feat(doctrine): W6 — prose sweep + BDR-077 + LRN-137 + plan execution notes

LRN-113 whole-surface sweep: client-handover x2 + commit-change prose
repointed to the two-mode reality; code-cleaner/status historic notes
kept (accurate). Memory: BDR-077 (full architecture), LRN-137
(mode-based re-tiering + fail-safe pin rule), journal. Plan carries
as-built EXECUTION NOTES.

.claude/memory/decisions.md

@@ -1058,3 +1058,6 @@ Supersedes the "Excluded: hotfix" clause of [[BDR-075]]. hotfix now wired (STEP
 
 ### BDR-076 — Dispatched judgment agents pinned OPUS; session model = orchestration + inline reflection ONLY [accepted] (2026-07-19)
 Reverses the BDR-066 rejected alternative "opus pins on audit agents (session-independent)". Context changed: session default now Fable (Mythos tier, /model 2026-07-19) — inherit meant every dispatched audit/challenge burned Fable quota, exactly the waste BDR-066 killed for executors. New rule: Fable does ONLY main-loop orchestration + reflection (brainstorm, plan, contract, synthesis, gates); EVERY dispatched subagent pinned. Pinned `model: opus` (big tier, session-independent; NEVER sonnet — silent audit downgrade, the thing old §F5 guarded): analyzer, plan-challenger, seo-analyzer, geo-analyzer, validator-analyzer + onboard's 6 general-purpose audit dispatches (`model="opus"`) + tour Phase B. NOT pinned (justified deviation from approved "7 agents"): interviewer + client-handover-writer — inline-load only, never dispatched → frontmatter pin inert + misleading (BDR-066 wave-4 precedent: its inert opus pin was dropped); they ARE the main loop = Fable per the rule. Explore built-in stays inherit (wave-3 decision conserved: no owned prompt, search feeds inline reflection). Local session pin `opus-4-8[1m]` dropped from `.claude/settings.local.json` (gitignored) — Fable default from settings.json now applies in this repo too. model-gate.md unchanged (still guards inline reflection, Fable-or-Opus = big). Census: model-routing.test.sh §3 flip + §11 (61 pass), loops-light 35 pass, full `make test` green. User directives via gate: "Opus partout" + "Supprimer le pin". Branch feature/opus-pin-audit-agents, unmerged.
+
+### BDR-077 — Model-tiering v2: 4-tier explicit routing, mode-based splits, no-inherit dispatches [accepted] (2026-07-19)
+Supersedes BDR-076 scope + amends BDR-066. Doctrine: session model (Fable) = main-loop reflection/orchestration/planning/logic ONLY; main-loop retention criteria = interactive | conversation-context access | orchestration decision | dispatch overhead > step cost. NOTHING dispatched inherits: typed agents = frontmatter pin, built-ins = `model=` at every call site (`fable` for skill-runner reflection children, else complexity tier). Spike+smoke proven: `model:"fable"` resolves claude-fable-5 (enum-validated, loud fail, no silent fallback); call-site override BEATS a typed pin (sonnet-pinned verifier ran haiku). Fail-safe pin rule: mixed-mode agents keep the HIGH tier as pin, overrides go DOWN — forgotten override over-tiers (cost), never downgrades judgment. Mode-based splits (commit-changer precedent generalized; file splits rejected): doc-syncer audit(opus)/patch(sonnet) — ALSO fixed a latent defect: /doc dispatched an agent whose STEP 8 interactive gate could never fire; gates hoisted to a DISPATCHER PROTOCOL section; handover-doc-writer synthesize(opus)/render(sonnet) via run-scoped `.audit/handover-draft-<RUNID>.md` + DRAFT COMPLETE sentinel; seo/geo collect(sonnet)/judge(OPUS PIN)/template(sonnet) via `.audit/*-signals-<RUNID>.md` + COLLECTION COMPLETE + fail-closed judge + dispatcher ERROR contract (mute/ERROR judge NEVER carried into templating; retry once, escalate). File split only for a genuinely new role: plugin-probe (sonnet, facts-only) + plugin-advisor repinned opus reasoner (fail-closed on missing PROBE REPORT) + lib/plugin-gate.md (checkpoint + apply gate, doc-commit ×N include pattern). Inline→dispatch conversions: scaffolder, onboarder, doc-commit steps ×5 flows — their sonnet pins were INERT since creation, now live; CHANGE SUMMARY crosses the doc dispatch into doc-commit (LRN-126 wire). Tier moves: validator-analyzer opus→sonnet (deterministic runner); commit-changer propose=opus/apply=pin; ship-feature/init-project code-review dispatches = opus explicit (WAS an inherit leak); client-handover-writer's 7 skill-runners = model:"fable". Every wave shipped an IN-WAVE planted-input smoke as its merge gate — all PASSED disk-verified. Census §12-18 (125 pass; one vacuous line-wrapped lock self-caught = LRN-093 live). 6 waves, branches feature/model-tiering-w1..w6, merged on user standing signal. Plan: challenged 3 blind lenses + 1 confirmation (1 BLOCKER closed by spike, 8 MAJORs + 8 MINORs closed by named changes, 0 deferred). Refs: `.claude/tasks/plans/2026-07-19-model-tiering-v2-{analysis,plan}.md`.