System prompts and routing
Why the system prompt affects which tier your request is routed to.
HiWay reads the system message to score complexity. A detailed role-play system prompt with many instructions signals a complex task — the scorer nudges routing toward a heavier tier. A short "You are a helpful assistant" stays neutral.
What the scorer looks for
- Length — long system prompts are often for complex agents, multi-step workflows, or structured output constraints.
- Tool instructions — "You have access to the following tools" pushes complexity up.
- Chain-of-thought primers — "think step by step", "reason carefully" are signals of heavier work.
- Code-domain keywords — "debug", "refactor", "architect" trigger the code weight.
Stable across requests
Because the scorer is deterministic, the same system prompt always produces the same tier delta. You can tune your app's system prompt to consistently hit a specific tier — HiWay won't surprise you with a different model on the next call.
Privacy note
The system prompt is scored in memory and immediately discarded. It is never logged, never stored, never sent anywhere except forward to the routed provider. This is the same guarantee as the user message content.