Struct RunReportParams 

pub struct RunReportParams<'a> {
    pub stats: &'a RunStats,
    pub reservoir_size: usize,
    pub run_start: Instant,
}

Parameters required to build a RunReport from a completed RunStats.

reservoir_size and run_start are not stored on RunStats (they are inputs to the run, not results). They are threaded through here to avoid polluting the core run type with output-layer concerns.

Invariant

run_start must be the Instant captured immediately before the first request was dispatched, so that completed_at - run_start correctly maps each result to its stage window.

Fields

stats: &'a RunStats

reservoir_size: usize

Configured reservoir cap (--result-buffer). Passed from CLI args.

run_start: Instant

Wall-clock instant at which the run started (before first request fired).

Why this field exists beyond the original spec: per_stage_reports buckets each RequestResult into a stage window by computing completed_at.checked_duration_since(run_start) and comparing it against the cumulative [stage_start, stage_end) offsets. Without this anchor, wall-clock timestamps cannot be mapped to stage windows.

Why from_params (fixed mode) accepts it but discards it: API uniformity. Both fixed and curve callers construct a single RunReportParams and pass it to from_params or from_params_with_curve without needing to know which variant requires run_start. Keeping one param struct prevents callers from branching on mode before building params.