Struct TierSelector 

pub struct TierSelector { /* private fields */ }

Type-safe selector for a specific model tier

This newtype wrapper validates that at least one endpoint exists for the specified tier at construction time, then provides type-safe selection from that tier.

Tier Selection for LLM Routing

When used by the LLM-based router, the tier choice impacts routing performance:

• FAST (8B): Lowest latency (~50-200ms) but may misroute complex requests. Risk of bad routing decisions outweighs latency savings.

• BALANCED (30B): Recommended default. Good reasoning for classification with acceptable latency (~100-500ms). Best balance of accuracy and speed.

• DEEP (120B): Highest accuracy but very slow (~2-5s). Router latency may exceed the time to just run the user query on BALANCED. Rarely worth it.

Construction-Time Validation

The tier is validated at construction (checks that at least one endpoint exists) and stored immutably. The selector cannot switch tiers after construction, but tier selection itself is a runtime parameter, not a compile-time guarantee.

Implementations

impl TierSelector

pub fn new(selector: Arc<ModelSelector>, tier: TargetModel) -> AppResult<Self>

Create a new TierSelector for the specified tier

Returns an error if the ModelSelector has no endpoints for the specified tier. This validation ensures the router can never be in an invalid state.

Arguments

• selector - The underlying ModelSelector
• tier - Which tier (Fast, Balanced, Deep) to select from

Errors

Returns AppError::Config if no endpoints are configured for the specified tier.

pub async fn select(&self, exclude: &ExclusionSet) -> Option<&ModelEndpoint>

Select an endpoint from this selector’s tier with health filtering and exclusion

Arguments

• exclude - Set of endpoint names to exclude (for retry logic)

Returns

• Some(&ModelEndpoint) if a healthy, non-excluded endpoint exists for this tier
• None if all endpoints for this tier are unhealthy or excluded

pub fn tier(&self) -> TargetModel

Get the tier this selector operates on

pub fn endpoint_count(&self) -> usize

Get the number of configured endpoints for this selector’s tier

pub fn health_checker(&self) -> &Arc<HealthChecker>

Get a reference to the health checker for external use (e.g., marking success/failure)

Trait Implementations

impl Debug for TierSelector

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.