From 5a79750eda8f646eb7083ef294239192a5af8e6d Mon Sep 17 00:00:00 2001
From: Vladimir Razuvaev <vladimir.razuvaev@gmail.com>
Date: Fri, 30 May 2025 23:26:45 +0200
Subject: [PATCH 1/3] failing test

---
 .../src/__tests__/regression.test.ts          | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/packages/apollo-forest-run/src/__tests__/regression.test.ts b/packages/apollo-forest-run/src/__tests__/regression.test.ts
index 22451bd21..ecd1541c0 100644
--- a/packages/apollo-forest-run/src/__tests__/regression.test.ts
+++ b/packages/apollo-forest-run/src/__tests__/regression.test.ts
@@ -998,3 +998,48 @@ test("correctly writes fragment on abstract type", () => {
     ],
   });
 });
+
+test("correctly handles optimistic cache.modify", () => {
+  const query = gql`
+    {
+      items {
+        id
+        name
+      }
+    }
+  `;
+  const foo = { __typename: "Foo", id: "1", name: "foo" };
+  const bar = { __typename: "Bar", id: "2", name: "bar" };
+  const cache = new ForestRun();
+
+  cache.write({
+    dataId: "ROOT_QUERY",
+    query,
+    result: {
+      items: [{ ...foo }, { ...bar }],
+    },
+  });
+
+  let optimisticModify;
+  const before = cache.diff({ query, optimistic: true });
+  cache.recordOptimisticTransaction(() => {
+    optimisticModify = cache.modify({
+      id: cache.identify(foo),
+      fields: { name: () => "fooChanged" },
+    });
+  }, "test");
+  const optimisticData = cache.diff({ query, optimistic: true });
+  cache.removeOptimistic("test");
+  const restoredData = cache.diff({ query, optimistic: true });
+
+  expect(before.result).toEqual({
+    items: [foo, bar],
+  });
+  expect(optimisticData.result).toEqual({
+    items: [{ ...foo, name: "fooChanged" }, bar],
+  });
+  expect(restoredData.result).toEqual({
+    items: [foo, bar],
+  });
+  expect(optimisticModify).toBe(true);
+});

From b0e6fa95b1f501ff2340ac18196b947ac26566c4 Mon Sep 17 00:00:00 2001
From: Vladimir Razuvaev <vladimir.razuvaev@gmail.com>
Date: Fri, 30 May 2025 23:43:02 +0200
Subject: [PATCH 2/3] Change files

---
 ...lo-forest-run-85adcd22-ca87-4f61-901a-565fc0b2a7ea.json | 7 +++++++
 1 file changed, 7 insertions(+)
 create mode 100644 change/@graphitation-apollo-forest-run-85adcd22-ca87-4f61-901a-565fc0b2a7ea.json

diff --git a/change/@graphitation-apollo-forest-run-85adcd22-ca87-4f61-901a-565fc0b2a7ea.json b/change/@graphitation-apollo-forest-run-85adcd22-ca87-4f61-901a-565fc0b2a7ea.json
new file mode 100644
index 000000000..638cd84fd
--- /dev/null
+++ b/change/@graphitation-apollo-forest-run-85adcd22-ca87-4f61-901a-565fc0b2a7ea.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix(apollo-forest-run): cache.modify within optimistic transaction",
+  "packageName": "@graphitation/apollo-forest-run",
+  "email": "vladimir.razuvaev@gmail.com",
+  "dependentChangeType": "patch"
+}

From 26d95d18fa29c656d939e040593937bf6530e96a Mon Sep 17 00:00:00 2001
From: Vladimir Razuvaev <vladimir.razuvaev@gmail.com>
Date: Fri, 30 May 2025 23:54:02 +0200
Subject: [PATCH 3/3] one more failing test

---
 packages/apollo-forest-run/src/__tests__/regression.test.ts | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/apollo-forest-run/src/__tests__/regression.test.ts b/packages/apollo-forest-run/src/__tests__/regression.test.ts
index ecd1541c0..e1869fcbf 100644
--- a/packages/apollo-forest-run/src/__tests__/regression.test.ts
+++ b/packages/apollo-forest-run/src/__tests__/regression.test.ts
@@ -1043,3 +1043,7 @@ test("correctly handles optimistic cache.modify", () => {
   });
   expect(optimisticModify).toBe(true);
 });
+
+test("definitely fails", () => {
+  expect(true).toBe(false);
+});