diff --git a/internal/db/db.go b/internal/db/db.go
index 29870a4..087debb 100644
--- a/internal/db/db.go
+++ b/internal/db/db.go
@@ -173,6 +173,11 @@ func runMigrations(d *sql.DB) error {
 		`ALTER TABLE dnd_character ADD COLUMN pending_cast TEXT NOT NULL DEFAULT ''`,
 		`ALTER TABLE dnd_character ADD COLUMN concentration_spell TEXT NOT NULL DEFAULT ''`,
 		`ALTER TABLE dnd_character ADD COLUMN concentration_expires_at DATETIME`,
+		// Phase 10 — subclass system. Subclass id is set at L5 via !subclass.
+		// last_subclass_respec_at gates the 30-day cooldown for changing it
+		// (separate from last_respec_at, which gates the full character wipe).
+		`ALTER TABLE dnd_character ADD COLUMN subclass TEXT NOT NULL DEFAULT ''`,
+		`ALTER TABLE dnd_character ADD COLUMN last_subclass_respec_at DATETIME`,
 	}
 	for _, stmt := range columnMigrations {
 		if _, err := d.Exec(stmt); err != nil {
diff --git a/internal/plugin/adventure.go b/internal/plugin/adventure.go
index f79f3e7..436e972 100644
--- a/internal/plugin/adventure.go
+++ b/internal/plugin/adventure.go
@@ -124,6 +124,7 @@ func (p *AdventurePlugin) Commands() []CommandDef {
 		{Name: "sheet", Description: "View your Adv 2.0 character sheet", Usage: "!sheet", Category: "Games"},
 		{Name: "abilities", Description: "List your Adv 2.0 class and race abilities", Usage: "!abilities", Category: "Games"},
 		{Name: "respec", Description: "Wipe and rebuild your Adv 2.0 character (5000 euros, 7-day cooldown)", Usage: "!respec", Category: "Games"},
+		{Name: "subclass", Description: "View or choose your Adv 2.0 subclass (unlocks at L5; change costs 500 euros, 30-day cooldown)", Usage: "!subclass [name|number]", Category: "Games"},
 		{Name: "check", Description: "Roll an Adv 2.0 skill check (d20 + ability modifier vs DC)", Usage: "!check <skill> [dc]", Category: "Games"},
 		{Name: "rest", Description: "Take an Adv 2.0 rest (`short`: 1h cooldown, partial heal — `long`: 24h, full heal, requires housing or inn)", Usage: "!rest short|long", Category: "Games"},
 		{Name: "arm", Description: "Pre-arm an active Adv 2.0 ability for next combat (consumes resource)", Usage: "!arm <ability>", Category: "Games"},
@@ -216,6 +217,9 @@ func (p *AdventurePlugin) OnMessage(ctx MessageContext) error {
 	if p.IsCommand(ctx.Body, "respec") {
 		return p.handleDnDRespecCmd(ctx)
 	}
+	if p.IsCommand(ctx.Body, "subclass") {
+		return p.handleDnDSubclassCmd(ctx, p.GetArgs(ctx.Body, "subclass"))
+	}
 	if p.IsCommand(ctx.Body, "check") {
 		return p.handleDnDCheckCmd(ctx, p.GetArgs(ctx.Body, "check"))
 	}
diff --git a/internal/plugin/dnd.go b/internal/plugin/dnd.go
index d6c6a6d..881cef4 100644
--- a/internal/plugin/dnd.go
+++ b/internal/plugin/dnd.go
@@ -176,6 +176,12 @@ type DnDCharacter struct {
 	PendingCast              string
 	ConcentrationSpell       string
 	ConcentrationExpiresAt   *time.Time
+	// Phase 10 — subclass.
+	// Subclass: empty until the player runs !subclass at L5+. Once set,
+	// changing requires `!subclass <name>` again subject to a 30-day
+	// cooldown (LastSubclassRespecAt) and 500-coin cost.
