Scenario: LEC Mismatch After Late ECO - Interview Scenario

Scenario

A post-synthesis ECO introduces non-equivalence at several compare points. Team members disagree whether the issue is mapping setup, intended latency movement, or a real functional bug.

OBSERVED METRIC
Mismatch count remains non-zero across reruns, with unstable compare-point mapping and inconsistent replay classification.

45-MINUTE INTERVIEW FLOW
0-5: define requirement and KPI
5-15: classify first divergence boundary
15-25: identify proving artifact packet
25-35: propose bounded fix with owner
35-45: define validation matrix and rollback

Common traps to avoid

• Escalating to waivers before first-divergence isolation.

• Forcing cycle-aligned checks on changes that require SEC semantics.

• Ignoring library primitive and clock-gating modeling differences.

Scenario debrief

Score scenario responses on assumption discipline, first-divergence analysis, proof-quality evidence, and release-safe mitigation.

requirements -> model -> proof status -> closure decision

closure confidence trend by risk tier

Debrief prompts

1. Which requirement failed first, and is that path legally reachable?

2. Which modeling assumption most influences this result?

3. What smallest reversible action improves confidence without hiding legal behavior?

Key takeaways

• Tie each proof claim to assumption boundaries and reachability evidence.

• Prefer minimal reversible fixes and preserve legal behavior visibility.

Common pitfalls

• Treating runtime reduction as proof-quality improvement without audits.

• Declaring closure while critical covers remain unreachable.

• Using broad waivers instead of first-divergence root-cause ownership.