Civil litigation is inherently a life-cycle process: what a lawyer drafts on day one constrains what unfolds at trial months later. Yet existing legal benchmarks evaluate isolated subtasks, and prior legal-agent simulators reinitialize each scenario from shared ground truth, leaving cross-stage causal dependencies unmodeled. We present LegalWorld, a life-cycle interactive environment that models Chinese civil litigation as a causally connected state chain of five stages (seven sub-scenarios), grounded in 75,309 paired Chinese civil judgments. We pair it with reusable infrastructure (local memory, global case memory, a Skill/Tool library) and Reflective Legal Skill (RLS), which distills completed trajectories into reusable procedural skills. Building on this environment, we construct LongJud-Bench to evaluate agent capability across all five connected stages. 18,992 ratings from 217 legal-background evaluators confirm that LegalWorld trajectories are procedurally faithful and role-consistent; cross-model evaluation reveals stage-level divergences invisible to aggregate scores (backbones within 4 overall points can differ by up to 15 normalized points on individual stages), and RLS yields consistent gains on both reflected and held-out cases. Detailed resources will be provided upon acceptance.