+	Subclass                 DnDSubclass
+	LastSubclassRespecAt     *time.Time
 	LastRespecAt    *time.Time
 	LastShortRestAt *time.Time
 	LastLongRestAt  *time.Time
@@ -204,18 +210,20 @@ func LoadDnDCharacter(userID id.UserID) (*DnDCharacter, error) {
 		       hp_current, hp_max, temp_hp, armor_class,
 		       pending_setup, auto_migrated, onboarding_sent, armed_ability,
 		       pending_cast, concentration_spell, concentration_expires_at,
+		       subclass, last_subclass_respec_at,
 		       last_respec_at, last_short_rest_at, last_long_rest_at,
 		       created_at, updated_at
 		FROM dnd_character WHERE user_id = ?`, string(userID))
 	c := &DnDCharacter{}
 	var pending, autoMig, onboard int
-	var raceStr, classStr string
+	var raceStr, classStr, subclassStr string
 	var uidStr string
 	err := row.Scan(&uidStr, &raceStr, &classStr, &c.Level, &c.XP,
 		&c.STR, &c.DEX, &c.CON, &c.INT, &c.WIS, &c.CHA,
 		&c.HPCurrent, &c.HPMax, &c.TempHP, &c.ArmorClass,
 		&pending, &autoMig, &onboard, &c.ArmedAbility,
 		&c.PendingCast, &c.ConcentrationSpell, &c.ConcentrationExpiresAt,
+		&subclassStr, &c.LastSubclassRespecAt,
 		&c.LastRespecAt, &c.LastShortRestAt, &c.LastLongRestAt,
 		&c.CreatedAt, &c.UpdatedAt)
 	if errors.Is(err, sql.ErrNoRows) {
@@ -227,6 +235,7 @@ func LoadDnDCharacter(userID id.UserID) (*DnDCharacter, error) {
 	c.UserID = id.UserID(uidStr)
 	c.Race = DnDRace(raceStr)
 	c.Class = DnDClass(classStr)
+	c.Subclass = DnDSubclass(subclassStr)
 	c.PendingSetup = pending == 1
 	c.AutoMigrated = autoMig == 1
 	c.OnboardingSent = onboard == 1
@@ -253,8 +262,9 @@ func SaveDnDCharacter(c *DnDCharacter) error {
 		    hp_current, hp_max, temp_hp, armor_class,
 		    pending_setup, auto_migrated, onboarding_sent, armed_ability,
 		    pending_cast, concentration_spell, concentration_expires_at,
+		    subclass, last_subclass_respec_at,
 		    last_respec_at, last_short_rest_at, last_long_rest_at, updated_at)
-		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
 		ON CONFLICT(user_id) DO UPDATE SET
 		    race=excluded.race, class=excluded.class,
 		    dnd_level=excluded.dnd_level, dnd_xp=excluded.dnd_xp,
@@ -270,6 +280,8 @@ func SaveDnDCharacter(c *DnDCharacter) error {
 		    pending_cast=excluded.pending_cast,
 		    concentration_spell=excluded.concentration_spell,
 		    concentration_expires_at=excluded.concentration_expires_at,
+		    subclass=excluded.subclass,
+		    last_subclass_respec_at=excluded.last_subclass_respec_at,
 		    last_respec_at=excluded.last_respec_at,
 		    last_short_rest_at=excluded.last_short_rest_at,
 		    last_long_rest_at=excluded.last_long_rest_at,
@@ -279,6 +291,7 @@ func SaveDnDCharacter(c *DnDCharacter) error {
 		c.HPCurrent, c.HPMax, c.TempHP, c.ArmorClass,
 		pending, autoMig, onboard, c.ArmedAbility,
 		c.PendingCast, c.ConcentrationSpell, c.ConcentrationExpiresAt,
+		string(c.Subclass), c.LastSubclassRespecAt,
 		c.LastRespecAt, c.LastShortRestAt, c.LastLongRestAt)
 	if err != nil {
 		return fmt.Errorf("save dnd_character: %w", err)
diff --git a/internal/plugin/dnd_setup.go b/internal/plugin/dnd_setup.go
index 7bfa3b3..300755f 100644
--- a/internal/plugin/dnd_setup.go
+++ b/internal/plugin/dnd_setup.go
@@ -383,6 +383,10 @@ func (p *AdventurePlugin) handleDnDRespecCmd(ctx MessageContext) error {
 	c.PendingSetup = true
 	c.AutoMigrated = false
 	c.LastRespecAt = &now
+	// Phase 10: full wipe also resets subclass state. Subclass-respec
+	// cooldown is dropped — at L1 with no class there's nothing to gate.
