diff --git a/assistant/src/daemon/handlers/sessions.ts b/assistant/src/daemon/handlers/sessions.ts
index 9df93fc40a5..d610e96cc2b 100644
--- a/assistant/src/daemon/handlers/sessions.ts
+++ b/assistant/src/daemon/handlers/sessions.ts
@@ -348,17 +348,20 @@ export function handleHistoryRequest(
     if (m.role === 'assistant' && m.id) {
       const linked = getAttachmentsForMessageUnscoped(m.id);
       if (linked.length > 0) {
-        // Skip embedding base64 data for attachments larger than 512KB to keep
-        // the history_response payload small enough for the client to decode
-        // reliably. The client fetches large attachment data lazily via HTTP.
+        // Skip embedding base64 data for large video attachments to keep the
+        // history_response payload small. Only videos have a lazy-fetch path on
+        // the client, so non-video attachments always keep their inline data.
         const MAX_INLINE_B64_SIZE = 512 * 1024;
-        attachments = linked.map((a) => ({
-          id: a.id,
-          filename: a.originalFilename,
-          mimeType: a.mimeType,
-          data: a.dataBase64.length > MAX_INLINE_B64_SIZE ? '' : a.dataBase64,
-          ...(a.dataBase64.length > MAX_INLINE_B64_SIZE ? { sizeBytes: a.sizeBytes } : {}),
-        }));
+        attachments = linked.map((a) => {
+          const omit = a.mimeType.startsWith('video/') && a.dataBase64.length > MAX_INLINE_B64_SIZE;
+          return {
+            id: a.id,
+            filename: a.originalFilename,
+            mimeType: a.mimeType,
+            data: omit ? '' : a.dataBase64,
+            ...(omit ? { sizeBytes: a.sizeBytes } : {}),
+          };
+        });
       }
     }
     return {
diff --git a/clients/macos/vellum-assistant/Features/Chat/MediaEmbeds/InlineVideoAttachmentView.swift b/clients/macos/vellum-assistant/Features/Chat/MediaEmbeds/InlineVideoAttachmentView.swift
index 80f11bb7b18..06ebb969f96 100644
--- a/clients/macos/vellum-assistant/Features/Chat/MediaEmbeds/InlineVideoAttachmentView.swift
+++ b/clients/macos/vellum-assistant/Features/Chat/MediaEmbeds/InlineVideoAttachmentView.swift
@@ -189,13 +189,19 @@ struct InlineVideoAttachmentView: View {
                 do {
                     let base64 = try await fetchAttachmentData(port: port, attachmentId: attachmentId)
                     guard let data = Data(base64Encoded: base64) else {
-                        await MainActor.run { isLoading = false }
+                        await MainActor.run {
+                            isLoading = false
+                            failed = true
+                        }
                         return
                     }
                     try data.write(to: destURL)
                     await MainActor.run { isLoading = false }
                 } catch {
-                    await MainActor.run { isLoading = false }
+                    await MainActor.run {
+                        isLoading = false
+                        failed = true
+                    }
                 }
             }
         } else {
@@ -211,7 +217,13 @@ struct InlineVideoAttachmentView: View {
             Task {
                 do {
                     let base64 = try await fetchAttachmentData(port: port, attachmentId: attachmentId)
-                    guard let data = Data(base64Encoded: base64) else { return }
+                    guard let data = Data(base64Encoded: base64) else {
+                        await MainActor.run {
+                            isLoading = false
+                            failed = true
+                        }
+                        return
+                    }
                     let fileURL = safeTempURL()
                     try data.write(to: fileURL)
                     await MainActor.run {