diff --git a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactFailurePresentation.swift b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactFailurePresentation.swift
index c9dd54d5f23c..84613453228f 100644
--- a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactFailurePresentation.swift
+++ b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactFailurePresentation.swift
@@ -258,6 +258,13 @@ public struct ChatArtifactFailurePresentation: Equatable, Sendable {
                 systemImage: "doc.badge.ellipsis",
                 allowsRetry: false
             )
+        case .unknown(let code):
+            self = Self(
+                title: Self.localized("chat.artifact.failure.unknown.title", defaultValue: "Unrecognized file error"),
+                message: Self.unknownMessage(code: code),
+                systemImage: "questionmark.circle",
+                allowsRetry: true
+            )
         }
     }
 
@@ -291,6 +298,20 @@ public struct ChatArtifactFailurePresentation: Equatable, Sendable {
         String(localized: key, defaultValue: defaultValue, bundle: .module)
     }
 
+    private static func unknownMessage(code: String?) -> String {
+        guard let code, !code.isEmpty else {
+            return localized(
+                "chat.artifact.failure.unknown.message",
+                defaultValue: "The Mac reported an error this version of cmux doesn't recognize. Try again, then update cmux on both devices."
+            )
+        }
+        let format = localized(
+            "chat.artifact.failure.unknown.coded_message",
+            defaultValue: "The Mac reported an error this version of cmux doesn't recognize (%@). Try again, then update cmux on both devices."
+        )
+        return String.localizedStringWithFormat(format, code)
+    }
+
     private static func tooLargeMessage(actualSize: Int64?, limit: Int64) -> String {
         let limitText = ByteCountFormatter.string(fromByteCount: limit, countStyle: .file)
         guard let actualSize else {
diff --git a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactInlineViewer.swift b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactInlineViewer.swift
index b0c6afac4676..31afaf54743c 100644
--- a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactInlineViewer.swift
+++ b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactInlineViewer.swift
@@ -165,6 +165,8 @@ public struct ChatArtifactInlineViewer: View {
             .chat
         case .terminal:
             .terminal
+        case .panel:
+            .panel
         case .workspaceChanges:
             .workspaceChanges
         case .unsupported:
diff --git a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactViewerModel.swift b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactViewerModel.swift
index a9918cf7d0f0..2776b6372bb1 100644
--- a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactViewerModel.swift
+++ b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Artifacts/ChatArtifactViewerModel.swift
@@ -339,7 +339,7 @@ final class ChatArtifactViewerModel {
         await temporaryFileStore.remove(temporaryFileURL)
     }
 
-    private static func state(
+    static func state(
         for error: any Error,
         stat: ChatArtifactStat?
     ) -> ChatArtifactViewerState {
diff --git a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Resources/Localizable.xcstrings b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Resources/Localizable.xcstrings
index febcf4b84000..e27cea8391d3 100644
--- a/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Resources/Localizable.xcstrings
+++ b/Packages/iOS/CmuxAgentChatUI/Sources/CmuxAgentChatUI/Resources/Localizable.xcstrings
@@ -330,6 +330,27 @@
         "ja": { "stringUnit": { "state": "translated", "value": "転送が中断されました" } }
       }
     },
+    "chat.artifact.failure.unknown.coded_message": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": { "stringUnit": { "state": "translated", "value": "The Mac reported an error this version of cmux doesn't recognize (%@). Try again, then update cmux on both devices." } },
+        "ja": { "stringUnit": { "state": "translated", "value": "Macがこのバージョンのcmuxでは認識できないエラーを報告しました（%@）。もう一度お試しのうえ、両方のデバイスでcmuxをアップデートしてください。" } }
+      }
+    },
+    "chat.artifact.failure.unknown.message": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": { "stringUnit": { "state": "translated", "value": "The Mac reported an error this version of cmux doesn't recognize. Try again, then update cmux on both devices." } },
+        "ja": { "stringUnit": { "state": "translated", "value": "Macがこのバージョンのcmuxでは認識できないエラーを報告しました。もう一度お試しのうえ、両方のデバイスでcmuxをアップデートしてください。" } }
+      }
+    },
+    "chat.artifact.failure.unknown.title": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": { "stringUnit": { "state": "translated", "value": "Unrecognized file error" } },
+        "ja": { "stringUnit": { "state": "translated", "value": "認識できないファイルエラー" } }
+      }
+    },
     "chat.artifact.failure.unsupported.message": {
       "extractionState": "manual",
       "localizations": {
diff --git a/Packages/iOS/CmuxAgentChatUI/Tests/CmuxAgentChatUITests/ChatArtifactFailurePresentationTests.swift b/Packages/iOS/CmuxAgentChatUI/Tests/CmuxAgentChatUITests/ChatArtifactFailurePresentationTests.swift
index 03f57c2fb10a..e883962eae21 100644
--- a/Packages/iOS/CmuxAgentChatUI/Tests/CmuxAgentChatUITests/ChatArtifactFailurePresentationTests.swift
+++ b/Packages/iOS/CmuxAgentChatUI/Tests/CmuxAgentChatUITests/ChatArtifactFailurePresentationTests.swift
@@ -43,6 +43,8 @@ struct ChatArtifactFailurePresentationTests {
             (.localStorageUnavailable, "Local storage unavailable", true),
             (.loadFailed, "Couldn't load file", true),
             (.tooLarge(limitBytes: 1_024), "File too large to preview", false),
+            (.unknown(code: "future_error"), "Unrecognized file error", true),
+            (.unknown(code: nil), "Unrecognized file error", true),
         ]
 
         #expect(unreachable.title == "Mac unreachable")