Constant RECOMPOSITION_TOLERANCE_M 

const RECOMPOSITION_TOLERANCE_M: f64 = 1e-4;

Maximum reconstructed-vertex residual (metres) a rotation-aware instance placement may carry and still be trusted (issue #3575). Compared against the ORIGINAL f32/f64 positions, before quantization, so it is independent of VERTEX_MULTIPLIER.

On /optimized a residual under this bound is invisible on the wire, since 0.1mm is that route’s quantization grain itself (quantize_position in parquet_optimized.rs). That argument does NOT carry to the flat route (#3888), which ships unquantized Float32 metres and has no grain to hide behind: there, a residual just under tolerance is a real displacement of a repeated element, up to 0.1mm per vertex against the bit-exact geometry the route used to emit. Kept at one bound for both because 0.1mm is below any BIM tolerance the downstream consumers work to, but it is a bound, not an invisibility. A group whose residual exceeds this falls back to the pre-#3575 content-hash dedup (each occurrence keeps its own baked mesh) instead of shipping a placement nobody verified.