diff --git a/apps/ios/Tests/IOSGatewayChatTransportTests.swift b/apps/ios/Tests/IOSGatewayChatTransportTests.swift
index 2071e3cd7c88..1ba54fe3d2e2 100644
--- a/apps/ios/Tests/IOSGatewayChatTransportTests.swift
+++ b/apps/ios/Tests/IOSGatewayChatTransportTests.swift
@@ -1,9 +1,9 @@
 import Foundation
-import OpenClawChatUI
 import OpenClawKit
 import OpenClawProtocol
 import Testing
 @testable import OpenClaw
+@testable import OpenClawChatUI
 
 struct IOSGatewayChatTransportTests {
     private actor RequestRecorder {
@@ -354,11 +354,104 @@ struct IOSGatewayChatTransportTests {
             #expect(message.messageSeq == 7)
             #expect(message.message?.role == "assistant")
             #expect(message.message?.content.first?.text == "agent reply")
+            #expect(message.message?.transcriptMessageID == "msg-1")
         default:
             Issue.record("expected .sessionMessage from session.message event, got \(String(describing: mapped))")
         }
     }
 
+    @Test @MainActor func `canonical transcript identity deduplicates replayed assistant messages`() {
+        let original = Self.canonicalAssistantMessage(timestamp: 1234.5)
+        let replay = Self.canonicalAssistantMessage(timestamp: 5678.5)
+
+        let messages = OpenClawChatViewModel.dedupeMessages([original, replay])
+
+        #expect(messages.count == 1)
+        #expect(messages.first?.transcriptMessageID == "canonical-assistant-1")
+    }
+
+    @Test @MainActor func `distinct transcript identities preserve identical assistant replies`() {
+        let first = Self.canonicalAssistantMessage(timestamp: 1234.5)
+        let second = Self.canonicalAssistantMessage(
+            timestamp: 1234.5,
+            transcriptMessageID: "canonical-assistant-2")
+
+        let messages = OpenClawChatViewModel.dedupeMessages([first, second])
+
+        #expect(messages.count == 2)
+        #expect(messages.map(\.transcriptMessageID) == ["canonical-assistant-1", "canonical-assistant-2"])
+    }
+
+    @Test @MainActor func `history reconciles a replay by its canonical transcript identity`() {
+        let original = Self.canonicalAssistantMessage(timestamp: 1234.5)
+        let replay = Self.canonicalAssistantMessage(timestamp: 5678.5)
+
+        let messages = OpenClawChatViewModel.reconcileMessageIDs(
+            previous: [original],
+            incoming: [replay])
+
+        #expect(messages.count == 1)
+        #expect(messages.first?.id == original.id)
+        #expect(messages.first?.timestamp == replay.timestamp)
+        #expect(messages.first?.transcriptMessageID == "canonical-assistant-1")
+    }
+
+    @Test @MainActor func `canonical adoption keeps the durable transcript identity`() {
+        let existing = OpenClawChatMessage(
+            role: "assistant",
+            content: [Self.assistantText],
+            timestamp: 1234.5)
+        let incoming = Self.canonicalAssistantMessage(timestamp: 5678.5)
+
+        let adopted = OpenClawChatViewModel.adoptingCanonicalMessage(incoming, over: existing)
+
+        #expect(adopted.id == existing.id)
+        #expect(adopted.timestamp == incoming.timestamp)
+        #expect(adopted.transcriptMessageID == "canonical-assistant-1")
+    }
+
+    @Test @MainActor func `user idempotency still reconciles an optimistic canonical echo`() {
+        let original = OpenClawChatMessage(
+            role: "user",
+            content: [Self.assistantText],
+            timestamp: 1234.5,
+            idempotencyKey: "run-1:user")
+        let echo = OpenClawChatMessage(
+            role: "user",
+            content: [Self.assistantText],
+            timestamp: 5678.5,
+            transcriptMessageID: "canonical-user-1",
+            idempotencyKey: "run-1:user")
+
+        let messages = OpenClawChatViewModel.reconcileMessageIDs(
+            previous: [original],
+            incoming: [echo])
+
+        #expect(messages.count == 1)
+        #expect(messages.first?.id == original.id)
+        #expect(messages.first?.transcriptMessageID == "canonical-user-1")
+    }
+
+    private static var assistantText: OpenClawChatMessageContent {
+        OpenClawChatMessageContent(
+            type: "text",
+            text: "agent reply",
+            mimeType: nil,
+            fileName: nil,
+            content: nil)
+    }
+
+    private static func canonicalAssistantMessage(
+        timestamp: Double,
+        transcriptMessageID: String = "canonical-assistant-1") -> OpenClawChatMessage
+    {
+        OpenClawChatMessage(
+            role: "assistant",
+            content: [self.assistantText],
+            timestamp: timestamp,
+            transcriptMessageID: transcriptMessageID)
+    }
+
     @Test func `maps sessions changed event to authoritative refresh signal`() {
         let payload = AnyCodable([
             "sessionKey": AnyCodable("agent:main:main"),
diff --git a/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatGatewayPayloadCodec.swift b/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatGatewayPayloadCodec.swift
index 6ec152fce86a..41620a9f293d 100644
--- a/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatGatewayPayloadCodec.swift
+++ b/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatGatewayPayloadCodec.swift
@@ -138,6 +138,22 @@ public enum OpenClawChatGatewayPayloadCodec {
                       payload,
                       as: OpenClawSessionMessageEventPayload.self)
             else { return nil }
+            if var canonicalMessage = message.message,
+               canonicalMessage.transcriptMessageID?
+                   .trimmingCharacters(in: .whitespacesAndNewlines).isEmpty != false,
+                   let messageID = message.messageId?.trimmingCharacters(in: .whitespacesAndNewlines),
+                   !messageID.isEmpty
+            {
+                // Live events carry durable transcript identity on their envelope.
+                // Preserve it on the row so history cannot replay the same message.
+                canonicalMessage.transcriptMessageID = messageID
+                return .sessionMessage(OpenClawSessionMessageEventPayload(
+                    sessionKey: message.sessionKey,
+                    agentId: message.agentId,
+                    message: canonicalMessage,
+                    messageId: message.messageId,
+                    messageSeq: message.messageSeq))
+            }
             return .sessionMessage(message)
         case "agent":
             guard let payload = frame.payload,
diff --git a/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatViewModel+HistoryReconciliation.swift b/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatViewModel+HistoryReconciliation.swift
index 08dedc173b78..8ac371108238 100644
--- a/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatViewModel+HistoryReconciliation.swift
+++ b/apps/shared/OpenClawKit/Sources/OpenClawChatUI/ChatViewModel+HistoryReconciliation.swift
@@ -92,6 +92,9 @@ extension OpenClawChatViewModel {
         if let idempotencyKey = Self.normalizedIdempotencyKey(message.idempotencyKey) {
             return [role, "idempotency", idempotencyKey].joined(separator: "|")
         }
+        if let transcriptMessageID = Self.normalizedTranscriptMessageID(message.transcriptMessageID) {
+            return [role, "transcript", transcriptMessageID].joined(separator: "|")
+        }
 
