Function readLiteMetadata

src/utils/sessionStorage.ts:4739–4813

* Reads the first and last ~64KB of a JSONL file and extracts lite metadata. * * Head (first 64KB): isSidechain, projectPath, teamName, firstPrompt. * Tail (last 64KB): customTitle, tag, PR link, latest gitBranch. * * Accepts a shared buffer to avoid per-file allocation overhead.

(
  filePath: string,
  fileSize: number,
  buf: Buffer,
)

 * Accepts a shared buffer to avoid per-file allocation overhead.
 */
async function readLiteMetadata(
  filePath: string,
  fileSize: number,
  buf: Buffer,
): Promise<LiteMetadata> {
  const { head, tail } = await readHeadAndTail(filePath, fileSize, buf)
  if (!head) return { firstPrompt: '', isSidechain: false }

  // Extract stable metadata from the first line via string search.
  // Works even when the first line is truncated (>64KB message).
  const isSidechain =
    head.includes('"isSidechain":true') || head.includes('"isSidechain": true')
  const projectPath = extractJsonStringField(head, 'cwd')
  const teamName = extractJsonStringField(head, 'teamName')
  const agentSetting = extractJsonStringField(head, 'agentSetting')

  // Prefer the last-prompt tail entry — captured by extractFirstPrompt at
  // write time (filtered, authoritative) and shows what the user was most
  // recently doing. Head scan is the fallback for sessions written before
  // last-prompt entries existed. Raw string scrapes of head are last resort
  // and catch array-format content blocks (VS Code <ide_selection> metadata).
  const firstPrompt =
    extractLastJsonStringField(tail, 'lastPrompt') ||
    extractFirstPromptFromChunk(head) ||
    extractJsonStringFieldPrefix(head, 'content', 200) ||
    extractJsonStringFieldPrefix(head, 'text', 200) ||
    ''

  // Extract tail metadata via string search (last occurrence wins).
  // User titles (customTitle field, from custom-title entries) win over
  // AI titles (aiTitle field, from ai-title entries). The distinct field
  // names mean extractLastJsonStringField naturally disambiguates.
  const customTitle =
    extractLastJsonStringField(tail, 'customTitle') ??
    extractLastJsonStringField(head, 'customTitle') ??
    extractLastJsonStringField(tail, 'aiTitle') ??
    extractLastJsonStringField(head, 'aiTitle')
  const summary = extractLastJsonStringField(tail, 'summary')
  const tag = extractLastJsonStringField(tail, 'tag')
  const gitBranch =
    extractLastJsonStringField(tail, 'gitBranch') ??
    extractJsonStringField(head, 'gitBranch')

  // PR link fields — prNumber is a number not a string, so try both
  const prUrl = extractLastJsonStringField(tail, 'prUrl')
  const prRepository = extractLastJsonStringField(tail, 'prRepository')
  let prNumber: number | undefined
  const prNumStr = extractLastJsonStringField(tail, 'prNumber')
  if (prNumStr) {
    prNumber = parseInt(prNumStr, 10) || undefined
  }
  if (!prNumber) {
    const prNumMatch = tail.lastIndexOf('"prNumber":')
    if (prNumMatch >= 0) {
      const afterColon = tail.slice(prNumMatch + 11, prNumMatch + 25)
      const num = parseInt(afterColon.trim(), 10)
      if (num > 0) prNumber = num
    }