Procore side: REST API v1.0 (/rest/v1.0/projects, commitments, direct costs endpoints), OAuth 2.0, webhook subscriptions for near-real-time triggers. SAP side: OData services on S/4HANA, BAPI where OData coverage is thin: BAPI_PO_CREATE1 / BAPI_PO_CHANGE for commitments and change orders, FI document posting for invoices (BKPF/BSEG), business partner master (BUT000 on S/4, LFA1/KNA1 on ECC), project structures (PROJ/PRPS), budget and planning (BPGE/COSP), actuals and commitment line items (COEP/COOI), billing (VBRK/VBRP). Middleware: SAP Integration Suite iFlows where the customer runs it; PI/PO or a dedicated lightweight service otherwise. All writes go through standard interfaces so SAP change documents and audit logs stay intact.