fix: avoid repeated activity history reads during streaming

Reuse the last committed activity records when comparing streaming saves instead of reading the full history for every update. Invalidate comparisons on close, data clearing and commits from other SQLite connections; preserve rollback and retry behavior.

Validation: 3 related test files / 121 tests passed; typecheck and lint passed. Ten consecutive saves now perform at most one full-history scan while preserving the WAL write reduction. Installed-app physical disk throughput remains unverified.

Release note: Reduce repeated database reads while streaming activity updates in conversations with large activity histories.

src/main/assistant/activity-history-io.test.ts

@@ -3,8 +3,8 @@ import { randomUUID } from 'node:crypto'
 import { mkdtempSync, rmSync, statSync } from 'node:fs'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
-import type { DatabaseSync } from 'node:sqlite'
-import { expect, it } from 'vitest'
+import { DatabaseSync } from 'node:sqlite'
+import { expect, it, vi } from 'vitest'
 import { AssistantDatabase } from './assistant-database'
 import { upgradeAssistantStorage } from './assistant-storage-upgrade'
 
@@ -43,12 +43,18 @@ it('migrates activity history and writes only changed records during streaming',
     expect(database.getActivityHistory()).toEqual({ records, legacyHistoryMayBeIncomplete: true })
     const migrated = (database as unknown as { database: DatabaseSync }).database
     migrated.exec('PRAGMA wal_checkpoint(TRUNCATE); PRAGMA wal_autocheckpoint=0')
+    const prepare = vi.spyOn(migrated, 'prepare')
     for (let index = 0; index < 10; index++) {
       records[0]!.detail += 'x'
       database.replaceActivityHistory({ records, legacyHistoryMayBeIncomplete: true })
     }
     const afterBytes = statSync(`${path}-wal`).size
-    console.log({ beforeBytes, afterBytes })
+    const historyScans = prepare.mock.calls.filter(([sql]) =>
+      /SELECT record_key, record_json FROM activity_history_records/.test(sql)
+    ).length
+    prepare.mockRestore()
+    console.log({ beforeBytes, afterBytes, historyScans })
+    expect(historyScans).toBeLessThanOrEqual(1)
     expect(afterBytes).toBeLessThan(beforeBytes / 100)
     database.replaceActivityHistory({ records, legacyHistoryMayBeIncomplete: true })
     expect(statSync(`${path}-wal`).size).toBe(afterBytes)
@@ -63,3 +69,46 @@ it('migrates activity history and writes only changed records during streaming',
     rmSync(directory, { recursive: true, force: true })
   }
 })
+
+it('keeps activity comparisons correct after rollback, external writes and clearing', () => {
+  const directory = mkdtempSync(join(tmpdir(), 'goodbuddy-save-io-'))
+  const path = join(directory, 'assistant.sqlite')
+  const database = new AssistantDatabase(path)
+  try {
+    database.initialize(directory)
+    const raw = (database as unknown as { database: DatabaseSync }).database
+    const snapshot = {
+      records: ['first', 'second'].map((id) => ({
+        id, conversationId: randomUUID(), requestId: randomUUID(),
+        scope: { kind: 'global' as const }, kind: 'tool' as const,
+        title: 'Tool', detail: 'initial', status: 'running' as const, createdAt: Date.now()
+      })),
+      legacyHistoryMayBeIncomplete: false
+    }
+    database.replaceActivityHistory(snapshot)
+    raw.exec(`CREATE TRIGGER reject_activity BEFORE UPDATE ON activity_history_records
+      WHEN json_extract(NEW.record_json, '$.id') = 'second'
+      BEGIN SELECT RAISE(ABORT, 'test failure'); END`)
+    for (const record of snapshot.records) record.detail = 'changed'
+    expect(() => database.replaceActivityHistory(snapshot)).toThrow('test failure')
+    expect(database.getActivityHistory().records.map((record) => record.detail)).toEqual(['initial', 'initial'])
+    raw.exec('DROP TRIGGER reject_activity')
+    database.replaceActivityHistory(snapshot)
+    expect(database.getActivityHistory()).toEqual(snapshot)
+
+    const external = new DatabaseSync(path)
+    try {
+      external.exec('DELETE FROM activity_history_records')
+    } finally {
+      external.close()
+    }
+    database.replaceActivityHistory(snapshot)
+    expect(database.getActivityHistory()).toEqual(snapshot)
+    database.clearAssistantData()
+    database.replaceActivityHistory(snapshot)
+    expect(database.getActivityHistory()).toEqual(snapshot)
+  } finally {
+    database.close()
+    rmSync(directory, { recursive: true, force: true })
+  }
+})