Struct FiberContext 

pub struct FiberContext {
    pub phase: Arc<str>,
    pub cycle: AtomicU64,
    pub controls: ControlMap,
}

Per-fiber execution context carried across the async call chain via a tokio::task_local! binding. Thread-locals are unsafe here because tokio’s work-stealing scheduler can migrate a task between worker threads at any .await; a task-local is bound to the task itself and survives migration.

Fields

phase: Arc<str>

Name of the phase this fiber is running under. Arc’d so two fibers under the same phase share one allocation.

cycle: AtomicU64

Current cycle ordinal. AtomicU64 rather than Cell so the context is Sync — tokio requires task-local values to be Send + Sync.

controls: ControlMap

SRD-89 — the current component’s control resolution, for this fiber’s execution: control name → live erased handle, walked up once from the fiber’s own phase component (nmbrs_metrics::component::Component::control_snapshot, first-match / nearest-wins) and read lock-free thereafter. It holds live handles, not values, so a servo retarget on the shared control is observed through it. Because each execution’s fibers carry their own phase component’s snapshot, a same-named control (concurrency / rate) resolves to that execution’s instance — uniformly in single-run and concurrent runs, with no session-root walk and no cross-talk. Empty for fibers spawned without a component (a control read then falls back to the session-root walk).