diff --git a/internal/plugin/adventure.go b/internal/plugin/adventure.go
index a2ade25..ec4d1de 100644
--- a/internal/plugin/adventure.go
+++ b/internal/plugin/adventure.go
@@ -220,6 +220,10 @@ func (p *AdventurePlugin) Init() error {
 	// migration walks dnd_character once at startup; idempotent via
 	// JobCompleted gate.
 	bootstrapPhase5BHPRefresh()
+	// J3 D8-d-fix: caster HP lift (casterHPMult in dnd.go). Refresh
+	// existing caster rows once at startup so the lift reaches live
+	// players without waiting for level-up.
+	bootstrapCasterHPRefresh()
 	// Phase R1 orphan-archive used to run here on every Init, but it
 	// over-archived: it treats any active dnd_zone_run row not linked to
 	// an active expedition as a legacy `!adventure dungeon` orphan, which
diff --git a/internal/plugin/bootstrap_caster_hp.go b/internal/plugin/bootstrap_caster_hp.go
new file mode 100644
index 0000000..ed8f64e
--- /dev/null
+++ b/internal/plugin/bootstrap_caster_hp.go
@@ -0,0 +1,84 @@
+package plugin
+
+import (
+	"log/slog"
+
+	"gogobee/internal/db"
+)
+
+// bootstrapCasterHPRefresh recomputes hp_max for caster characters after
+// the J3 D8-d-fix caster HP multiplier (casterHPMult in dnd.go) shipped.
+// Without this, existing caster rows keep their pre-lift hp_max until
+// the next computeMaxHP recall (level-up / reset). Mirrors
+// bootstrapPhase5BHPRefresh — only ever raises hp_max, preserves the
+// absolute wound (delta added to hp_current, capped at new max). Run
+// once per startup, idempotent via db.JobCompleted.
+func bootstrapCasterHPRefresh() {
+	const jobName = "caster_hp_refresh_v1"
+	if db.JobCompleted(jobName, "once") {
+		return
+	}
+
+	d := db.Get()
+	rows, err := d.Query(`
+		SELECT user_id, class, con_score, dnd_level, hp_max, hp_current
+		FROM dnd_character WHERE dnd_level > 0`)
+	if err != nil {
+		slog.Error("caster hp refresh: enumerate failed", "err", err)
+		return
+	}
+	defer rows.Close()
+
+	type row struct {
+		userID    string
+		class     DnDClass
+		conScore  int
+		level     int
+		hpMax     int
+		hpCurrent int
+	}
+	var batch []row
+	for rows.Next() {
+		var r row
+		var classStr string
+		if err := rows.Scan(&r.userID, &classStr, &r.conScore, &r.level, &r.hpMax, &r.hpCurrent); err != nil {
+			slog.Warn("caster hp refresh: scan failed", "err", err)
+			continue
+		}
+		r.class = DnDClass(classStr)
+		batch = append(batch, r)
+	}
+
+	refreshed := 0
+	for _, r := range batch {
+		if casterHPMult(r.class) == 1.0 {
+			continue
+		}
+		conMod := abilityModifier(r.conScore)
+		newMax := computeMaxHP(r.class, conMod, r.level)
+		if newMax <= r.hpMax {
+			continue
+		}
+		delta := newMax - r.hpMax
+		newCurrent := r.hpCurrent + delta
+		if newCurrent > newMax {
+			newCurrent = newMax
+		}
+		if newCurrent < 1 {
+			newCurrent = 1
+		}
+		if _, err := d.Exec(`UPDATE dnd_character
+			SET hp_max = ?, hp_current = ?, updated_at = CURRENT_TIMESTAMP
+			WHERE user_id = ?`,
+			newMax, newCurrent, r.userID); err != nil {
+			slog.Warn("caster hp refresh: update failed", "user", r.userID, "err", err)
+			continue
+		}
+		refreshed++
+	}
+
+	db.MarkJobCompleted(jobName, "once")
+	if refreshed > 0 {
+		slog.Info("caster hp refresh: refreshed caster HPMax to D8-d-fix floor", "count", refreshed)
+	}
+}
diff --git a/internal/plugin/dnd.go b/internal/plugin/dnd.go
index 6f6f18d..e9a0cf1 100644
--- a/internal/plugin/dnd.go
+++ b/internal/plugin/dnd.go
@@ -161,6 +161,20 @@ func abilityModifier(score int) int {
 // startup to refresh stale rows.
 const phase5BHPMult = 1.5
 
+// casterHPMult is the J3 D8-d-fix caster durability lift. T4 sim showed
+// caster HPMax sat ~30% below martial (~95 vs 141 at L10) and the AC-floor
+// lift alone wasn't enough to crack the wall. Applied multiplicatively in
+// computeMaxHP on top of phase5BHPMult so the existing Phase 5-B floor
+// stays intact for martials. Refreshed for existing rows by
+// bootstrapCasterHPRefresh (job key caster_hp_refresh_v1).
