# Progress — Challenger 1 (Milestone M4 Iteration 2)

**Last visited**: 2026-10-09T09:02:30Z
**Status**: VERDICT_READY

## Steps
- [x] Read DISPATCH.md, ORIGINAL_REQUEST.md, PROJECT.md, worker_m4_remediation_2/handoff.md
- [x] Initialize BRIEFING.md and progress.md
- [x] Inspect code changes in `05_Production_Pipeline/production_orchestrator.py`
- [x] Create independent empirical test script for fallback concat with silent clips (`tests/test_challenger1_m4_empirical_probe.py`)
- [x] Run live empirical probe and analyze results (ffprobe resolution, silent audio generation, AAC 48kHz stereo) -> 4/4 PASS
- [x] Run test suite `python -m pytest tests/test_adversarial_m4_audio_concat_probe.py -v` -> 5/5 PASS
- [x] Run test suite `python -m pytest tests/test_production_pipeline_m4.py -k "test_05_fallback" -v` -> 1/1 PASS
- [x] Run full test suites for regression check (`test_m2_hygiene.py`, `test_production_pipeline_m4.py`, `test_critic_gate.py`) -> 52/52 PASS
- [x] Formulate verdict (APPROVE)
- [ ] Author handoff.md
- [ ] Notify parent orchestrator