diff --git a/gogobee_long_expedition_plan.md b/gogobee_long_expedition_plan.md
index 39c8aeb..9ee5485 100644
--- a/gogobee_long_expedition_plan.md
+++ b/gogobee_long_expedition_plan.md
@@ -153,7 +153,20 @@ Each successful background walk now logs a `walk` entry (`appendExpeditionLog(..
 
 **D8-a (shipped 2026-05-27, this session):** quick data-layer cleanup. Bard L1 prepared list gained `thunderwave`; L2 gained `heat_metal`. Cleric L1 gained `inflict_wounds`. `shatter` overlay Classes broadened to mage/bard/sorcerer (overlay was already unioning via `mergeClassList`, so this is defensive). New `simPickSpiritualWeapon` runs before `simPickSpell` in `simPickCombatAction`: cleric with an L2 slot + spiritual_weapon prepared + `sess.Statuses.BuffSpiritProc == 0` opens the fight with it, picking up the existing `spiritWeaponStrike` per-round bonus-action attack. **Measured impact (L10, n=100/zone, heavy preset):** cleric 21.0 → 23.2% (+2.2pp), bard 34.2 → 32.8% (within noise). T3+ wall unchanged — the data fixes are correct but the picker math is what's binding. Files touched: `internal/plugin/dnd_spells_data.go:192`, `internal/plugin/dnd_spells.go:822,881,884`, `internal/plugin/expedition_sim.go:simPickCombatAction + new simPickSpiritualWeapon`. All green.
 
-**D8-b (TODO next session): sim picker upcasting.** At L10 a bard has 3×L1 + 3×L2 + 3×L3 + 3×L4 + 2×L5 = 14 slots, but no damage spell at L3/L4/L5 native level — the picker leaves those slots un-spent because it doesn't upcast. Wizard/sorcerer hit the same wall above their highest native-level damage spell.
+**D8-b (implemented 2026-05-27, **inert** — see D8-prereq below): sim picker upcasting.** `simPickSpell` (`internal/plugin/expedition_sim.go:933`) now enumerates one candidate per available slot ≥ native for every prepared damage spell, scored via `spellExpectedDamage(sp, slotLevel, c.Level)`. Cantrips contribute a single slot-0 candidate. Tie-break: highest slot first, then highest expDmg. When the winning slot exceeds the spell's native level, the picker returns `"<id> --upcast N"` so `parseCombatCast` upcasts in the engine. Build + tests green.
+
+**Measured impact: nothing.** d8b corpus (`sim_results/d8b_corpus.jsonl`, same matrix as d7d) lands every class within ±1.5pp of the d7d baseline — bard −1.0, cleric −0.4, mage −1.2, sorcerer +1.4, warlock −0.8, druid +0.6, martials ±0.2. Pure noise band. Expected bard +5–10pp / mage+sorcerer+warlock +2–8pp never materialized.
+
+**Root cause (discovered post-corpus, this session):** `simPickSpell` is **dead code** in the current sim path. Commit `68ed8e7` ("Long expeditions D3: compact autopilot auto-resolves boss rooms") added a `!compact` gate at `dnd_expedition_cmd.go:810` so compact autopilot inline-resolves boss/elite rooms via `resolveCombatRoom` → `runZoneCombat` → `SimulateCombat` instead of returning `stopBoss/stopElite` for `autoResolveCombat` to handle. The sim uses `compact=true` (`expedition_sim.go:433`), so `autoResolveCombat` — the only caller of `simPickCombatAction`/`simPickSpell` — never fires. Verified empirically: a stderr-traced `simPickSpell` produced zero hits across full bard/cleric L10 runs.
+
+This rewrites the picker-era retrospective. **J2's `baseline_j2a_v2_all10.jsonl` (bard 40%, cleric 39%) was measured before D3, with the picker live.** d7d's L10 baseline (bard 34%, cleric 21%) was measured *after* D3, with the picker disconnected — that ~6–18pp drop is the post-D3 caster regression, not "long-expedition mechanics didn't help casters" as the d7d writeup framed it. D8-a's "+2.2pp cleric" was also noise (1σ ≈ 1.8pp on n=500).
+
+**D8-prereq (TODO next session, **blocks D8-b/c**): re-wire the sim to the turn-based path.** Option 1 from the discovery write-up: add a sim-only flag (e.g. `SimRunner.turnBasedBossFights = true`, or a third compact mode) so `runAutopilotWalk` returns `stopBoss`/`stopElite` for the sim even though it's running compact — production stays compact-inline. Then `autoResolveCombat` fires for sim boss/elite rooms, `simPickSpell` (with D8-b upcasting) drives those fights, and we can finally measure the picker's real lift.
+
+- Touch: probably a third arg to `runAutopilotWalk` or an `s.P.simMode` flag the dnd_expedition_cmd reads alongside compact. Be careful — the inline-resolve path also runs harvest, loot, threat; if we surface stopBoss/stopElite earlier, those bookkeeping steps still need to happen at the right moment. Probably simplest: split `compact` into `compactRendering` (keep) and `compactCombatInline` (sim turns this off).
+- Validation: re-run the d7d/d8b matrix. Acceptance: casters move materially (bard/mage/sorcerer/warlock into the 40–60% band at T1–T3 like the J2 baseline). If they don't, D8-b's expDmg model is wrong and we need a deeper rework, not just rewiring.
+
+**D8-b/c are deferred** until the prereq lands. D8-b code stays in-tree (it's correct, just inert today, and will turn on as soon as the wire reconnects).
 