+	c.Subclass = ""
+	c.LastSubclassRespecAt = nil
 	// Save the wipe BEFORE debiting euros (audit fix B). If save fails, the
 	// player's old state survives and they keep their euros — better than
 	// a destructive debit-without-wipe.
diff --git a/internal/plugin/dnd_sheet.go b/internal/plugin/dnd_sheet.go
index 07006e0..239e656 100644
--- a/internal/plugin/dnd_sheet.go
+++ b/internal/plugin/dnd_sheet.go
@@ -77,6 +77,13 @@ func renderDnDSheet(c *DnDCharacter, adv *AdventureCharacter, equip map[Equipmen
 		name = adv.DisplayName
 	}
 	b.WriteString(fmt.Sprintf("⚔️ **%s** — Level %d %s %s\n", name, c.Level, ri.Display, ci.Display))
+	if c.Subclass != "" {
+		if si, ok := subclassInfo(c.Subclass); ok {
+			b.WriteString(fmt.Sprintf("    _%s_\n", si.Display))
+		}
+	} else if c.Level >= dndSubclassMinLevel {
+		b.WriteString("    _Subclass: unchosen — run `!subclass`_\n")
+	}
 	b.WriteString(strings.Repeat("─", 36) + "\n")
 
 	// Vitals
diff --git a/internal/plugin/dnd_subclass.go b/internal/plugin/dnd_subclass.go
new file mode 100644
index 0000000..4822f3c
--- /dev/null
+++ b/internal/plugin/dnd_subclass.go
@@ -0,0 +1,209 @@
+package plugin
+
+import (
+	"sort"
+	"strings"
+)
+
+// Phase 10 — subclass registry. Implements `gogobee_subclass_system.md`:
+// 15 subclasses (3 per class × 5 classes), unlocked at L5 via !subclass.
+//
+// SUB1 (this file + dnd_subclass_cmd.go) covers identity only — selection,
+// storage, !respec, sheet display. Mechanical effects of L5/7/10/15
+// abilities arrive in SUB2/SUB3.
+//
+// Forward-deps that aren't built yet are deliberately stubbed: Beast
+// Master picks the subclass even though the Phase 15 pet rework hasn't
+// landed; Necromancer Animate Dead waits on an undead-summon engine.
+
+type DnDSubclass string
+
+const (
+	// Fighter
+	SubclassChampion     DnDSubclass = "champion"
+	SubclassBattleMaster DnDSubclass = "battle_master"
+	SubclassBerserker    DnDSubclass = "berserker"
+	// Rogue
+	SubclassThief           DnDSubclass = "thief"
+	SubclassAssassin        DnDSubclass = "assassin"
+	SubclassArcaneTrickster DnDSubclass = "arcane_trickster"
+	// Mage
+	SubclassEvocation  DnDSubclass = "evocation"
+	SubclassAbjuration DnDSubclass = "abjuration"
+	SubclassNecromancy DnDSubclass = "necromancy"
+	// Cleric
+	SubclassLifeDomain     DnDSubclass = "life_domain"
+	SubclassWarDomain      DnDSubclass = "war_domain"
+	SubclassTrickeryDomain DnDSubclass = "trickery_domain"
+	// Ranger
+	SubclassHunter       DnDSubclass = "hunter"
+	SubclassBeastMaster  DnDSubclass = "beast_master"
+	SubclassGloomStalker DnDSubclass = "gloom_stalker"
+)
+
+// DnDSubclassInfo — registry row. Tagline summarizes identity in one line
+// (used in selection prompt). Flavor is the TwinBee narration line shown
+// on selection (per design doc §7).
+type DnDSubclassInfo struct {
+	ID      DnDSubclass
+	Class   DnDClass
+	Display string
+	Tagline string
+	Flavor  string
+}
+
+// dndSubclassRegistry — 15 entries, ordered first by class (Fighter,
+// Rogue, Mage, Cleric, Ranger) then by the design doc's listed order
+// within each class. The selection prompt presents them in this order.
