[LiteLLM] Cost tracking silently returns cost=0 / "This model isn't mapped yet" for newer models when the remote model cost map fetch fails and the bundled backup is older

Cause (Maintainer-confirmed cause): Cost lookup is post-call inside a try/catch: a missing entry logs a warning and sets cost=0 instead of failing. The fallback to the stale bundled map was completely silent before the incident remediation; in the January 2026 incident a malformed JSON commit on main caused a JSONDecodeError on fetch. Fix status: fixed_upstream Workaround (not a fix): Set custom model pricing (input_cost_per_token/output_cost_per_token) in model_info for unmapped models; set LITELLM_LOCAL_MODEL_COST_MAP=True for deterministic zero-network imports (then pricing only comes from the installed package). Misleading approaches: - Treating the 'isn't mapped yet' message as a routing or provider error: calls are not blocked, only cost is lost. Limitations: - The exact release that first shipped the fallback warning is not stated in the incident report. Unknowns: - Which package versions' backup maps include a given new model Evidence (public sources, summarized; not reproduced by this contributor): - https://github.com/BerriAI/litellm-docs/blob/main/blog/model_cost_map_incident/index.md (release_notes, 2026-02-10, maintainer_confirmed_cause): Incident report: a malformed model_prices_and_context_window.json on main made the import-time fetch fail and LiteLLM silently fell back to a stale local backup, so older installs lost cost tracking for newer models; remediation added CI validation, a fallback warning log and integrity checks, and documents LITELLM_LOCAL_MODEL_COST_MAP=True. - https://github.com/BerriAI/litellm/blob/main/litellm/utils.py (official_docs, unknown, documented_behavior): The not-mapped message text is "This model isn't mapped yet. model={model}, custom_llm_provider={provider}. Add it here - ...model_prices_and_context_window.json." Search phrasings: litellm spend shows 0 for new model; litellm This model isn't mapped yet cost tracking; LITELLM_LOCAL_MODEL_COST_MAP stale model cost map; litellm model cost map fetch failed fallback backup Evidence basis (self-declared by the contributing chat client): public_source.