Function fileHistoryMakeSnapshot

src/utils/fileHistory.ts:200–344

(
  updateFileHistoryState: (
    updater: (prev: FileHistoryState) => FileHistoryState,
  ) => void,
  messageId: UUID,
)

 * Adds a snapshot in the file history and backs up any modified tracked files.
 */
export async function fileHistoryMakeSnapshot(
  updateFileHistoryState: (
    updater: (prev: FileHistoryState) => FileHistoryState,
  ) => void,
  messageId: UUID,
): Promise<void> {
  if (!fileHistoryEnabled()) {
    return undefined
  }

  // Phase 1: capture current state with a no-op updater so we know which
  // files to back up. Returning the same reference keeps this a true no-op
  // for any wrapper that honors same-ref returns (src/CLAUDE.md wrapper
  // rule). Wrappers that unconditionally spread will trigger one extra
  // re-render; acceptable for a once-per-turn call.
  let captured: FileHistoryState | undefined
  updateFileHistoryState(state => {
    captured = state
    return state
  })
  if (!captured) return // updateFileHistoryState was a no-op stub (e.g. mcp.ts)

  // Phase 2: do all IO async, outside the updater.
  const trackedFileBackups: Record<string, FileHistoryBackup> = {}
  const mostRecentSnapshot = captured.snapshots.at(-1)
  if (mostRecentSnapshot) {
    logForDebugging(`FileHistory: Making snapshot for message ${messageId}`)
    await Promise.all(
      Array.from(captured.trackedFiles, async trackingPath => {
        try {
          const filePath = maybeExpandFilePath(trackingPath)
          const latestBackup =
            mostRecentSnapshot.trackedFileBackups[trackingPath]
          const nextVersion = latestBackup ? latestBackup.version + 1 : 1

          // Stat the file once; ENOENT means the tracked file was deleted.
          let fileStats: Stats | undefined
          try {
            fileStats = await stat(filePath)
          } catch (e: unknown) {
            if (!isENOENT(e)) throw e
          }

          if (!fileStats) {
            trackedFileBackups[trackingPath] = {
              backupFileName: null, // Use null to denote missing tracked file
              version: nextVersion,
              backupTime: new Date(),
            }
            logEvent('tengu_file_history_backup_deleted_file', {
              version: nextVersion,
            })
            logForDebugging(
              `FileHistory: Missing tracked file: ${trackingPath}`,
            )
            return
          }