fix(mongodb): preserve JSON-looking string values

apps/desktop/src/components/document/DocumentBrowser.vue

@@ -305,7 +305,7 @@ async function gridSave(changes: DocumentGridChanges) {
       continue;
     }
 
-    const updateDoc = buildMongoUpdateDocument(dirtyCols, cols);
+    const updateDoc = buildMongoUpdateDocument(dirtyCols, cols, documents.value[rowIdx]);
     if (Object.keys(updateDoc).length === 0) continue;
     await api.documentUpdateDocument(props.connectionId, props.database, props.collection, String(id), JSON.stringify(updateDoc));
   }
@@ -382,7 +382,7 @@ async function previewDocumentChanges(changes: DocumentGridChanges): Promise<str
       const routing = documentRoutingFromGridRow(row, columns);
       stmts.push(`POST /${coll}/_update/${elasticsearchPathIdPreview(String(id))}${elasticsearchRoutingPreview(routing)}\n${JSON.stringify({ doc: updateDoc.$set ?? updateDoc }, null, 2)}`);
     } else {
-      const updateDoc = buildMongoUpdateDocument(dirtyCols, columns);
+      const updateDoc = buildMongoUpdateDocument(dirtyCols, columns, documents.value[rowIdx]);
       stmts.push(`db.${coll}.updateOne({_id: ${mongoIdPreview(id)}}, ${formatMongoShellLiteral(updateDoc)})`);
     }
   }

apps/desktop/src/components/layout/ContentArea.vue

@@ -391,7 +391,7 @@ const mongoQueryResultSaveHandler = computed<CustomSaveHandler | undefined>(() =
       const row = changes.rows[rowIdx];
       const id = row?.[idColIdx];
       if (id === null || id === undefined || String(id).trim() === "") continue;
-      const updateDoc = buildMongoUpdateDocument(dirtyCols, changes.columns);
+      const updateDoc = buildMongoUpdateDocument(dirtyCols, changes.columns, tab.result?.mongo_documents?.[rowIdx]);
       if (Object.keys(updateDoc).length === 0) continue;
       await api.mongoUpdateDocument(tab.connectionId, tab.database, target.collection, String(id), JSON.stringify(updateDoc));
     }
@@ -405,7 +405,7 @@ const mongoQueryResultSaveHandler = computed<CustomSaveHandler | undefined>(() =
       const row = changes.rows[rowIdx];
       const id = row?.[idColIdx];
       if (id === null || id === undefined || String(id).trim() === "") continue;
-      const updateDoc = buildMongoUpdateDocument(dirtyCols, changes.columns);
+      const updateDoc = buildMongoUpdateDocument(dirtyCols, changes.columns, tab.result?.mongo_documents?.[rowIdx]);
       if (Object.keys(updateDoc).length === 0) continue;
       stmts.push(`${mongoCollectionExpression(target.collection)}.updateOne({_id: ${mongoIdPreview(id)}}, ${formatMongoShellLiteral(updateDoc)})`);
     }

apps/desktop/src/lib/mongo/mongoDocumentValues.ts

@@ -31,6 +31,20 @@ export function parseMongoDocumentInputValue(raw: MongoInputValue): unknown {
   return raw;
 }
 
+function parseMongoExistingFieldInputValue(raw: Exclude<MongoInputValue, null>, originalValue: unknown): unknown {
+  // Objects and arrays are serialized into grid text too, so the raw document
+  // is the only reliable way to distinguish them from JSON-shaped BSON strings.
+  if (typeof originalValue === "string") {
+    return typeof raw === "string" ? raw : String(raw);
+  }
+  return parseMongoDocumentInputValue(raw);
+}
+
+function mongoDocumentFieldValue(document: unknown, field: string): unknown {
+  if (!document || typeof document !== "object" || Array.isArray(document)) return undefined;
+  return (document as Record<string, unknown>)[field];
+}
+
 function legacyMongoDateDisplayToExtendedJson(value: string): { $date: string } | null {
   const match = value.match(LEGACY_MONGO_DATE_DISPLAY_PATTERN);
   if (!match) return null;
@@ -38,7 +52,7 @@ function legacyMongoDateDisplayToExtendedJson(value: string): { $date: string }
   return { $date: `${date}T${time}.${millis.padEnd(3, "0")}Z` };
 }
 
