Function restoreAttributionStateFromSnapshots

src/utils/commitAttribution.ts:840–870

(
  snapshots: AttributionSnapshotMessage[],
)

 * Restore attribution state from snapshot messages.
 */
export function restoreAttributionStateFromSnapshots(
  snapshots: AttributionSnapshotMessage[],
): AttributionState {
  const state = createEmptyAttributionState()

  // Snapshots are full-state dumps (see stateToSnapshotMessage), not deltas.
  // The last snapshot has the most recent count for every path — fileStates
  // never shrinks. Iterating and SUMMING counts across snapshots causes
  // quadratic growth on restore (837 snapshots × 280 files → 1.15 quadrillion
  // "chars" tracked for a 5KB file over a 5-day session).
  const lastSnapshot = snapshots[snapshots.length - 1]
  if (!lastSnapshot) {
    return state
  }

  state.surface = lastSnapshot.surface
  for (const [path, fileState] of Object.entries(lastSnapshot.fileStates)) {
    state.fileStates.set(path, fileState)
  }

  // Restore prompt counts from the last snapshot (most recent state)
  state.promptCount = lastSnapshot.promptCount ?? 0
  state.promptCountAtLastCommit = lastSnapshot.promptCountAtLastCommit ?? 0
  state.permissionPromptCount = lastSnapshot.permissionPromptCount ?? 0
  state.permissionPromptCountAtLastCommit =
    lastSnapshot.permissionPromptCountAtLastCommit ?? 0
  state.escapeCount = lastSnapshot.escapeCount ?? 0
  state.escapeCountAtLastCommit = lastSnapshot.escapeCountAtLastCommit ?? 0

  return state
}

/**
 * Restore attribution state from log snapshots on session resume.