Variable METRIC_FIELDS`Const`

METRIC_FIELDS: readonly [
    "context_pct",
    "tokens_in",
    "tokens_out",
    "tokens_cache_read",
    "tokens_cache_write",
    "tokens_cache_write_1h",
    "subagents",
    "background_jobs",
    "api_retries",
    "progress_events",
] = ...

Number members of run_metrics.v1 an adapter may set (/metrics/<field>).