- `[2026-07-08]` **DPO was silently running 3 epochs (harness gap) → KILLED at epoch 1.2, retargeted to 0.3
  epochs (operator call).** Root cause: `DpoConfig` had NO `epochs` field + `_dpo_config_kwargs` didn't pass
  `num_train_epochs` → DPO fell through to trl DPOConfig's default 3.0 (SFT correctly pins 1 via SftConfig.epochs
  + _sft_config_kwargs). Objective SATURATED by ~epoch 0.27 (loss~0, grad~0, acc 1.0, margins~27 flat — the
  off-policy qwopus rejected pairs are trivially separable), so epochs ~0.3→3 were pure over-optimization + a
  ~6.5h outage. No mid-run checkpoint (save_steps 500 > total steps; save only at end) → killing lost the run.
  FIX (3 edits to deployed harness, mtf-dev to canonicalize): `DpoConfig.epochs: float = 1` (mirrors SftConfig,
  float for fractions); `_dpo_config_kwargs` now passes `"num_train_epochs": cfg.epochs`; recipe `dpo.epochs: 0.3`.
  GPU-free verified (dpo.epochs=0.3 → num_train_epochs=0.3). Relaunched at 0.3 epoch (~30min precompute + ~12min
  train = ~45min). **DONE + SANITY-CHECKED (exit 0, ~70min wall: ~30min fixed precompute + 45 steps @ ~51s/step;
  train_loss 1.4e-5 @ epoch 0.301).** Fresh `data/spike/dpo_adapter/adapter_model.safetensors` (123MB) + checkpoint-45
  banked. **3-way greedy sanity (base vs SFT vs DPO, via peft load + disable_adapter/set_adapter on GPU0):
  ALL THREE DISTINCT** (base≠sft≠dpo) → full SFT→DPO pipeline applies end-to-end at inference. **DPO 0.3ep is
  COHERENT, fluent, NOT degenerate** (early-stop avoided over-optimization) but the quality delta on a neutral
  literary prompt is SUBTLE (DPO shares SFT's structure — it continues from it — with minor stylistic drift,
  arguably slightly MORE genre-clichéd). Verdict: mechanics proven, quality gain modest as predicted for 0.3ep
  on off-policy pairs; the real unlock remains on-policy rejected regen + on-domain (explicit E-RP) eval +
  the LitBench/holdout run. gen+rp RESTORED healthy. Next: serve fork (SGLang-finish vs merge) on the DPO
  adapter — same rekey_lora_for_vllm.py (zero-z) applies unchanged (mtf-dev confirmed).