---
title: Failovers & JSON Repair
description: Resilient model fallbacks, rate limit retries, and automatic schema repair.
sidebar:
  order: 5
  label: Failovers & JSON Repair
---

## Failover Chains & Automatic JSON Repair

Production agent pipelines must withstand upstream API outages, transient rate limits (HTTP 429), and syntax errors in LLM JSON generation.

---

## Fallback Failover Chains

You can define ordered fallback model lists per agent role in `niki.toml`. If the primary model returns a 5xx server error, rate limit timeout, or fails after retries, NIKI seamlessly fails over to the next configured fallback:

```toml
[agents.planner]
provider  = "anthropic"
model     = "claude-sonnet-4-20250514"
fallbacks = [
  { provider = "openai", model = "gpt-4o" },
  { provider = "openrouter", model = "deepseek/deepseek-r1" }
]
```

---

## Automatic JSON Repair

Agents frequently return markdown-wrapped JSON code fences (` ```json `), trailing commas, or unescaped quotes.

NIKI includes a deterministic AST-based JSON repair engine:
1. Strips markdown fences, preamble text, and comments.
2. Fixes trailing commas and missing bracket closures.
3. Attempts multi-pass schema re-parsing before triggering an agent retry prompt.