-export function buildMongoUpdateDocument(changes: Map<number, MongoInputValue>, columns: string[]): Record<string, unknown> {
+export function buildMongoUpdateDocument(changes: Map<number, MongoInputValue>, columns: string[], originalDocument?: unknown): Record<string, unknown> {
   const setFields: Record<string, unknown> = {};
   const unsetFields: Record<string, unknown> = {};
   for (const [colIdx, newVal] of changes) {
@@ -47,7 +61,7 @@ export function buildMongoUpdateDocument(changes: Map<number, MongoInputValue>,
     if (newVal === null) {
       unsetFields[col] = "";
     } else {
-      setFields[col] = parseMongoDocumentInputValue(newVal);
+      setFields[col] = parseMongoExistingFieldInputValue(newVal, mongoDocumentFieldValue(originalDocument, col));
     }
   }
   const doc: Record<string, unknown> = {};
@@ -66,7 +80,7 @@ export function applyMongoGridChangesToDocument(document: unknown, changes: Map<
     if (newVal === null) {
       delete updated[column];
     } else {
-      updated[column] = parseMongoDocumentInputValue(newVal);
+      updated[column] = parseMongoExistingFieldInputValue(newVal, updated[column]);
     }
   }
   return updated;

packages/app-tests/mongoDocumentValues.test.ts

@@ -36,6 +36,70 @@ test("builds Mongo grid updates with set and unset operators", () => {
   });
 });
 
+test("preserves JSON-shaped strings when updating existing Mongo fields", () => {
+  const original = {
+    _id: "1",
+    answer: '{"action":"New","values":[1]}',
+    tagsText: '["draft"]',
+    profile: { role: "admin" },
+  };
+  const changes = new Map<number, string | number | boolean | null>([
+    [1, '{\n  "action": "Updated",\n  "values": [\n    1,\n    2\n  ]\n}'],
+    [2, '[\n  "published"\n]'],
+    [3, '{"role":"maintainer"}'],
+  ]);
+
+  const update = buildMongoUpdateDocument(changes, ["_id", "answer", "tagsText", "profile"], original);
+
+  assert.deepEqual(update, {
+    $set: {
+      answer: '{\n  "action": "Updated",\n  "values": [\n    1,\n    2\n  ]\n}',
+      tagsText: '[\n  "published"\n]',
+      profile: { role: "maintainer" },
+    },
+  });
+  assert.equal(formatMongoShellLiteral(update), '{"$set":{"answer":"{\\n  \\"action\\": \\"Updated\\",\\n  \\"values\\": [\\n    1,\\n    2\\n  ]\\n}","tagsText":"[\\n  \\"published\\"\\n]","profile":{"role":"maintainer"}}}');
+});
+
+test("preserves existing Mongo strings that resemble typed literals", () => {
+  const original = {
+    _id: "1",
+    numericText: "42",
+    booleanText: "true",
+    dateText: 'ISODate("2026-01-01T00:00:00.000Z")',
+    quotedText: '"literal"',
+  };
+  const changes = new Map<number, string | number | boolean | null>([
+    [1, "43"],
+    [2, "false"],
+    [3, 'ISODate("2026-02-01T00:00:00.000Z")'],
+    [4, '"changed"'],
+  ]);
+
+  assert.deepEqual(buildMongoUpdateDocument(changes, ["_id", "numericText", "booleanText", "dateText", "quotedText"], original), {
+    $set: {
+      numericText: "43",
+      booleanText: "false",
+      dateText: 'ISODate("2026-02-01T00:00:00.000Z")',
+      quotedText: '"changed"',
+    },
+  });
+});
+
+test("keeps JSON inference for fields without an existing Mongo type", () => {
+  const changes = new Map<number, string | number | boolean | null>([
+    [1, '{"enabled":true}'],
+    [2, "42"],
+  ]);
+
+  assert.deepEqual(buildMongoUpdateDocument(changes, ["_id", "newObject", "newNumber"], { _id: "1" }), {
+    $set: {
+      newObject: { enabled: true },
+      newNumber: 42,
+    },
+  });
+});
+
 test("applies saved Mongo grid changes to the raw preview document", () => {
   const original = {
     _id: "1",
@@ -62,6 +126,24 @@ test("applies saved Mongo grid changes to the raw preview document", () => {
   });
 });
 
+test("applies Mongo grid edits without converting existing JSON strings", () => {
+  const original = {
+    _id: "1",
+    answer: '{"action":"New"}',
+    profile: { role: "admin" },
+  };
+  const changes = new Map<number, string | number | boolean | null>([
+    [1, '{\n  "action": "Updated"\n}'],
+    [2, '{"role":"maintainer"}'],
+  ]);
+
+  assert.deepEqual(applyMongoGridChangesToDocument(original, changes, ["_id", "answer", "profile"]), {
+    _id: "1",
+    answer: '{\n  "action": "Updated"\n}',
+    profile: { role: "maintainer" },
+  });
+});
+
 test("builds Mongo inserts with parsed date values", () => {
   assert.deepEqual(buildMongoInsertDocument(["ignored", 'new Date("2026-06-10T13:59:31.287Z")'], ["_id", "createdAt"]), {
     createdAt: { $date: "2026-06-10T13:59:31.287Z" },