llm_directed: directed sex (breed offspring + select on verifier) — E10 in real weights

Adds the "directed sex" operator (E10) the moe regime-flip pointed to: don't
commit to one a-priori blend — breed a population of recombinant offspring
(specialists merged at Dirichlet-sampled weights), score each on a held-out
validation split with the verifier, and keep the fittest, reported on a fresh
test split. Two breeding objectives: best-overall and best-worst-family.
src/llm/directed.py + kind llm_directed, reusing the cached specialists.

Result — refinements pay off in proportion to how far the uniform soup is from
optimal:
- 0.5B (soup dilutes): directed selection beats soup on the bred objective —
  directed_overall 0.69 > soup 0.64; directed_balanced worst-family 0.37 > 0.26.
  Riders: single-objective selection trades off the other axis (overall-breed
  tanks lists to 0.17); a global blend still trails per-input routing (0.74).
- 7B (Imperial CX3, soup already composes to ceiling on near-saturated families,
  strings/arith 1.00): directed ~= soup (0.868 ~ 0.873, marginally below via a
  val/test overfit gap) — no fitter offspring to breed.

Through-line across all four LLM runs: "merge, don't average" and its refinements
(routing, directed selection) are weak-base / suboptimal-default phenomena — they
help at 0.5B and are inert at 7B. Honest limitation kept in the writeup: the 7B
families are near-saturated, which caps the headroom; a harder unsaturated
benchmark is the fair next test.

Also folds in the two llm_moe local manifest/config files missed in 8da0dac.
+3 directed unit tests (130 green). Results in results/llm_directed{,_hpc}/
(parquet gitignored).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -95,6 +95,8 @@ E4's whole purpose is to isolate the effect of teacher **decorrelation ρ**, so
 
 **Finding (2026-07-05, `llm_moe_hpc` — the regime *flips* at 7B; "merge, don't average" is a weak-base law).** Re-ran `llm_moe` at **Qwen2.5-7B-Instruct** (L40S, 9 min, reusing the cached 7B specialists). **The union-vs-fusion ordering inverts:** at 0.5B union won (routing 0.74 > soup 0.64); at 7B **fusion wins — soup 0.87 > routing 0.84 > max_merge 0.78.** Mechanism, and it's the deep point: **routing *selects* one intact specialist so it is capped at the best parent per family** (lists 0.57 = spec_lists, strings 0.97 = spec_strings), whereas **fusion *blends* deltas and, at a capable base, composes *beyond* any parent** (soup lists 0.62 > spec 0.57, strings 1.00 > spec 0.97). Selection can't synthesise something better than its best component; averaging-that-composes can. So the E4/E8 "merge, don't average" law is **regime-dependent — a weak-parent / small-model law, not universal**: union wins exactly when averaging *dilutes* (0.5B), fusion wins once the base has headroom to *compose* (7B). This refines rather than contradicts E8 (whose additive-landscape `max>mean` assumed no compositional headroom). The operator to actually want is **fusion-that-composes + selection over recombinant offspring** = the "directed sex" ideal (E10), the natural next experiment. `results/llm_moe_hpc/` (README + regime-aware figure title). Riders unchanged: learned router trivially perfect (lexical families), `max_merge` the weakest union (not input-adaptive).
 
+**Finding (2026-07-05, `llm_directed` — directed sex in weights; refinements pay off only when the default blend is suboptimal).** E10 in real LLM weights (`src/llm/directed.py`, `kind: llm_directed`): breed a *population* of recombinant offspring (specialists merged at Dirichlet-sampled weights), score each against the verifier on a held-out **validation** split, keep the fittest — reported on a fresh **test** split (no selection-on-test leakage). Two breeding objectives (best-overall, best-worst-family). **The value scales with how far the uniform soup is from optimal, giving a clean regime split:** **0.5B** — soup dilutes, so directed selection beats it (`directed_overall` 0.69 > soup 0.64; `directed_balanced` worst-family 0.37 > soup 0.26), though single-objective selection trades off the other axis (breeding for overall tanks the rare `lists` to 0.17) and a *global* blend still trails per-input **routing** (0.74). **7B** — soup already *composes* to the ceiling on these near-saturated families (strings & arith at 1.00), so directed selection finds nothing better: **directed 0.868 ≈ soup 0.873** (marginally below, a val/test overfit gap). **Honest limitation:** the 7B families are near-saturated (2/3 at 1.00), which structurally caps the headroom — this run can't separate "directed sex doesn't help at scale" from "these tasks are too easy at 7B"; a *harder, unsaturated* benchmark is the fair next test. **Through-line across all four LLM runs:** "merge, don't average" and its refinements (routing, directed selection) are **weak-base / suboptimal-default** phenomena — they pay off at 0.5B (soup far from optimal) and are inert at 7B (soup near-optimal on saturated tasks). `configs/llm/{directed,directed_hpc}.yaml`, `plot_llm_directed.py`, `results/llm_directed{,_hpc}/`, `hpc/llm_directed.pbs`, +3 tests (130 green).
+
 ## Build order (blueprint §7) — respect the gate
 
 1. Scaffold: repo layout (§5), container, pytest skeleton, config system, seeding utils. `make test` green.