Function readBridgePointerAcrossWorktrees

src/bridge/bridgePointer.ts:129–184

(
  dir: string,
)

 * the right file on resume failure.
 */
export async function readBridgePointerAcrossWorktrees(
  dir: string,
): Promise<{ pointer: BridgePointer & { ageMs: number }; dir: string } | null> {
  // Fast path: current dir. Covers standalone bridge (always matches) and
  // REPL bridge when no worktree mutation happened.
  const here = await readBridgePointer(dir)
  if (here) {
    return { pointer: here, dir }
  }

  // Fanout: scan worktree siblings. getWorktreePathsPortable has a 5s
  // timeout and returns [] on any error (not a git repo, git not installed).
  const worktrees = await getWorktreePathsPortable(dir)
  if (worktrees.length <= 1) return null
  if (worktrees.length > MAX_WORKTREE_FANOUT) {
    logForDebugging(
      `[bridge:pointer] ${worktrees.length} worktrees exceeds fanout cap ${MAX_WORKTREE_FANOUT}, skipping`,
    )
    return null
  }

  // Dedupe against `dir` so we don't re-stat it. sanitizePath normalizes
  // case/separators so worktree-list output matches our fast-path key even
  // on Windows where git may emit C:/ vs stored c:/.
  const dirKey = sanitizePath(dir)
  const candidates = worktrees.filter(wt => sanitizePath(wt) !== dirKey)

  // Parallel stat+read. Each readBridgePointer is a stat() that ENOENTs
  // for worktrees with no pointer (cheap) plus a ~100-byte read for the
  // rare ones that have one. Promise.all → latency ≈ slowest single stat.
  const results = await Promise.all(
    candidates.map(async wt => {
      const p = await readBridgePointer(wt)
      return p ? { pointer: p, dir: wt } : null
    }),
  )

  // Pick freshest (lowest ageMs). The pointer stores environmentId so
  // resume reconnects to the right env regardless of which worktree
  // --continue was invoked from.
  let freshest: {
    pointer: BridgePointer & { ageMs: number }
    dir: string
  } | null = null
  for (const r of results) {
    if (r && (!freshest || r.pointer.ageMs < freshest.pointer.ageMs)) {
      freshest = r
    }
  }
  if (freshest) {
    logForDebugging(
      `[bridge:pointer] fanout found pointer in worktree ${freshest.dir} (ageMs=${freshest.pointer.ageMs})`,
    )
  }
  return freshest
}

/**