diff --git a/Sources/AblyChat/ChatAPI.swift b/Sources/AblyChat/ChatAPI.swift
index 947a4f1f..5142db50 100644
--- a/Sources/AblyChat/ChatAPI.swift
+++ b/Sources/AblyChat/ChatAPI.swift
@@ -32,22 +32,10 @@ internal final class ChatAPI: Sendable {
         // (CHA-M3b) A message may be sent without metadata or headers. When these are not specified by the user, they must be omitted from the REST payload.
         if let metadata = params.metadata {
             body["metadata"] = metadata
-
-            // (CHA-M3c) metadata must not contain the key ably-chat. This is reserved for future internal use. If this key is present, the send call shall terminate by throwing an ErrorInfo with code 40001.
-            if metadata.contains(where: { $0.key == "ably-chat" }) {
-                throw ARTErrorInfo.create(withCode: 40001, message: "metadata must not contain the key `ably-chat`")
-            }
         }
 
         if let headers = params.headers {
             body["headers"] = headers
-
-            // (CHA-M3d) headers must not contain a key prefixed with ably-chat. This is reserved for future internal use. If this key is present, the send call shall terminate by throwing an ErrorInfo with code 40001.
-            if headers.keys.contains(where: { keyString in
-                keyString.hasPrefix("ably-chat")
-            }) {
-                throw ARTErrorInfo.create(withCode: 40001, message: "headers must not contain any key with a prefix of `ably-chat`")
-            }
         }
 
         let response: SendMessageResponse = try await makeRequest(endpoint, method: "POST", body: body)
diff --git a/Tests/AblyChatTests/ChatAPITests.swift b/Tests/AblyChatTests/ChatAPITests.swift
index 53691da9..4c37d4df 100644
--- a/Tests/AblyChatTests/ChatAPITests.swift
+++ b/Tests/AblyChatTests/ChatAPITests.swift
@@ -5,65 +5,6 @@ import Testing
 struct ChatAPITests {
     // MARK: sendMessage Tests
 
-    // @spec CHA-M3c
-    @Test
-    func sendMessage_whenMetadataHasAblyChatAsKey_throws40001() async {
-        // Given
-        let realtime = MockRealtime.create()
-        let chatAPI = ChatAPI(realtime: realtime)
-        let roomId = "basketball::$chat::$chatMessages"
-        let expectedError = ARTErrorInfo.create(withCode: 40001, message: "metadata must not contain the key `ably-chat`")
-
-        await #expect(
-            performing: {
-                // When
-                try await chatAPI.sendMessage(roomId: roomId, params: .init(text: "hello", metadata: ["ably-chat": .null]))
-            }, throws: { error in
-                // Then
-                error as? ARTErrorInfo == expectedError
-            }
-        )
-    }
-
-    // @specOneOf(1/2) CHA-M3d
-    @Test
-    func sendMessage_whenHeadersHasAnyKeyWithPrefixOfAblyChat_throws40001() async {
-        // Given
-        let realtime = MockRealtime.create {
-            (MockHTTPPaginatedResponse.successSendMessage, nil)
-        }
-        let chatAPI = ChatAPI(realtime: realtime)
-        let roomId = "basketball::$chat::$chatMessages"
-        let expectedError = ARTErrorInfo.create(withCode: 40001, message: "headers must not contain any key with a prefix of `ably-chat`")
-
-        await #expect(
-            performing: {
-                // When
-                try await chatAPI.sendMessage(roomId: roomId, params: .init(text: "hello", headers: ["ably-chat123": .null]))
-            }, throws: { error in
-                // then
-                error as? ARTErrorInfo == expectedError
-            }
-        )
-    }
-
-    // @specOneOf(2/2) CHA-M3d
-    @Test
-    func sendMessage_whenHeadersHasAnyKeyWithSuffixOfAblyChat_doesNotThrowAnyError() async {
-        // Given
-        let realtime = MockRealtime.create {
-            (MockHTTPPaginatedResponse.successSendMessage, nil)
-        }
-        let chatAPI = ChatAPI(realtime: realtime)
-        let roomId = "basketball::$chat::$chatMessages"
-
-        // Then
-        await #expect(throws: Never.self, performing: {
-            // When
-            try await chatAPI.sendMessage(roomId: roomId, params: .init(text: "hello", headers: ["123ably-chat": .null]))
-        })
-    }
-
     @Test
     func sendMessage_whenSendMessageReturnsNoItems_throwsNoItemInResponse() async {
         // Given