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Literature — does GRPO/RLVR move a Qwen-class base?

Papers that bear on the ladder's bet. Short version: the field largely agrees with our weekend null — on Qwen, GRPO/RLVR mostly sharpens what the base already does; it rarely adds capability the base can't sample. A minority show real expansion, but only with scale/diversity/compute we don't have on 48GB. Mapped to strat.md hypotheses.

The "GRPO won't add much" side (supports H3, and explains the weekend pass@1==pass@8)

  • Yue et al., "Does RL Really Incentivize Reasoning Capacity Beyond the Base Model?" NeurIPS'25 · 2504.13837 · repo. The most directly relevant. RLVR (incl. GRPO) beats base at pass@1 but base matches or beats the RL model at large pass@k — RL narrows the output distribution toward already- sample-able correct paths, it doesn't widen the reasoning boundary. This is exactly our weekend result (pass@1 == pass@8 == 14.3%): nothing new to amplify. Their contrast: distillation (≈ our SFT warm-start) genuinely adds new patterns. → backs H3 and the "SFT is the mover" thesis.

  • Shao/Li et al., "Spurious Rewards: Rethinking Training Signals in RLVR" 2506.10947 · interconnects writeup. GRPO on Qwen2.5-Math gains ~21pts on MATH-500 with random/spurious rewards (vs 29 with real) — because GRPO's clip bias amplifies pretrained code-reasoning priors. Crucial caveat: this is Qwen-specific — it does NOT replicate on Llama/OLMo. So a Qwen gain may be eliciting priors, not learning the reward. → our two-model probe (jac-trained vs fresh qwen3coder) is the right control; if both move identically regardless of jac-SFT, suspect prior-elicitation not learning.

  • "RLVR makes models faster, not smarter"promptfoo summary. Practitioner-level restatement of the same: efficiency gain, not capability gain.

The σ=0 / vanishing-advantage mechanism (validates our body_sim scar)

  • DAPO · 2503.14476 · site. Names our exact failure: when every rollout in a group is all-correct or all-wrong, group variance → 0 → zero gradient. DAPO's fix = dynamic sampling (oversample, drop 0/1-accuracy groups, refill with mixed-quality). We solve the same problem differently: a dense body_sim term that gives within-group variance even at 0% pass. → validates carried scar #2. Possible upgrade for the raw-base-GRPO control: add DAPO dynamic-sampling so the σ=0 control fails for the right reason.
  • EBPO (2602.05165), "Gradient Starvation in Binary-Reward GRPO" (2605.07689) — more variants of the same saturated-regime zero-gradient diagnosis + fixes. Confirms it's a known structural GRPO flaw, not our harness bug.

The "RL CAN expand" counter-side (the falsifier for H3 — what would prove us wrong)

  • ProRL · 2505.24864. Prolonged RL (much longer training, KL control, diverse tasks) does push reasoning past the base — pass@k boundary widens, not just pass@1. The condition we likely can't meet on 48GB/LoRA: needs scale, many tasks, full-ish training. Reading: if any rung shows real holdout lift from GRPO, ProRL is why.
  • "RLVR Implicitly Incentivizes Correct Reasoning in Base LLMs" · 2506.14245. Argues RLVR does instill correct-reasoning signal (nuance against Yue). Healthy adversarial read.

Takeaway for the ladder

The weekend null is the expected outcome per Yue + Spurious Rewards, not a harness failure — at our scale (30B, LoRA, ~50 tasks, exact-stdout) GRPO has little headroom to amplify. The ladder's value is measuring the SFT curve (the proven mover) and pinning GRPO's marginal lift at exactly 0 with the controls. To give GRPO its best honest shot (and possibly falsify H3), the literature points to: more tasks (ProRL's diversity), DAPO dynamic sampling on the control, and reading pass@k not pass@1 (Yue).