+func casterHPMult(class DnDClass) float64 {
+	switch class {
+	case ClassCleric, ClassDruid, ClassBard, ClassWarlock, ClassMage, ClassSorcerer:
+		return 1.25
+	}
+	return 1.0
+}
+
 // computeMaxHP — D&D5e style. L1: full HP die + CON mod (min 1).
 // Per level after: average HP die (roundup of die/2 + 1) + CON mod.
 // The result is scaled by phase5BHPMult — see that constant for the
@@ -181,8 +195,8 @@ func computeMaxHP(class DnDClass, conMod, level int) int {
 		}
 		hp += gain
 	}
-	// Phase 5-B player power floor — round to nearest int.
-	scaled := int(float64(hp)*phase5BHPMult + 0.5)
+	// Phase 5-B player power floor + J3 D8-d-fix caster lift — round to nearest int.
+	scaled := int(float64(hp)*phase5BHPMult*casterHPMult(class) + 0.5)
 	if scaled < 1 {
 		scaled = 1
 	}
@@ -197,10 +211,16 @@ func computeAC(class DnDClass, dexMod int) int {
 	switch class {
 	case ClassFighter, ClassPaladin:
 		floor = 6 // heavy/medium-armor baseline
-	case ClassCleric, ClassRanger, ClassDruid:
+	case ClassCleric, ClassDruid:
+		floor = 5
+	case ClassRanger:
 		floor = 3
-	case ClassRogue, ClassBard, ClassWarlock:
+	case ClassBard, ClassWarlock:
+		floor = 3
+	case ClassRogue:
 		floor = 1
+	case ClassMage, ClassSorcerer:
+		floor = 2
 	}
 	return 10 + dexMod + floor
 }
diff --git a/internal/plugin/dnd_test.go b/internal/plugin/dnd_test.go
index 4250fa0..3fc8efe 100644
--- a/internal/plugin/dnd_test.go
+++ b/internal/plugin/dnd_test.go
@@ -70,10 +70,10 @@ func TestComputeMaxHP_MageLevel5(t *testing.T) {
 	// Mage d6, CON +1
 	// L1: 6 + 1 = 7
 	// L2-5: 4 levels × (avg 4 + 1) = 4 × 5 = 20
-	// Raw total: 27; Phase 5-B: 27 × 1.5 = 40.5 → 41 (round half-up).
+	// Raw total: 27; Phase 5-B × casterHPMult: 27 × 1.5 × 1.25 = 50.625 → 51.
 	got := computeMaxHP(ClassMage, 1, 5)
-	if got != 41 {
-		t.Errorf("Mage L5 (CON+1) = %d, want 41 (27 raw × phase5BHPMult)", got)
+	if got != 51 {
+		t.Errorf("Mage L5 (CON+1) = %d, want 51 (27 raw × phase5BHPMult × casterHPMult)", got)
 	}
 }
 
@@ -94,8 +94,12 @@ func TestComputeAC(t *testing.T) {
 		{ClassFighter, 0, 16},  // 10 + 0 + 6
 		{ClassFighter, 2, 18},  // 10 + 2 + 6
 		{ClassRogue, 3, 14},    // 10 + 3 + 1
-		{ClassMage, 0, 10},     // 10 + 0 + 0
-		{ClassCleric, 1, 14},   // 10 + 1 + 3
+		{ClassMage, 0, 12},     // 10 + 0 + 2 (D8-d-fix caster floor)
+		{ClassSorcerer, 1, 13}, // 10 + 1 + 2
+		{ClassCleric, 1, 16},   // 10 + 1 + 5 (D8-d-fix caster floor)
+		{ClassDruid, 0, 15},    // 10 + 0 + 5
+		{ClassBard, 2, 15},     // 10 + 2 + 3 (D8-d-fix caster floor)
+		{ClassWarlock, 0, 13},  // 10 + 0 + 3
 		{ClassRanger, 2, 15},   // 10 + 2 + 3
 	}
 	for _, c := range cases {