         let timestamp: String = {
             guard let value = message.timestamp, value.isFinite else { return "" }
@@ -146,6 +149,11 @@ extension OpenClawChatViewModel {
         return trimmed.isEmpty ? nil : trimmed
     }
 
+    private static func normalizedTranscriptMessageID(_ id: String?) -> String? {
+        let trimmed = id?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
+        return trimmed.isEmpty ? nil : trimmed
+    }
+
     static func adoptingCanonicalMessage(
         _ incoming: OpenClawChatMessage,
         over existing: OpenClawChatMessage) -> OpenClawChatMessage
@@ -157,6 +165,7 @@ extension OpenClawChatViewModel {
                 in: incoming.content,
                 from: existing.content),
             timestamp: incoming.timestamp ?? existing.timestamp,
+            transcriptMessageID: incoming.transcriptMessageID ?? existing.transcriptMessageID,
             idempotencyKey: incoming.idempotencyKey,
             toolCallId: incoming.toolCallId,
             toolName: incoming.toolName,
@@ -696,6 +705,9 @@ extension OpenClawChatViewModel {
         if let idempotencyKey = normalizedIdempotencyKey(message.idempotencyKey) {
             return "\(message.role)|idempotency|\(idempotencyKey)"
         }
+        if let transcriptMessageID = normalizedTranscriptMessageID(message.transcriptMessageID) {
+            return "\(message.role)|transcript|\(transcriptMessageID)"
+        }
         guard let timestamp = message.timestamp else { return nil }
         let text = message.content.compactMap(\.text).joined(separator: "\n")
             .trimmingCharacters(in: .whitespacesAndNewlines)