Q143: earlier messages come from the database, page by page, back to the first one

Review limit (5) reached; the last finding (exhaustion latched) is fixed
by taking it from each latest hasMore.

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

tests/unit/chat-thread-history.test.ts

@@ -6,7 +6,7 @@ import { DatabaseConnection } from "../../src/main/database/connection";
 import { OrganizationService } from "../../src/main/services/organization-service";
 import { ChatService } from "../../src/main/services/chat-service";
 import { SnapshotService } from "../../src/main/services/snapshot-service";
-import { threadHistory } from "../../src/main/services/chat-history";
+import { spaceHistory, threadHistory } from "../../src/main/services/chat-history";
 
 describe("a thread's history", () => {
   test("holds the whole thread even after newer traffic pushed it out of the recent window", () => {
@@ -37,3 +37,42 @@ describe("a thread's history", () => {
     connection.close();
   }, 60_000);
 });
+
+describe("a conversation's history", () => {
+  test("pages back from the earliest loaded message to the very first, beyond the recent window", () => {
+    const connection = new DatabaseConnection(join(tmpdir(), `ac-space-history-${randomUUID()}.db`));
+    const chat = new ChatService(connection.db);
+    let orgId = "";
+    connection.transaction(() => {
+      orgId = new OrganizationService(connection.db).createOrganization({ organizationName: "Acme", employeeName: "Yang", mission: "m", goal: "g" });
+    });
+    const employeeId = (connection.db.prepare("select id from employees where org_id = ?").get(orgId) as { id: string }).id;
+    const spaceId = (connection.db.prepare("select id from chat_spaces where org_id = ? and name = 'general'").get(orgId) as { id: string }).id;
+    const ids: string[] = [];
+    for (let index = 0; index < 250; index += 1) {
+      ids.push(connection.transaction(() => chat.sendMessage({
+        orgId, spaceId, threadId: null, senderType: "employee", senderId: employeeId, bodyMd: `Line ${index}`, attachmentFileIds: [],
+      })));
+    }
+    // Every message shares one instant, so only insertion order can page them correctly.
+    connection.db.prepare("update chat_messages set created_at = '2026-03-01T00:00:00.000Z' where space_id = ?").run(spaceId);
+    const first = spaceHistory(connection.db, orgId, spaceId, ids[200], { limit: 120 });
+    expect(first.messages.map((message) => message.bodyMd)).toEqual(Array.from({ length: 120 }, (_, index) => `Line ${index + 80}`));
+    expect(first.hasMore).toBe(true);
+    const last = spaceHistory(connection.db, orgId, spaceId, first.messages[0].id, { limit: 120 });
+    expect(last.messages.map((message) => message.bodyMd)).toEqual(Array.from({ length: 80 }, (_, index) => `Line ${index}`));
+    expect(last.hasMore).toBe(false);
+    // The loaded range refreshes in one query from its oldest message up to the cursor, edits included.
+    connection.db.prepare("update chat_messages set body_md = 'Line 0 (edited)' where id = ?").run(ids[0]);
+    const refreshed = spaceHistory(connection.db, orgId, spaceId, ids[200], { fromMessageId: ids[0] });
+    expect(refreshed.messages.map((message) => message.bodyMd)).toEqual(["Line 0 (edited)", ...Array.from({ length: 199 }, (_, index) => `Line ${index + 1}`)]);
+    expect(refreshed.hasMore).toBe(false);
+    expect(spaceHistory(connection.db, orgId, spaceId, ids[200], { fromMessageId: ids[1] }).hasMore).toBe(true);
+    // Each page carries the threads of its messages, which the snapshot may have dropped.
+    expect(refreshed.threads.map((thread) => thread.rootMessageId).sort()).toEqual(ids.slice(0, 200).sort());
+    // With nothing loaded, the newest messages come first.
+    expect(spaceHistory(connection.db, orgId, spaceId, null, { limit: 2 }).messages.map((message) => message.bodyMd)).toEqual(["Line 248", "Line 249"]);
+    expect(() => spaceHistory(connection.db, orgId, spaceId, "msg_elsewhere", { limit: 10 })).toThrow("The earliest loaded message is not in this conversation.");
+    connection.close();
+  }, 60_000);
+});