 - Touch: `simPickSpell` in `internal/plugin/expedition_sim.go` (~line 903). For each prepared damage spell, instead of one candidate at `sp.Level`, enumerate candidates at every available slot level ≥ `sp.Level` where a slot is open. Use `spellExpectedDamage(sp, slotLevel, c.Level)` for the upcast scaling — that helper already exists and handles the "+1 die per slot above native" pattern in `rollSpellDamageDice` (`internal/plugin/dnd_spell_combat.go:387-418`).
 - Tie-break still: highest slot first (preserve high-slot supremacy), then highest expDmg. But now a bard at L10 with shatter can spend its L5 slot on shatter@L5 = 6d8 ≈ 27 instead of leaving it un-spent.
diff --git a/internal/plugin/expedition_sim.go b/internal/plugin/expedition_sim.go
index 62a7d58..61b2a72 100644
--- a/internal/plugin/expedition_sim.go
+++ b/internal/plugin/expedition_sim.go
@@ -930,8 +930,10 @@ func simPickSpiritualWeapon(c *DnDCharacter, uid id.UserID, sess *CombatSession)
 	return "spiritual_weapon"
 }
 
-// simPickSpell returns the spell ID a competent player would cast this
-// turn, or "" when no usable spell is available (forcing a !attack).
+// simPickSpell returns the spell argument a competent player would pass
+// to !cast this turn, or "" when no usable spell is available (forcing a
+// !attack). The return value is fed straight to handleCombatCastCmd, so
+// upcast picks come back as `"<spell_id> --upcast N"`.
 // Selection rules:
 //   - Only damage-effect spells (damage_attack / damage_save / damage_auto).
 //     Control/buff/heal are out (J2c sweep showed control scoring at
@@ -939,12 +941,13 @@ func simPickSpiritualWeapon(c *DnDCharacter, uid id.UserID, sess *CombatSession)
 //     no headroom worth the complexity). Healing is handled by the
 //     consumable-first branch in simPickCombatAction.
 //   - Reaction-cast spells are excluded (engine rejects them).
-//   - Non-cantrips require an available slot at their native level (no
-//     upcasting — preserves high slots for high-level spells).
-//   - Among feasible candidates, prefer higher slot level; tie-break on
+//   - For each prepared leveled spell, enumerate one candidate per
+//     available slot at level ≥ native (D8-b, aggressive upcasting).
+//     spellExpectedDamage handles the +1-die-per-slot-above-native
+//     scaling. Cantrips contribute one slot-0 candidate.
+//   - Among feasible candidates, prefer higher slot level (preserves
+//     high-slot supremacy and burns the big slots first); tie-break on
 //     expected damage from the dice string.
-//
-// Returns the spell ID for handleCombatCastCmd.
 func simPickSpell(c *DnDCharacter, uid id.UserID) string {
 	known, err := listKnownSpells(uid)
 	if err != nil || len(known) == 0 {
@@ -952,9 +955,10 @@ func simPickSpell(c *DnDCharacter, uid id.UserID) string {
 	}
 	slots, _ := getSpellSlots(uid)
 	type cand struct {
-		id     string
-		level  int
-		expDmg float64
+		id          string
+		slot        int
+		nativeLevel int
+		expDmg      float64
 	}
 	var cands []cand
 	for _, k := range known {
@@ -983,24 +987,40 @@ func simPickSpell(c *DnDCharacter, uid id.UserID) string {
 		if !onList {
 			continue
 		}
-		if sp.Level > 0 {
-			pair, ok := slots[sp.Level]
+		if sp.Level == 0 {
+			cands = append(cands, cand{id: sp.ID, slot: 0, nativeLevel: 0, expDmg: spellExpectedDamage(sp, 0, c.Level)})
+			continue
+		}
+		// simMaxSlot mirrors parseCombatCast's slot-level cap; anything
+		// above it would be rejected by the cast handler anyway.
+		const simMaxSlot = 5
+		for sl := sp.Level; sl <= simMaxSlot; sl++ {
+			pair, ok := slots[sl]
 			if !ok || pair[0]-pair[1] <= 0 {
 				continue
 			}
+			cands = append(cands, cand{
+				id:          sp.ID,
+				slot:        sl,
+				nativeLevel: sp.Level,
+				expDmg:      spellExpectedDamage(sp, sl, c.Level),
+			})
 		}
-		cands = append(cands, cand{id: sp.ID, level: sp.Level, expDmg: spellExpectedDamage(sp, sp.Level, c.Level)})
 	}
 	if len(cands) == 0 {
 		return ""
 	}
 	sort.Slice(cands, func(i, j int) bool {
-		if cands[i].level != cands[j].level {
-			return cands[i].level > cands[j].level
+		if cands[i].slot != cands[j].slot {
+			return cands[i].slot > cands[j].slot
 		}
 		return cands[i].expDmg > cands[j].expDmg
 	})
-	return cands[0].id
+	best := cands[0]
+	if best.slot > best.nativeLevel && best.nativeLevel > 0 {
+		return fmt.Sprintf("%s --upcast %d", best.id, best.slot)
+	}
+	return best.id
 }
 
 // applyAutoCamp drives the production camp scheduler under the sim's