoutProtocol.complete.method:
+            client = client.on(CheckoutProtocol.complete) { checkout in
+                forwardEnvelope(type: method, payload: checkout, dispatch: dispatch)
+            }
+        case CheckoutProtocol.error.method:
+            client = client.on(CheckoutProtocol.error) { error in
+                forwardEnvelope(type: method, payload: error, dispatch: dispatch)
+            }
+        case CheckoutProtocol.lineItemsChange.method:
+            client = client.on(CheckoutProtocol.lineItemsChange) { checkout in
+                forwardEnvelope(type: method, payload: checkout, dispatch: dispatch)
+            }
+        case CheckoutProtocol.messagesChange.method:
+            client = client.on(CheckoutProtocol.messagesChange) { checkout in
+                forwardEnvelope(type: method, payload: checkout, dispatch: dispatch)
+            }
         case CheckoutProtocol.start.method:
             client = client.on(CheckoutProtocol.start) { checkout in
                 forwardEnvelope(type: method, payload: checkout, dispatch: dispatch)
             }
+        case CheckoutProtocol.totalsChange.method:
+            client = client.on(CheckoutProtocol.totalsChange) { checkout in
+                forwardEnvelope(type: method, payload: checkout, dispatch: dispatch)
+            }
         default:
             continue
         }
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/Tests/ProtocolRelayTests.swift b/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/Tests/ProtocolRelayTests.swift
index eec25bde..09a25d88 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/Tests/ProtocolRelayTests.swift
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/ios/Tests/ProtocolRelayTests.swift
@@ -67,6 +67,53 @@ struct ProtocolRelayTests {
         #expect(firstItem["imageUrl"] as? String == "https://example.com/image.png")
     }
 
+    @MainActor
+    @Test func relayDispatchesEnvelopeForEveryPublicCheckoutStateEvent() async throws {
+        let methods = [
+            "ec.complete",
+            "ec.line_items.change",
+            "ec.messages.change",
+            "ec.start",
+            "ec.totals.change"
+        ]
+
+        for method in methods {
+            var captured: String?
+            let client = makeRelayClient(
+                subscribedMethods: [method],
+                dispatch: { json in captured = json }
+            )
+
+            _ = await client.process(checkoutNotificationFixture(method: method))
+
+            let json = try #require(captured)
+            let parsed = try #require(JSONSerialization.jsonObject(with: Data(json.utf8)) as? [String: Any])
+            #expect(parsed["type"] as? String == method)
+            let payload = try #require(parsed["payload"] as? [String: Any])
+            #expect(payload["id"] as? String == "checkout-123")
+        }
+    }
+
+    @MainActor
+    @Test func relayDispatchesEnvelopeOnEcError() async throws {
+        var captured: String?
+        let client = makeRelayClient(
+            subscribedMethods: ["ec.error"],
+            dispatch: { json in captured = json }
+        )
+
+        _ = await client.process(ecErrorNotificationFixture)
+
+        let json = try #require(captured)
+        let parsed = try #require(JSONSerialization.jsonObject(with: Data(json.utf8)) as? [String: Any])
+        #expect(parsed["type"] as? String == "ec.error")
+        let payload = try #require(parsed["payload"] as? [String: Any])
+        let messages = try #require(payload["messages"] as? [[String: Any]])
+        #expect(messages.first?["content"] as? String == "Something went wrong")
+        let ucp = try #require(payload["ucp"] as? [String: Any])
+        #expect(ucp["status"] as? String == "error")
+    }
+
     @MainActor
     @Test func relayIgnoresMethodsNotInSubscribedList() async throws {
         var captured: String?
@@ -91,6 +138,13 @@ private struct SnakePayload: Codable {
     }
 }
 
+private func checkoutNotificationFixture(method: String) -> String {
+    ecStartNotificationFixture.replacingOccurrences(
+        of: "\"method\": \"ec.start\"",
+        with: "\"method\": \"\(method)\""
+    )
+}
+
 private let ecStartNotificationFixture = #"""
 {
   "jsonrpc": "2.0",
@@ -129,3 +183,25 @@ private let ecStartNotificationFixture = #"""
   }
 }
 """#
+
+private let ecErrorNotificationFixture = #"""
+{
+  "jsonrpc": "2.0",
+  "method": "ec.error",
+  "params": {
+    "error": {
+      "ucp": {
+        "version": "2026-04-08",
+        "status": "error"
+      },
+      "messages": [
+        {
+          "type": "error",
+          "content": "Something went wrong",
+          "severity": "recoverable"
+        }
+      ]
+    }
+  }
+}
+"""#
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/components/AcceleratedCheckoutButtons.tsx b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/components/AcceleratedCheckoutButtons.tsx
index 5fb44caf..b62a560a 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/components/AcceleratedCheckoutButtons.tsx
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/components/AcceleratedCheckoutButtons.tsx
@@ -115,7 +115,7 @@ interface CommonAcceleratedCheckoutButtonsProps {
   /**
    * Checkout Protocol event handlers scoped to this button instance.
    *
-   * Currently supports CheckoutProtocol.start.
+   * Supports all public Checkout Protocol notification events.
    */
   events?: ProtocolHandlers;
 
