# Open-Weight Cascade

> Build a multi-model cascade where the lower tiers are deliberately open-weight, self-hostable models that can run inside the operator's boundary, a...

- **Category**: Agentic AI
- **Subcategory**: Routing & Composition
- **Canonical URL**: https://designpattern.fyi/patterns/open_weight_cascade/

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## Description
**Intent**: Build a multi-model cascade where the lower tiers are deliberately open-weight, self-hostable models that can run inside the operator's boundary, and only escalations cross to a hosted frontier model — giving cost arbitrage *and* a sovereign fast-path.
**Context**: An operator in a regulated environment — a European bank, a healthcare provider, a government agency — is building an agent and wants both the cost benefits of a multi-tier model cascade and the assurance that sensitive data does not leave their controlled boundary. Open-weight models that can be self-hosted have become capable enough to handle most requests at low cost, but a small share of hard requests still benefit from a hosted frontier model. The operator already runs at least one open-weight model on infrastructure they control.
**Solution**: Stratify requests by sensitivity *and* difficulty before routing. (1) Sensitive requests: forced down the open-weight path even if confidence is low; degrade gracefully or refuse rather than escalate. (2) Insensitive easy requests: small open-weight model. (3) Insensitive hard requests: escalate to hosted frontier model. The router enforces the sensitivity classification before any model call.


## Use Cases
- Sensitive requests must stay inside an operator-controlled boundary even when borderline.
- Insensitive easy requests can be served cheaply by a small open-weight model.
- Insensitive hard requests can be safely escalated to a hosted frontier model.





## Trade-offs


### Advantages

- Compliant fast-path for sensitive workloads.

- Cost arbitrage on the insensitive path.

- Operator can swap model tiers without re-architecting.




### Considerations & Drawbacks

- Sensitivity classifier is the new failure surface.

- Quality cliff at the sensitive boundary if the open-weight tier under-performs.

- Operational overhead of running two stacks.







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**Reference**: [Original Source](https://www.agentpatternscatalog.org/patterns/open-weight-cascade/)