A request served from a different service tier is never reported

• Status: Todo
• Kind: Bug
• Authors: jp
• Date: 2026-09-08

assistant.model.parameters.service_tier asks a provider for a grade of capacity, and JP refuses the query when the provider sells no equivalent. It cannot refuse what the provider accepts and then serves from somewhere else, and today it does not notice either.

Every provider reports which tier actually served the request. JP reads none of them:

• OpenAI and OpenRouter return service_tier at the top level of the response.
• Anthropic returns usage.service_tier and usage.speed.
• Cerebras returns service_tier_used for a request that asked for auto.

jp_openrouter::types::response::ChatCompletion has no service_tier field, and the OpenRouter provider never sets the request's usage flag either, so Usage.cost is unpopulated as well.

Why it matters

The tier decides what the request costs, so a substitution the user cannot see is a silent billing change. Named inputs that reach it:

• jp q --model openrouter/anthropic/claude-opus-5 --tier flex "...". OpenRouter documents that flex's no-fallback guarantee holds only when flex endpoints exist: with an empty flex pool "the request routes normally at standard rates". Anthropic on OpenRouter is priority-only, so this model has no flex pool and the query succeeds at the regular price.
• An OpenAI flex request shed to default under load.
• speed: "fast" on Claude Opus 4.6, which Anthropic documents as running at standard speed and standard rates while reporting usage.speed: "standard".

Each is contained to one request, but none is visible, which is what makes this worth fixing rather than recording.

Scope

Parse the served tier per provider, record it alongside the turn, and tell the user when it differs from what they asked for.

A warn! does not discharge this on its own: configure_tracing maps default verbosity to LevelFilter::ERROR, so the report has to reach the printer's notice channel to be seen at all. That dependency is the reason this is not a one-line change, and it is shared with the wider question of how contained degradations get surfaced (see T-0dd9cpr and RFD 048).

Out of scope: predicting a substitution before dispatch. That would need OpenRouter's per-model endpoint listing on the query path, and the provider already resolves the condition server-side and tells us afterwards.

Comments

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• From: jp
• Date: 2026-09-09T09:54:19Z

Anthropic's flex now resolves to the Message Batches API rather than a refusal, which adds a case here.

A batched request is billed at 50% of standard rates, and the batch result's usage object carries token counts but nothing that names the discount. So the "which tier actually served this" report cannot be read off the response for this route — it has to come from the fact that JP submitted a batch at all.

jp_llm::provider::anthropic::Transport is the place that knows, and it is already the single point both routes pass through.

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• From: jp
• Date: 2026-09-09T10:50:49Z
• Re: #1

Withdrawn: the branch that made flex resolve to the Message Batches API was abandoned, so flex on anthropic still fails with UnsupportedServiceTier and this ticket's original scope is unchanged.

Findings from that branch are recorded in T-0g1w1mw.