@@ -437,10 +437,11 @@ function routeProtocolDispatchEnvelope(
     return;
   }
 
-  const handler = (events as Record<
-    string,
-    ((payload: unknown) => void) | undefined
-  > | undefined)?.[envelope.type];
+  const handler = (
+    events as
+      | Record<string, ((payload: unknown) => void) | undefined>
+      | undefined
+  )?.[envelope.type];
 
   if (handler == null) {
     return;
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts
index a3fb8a12..2129f346 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.d.ts
@@ -23,7 +23,12 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SO
 
 import type {CheckoutException} from './errors';
 import type {ProtocolHandlers} from './protocol';
-export type {Checkout, CheckoutProtocolPayloads, ProtocolHandlers} from './protocol';
+export type {
+  Checkout,
+  CheckoutProtocolPayloads,
+  ErrorResponse,
+  ProtocolHandlers,
+} from './protocol';
 
 export type Maybe<T> = T | undefined;
 
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.ts
index 2473be19..5e974c24 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/index.ts
@@ -67,6 +67,7 @@ import {CheckoutProtocol} from './protocol';
 import type {
   Checkout,
   CheckoutProtocolPayloads,
+  ErrorResponse,
   ProtocolHandlers,
 } from './protocol';
 
@@ -155,12 +156,14 @@ class ShopifyCheckout implements ShopifyCheckoutKit {
       .map(([method]) => method);
 
     if (dispatcher) {
-      this.dispatchSubscription = RNShopifyCheckoutKit.onDispatch(envelopeJson => {
-        dispatcher(envelopeJson);
-        if (isTerminalDispatchEnvelope(envelopeJson)) {
-          this.releaseDispatchSubscription();
-        }
-      });
+      this.dispatchSubscription = RNShopifyCheckoutKit.onDispatch(
+        envelopeJson => {
+          dispatcher(envelopeJson);
+          if (isTerminalDispatchEnvelope(envelopeJson)) {
+            this.releaseDispatchSubscription();
+          }
+        },
+      );
     }
 
     RNShopifyCheckoutKit.present(checkoutUrl, subscribedMethods);
@@ -396,10 +399,12 @@ class ShopifyCheckout implements ShopifyCheckoutKit {
       const protocolHandler =
         protocol == null
           ? undefined
-          : (protocol as Record<
-              string,
-              ((payload: unknown) => void) | undefined
-            >)[type];
+          : (
+              protocol as Record<
+                string,
+                ((payload: unknown) => void) | undefined
+              >
+            )[type];
 
       if (protocolHandler) {
         if (!isPlainObject(payload)) {
@@ -673,6 +678,7 @@ export type {
   CheckoutException,
   CheckoutProtocolPayloads,
   Configuration,
+  ErrorResponse,
   Features,
   GeolocationRequestEvent,
   IosColors,
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/protocol.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/protocol.ts
index 9f5d3c1b..710075bd 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/protocol.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/src/protocol.ts
@@ -21,16 +21,26 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
 
-import type {Checkout} from '@shopify/checkout-kit-protocol';
+import type {Checkout, ErrorResponse} from '@shopify/checkout-kit-protocol';
 
-export type {Checkout} from '@shopify/checkout-kit-protocol';
+export type {Checkout, ErrorResponse} from '@shopify/checkout-kit-protocol';
 
 export const CheckoutProtocol = {
+  complete: 'ec.complete',
+  error: 'ec.error',
+  lineItemsChange: 'ec.line_items.change',
+  messagesChange: 'ec.messages.change',
   start: 'ec.start',
+  totalsChange: 'ec.totals.change',
 } as const;
 
 export interface CheckoutProtocolPayloads {
+  'ec.complete': Checkout;
+  'ec.error': ErrorResponse;
+  'ec.line_items.change': Checkout;
+  'ec.messages.change': Checkout;
   'ec.start': Checkout;
+  'ec.totals.change': Checkout;
 }
 
 export type ProtocolHandlers = Partial<{
diff --git a/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/protocol.test.ts b/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/protocol.test.ts
index e30528ff..136b41d9 100644
--- a/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/protocol.test.ts
+++ b/platforms/react-native/modules/@shopify/checkout-kit-react-native/tests/protocol.test.ts
@@ -1,33 +1,93 @@
 import {
   CheckoutProtocol,
   type Checkout,
+  type ErrorResponse,
   type ProtocolHandlers,
 } from '../src';
 
