# example Audited Bridge Artifact F: Real Fibonacci Fusion Data → RU Contraction Certificate

## Overview

RU is a certificate engine for universality and obstructions in constrained nonnegative propagation. Host structures supply finite inputs. Outputs are audited certificates or finite obstruction witnesses.

## What is shipped

| Artifact | Role | Path |
|---|---|---|
| Real host fusion data | Fusion rules + N_tau matrix | `sources/host_data/fibonacci_fusion_data.json` |
| Host instance model | Constraint graph + templates derived from N_tau | `sources/ru_bridge/fibonacci_realhost_contraction_model.json` |
| RU robust certificate | Tight core, Doeblin witness, RC1, rate pack, ε* | `sources/ru/robust_certificate_fibonacci_realhost_contraction.json` |
| Bridge wrapper | Reduction record + certified claim | `sources/ru_bridge/bridge_certificate_fibonacci_realhost_contraction.json` |

## What is certified (concrete)

- N_tau is nonnegative but not strictly positive.
- The length-2 product N_tau² is strictly positive, giving a Doeblin witness with δ=1 and U=2.
- The tight core is aperiodic and RC1 holds with B=0 on the tight core.
- Therefore normalized propagation contracts projectively with τ = 1/3 and an explicit exponential rate (see rate_pack).

## Why this is a -grade anchor

A reader can now audit a real host dataset end-to-end:

host fusion rules → fusion matrix → constrained propagation instance → robust RU certificate → explicit contraction rate.

No narrative leap is required.
