Q195: a change reloads only what is not already shown, and the snapshot stops carrying records the window never reads

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/unit/data-version.test.ts

@@ -0,0 +1,35 @@
+import { randomUUID } from "node:crypto";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { describe, expect, test } from "vitest";
+import { DatabaseConnection } from "../../src/main/database/connection";
+import { SnapshotService } from "../../src/main/services/snapshot-service";
+import { bumpDataVersion, currentDataVersion } from "../../src/main/services/data-version";
+import { supersedes } from "../../src/renderer/src/app/snapshot-order";
+
+describe("data version", () => {
+  test("a snapshot read after a change carries that change's version, so its own change event needs no reload", () => {
+    const connection = new DatabaseConnection(join(tmpdir(), `ac-data-version-${randomUUID()}.db`));
+    const snapshot = new SnapshotService(connection.db);
+    const before = snapshot.load().dataVersion;
+    const announced = bumpDataVersion();
+    const after = snapshot.load();
+    expect(after.dataVersion).toBe(announced);
+    expect(announced).toBeGreaterThan(before);
+    // A later change is newer than what is shown, so it is reloaded.
+    expect(bumpDataVersion()).toBeGreaterThan(after.dataVersion);
+    expect(currentDataVersion()).toBe(after.dataVersion + 1);
+    // Records the window never reads are not shipped with every reload.
+    expect(Object.keys(after)).not.toEqual(expect.arrayContaining(["operationalEvents", "featureFlags", "approvalAssignments", "roleGrants"]));
+    connection.close();
+  });
+});
+
+describe("snapshot order", () => {
+  test("a late answer read at an older version never replaces newer data on screen", () => {
+    expect(supersedes(2, 1)).toBe(false);
+    expect(supersedes(2, 2)).toBe(true);
+    expect(supersedes(2, 3)).toBe(true);
+    expect(supersedes(-1, 0)).toBe(true);
+  });
+});