# Compatibility is a gate, not a suggestion
[Content hub](/en/ai/content)
- type: article
- published_at: 2026-08-12
- tags: compatibility, policy, setup
See how exact versions, harness support and policy checks turn a proposed setup into a deterministic plan or a useful refusal.
## Content
A useful setup is more than a list of attractive components. Every pinned version must fit the target harness, platform and trust policy before a provider can apply it.
## Start with exact inputs
The builder receives exact component versions and a concrete target. It does not silently upgrade, replace or reinterpret them while checking the graph.
## Separate the gates
- Schema and dependency constraints decide whether the graph is structurally valid.
- Harness and platform support decide whether the target can execute it.
- Trust and consent policy decide whether the operation is permitted.
## Make refusal actionable
A failed gate should identify the incompatible edge or missing consent. The operator can then change the proposed plan explicitly instead of discovering an implicit substitution after installation.