From 011a258ba82b46f8a939f2ff64fee9f26f82dcfb Mon Sep 17 00:00:00 2001
From: stopachka <stepan.p@gmail.com>
Date: Sun, 15 Mar 2026 12:30:15 -0700
Subject: [PATCH] [codex] Preserve required constraints when creating links

---
 .../platform/__tests__/src/migrations.test.ts | 61 +++++++++++++++++++
 .../packages/platform/src/migrationUtils.ts   |  2 +-
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/client/packages/platform/__tests__/src/migrations.test.ts b/client/packages/platform/__tests__/src/migrations.test.ts
index 3abd1ea72f..82fa379d67 100644
--- a/client/packages/platform/__tests__/src/migrations.test.ts
+++ b/client/packages/platform/__tests__/src/migrations.test.ts
@@ -1,6 +1,7 @@
 import { expect, test as test } from 'vitest';
 import { i } from '@instantdb/core';
 import {
+  convertTxSteps,
   diffSchemas,
   Identifier,
   MigrationTx,
@@ -595,6 +596,66 @@ test('make link optional', async () => {
   expect(found).toBeDefined();
 });
 
+test('create required link', async () => {
+  const result = await diffSchemas(
+    i.schema({
+      entities: {
+        albums: i.entity({
+          name: i.string(),
+        }),
+        songs: i.entity({
+          name: i.string(),
+        }),
+      },
+      links: {},
+    }),
+    i.schema({
+      entities: {
+        albums: i.entity({
+          name: i.string(),
+        }),
+        songs: i.entity({
+          name: i.string(),
+        }),
+      },
+      links: {
+        songAlbum: {
+          forward: {
+            on: 'albums',
+            has: 'many',
+            label: 'songs',
+            required: true,
+          },
+          reverse: { on: 'songs', has: 'one', label: 'albums' },
+        },
+      },
+    }),
+    createChooser([]),
+    systemCatalogIdentNames,
+  );
+
+  expectTxType(result, 'add-attr', 1);
+
+  const addAttr = result.find(
+    (tx) =>
+      tx.type === 'add-attr' &&
+      tx.identifier.namespace === 'albums' &&
+      tx.identifier.attrName === 'songs',
+  );
+  expect(addAttr).toMatchObject({
+    type: 'add-attr',
+    'required?': true,
+  });
+
+  const requiredPlanStep = convertTxSteps(result, []).find(
+    (step) =>
+      step[0] === 'required' &&
+      step[1]['forward-identity'][1] === 'albums' &&
+      step[1]['forward-identity'][2] === 'songs',
+  );
+  expect(requiredPlanStep).toBeDefined();
+});
+
 test('system catalog attrs are ignored when adding entities', async () => {
   const result = await diffSchemas(
     i.schema({
diff --git a/client/packages/platform/src/migrationUtils.ts b/client/packages/platform/src/migrationUtils.ts
index 1980ea4db0..7d5f8f1c1c 100644
--- a/client/packages/platform/src/migrationUtils.ts
+++ b/client/packages/platform/src/migrationUtils.ts
@@ -35,7 +35,7 @@ export const linkDefToNewAttrTx = (link: AnyLink): MigrationTx => {
     'checked-data-type': null,
     'index?': false,
     ...uniqueAndCardinality,
-    'required?': false,
+    'required?': !!link.forward.required,
     identifier: {
       attrName: link.forward.label,
       namespace: link.forward.on,