No $7.5B in the docs: what OpenRouter's 7-day spend window does to your backend

The figure on the card in front of this brief is not in the material we were given. Neither the Auto Router documentation nor LangSmith's metadata reference states a price, a valuation, or any dollar amount for OpenRouter [cA]. So the $7.5B goes unexplained here, and the mechanism gets the space instead, because the mechanism is what ends up in your traces.

Roughly thirty task types multiplied by the five cost bands the `cost_tier` setting exposes ^[5] gives about 150 routing buckets ^[14], each one continuously repriced by people who do not work for you. OpenRouter is direct about the tempo: when developers migrate a workload to a new model, the router follows within days, with no retraining and no manual curation ^[4].

The measurement consequence is arithmetic rather than opinion. Two evaluation runs seven or more days apart rank candidates from trailing windows that share no data at all ^[15]. Your repository is unchanged across that gap; the backend is not.

Identification runs backwards too. You learn which model answered from the `model` field in the response ^[8], while LangSmith will only compute cost when `ls_provider` and `ls_model_name` are supplied together and matched against its pricing database ^[11]. That pair is an input to your logging whose value now arrives with the reply. The same reference suggests hiding routing and guardrail subspans from the Messages view ^[12], sensible for transcript hygiene and unhelpful for the one decision you would want to reconstruct later.

The hard edge available is the candidate list: wildcard `allowed_models` patterns, `excluded_models` applied afterwards, and a 404 reading `No models match your request and model restrictions` when nothing survives ^[13]. Failure is otherwise engineered out, since unavailable classification or rankings fall back to a default model set rather than erroring ^[7]. Graceful, and one more way the answer moves without telling you.