fix(grid): show real save error message instead of [object Object]

apps/desktop/src/lib/backend/errorUtils.ts

@@ -283,9 +283,11 @@ export function formatError(e: unknown): string {
     }
   }
 
-  // Fallback: attempt to stringify
+  // Fallback: prefer bounded nested text (message/reason/detail, .error/.backendError)
+  // over raw string coercion so object-shaped failures never degrade to "[object Object]".
+  const fallback = boundedFallbackText(e);
   try {
-    return sanitizeBackendErrorMessage(String(e));
+    return sanitizeBackendErrorMessage(fallback ?? String(e));
   } catch {
     return "Unknown error occurred";
   }

apps/desktop/src/lib/dataGrid/__tests__/dataGridSql.spec.ts

@@ -0,0 +1,35 @@
+import { describe, expect, it } from "vitest";
+import { normalizeDataGridSaveError } from "@/lib/dataGrid/dataGridSql";
+
+describe("normalizeDataGridSaveError", () => {
+  it("extracts a message from an object-shaped save failure", () => {
+    expect(normalizeDataGridSaveError("mysql", { message: "Duplicate entry for key id" })).toBe("Duplicate entry for key id");
+  });
+
+  it("extracts messages from nested backend request errors", () => {
+    expect(normalizeDataGridSaveError("mysql", { error: { message: "Column count does not match" } })).toBe("Column count does not match");
+  });
+
+  it("keeps Error messages and database-specific guidance intact", () => {
+    expect(normalizeDataGridSaveError("mysql", new Error("save failed"))).toBe("save failed");
+    expect(normalizeDataGridSaveError("hive", new Error("Error 10294: update is disabled"))).toContain("Hive UPDATE/DELETE");
+  });
+
+  it("prefers the Error message over a backend envelope without detail", () => {
+    const sqlError = Object.assign(new Error("Duplicate entry '1' for key 'PRIMARY'"), {
+      backendError: {
+        version: 1,
+        code: "DBX-JDBC-4001",
+        messageKey: "backendErrors.jdbc.sqlFailed",
+        messageParams: { stage: "execute" },
+        source: "jdbc_agent",
+        operationOutcome: "unknown",
+      },
+    });
+    expect(normalizeDataGridSaveError("mysql", sqlError)).toBe("Duplicate entry '1' for key 'PRIMARY'");
+  });
+
+  it("extracts messages from nested backendError envelopes", () => {
+    expect(normalizeDataGridSaveError("mysql", { backendError: { message: "Connection refused" } })).toBe("Connection refused");
+  });
+});

apps/desktop/src/lib/dataGrid/dataGridSql.ts

@@ -1,5 +1,6 @@
 import type { DatabaseType } from "@/types/database";
 import * as api from "@/lib/backend/api";
+import { formatError } from "@/lib/backend/errorUtils";
 
 export type GridCellValue = string | number | boolean | null | unknown[] | { [key: string]: unknown };
 
@@ -167,8 +168,15 @@ export function buildHiveTablePropertiesSql(options: HiveTablePropertiesSqlOptio
   return api.buildHiveTablePropertiesSql(options);
 }
 
+function formatDataGridSaveError(error: unknown): string {
+  if (error instanceof Error && error.message) {
+    return error.message;
+  }
+  return formatError(error);
+}
+
 export function normalizeDataGridSaveError(databaseType: DatabaseType | undefined, error: unknown): string {
-  const message = error instanceof Error ? error.message : String(error);
+  const message = formatDataGridSaveError(error);
   if ((databaseType === "hive" || databaseType === "argo") && /Attempt to do update or delete|Error 10294/i.test(message)) {
     return "Hive UPDATE/DELETE are not enabled for this table or server. Add rows with INSERT, or enable ACID transactional tables in Hive before editing/deleting existing rows.";
   }