502 — Upstream unavailable

{
  "error": {
    "code":           "upstream_unavailable",
    "message":        "All fallback candidates failed.",
    "fallback_chain": [
      { "model": "anthropic/claude-haiku-4-5", "error": "timeout" },
      { "model": "openai/gpt-4o-mini",         "error": "503" },
      { "model": "mistral/mistral-small",      "error": "503" }
    ]
  }
}

What HiWay did

HiWay routed to the primary model, the provider returned an error. Provider fallback kicked in and tried up to 2 more candidates. All three failed. HiWay surfaced the chain so you can see which providers were attempted.

What to do

• Check the status page of the primary provider (status.anthropic.com / status.openai.com / status.mistral.ai).
• Make sure you have provider keys for at least two providers in Settings → Providers — single-provider setups can't benefit from fallback.
• Retry after a short backoff. Most 502s are short incidents.