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>

src/main/services/chat-history.ts

@@ -1,5 +1,5 @@
 import type { DatabaseSync } from "node:sqlite";
-import type { ThreadHistory } from "../../shared/chat-domain";
+import type { SpaceHistoryPage, ThreadHistory } from "../../shared/chat-domain";
 import { camel } from "./snapshot-service";
 
 /** Every message of one thread with its attachments, mentions and commands, however far back it started. */
@@ -14,3 +14,47 @@ export function threadHistory(db: DatabaseSync, orgId: string, threadId: string)
     slashInvocations: rows("select s.* from chat_slash_invocations s join chat_messages m on m.id = s.message_id where m.thread_id = ?"),
   };
 }
+
+type Row = Record<string, unknown>;
+
+/** Which older messages to return: the next page before the cursor, or every message from a loaded one up to the cursor. */
+export type HistoryScope = { limit: number } | { fromMessageId: string };
+
+/** A conversation's messages before a loaded one (or its newest when none is loaded), in time then insertion order, with what they carry. */
+export function spaceHistory(db: DatabaseSync, orgId: string, spaceId: string, beforeMessageId: string | null, scope: HistoryScope): SpaceHistoryPage {
+  if (!db.prepare("select id from chat_spaces where id = ? and org_id = ?").get(spaceId, orgId)) throw new Error("Chat space was not found.");
+  const position = (messageId: string, what: string) => {
+    const row = db.prepare("select created_at, rowid from chat_messages where id = ? and space_id = ? and org_id = ?")
+      .get(messageId, spaceId, orgId) as { created_at: string; rowid: number } | undefined;
+    if (!row) throw new Error(`The ${what} is not in this conversation.`);
+    return [row.created_at, row.rowid] as const;
+  };
+  const conditions = ["space_id = ?"];
+  const params: Array<string | number> = [spaceId];
+  if (beforeMessageId !== null) {
+    conditions.push("(created_at, rowid) < (?, ?)");
+    params.push(...position(beforeMessageId, "earliest loaded message"));
+  }
+  if ("fromMessageId" in scope) {
+    conditions.push("(created_at, rowid) >= (?, ?)");
+    params.push(...position(scope.fromMessageId, "oldest loaded message"));
+  }
+  const limit = "limit" in scope ? scope.limit : -1;
+  const rows = db.prepare(`select *, rowid as seq from chat_messages where ${conditions.join(" and ")} order by created_at desc, rowid desc limit ?`)
+    .all(...params, limit === -1 ? -1 : limit + 1) as Row[];
+  const page = (limit === -1 ? rows : rows.slice(0, limit)).reverse();
+  const oldest = page[0];
+  const hasMore = limit !== -1 ? rows.length > limit : oldest !== undefined && db.prepare(`
+    select 1 from chat_messages where space_id = ? and (created_at, rowid) < (?, ?) limit 1
+  `).get(spaceId, oldest.created_at as string, oldest.seq as number) !== undefined;
+  const ids = JSON.stringify(page.map((row) => row.id));
+  const carried = <T>(sql: string) => (db.prepare(sql).all(ids) as Row[]).map((row) => camel(row) as T);
+  return {
+    messages: page.map(({ seq: _seq, ...row }) => camel(row) as unknown as SpaceHistoryPage["messages"][number]),
+    attachments: carried("select * from chat_attachments where message_id in (select value from json_each(?)) order by message_id"),
+    mentions: carried("select * from chat_mentions where message_id in (select value from json_each(?)) order by message_id, offset_start"),
+    slashInvocations: carried("select * from chat_slash_invocations where message_id in (select value from json_each(?)) order by message_id"),
+    threads: carried("select * from chat_threads where id in (select thread_id from chat_messages where id in (select value from json_each(?)))"),
+    hasMore,
+  };
+}