diff --git a/src/OutlookAddin.Core/Services/EspoCrmClient.cs b/src/OutlookAddin.Core/Services/EspoCrmClient.cs
index 7dadfaa..af50309 100644
--- a/src/OutlookAddin.Core/Services/EspoCrmClient.cs
+++ b/src/OutlookAddin.Core/Services/EspoCrmClient.cs
@@ -209,9 +209,10 @@ namespace MarcusLaw.OutlookAddin.Core.Services
 
             var mime = string.IsNullOrWhiteSpace(contentType) ? "application/octet-stream" : contentType;
             var dataUri = "data:" + mime + ";base64," + base64Content;
-            // Some EspoCRM versions read the binary from the field named in the
-            // `field` property (i.e. "file"); others from "contents". Emit BOTH
-            // so we work across versions.
+            // Per the official EspoCRM API docs (POST /Attachment), the binary
+            // is sent in the "file" field as a data-URI. The previous extra
+            // "contents" alias was an undocumented legacy that strict tenants
+            // reject with 400.
             var payload = new Dictionary<string, object?>
             {
                 ["name"] = fileName,
@@ -219,7 +220,6 @@ namespace MarcusLaw.OutlookAddin.Core.Services
                 ["role"] = "Attachment",
                 ["relatedType"] = "Document",
                 ["field"] = "file",
-                ["contents"] = dataUri,
                 ["file"] = dataUri
             };
 
@@ -291,25 +291,50 @@ namespace MarcusLaw.OutlookAddin.Core.Services
         {
             if (string.IsNullOrWhiteSpace(caseId)) return new List<DocumentFolder>();
 
-            // EspoCRM doesn't have a Case → Document relationship by default,
-            // so /Case/{id}/documents 404s. Query Document directly filtered
-            // by the polymorphic parent fields and dedupe the folderId hits.
+            // Some EspoCRM installs reject filtering by polymorphic parentType
+            // with a 400. ParentId is a regular string field, and an ID alone
+            // is unique enough — we'll filter just by that. We additionally
+            // verify parentType client-side to be safe.
             var path =
-                "Document?select=" + Uri.EscapeDataString("id,folderId,folderName") +
+                "Document?select=" + Uri.EscapeDataString("id,folderId,folderName,parentType") +
                 "&where[0][type]=equals" +
-                "&where[0][attribute]=parentType" +
-                "&where[0][value]=Case" +
-                "&where[1][type]=equals" +
-                "&where[1][attribute]=parentId" +
-                "&where[1][value]=" + Uri.EscapeDataString(caseId) +
+                "&where[0][attribute]=parentId" +
+                "&where[0][value]=" + Uri.EscapeDataString(caseId) +
                 "&maxSize=200";
+
+            // Hand-rolled error capture (instead of GetJsonAsync) so a 400 from
+            // a picky tenant ends up in the log with body + X-Status-Reason.
+            HttpResponseMessage? response = null;
             try
             {
-                var response = await GetJsonAsync<EspoListResponse<DocumentEntity>>(path, cancellationToken).ConfigureAwait(false);
+                response = await ExecuteAsync(HttpMethod.Get, path, null, cancellationToken).ConfigureAwait(false);
+                if (!response.IsSuccessStatusCode)
+                {
+                    var errBody = await ReadBodyAsync(response).ConfigureAwait(false);
+                    var reason = response.Headers.TryGetValues("X-Status-Reason", out var v)
+                        ? string.Join(",", v) : "(none)";
+                    _logger.Warning(
+                        "ListFoldersUsedInCase({CaseId}): {Status} (X-Status-Reason={Reason}) body={Body}",
+                        caseId, response.StatusCode, reason,
+                        string.IsNullOrEmpty(errBody) ? "(empty)" : Truncate(errBody, 500));
+                    return new List<DocumentFolder>();
+                }
+                var body = await ReadBodyAsync(response).ConfigureAwait(false);
+                var parsed = JsonSerializer.Deserialize<EspoListResponse<DocumentEntity>>(body, JsonOptions)
+                             ?? new EspoListResponse<DocumentEntity>();
+
                 var seen = new HashSet<string>(StringComparer.Ordinal);
                 var folders = new List<DocumentFolder>();
-                foreach (var doc in response.List)
+                foreach (var doc in parsed.List)
                 {
+                    // Defensive: if the server returns docs from other parents
+                    // (shouldn't, but ID collisions are theoretically possible),
+                    // drop them.
+                    if (!string.IsNullOrEmpty(doc.ParentType) &&
+                        !string.Equals(doc.ParentType, "Case", StringComparison.OrdinalIgnoreCase))
+                    {
+                        continue;
+                    }
                     if (string.IsNullOrEmpty(doc.FolderId)) continue;
                     if (!seen.Add(doc.FolderId!)) continue;
                     folders.Add(new DocumentFolder
@@ -320,7 +345,7 @@ namespace MarcusLaw.OutlookAddin.Core.Services
                 }
                 _logger.Information(
                     "ListFoldersUsedInCase({CaseId}) → {DocumentCount} documents, {FolderCount} distinct folders",
-                    caseId, response.List.Count, folders.Count);
+                    caseId, parsed.List.Count, folders.Count);
                 return folders;
             }
             catch (Exception ex)
@@ -328,6 +353,10 @@ namespace MarcusLaw.OutlookAddin.Core.Services
                 _logger.Warning(ex, "ListFoldersUsedInCaseAsync({CaseId}) failed", caseId);
                 return new List<DocumentFolder>();
             }
+            finally
+            {
+                response?.Dispose();
+            }
         }
 
         public async Task<EspoListResponse<DocumentFolder>> ListDocumentFoldersAsync(CancellationToken cancellationToken = default)
diff --git a/src/OutlookAddin.UI/ViewModels/SaveAttachmentsViewModel.cs b/src/OutlookAddin.UI/ViewModels/SaveAttachmentsViewModel.cs
index e427269..5021f97 100644
--- a/src/OutlookAddin.UI/ViewModels/SaveAttachmentsViewModel.cs
+++ b/src/OutlookAddin.UI/ViewModels/SaveAttachmentsViewModel.cs
@@ -111,11 +111,20 @@ namespace MarcusLaw.OutlookAddin.UI.ViewModels
 
             try
             {
-                var folders = await _client.ListFoldersUsedInCaseAsync(caseId!).ConfigureAwait(true);
-                foreach (var folder in folders)
+                // First try: folders that are already in use for THIS case
+                // (the user's mental model — most relevant suggestions).
+                var caseFolders = await _client.ListFoldersUsedInCaseAsync(caseId!).ConfigureAwait(true);
+                if (caseFolders.Count > 0)
                 {
-                    Folders.Add(folder);
+                    foreach (var folder in caseFolders) Folders.Add(folder);
+                    return;
                 }
+
+                // Fallback: list every DocumentFolder in the tenant, so the
+                // user still has somewhere to put the file even on the very
+                // first upload to a case.
+                var global = await _client.ListDocumentFoldersAsync().ConfigureAwait(true);
+                foreach (var folder in global.List) Folders.Add(folder);
             }
             catch (Exception ex)
             {