Impedance and return-path risk evidence

ZapTrace emits explicit impedance assumptions and return-path diagnostics as machine-readable evidence. This is a heuristic pre-check, not a field solver and not fabricator stackup approval.

Inputs

The report consumes:

Net.constraints.impedance_target
Net.constraints.return_path_net
Net.constraints.is_high_current

Report

build_impedance_return_path_report(design) returns assumption counts, diagnostic counts, human-review status, blocking status, assumptions, diagnostics, and limitations.

Each impedance assumption records net id/name, target impedance, assumed Er, copper thickness, dielectric height, and method.

Policy

• Explicit impedance assumptions are recorded for controlled-impedance nets.
• Nets that need a return path but have no return_path_net become human-review-required.
• Future plane-geometry gates can mark actual discontinuities as blocked=true.

Proof-pack sign-off

human_review_required=true and blocked=false -> impedance-return-path requires human review
blocked=true                                -> impedance-return-path blocks autonomous-pass
passed=true with no diagnostics             -> impedance-return-path passes