- /metrics endpoint: request/token/latency counters, tok/s gauge, build info (std-only, no deps) - usage.duration_ms + usage.tokens_per_second in non-streaming and streaming responses - /health now reports uptime_s, n_ctx, version - MAX_TOKENS env config (hard cap, default 2048; 0 = unlimited) - metrics unit tests (counters, prometheus shape, uptime monotonic)