Function refreshUpdateCheck

src/upgrade/update-check.ts:168–195

(deps: UpdateCheckDeps = {})

 * backoff) and return the current notice, or null. Never throws.
 */
export async function refreshUpdateCheck(deps: UpdateCheckDeps = {}): Promise<string | null> {
  const d = resolveDeps(deps);
  if (updateCheckDisabled(d.env)) return null;

  const cached = readUpdateCheckCache(d.dir);
  const nowMs = d.now();
  if (cacheIsFresh(cached, nowMs)) return noticeFrom(cached, d);

  try {
    const latest = canonicalVersionTag(await d.resolveLatest());
    // A response that isn't version-shaped is a failure, not a result —
    // fall through to the backoff path and keep the previous known-good tag.
    if (!latest) throw new Error('release feed returned a non-version tag');
    const next: UpdateCheckCacheFile = { lastAttemptAt: nowMs, lastSuccessAt: nowMs, latest };
    writeUpdateCheckCache(d.dir, next);
    return noticeFrom(next, d);
  } catch {
    // Record the attempt (starts the backoff) but KEEP the previous latest —
    // a transient outage must not hide an already-known update.
    const next: UpdateCheckCacheFile = {
      lastAttemptAt: nowMs,
      lastSuccessAt: cached?.lastSuccessAt,
      latest: cached?.latest,
    };
    writeUpdateCheckCache(d.dir, next);
    return noticeFrom(next, d);
  }
}

// Per-process memo so the sync read path (MCP initialize, codegraph_status)
// touches the disk at most once a minute, not once per handshake.