The "[Billing] Using fallback pricing for model: X" warn was emitted on
every request for any model not in LiteLLM but matched by getFallbackPricing
(e.g. "glm-5.2" substring-matches the "glm-5" fallback price). Via the stdlib
log bridge it is inferred as WARN and persisted to ops_system_logs, producing
tens of thousands of rows/day. It fired even when channel pricing already
overrides the price, and from several call sites (resolver, account-stats
pricing, non-channel billing, admin lookup).
Dedup the warn at the source (BillingService.GetModelPricing) via a sync.Map
keyed by the already-lowercased model name, so each model logs at most once
per process while keeping one audit line. Billing amounts are unchanged.
Also clarify the model/mapping pattern conflict error to state that names are
matched case-insensitively, so an existing entry (e.g. "GLM-5.2") already
covers all case variants and the lowercase variant need not be added — the
behavior the issue mistook for a case-sensitivity bug.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
