Function loadTranscriptFile

source code/utils/sessionStorage.ts:3474–3815

(
  filePath: string,
  opts?: { keepAllLeaves?: boolean },
)

 * Returns the messages, summaries, custom titles, tags, file history snapshots, and attribution snapshots.
 */
export async function loadTranscriptFile(
  filePath: string,
  opts?: { keepAllLeaves?: boolean },
): Promise<{
  messages: Map<UUID, TranscriptMessage>
  summaries: Map<UUID, string>
  customTitles: Map<UUID, string>
  tags: Map<UUID, string>
  agentNames: Map<UUID, string>
  agentColors: Map<UUID, string>
  agentSettings: Map<UUID, string>
  prNumbers: Map<UUID, number>
  prUrls: Map<UUID, string>
  prRepositories: Map<UUID, string>
  modes: Map<UUID, string>
  worktreeStates: Map<UUID, PersistedWorktreeSession | null>
  fileHistorySnapshots: Map<UUID, FileHistorySnapshotMessage>
  attributionSnapshots: Map<UUID, AttributionSnapshotMessage>
  contentReplacements: Map<UUID, ContentReplacementRecord[]>
  agentContentReplacements: Map<AgentId, ContentReplacementRecord[]>
  contextCollapseCommits: ContextCollapseCommitEntry[]
  contextCollapseSnapshot: ContextCollapseSnapshotEntry | undefined
  leafUuids: Set<UUID>
}> {
  const messages = new Map<UUID, TranscriptMessage>()
  const summaries = new Map<UUID, string>()
  const customTitles = new Map<UUID, string>()
  const tags = new Map<UUID, string>()
  const agentNames = new Map<UUID, string>()
  const agentColors = new Map<UUID, string>()
  const agentSettings = new Map<UUID, string>()
  const prNumbers = new Map<UUID, number>()
  const prUrls = new Map<UUID, string>()
  const prRepositories = new Map<UUID, string>()
  const modes = new Map<UUID, string>()
  const worktreeStates = new Map<UUID, PersistedWorktreeSession | null>()
  const fileHistorySnapshots = new Map<UUID, FileHistorySnapshotMessage>()
  const attributionSnapshots = new Map<UUID, AttributionSnapshotMessage>()
  const contentReplacements = new Map<UUID, ContentReplacementRecord[]>()
  const agentContentReplacements = new Map<
    AgentId,
    ContentReplacementRecord[]
  >()
  // Array, not Map — commit order matters (nested collapses).
  const contextCollapseCommits: ContextCollapseCommitEntry[] = []
  // Last-wins — later entries supersede.
  let contextCollapseSnapshot: ContextCollapseSnapshotEntry | undefined

  try {
    // For large transcripts, avoid materializing megabytes of stale content.
    // Single forward chunked read: attribution-snapshot lines are skipped at
    // the fd level (never buffered), compact boundaries truncate the
    // accumulator in-stream. Peak allocation is the OUTPUT size, not the
    // file size — a 151 MB session that is 84% stale attr-snaps allocates
    // ~32 MB instead of 159+64 MB. This matters because mimalloc does not
    // return those pages to the OS even after JS-level GC frees the backing
    // buffers (measured: arrayBuffers=0 after Bun.gc(true) but RSS stuck at
    // ~316 MB on the old scan+strip path vs ~155 MB here).