# Contract (P0)
**Question**: Walrasian equilibrium of 2-agent, 2-good Cobb-Douglas exchange economy; good 2 numeraire (p2=1).
**Estimands**: p=p1/p2 (closed form); allocation x1_A,x2_A,x1_B,x2_B; aggregate excess demand of good 1 at p (should be 0); Walras residual p*z1+z2 (identically 0); numerical root of z1(p) as independent validation.
**Assumptions**: Cobb-Douglas with 0<alpha_i<1 => interior demands x1_i=alpha_i*m_i/p, x2_i=(1-alpha_i)*m_i, m_i=p*e1_i+e2_i; strictly positive endowments; normalisation p2=1. Unique equilibrium since z1 strictly decreasing in p.
**Outputs**: out/results.json (task_id, price_ratio_p1_over_p2, x1_A, x2_A, x1_B, x2_B, excess_demand_good1, walras_law_residual, aggregate_endowment_good1, aggregate_endowment_good2, price_ratio_numerical, feasibility, feasibility_reason, data_issues, n_input_rows, n_analysed, random_seed); out/report.md (6 sections); out/analysis.py; out/claims.json.
**Information rules**: only data/; numerical validation must root-find z1(p) directly, not evaluate the closed form; report every data problem in data_issues.
**Invalidity**: non-positive endowments, alpha outside (0,1), missing agent; inconsistent inputs must be detected and resolved explicitly.