Distances and geo sidecars

Both live under sidecars/ of a collection, are referenced by sha256-pinned collection-relative paths, and are hashed over their uncompressed canonical JSON bytes (gzip mtime=0).

Distances (mamut-distances v1, mamut_routing_lib.distances)

One sidecar per (base, metric): the full (n+1) × (n+1) matrix of the fastest (free-flow travel times) or shortest (path lengths) metric, rounded to the family's precision (3 decimals). Slim instances reference it through arc_costs_source.model = "distances-sidecar". Generation gate: the fastest sidecar of a base equals the free-flow node-to-node times of its road-graph sidecar after the same rounding. Above a size threshold the bytes are not committed, only the pin; mamut-tools generate materialize-distances rebuilds them.

Geo (mamut-geo v3, mamut_routing_lib.geo)

One sidecar per base (<base>.geo.json[.gz]), shared by every problem-type layer: per-node geodetic (lat, lon) and local ENU positions, the reference frame, and for n <= 100 a complete road-path cache over all ordered node pairs for the fastest and shortest metrics in an indexed encoding (one vertex_lonlat table plus per-metric maps from "i-j" arc keys to index lists), about five times smaller gzipped than repeated polylines. It is static: BKS changes never touch it (v3 retired the growing road_cache of the old meta.json).

Purely informative: the checker never reads it; the website and the workbench draw with it. Route polylines of BKS for larger instances come from the website's route-geometry cache, computed by the tools' road engine and keyed by BKS sha256.