+const checkoutPayloadMethods = [
+  CheckoutProtocol.complete,
+  CheckoutProtocol.lineItemsChange,
+  CheckoutProtocol.messagesChange,
+  CheckoutProtocol.start,
+  CheckoutProtocol.totalsChange,
+] as const;
+
 describe('CheckoutProtocol', () => {
   describe('runtime values', () => {
-    it('exposes ec.start as the literal method string', () => {
-      expect(CheckoutProtocol.start).toBe('ec.start');
+    it('exposes all public checkout protocol notification method strings', () => {
+      expect(CheckoutProtocol).toEqual({
+        complete: 'ec.complete',
+        error: 'ec.error',
+        lineItemsChange: 'ec.line_items.change',
+        messagesChange: 'ec.messages.change',
+        start: 'ec.start',
+        totalsChange: 'ec.totals.change',
+      });
+      expect(CheckoutProtocol).not.toHaveProperty('buyerChange');
     });
   });
 
   describe('ProtocolHandlers typing', () => {
-    it('accepts a handler keyed by CheckoutProtocol.start', () => {
+    it('accepts handlers keyed by every public CheckoutProtocol event', () => {
       const handlers: ProtocolHandlers = {
-        [CheckoutProtocol.start]: chk => {
-          expect(typeof chk.id).toBe('string');
+        [CheckoutProtocol.complete]: checkout => {
+          expect(typeof checkout.id).toBe('string');
+        },
+        [CheckoutProtocol.error]: error => {
+          expect(error.messages).toBeDefined();
+        },
+        [CheckoutProtocol.lineItemsChange]: checkout => {
+          expect(typeof checkout.id).toBe('string');
+        },
+        [CheckoutProtocol.messagesChange]: checkout => {
+          expect(typeof checkout.id).toBe('string');
+        },
+        [CheckoutProtocol.start]: checkout => {
+          expect(typeof checkout.id).toBe('string');
+        },
+        [CheckoutProtocol.totalsChange]: checkout => {
+          expect(typeof checkout.id).toBe('string');
         },
       };
 
+      expect(typeof handlers[CheckoutProtocol.complete]).toBe('function');
+      expect(typeof handlers[CheckoutProtocol.error]).toBe('function');
+      expect(typeof handlers[CheckoutProtocol.lineItemsChange]).toBe(
+        'function',
+      );
+      expect(typeof handlers[CheckoutProtocol.messagesChange]).toBe('function');
       expect(typeof handlers[CheckoutProtocol.start]).toBe('function');
+      expect(typeof handlers[CheckoutProtocol.totalsChange]).toBe('function');
+    });
+
+    it('infers Checkout as the payload type for checkout-state events', () => {
+      type HandlerMap = ProtocolHandlers;
+      type CheckoutPayloadMethod = (typeof checkoutPayloadMethods)[number];
+      type CheckoutPayloadParam<K extends CheckoutPayloadMethod> = Parameters<
+        NonNullable<HandlerMap[K]>
+      >[0];
+
+      type AllCheckoutPayloads = {
+        [K in CheckoutPayloadMethod]: Checkout extends CheckoutPayloadParam<K>
+          ? CheckoutPayloadParam<K> extends Checkout
+            ? true
+            : false
+          : false;
+      }[CheckoutPayloadMethod];
+
+      const _typeCheck: AllCheckoutPayloads = true;
+
+      expect(_typeCheck).toBe(true);
     });
 
-    it('infers Checkout as the start handler payload type', () => {
-      type StartHandler = NonNullable<ProtocolHandlers['ec.start']>;
-      type StartParam = Parameters<StartHandler>[0];
+    it('infers ErrorResponse as the error handler payload type', () => {
+      type ErrorHandler = NonNullable<ProtocolHandlers['ec.error']>;
+      type ErrorParam = Parameters<ErrorHandler>[0];
 
-      const _typeCheck: Checkout extends StartParam ? true : false = true;
-      const _reverseCheck: StartParam extends Checkout ? true : false = true;
+      const _typeCheck: ErrorResponse extends ErrorParam ? true : false = true;
+      const _reverseCheck: ErrorParam extends ErrorResponse ? true : false =
+        true;
 
       expect(_typeCheck).toBe(true);
       expect(_reverseCheck).toBe(true);