Migrate From a Closed API Model to an Open-Weight Model Without Breaking Your App
Swap the model behind a production feature without a rewrite or a silent quality regression, in about half a day.
Download workflow config (JSON)How the data moves
This is a handoff plan, not an automatic integration. Review outputs before the next step. Unlabeled arrows show order, not a verified data format. Use the capability links to explore tool substitutions.
Step 1
Baseline Your Current Model's Real Outputs
Pull 30-50 real production prompts and their current responses, logged through LangSmith rather than reconstructed from memory. This baseline is what every candidate replacement gets measured against, not a handful of hand-picked examples that flatter whichever model you're hoping to switch to.
Step 2
Test Candidate Models Without Touching Your App's Code
Route the same baseline prompts through OpenRouter to a few open-weight candidates side by side. OpenRouter's single API surface means you're comparing model outputs, not rewriting integration code for each candidate.
Step 3
Score the Replacement Against the Baseline
Use Braintrust to score each candidate's outputs against your baseline on the criteria that actually matter for this feature, correctness, tone, format, whatever you'd have caught in review. A model that's cheaper but scores worse on the dimension your users notice isn't a win.
Step 4
Cut Over Gradually With a Rollback Path
Once a candidate wins, route a small percentage of real traffic to it through OpenRouter first, watching error rates and user-facing quality signals before increasing the share. Keep the old model's routing config in place and ready, not deleted, until the new one has run clean for a real stretch of production traffic.
Time Required
4-6 hours
Expected Result
Your application running on an open-weight model instead of a closed API, with evidence the swap didn't degrade output quality and a rollback path if it did.
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