Function pre_flight_reserve 

pub async fn pre_flight_reserve(budget: &PluginBudget) -> f64

Sleep if the projected budget is too low, then atomically reserve an estimated cost for the upcoming request.

Returns the reserved point amount. Every exit path after this call — both success and error — must call release_reservation with the returned value to prevent the pending balance growing indefinitely.

The Mutex guard is released before the .await to satisfy Send bounds.

Example

use stygian_graph::adapters::graphql_throttle::{
    CostThrottleConfig, PluginBudget, pre_flight_reserve, release_reservation,
};

let budget = PluginBudget::new(CostThrottleConfig::default());
let reserved = pre_flight_reserve(&budget).await;
// ... send the request ...
release_reservation(&budget, reserved).await;