---
slug: model-cost-map-incident
title: "Incident Report: Invalid model cost map on main"
date: 2026-02-10T10:00:00
authors:
  - name: Ishaan Jaffer
    title: "CTO, LiteLLM"
    url: https://www.linkedin.com/in/ishaanjaffer/
    image_url: https://pbs.twimg.com/profile_images/1613813310264340481/lz54oEiB_400x400.jpg
tags: [incident-report, stability]
hide_table_of_contents: false
---

**Date:** January 27, 2026
**Duration:** ~20 minutes
**Severity:** Low
**Status:** Resolved

## Summary

A malformed JSON entry in `model_prices_and_context_window.json` was merged to `main` ([`562f0a0`](https://github.com/BerriAI/litellm/commit/562f0a028251750e3d75386bee0e630d9796d0df)). This caused LiteLLM to silently fall back to a stale local copy of the model cost map. Users on older package versions lost cost tracking for newer models only (e.g. `azure/gpt-5.2`). No LLM calls were blocked.

- **LLM calls and proxy routing:** No impact.
- **Cost tracking:** Impacted for newer models not present in the local backup. Older models were unaffected. The incident lasted ~20 minutes until the commit was reverted.

{/* truncate */}

---

## Background

The model cost map is not in the request path. It is used after the LLM response comes back, inside a try/catch, to calculate spend. A missing entry never blocks a call.

```mermaid
flowchart TD
    A["1. litellm.completion() receives request
    litellm/main.py"] --> B["2. Route to provider
    litellm/litellm_core_utils/get_llm_provider_logic.py"]
    B --> C["3. LLM returns response
    litellm/main.py"]
    C --> D["4. Post-call: look up model in cost map
    litellm/cost_calculator.py"]
    D -->|"found"| E["5a. Attach cost to response"]
    D -->|"not found (try/catch)"| F["5b. Log warning, set cost=0"]
    E --> G["6. Return response to caller"]
    F --> G

    style D fill:#fff3cd,stroke:#ffc107
    style F fill:#fff3cd,stroke:#ffc107
    style E fill:#d4edda,stroke:#28a745
    style G fill:#d4edda,stroke:#28a745
```

Both paths return a response to the caller. When the cost map lookup fails, the only difference is `cost=0` on that request.

---

## Root cause

LiteLLM fetches the model cost map from GitHub `main` at import time. If the fetch fails, it falls back to a local backup bundled with the package. Before this incident, the fallback was completely silent -- no warning was logged.

A contributor PR introduced an extra `{` bracket, producing invalid JSON. The remote fetch failed with `JSONDecodeError`, triggering the silent fallback. Users on older package versions had backup files missing newer models.

**Timeline:**

1. Malformed JSON merged to `main`
2. LiteLLM installations fall back to local backup on next import
3. Users report `"This model isn't mapped yet"` for newer models
4. Bad commit identified and reverted (~20 minutes)

---

## Remediation

| # | Action | Status | Code |
|---|---|---|---|
| 1 | CI validation on `model_prices_and_context_window.json` | ✅ Done | [`test-model-map.yaml`](https://github.com/BerriAI/litellm/blob/main/.github/workflows/test-model-map.yaml) |
| 2 | Warning log on fallback to local backup | ✅ Done | [`get_model_cost_map.py#L57-L68`](https://github.com/BerriAI/litellm/blob/main/litellm/litellm_core_utils/get_model_cost_map.py#L57-L68) |
| 3 | `GetModelCostMap` class with integrity validation helpers | ✅ Done | [`get_model_cost_map.py#L24-L149`](https://github.com/BerriAI/litellm/blob/main/litellm/litellm_core_utils/get_model_cost_map.py#L24-L149) |
| 4 | Resilience test suite (bad hosted map, fallback, completion) | ✅ Done | [`test_model_cost_map_resilience.py#L150-L291`](https://github.com/BerriAI/litellm/blob/main/tests/llm_translation/test_model_cost_map_resilience.py#L150-L291) |
| 5 | Test that backup model cost map always exists and contains common models | ✅ Done | [`test_model_cost_map_resilience.py#L213-L228`](https://github.com/BerriAI/litellm/blob/main/tests/llm_translation/test_model_cost_map_resilience.py#L213-L228) |

Enterprises that require zero external dependencies at import time can set `LITELLM_LOCAL_MODEL_COST_MAP=True` to skip the GitHub fetch entirely.

---

## Other dependencies on external resources

| Dependency | Impact if unavailable | Fallback |
|---|---|---|
| Model cost map (GitHub) | Cost tracking for newer models | Local backup (now with warning) |
| JWT public keys (IDP/SSO) | Auth fails | None |
| OIDC UserInfo (IDP/SSO) | Auth fails | None |
| HuggingFace model API | HF provider calls fail | None |
| Ollama tags (localhost) | Ollama model list stale | Static list |