Phase transition to causal symmetry reveals operational autonomy in sociotechnical systems

Complex adaptive systems persist through continuous transformation, yet the dynamical principles governing their long-term stability remain poorly characterized. Here we analyze 50 large-scale collaborative ecosystems spanning 11,042 system-months to quantify the emergence of operational autonomy. We develop an order parameter (Gamma) measuring structural persistence amid component turnover and characterize directional coupling between organizational architecture and collective activity. Gamma exhibits a bimodal distribution (Hartigan p=0.0126; Delta BIC = 2,000), identifying two regimes: an exploratory phase of high variance and a mature phase with 1.77x variance collapse. Granger analysis reveals causal symmetrization at maturity - the structure-activity coupling ratio shifts from 0.71 (activity-driven) to 0.94 (bidirectional), indicating that architecture increasingly constrains collective coordination. A viability index, combining activity and structure, outperforms activity-based prediction (AUC = 0.88 vs 0.81), identifying 'zombie' systems where high churn masks structural decay. This extends recent work by Ait et al., who identified 'zombie' projects exhibiting activity without development based on non-coding contributions. Our metric identifies structural zombies: projects where coding activity persists but fails to preserve architectural invariants. These results establish causal symmetrization as an empirically validated signature of self-organizing autonomy applicable across complex collaborative systems - a dynamical regime previously theorized in biological contexts but here demonstrated and measured in artificial ones.