diff --git a/@packages/imessage/Sources/IMessageSync/BlobSyncManager.swift b/@packages/imessage/Sources/IMessageSync/BlobSyncManager.swift
index d3134e5..30ea9c1 100644
--- a/@packages/imessage/Sources/IMessageSync/BlobSyncManager.swift
+++ b/@packages/imessage/Sources/IMessageSync/BlobSyncManager.swift
@@ -169,8 +169,19 @@ final class BlobSyncManager: @unchecked Sendable {
     private func uploadBlob(id: String, data: Data, contentType: String) async throws -> String {
         let path = "/client/imessage/attachments/\(id)/blob"
 
-        let responseData = try await apiClient.authenticatedMultipartUpload(path) { form in
-            form.append(data, withName: "blob", fileName: "blob", mimeType: contentType)
+        // Diagnostic: token presence at upload time
+        let tokenPresent = ((try? apiClient.getAuthToken()) ?? nil) != nil
+        log.info("BlobSyncManager: uploadBlob id=\(id) bytes=\(data.count) tokenPresent=\(tokenPresent)")
+
+        let responseData: Data
+        do {
+            responseData = try await apiClient.authenticatedMultipartUpload(path) { form in
+                form.append(data, withName: "blob", fileName: "blob", mimeType: contentType)
+            }
+        } catch {
+            let ns = error as NSError
+            log.warning("BlobSyncManager: uploadBlob error id=\(id) domain=\(ns.domain) code=\(ns.code) desc=\(error.localizedDescription) full=\(String(describing: error))")
+            throw error
         }
 
         let json = JSON(responseData)