Does letting walkers search around their own finds make the fly find more?

EXPERIMENTS.md · lines 12676–12695

E202–E205 — the three fixes, one at a time, then together (2026-09-19 08:47; queued after E201 and E173c)

Correction to the E195/E195b tables above: the log's ± is the standard error over seeds (sd/√n), not the population sd; score_arms.py reports the ddof-1 sd. Baseline = E195b fly: AUC_Q 73.54 (s.e. 16.25, sd 23), 158 finds (sd 24), last-window finds 123 / 113, mean find depth −61.9; elitist 88.90 / 169.5 / last-window 147, 139 / depth −74.4 (seed mean). Code: branch fly-competitive (local search in Forager, imagination + history in FlyGenerator, prediction_error in mushroom.py, flags + diagnostics in stage_b; flags off reproduce E195b bit-for-bit by construction and by test). Predictions, each before its run:

• E202 local search (FORAGER_LOCAL_SEARCH=1): last-window finds ≥ 139 (elitist's floor) and distinct finds ≥ 170; AUC_Q within one seed-sd of elitist. If the last window does not move, the stall is not the walkers' memory and the anchor mechanism is wrong as built.
• E203 imagination (FORAGER_IMAGINE=4): mean find depth deeper by ≥ 5 meV than −61.9; finds unchanged within sd. Void if E201's score–reward correlation is < 0.2.
• E204 RPE (FORAGER_RPE=bennett): score–reward correlation up by ≥ 0.10 over E201's live arm; AUC_Q not worse.
• E205 all three vs elitist, 3 seeds: fly AUC_Q ≥ elitist − one seed-sd, finds ≥ elitist, depth within 5 meV of elitist's. If E205 fails after E202 passed, the pieces interfere and the combination is retuned one flag at a time, not all together.

EXPERIMENTS.md · lines 12860–12873

E202 result (2026-09-20 01:05) — local search FALSIFIED on both restated bars. fly + FORAGER_LOCAL_SEARCH=1: AUC_Q 86.5 (seeds 98.6 / 74.3), 146.5 finds (184 / 109), depth −68.1, ρ 0.69, windows [160,178,196,196] and [185,157,138,50]. Baseline E201b fly: 136.9, 284 finds (300 / 268), depth −66.8. Bars: finds ≥ 307 → 146.5, failed; depth ≤ −72 → −68.1, failed (moved 1.3 meV, not 5). Local search halves the fly's finds and triples its seed spread. The pre-registered fallback applies as written: the stall was not the walkers' memory and the anchor mechanism is wrong as built. Mechanism, from the windows: the fly was never stalling (E201b's windows rise), so anchoring trades away the coverage that is its advantage — an anchored walker circles its find and its proposals are then rejected by the 0.05 novelty filter, wasting the slot; seed 1 shows the collapse late (189 → 50 in the last window). Approach 1 is dead as designed. If it is revisited it needs the novelty filter and the anchor radius reconciled, and that is a new design, not a tuning. E203 (imagination) is running; E204 and E205 follow. E205's premise weakens with E202: "all three together" is now imagination + the Bennett rule.