epistasis_predicts: functional conflict, not weight geometry, predicts merge failure pre-merge

The decisive experiment from the external review. 39 LoRA parent pairs
(0.5B, 3 seeds) on three axes decorrelated by construction: conflict
(contradictory conventions on shared prompts, private budgets fixed),
compat (same prompts, SAME convention — overlap without conflict), and
duration (weight divergence, zero conflict). Six pre-merge predictors;
primary outcome = merge penalty (parent potential − merged achieved).

League table (Spearman vs penalty, n=39): functional measures predict
(dis_raw +0.460, epi_conf +0.446, p<0.005); geometry collapses
(delta_cos +0.03, delta_l2 +0.17 n.s.); gradient alignment weak (−0.35);
performance ~0. The first grid's apparent geometry win (+0.60) was an
overlap/volume artifact — the compat control axis (added for exactly
this) exposed and killed it: same overlap and data volume, zero penalty.
Honest riders in the README: confidence weighting does not beat raw
disagreement as a rank predictor (pre-registered internal prediction not
confirmed; it does double the conflict/compat level contrast), and
|rho|~0.45 is bounded by 0.5B merge-outcome noise (7B is the firm-up).

Also: micro-batched gradient accumulation (OOM fix on the shared 16GB
GPU), exact r-space LoRA-delta geometry (brute-force-verified test,
151 green), systemd-run runbook lesson (tmux dies with the SSH session
scope on this box).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BkRLcc18rwT2Lysu6PbG7v

tasks/lessons.md

@@ -13,3 +13,9 @@ is about (output-mean vs weight-average vs max-with-oracle vs routing are differ
 different budgets); (4) don't write "nobody has / none imports" — invite no priority disputes; say
 "to our knowledge" and state the positive contribution; (5) negative results (E13b) are strengths —
 lead with them; (6) "control theory" needs states/controls/dynamics/rule or it's a "framework".
+
+**2026-08-11 — tmux does NOT survive SSH disconnects on this machine.** The tmux server starts inside
+the SSH session's systemd scope and gets reaped on logout (lost ~20 min of the epistasis grid; GG:
+"SSH disconnected"). Reliable pattern here: `systemd-run --user --collect --unit=<name>
+--working-directory="$PWD" bash -c '<cmd>'` — lands in user@.service (kept alive by the desktop
+session), survives disconnects; check with `systemctl --user is-active <name>`, logs via redirect.

tasks/workorder-pnas-submission.md

@@ -111,8 +111,15 @@ re-run md2tex + tectonic at that point)
   - 0.5B: seeds 1–5 × {merge, moe, directed} × {easy, hard}. 7B on CX3: seeds 1–3 × hard
     {merge, moe, directed} (8–25 min walltimes → trivial). Aggregate figures with 95% CI; update
     READMEs; the headroom law now carries error bars.
-- [ ] **`epistasis_predicts` — the DECISIVE experiment (from the external review, 2026-08-11; highest
-  priority after llm_speciation lands).** The review's exact bar: population-genetic quantities must
+- [x] **`epistasis_predicts` — the DECISIVE experiment — DONE (2026-08-11, 0.5B, 39 pairs, 3 seeds).**
+  *Verdict: functional conflict measured pre-merge PREDICTS merge failure (dis_raw rho=+0.46,
+  epi_conf +0.45, both p<0.005); weight geometry does NOT (delta_cos +0.03, delta_l2 +0.17 n.s.);
+  gradient alignment weakly informative (-0.35). The first grid's apparent geometry win (+0.60) was an
+  overlap artifact, exposed and killed by the added `compat` control axis (same overlap+volume, no
+  conflict, zero penalty). Honest rider: confidence weighting did NOT beat raw disagreement as a rank
+  predictor (internal prediction not confirmed; it does give a 2x vs 1.5x conflict/compat contrast in
+  levels). |rho|~0.45 bounded by 0.5B merge noise — 7B replication is the firm-up.
+  results/llm_epistasis{,_compat}/ + figure.* The review's exact bar: population-genetic quantities must
   *predict* (not re-describe) — forecast merge success **before merging**, and beat existing
   predictors. Design, reusing the llm_speciation machinery:
   1. Parents with independently controlled interaction structure: sweep `conflict_frac` (ground-truth