static UA: OnceLock<String>Expand description
Cached claude-code/<version> User-Agent, probed once per process.
User-Agent native CLI sends on /api/oauth/usage, captured from
mitmdump 2026-05-26 against claude CLI 2.1.133: claude-code/<version>,
no parens, no (external, cli) suffix - distinct from the
/v1/messages UA shape. Only a successful probe is cached; a failure
re-probes on the next call rather than pinning a stale fallback
that would lie about which version is running.