Route through a gateway with a tested open-weights fallback

The Stack

Steps

1. 1

   Write the failover config and validate it

   Point at a gateway base_url, set your primary, and pin a fallback that is open-weights, dated with when you last tested it, and carries the smoke prompts you ran. CI checks all of that is present, so the config cannot pass with an untested or recallable fallback. Actually failing over needs keys and is fenced.

   cat > failover.json <<'JSON'
   {
     "base_url": "https://openrouter.ai/api/v1",
     "primary": "anthropic/claude-fable-5",
     "fallback": {
       "model": "z-ai/glm-5.2",
       "open_weights": true,
       "tested_on": "2026-07-01",
       "smoke_prompts": ["summarize this ticket", "extract the invoice fields", "draft a reply in my voice"]
     }
   }
   JSON
   node -e '
   const fs = require("fs");
   const c = JSON.parse(fs.readFileSync("failover.json", "utf8"));
   function bad(m) { console.error("BAD: " + m); process.exit(1); }
   if (!c.base_url) bad("no gateway base_url (route through a gateway, do not hard-wire a model)");
   if (!c.primary) bad("no primary model set");
   const f = c.fallback || {};
   if (!f.model) bad("no fallback model set");
   if (f.model === c.primary) bad("fallback must differ from the primary");
   if (f.open_weights !== true) bad("fallback must be open-weights (a hosted fallback can be recalled too)");
   const parts = String(f.tested_on || "").split("-");
   if (parts.length !== 3 || !parts[0]) bad("fallback needs a tested_on date (a backup you never ran is a hope)");
   const sp = f.smoke_prompts || [];
   if (!Array.isArray(sp) || sp.length < 1) bad("fallback needs at least one smoke prompt you actually ran");
   console.log("config OK: gateway primary " + c.primary + " with tested open-weights fallback " + f.model + " (tested " + f.tested_on + ", " + sp.length + " smoke prompt(s))");
   '

2. 2

   Rehearse the failover (the model step, not checked by CI)

   Run your smoke prompts through the fallback for real, on a schedule, and confirm it holds up on the tasks that matter. When the primary vanishes, flip one line to the fallback. Keep your prompts and context in a portable form so the switch is copy-and-paste, not a rebuild. The runs and quality are fenced.