Function walkChainBeforeParse

src/utils/sessionStorage.ts:3307–3467

(buf: Buffer)

}

function walkChainBeforeParse(buf: Buffer): Buffer {
  const NEWLINE = 0x0a
  const OPEN_BRACE = 0x7b
  const QUOTE = 0x22
  const PARENT_PREFIX = Buffer.from('{"parentUuid":')
  const UUID_KEY = Buffer.from('"uuid":"')
  const SIDECHAIN_TRUE = Buffer.from('"isSidechain":true')
  const UUID_LEN = 36
  const TS_SUFFIX = Buffer.from('","timestamp":"')
  const TS_SUFFIX_LEN = TS_SUFFIX.length
  const PREFIX_LEN = PARENT_PREFIX.length
  const KEY_LEN = UUID_KEY.length

  // Stride-3 flat index of transcript messages: [lineStart, lineEnd, parentStart].
  // parentStart is the byte offset of the parent uuid's first char, or -1 for null.
  // Metadata lines (summary, mode, file-history-snapshot, etc.) go in metaRanges
  // unfiltered - they lack the parentUuid prefix and downstream needs all of them.
  const msgIdx: number[] = []
  const metaRanges: number[] = []
  const uuidToSlot = new Map<string, number>()

  let pos = 0
  const len = buf.length
  while (pos < len) {
    const nl = buf.indexOf(NEWLINE, pos)
    const lineEnd = nl === -1 ? len : nl + 1
    if (
      lineEnd - pos > PREFIX_LEN &&
      buf[pos] === OPEN_BRACE &&
      buf.compare(PARENT_PREFIX, 0, PREFIX_LEN, pos, pos + PREFIX_LEN) === 0
    ) {
      // `{"parentUuid":null,` or `{"parentUuid":"<36 chars>",`
      const parentStart =
        buf[pos + PREFIX_LEN] === QUOTE ? pos + PREFIX_LEN + 1 : -1
      // The top-level uuid is immediately followed by `","timestamp":"` in
      // user/assistant/attachment entries (the create* helpers put them
      // adjacent; both always defined). But the suffix is NOT unique:
      //   - agent_progress entries carry a nested Message in data.message,
      //     serialized BEFORE top-level uuid — that inner Message has its
      //     own uuid,timestamp adjacent, so its bytes also satisfy the
      //     suffix check.
      //   - mcpMeta/toolUseResult come AFTER top-level uuid and hold
      //     server-controlled Record<string,unknown> — a server returning
      //     {uuid:"<36>",timestamp:"..."} would also match.
      // Collect all suffix matches; a single one is unambiguous (common
      // case), multiple need a brace-depth check to pick the one at
      // JSON nesting depth 1. Entries with NO suffix match (some progress
      // variants put timestamp BEFORE uuid → `"uuid":"<36>"}` at EOL)
      // have only one `"uuid":"` and the first-match fallback is sound.
      let firstAny = -1
      let suffix0 = -1
      let suffixN: number[] | undefined
      let from = pos
      for (;;) {
        const next = buf.indexOf(UUID_KEY, from)
        if (next < 0 || next >= lineEnd) break
        if (firstAny < 0) firstAny = next
        const after = next + KEY_LEN + UUID_LEN