**Motivations:**
- Instrument the C3 “final lock” as a citeable deterministic artefact
- Provide a reproducible check over Lift(B12) at palier 2^13 using D8/Fusion witnesses
**Root causes:**
- C3 lacked a machine-checkable artefact aligned with the run-report standard
**Correctifs:**
- Add a deterministic verifier that checks fusion witnesses (m<n and U(m)=U^t(n)) and aggregates N* where computable
**Evolutions:**
- Version C3 verification artefacts under docs/artefacts
- Add run report profile c3_local_descent (sha256 + metrics)
- Document the new profile and reference the artefacts in the proof plan
**Pages affectées:**
- applications/collatz/collatz_k_scripts/collatz_verify_c3_local_descent.py
- docs/artefacts/collatz/c3_local_descent/verification_c3_local_descent.json
- docs/artefacts/collatz/c3_local_descent/verification_c3_local_descent.md
- applications/collatz/collatz_k_scripts/collatz_generate_run_report.py
- docs/collatz_run_report_2026-03-09_c3_local_descent.md
- docs/collatz_run_report_format.md
- docs/features/collatz_run_report_generator.md
- docs/features/collatz_c3_local_descent_verification.md
- applications/collatz/collatz_k_scripts/plan_lemmes_manquants_et_programme_de_preuve.md
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