wassname
8d170a0753
It was a fixed-budget regularizer dressed up as a detector — by
construction, quantile gate dropped exactly drop_top_frac of axes per
step regardless of whether anything was genuinely suspicious. The susp
diagnostic column was 100% determined by the config knob, zero
information content.
The principled defense against noise axes is extract-time tau_axis
(drop singular axes below noise floor once at save), not a runtime
quantile. In high-d (r=2560), expected damage from carrying a noise
axis through to runtime projection is ~||g||/sqrt(r) ≈ 2%/axis, so
the cost is bounded anyway.
Kept: load_v_hack still returns (v_hack, v_sv) tuple for callers that
need S values offline. The _sv/{name} keys remain in saved files for
future use (extract-time tau_axis, diagnostics).
Per-source cin (cin_s, cin_t) stays — that's the actual discriminator
for whether v_hack projects hack > non-hack. #51 already showed
cin_t/cin_s ~= 2.0 across early steps, so the direction is doing real
work.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
projected_grpo
SVD-basis gradient projection vs RL reward hacking. Tests whether projecting the training gradient orthogonal to an extracted hack-direction (in the SVD-of-W basis) reduces reward-hack rate in GRPO without tanking pass rate.
Built on Ariahw, Engels & Nanda's rl-rewardhacking LeetCode benchmark. Method differs from concurrent work (Wu & Tang 2026, "Advantage Modification") by intervening at the gradient level rather than the advantage level.
See docs/spec.md, docs/brainstorm/extracted_prefs.md, and docs/papers/.
Quick start
uv sync
just fast-dev-run # tiny-random model, ~1-2 min, real pipeline end-to-end
just smoke-vanilla # vanilla pathway smoke
just smoke-projected # projected pathway smoke
just download-model # warm Qwen3-4B cache (full preset peaks ~73GB on 96GB)
just queue-full # queue extract + 3-seed vanilla + 3-seed projected sweep
See RESEARCH_JOURNAL.md for session-by-session findings,
including the 2026-05-23 grader-bug discovery that invalidated all prior gt=0
measurements and the move from Qwen3.5-2B to Qwen3-4B (reference substrate).
Hypotheses (preregistered)
See spec.md. Headline: H1 — gradient projection in SVD basis against a v_hack extracted from ~60-80 contrastive pairs reduces reward hack rate by
=30pp absolute vs vanilla GRPO at matched LeetCode pass rate (±10pp).