+var dndSubclassRegistry = []DnDSubclassInfo{
+	// Fighter
+	{SubclassChampion, ClassFighter, "Champion",
+		"Raw power, brutal efficiency.",
+		"You've chosen the old way. No tricks, no systems. Just you, and the blade, and the next hit. TwinBee approves of this directness."},
+	{SubclassBattleMaster, ClassFighter, "Battle Master",
+		"Tactical superiority, maneuver control.",
+		"Maneuvers, dice, control of the engagement. TwinBee notes that the smartest fighter in the room rarely throws the first punch."},
+	{SubclassBerserker, ClassFighter, "Berserker",
+		"Rage-fueled destruction, high risk/reward.",
+		"Rage as a tool, exhaustion as a tax. TwinBee files this under 'load-bearing recklessness'."},
+
+	// Rogue
+	{SubclassThief, ClassRogue, "Thief",
+		"Speed, opportunism, fast hands.",
+		"Quick fingers, quicker exits. TwinBee suspects the locks of the world have been put on notice."},
+	{SubclassAssassin, ClassRogue, "Assassin",
+		"Setup and execution; devastating openers.",
+		"Patience, then violence, then nothing. TwinBee respects the economy of motion."},
+	{SubclassArcaneTrickster, ClassRogue, "Arcane Trickster",
+		"Stealth plus a slice of Mage spellcasting.",
+		"Magic in the hands of a Rogue. TwinBee considers this the universe's way of apologizing for giving you low HP."},
+
+	// Mage
+	{SubclassEvocation, ClassMage, "Evocation",
+		"Pure damage output. The glass cannon perfected.",
+		"You picked the path of the louder spell. TwinBee finds this aesthetically pleasing and structurally alarming."},
+	{SubclassAbjuration, ClassMage, "Abjuration",
+		"Wards, shields, counterspells.",
+		"You'd rather not get hit, and you've made it your specialty. TwinBee approves of this kind of foresight."},
+	{SubclassNecromancy, ClassMage, "Necromancy",
+		"Control undead and drain life.",
+		"Undeath as a tool rather than a state. TwinBee has opinions about this. TwinBee is keeping them to itself."},
+
+	// Cleric
+	{SubclassLifeDomain, ClassCleric, "Life Domain",
+		"Maximum healing output. Party support anchor.",
+		"Healing as discipline, not afterthought. TwinBee notes the party will live longer because of you, whether they thank you or not."},
+	{SubclassWarDomain, ClassCleric, "War Domain",
+		"Combat Cleric — extra attacks, martial weapons.",
+		"You came to fight, not to mediate. TwinBee finds this clarifying."},
+	{SubclassTrickeryDomain, ClassCleric, "Trickery Domain",
+		"Illusion, misdirection, chaos.",
+		"A Cleric who lies for a living. TwinBee delights in the implied theological complications."},
+
+	// Ranger
+	{SubclassHunter, ClassRanger, "Hunter",
+		"Zone specialist; bonuses against enemy types.",
+		"You read the terrain before you draw the bow. TwinBee finds this professionalism rare and welcome."},
+	{SubclassBeastMaster, ClassRanger, "Beast Master",
+		"Deep Ranger–pet bond. Pet as combat partner.",
+		"You and your pet, all the way down. TwinBee finds this genuinely moving and declines to be embarrassed about that."},
+	{SubclassGloomStalker, ClassRanger, "Gloom Stalker",
+		"Darkness specialist. Exceptional underground.",
+		"You were already good in the dark. Now you're better. TwinBee notes: the Underdark is waiting."},
+}
+
+// subclassInfo returns the registry row for id, or (zero, false).
+func subclassInfo(id DnDSubclass) (DnDSubclassInfo, bool) {
+	for _, s := range dndSubclassRegistry {
+		if s.ID == id {
+			return s, true
+		}
+	}
+	return DnDSubclassInfo{}, false
+}
+
+// subclassesForClass returns the 3 subclasses available to a given class,
+// in registry/design-doc order.
+func subclassesForClass(class DnDClass) []DnDSubclassInfo {
+	out := make([]DnDSubclassInfo, 0, 3)
+	for _, s := range dndSubclassRegistry {
+		if s.Class == class {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
+// resolveSubclassInput maps user-supplied input ("1", "champion",
+// "battle master", "BattleMaster") to a subclass id valid for the given
+// class. Returns ("", false) if no match.
+func resolveSubclassInput(class DnDClass, input string) (DnDSubclass, bool) {
+	subs := subclassesForClass(class)
+	if len(subs) == 0 {
+		return "", false
+	}
+	trimmed := strings.TrimSpace(input)
+	if trimmed == "" {
+		return "", false
+	}
+	// Numeric: "1", "2", "3".
+	if len(trimmed) == 1 && trimmed[0] >= '1' && trimmed[0] <= '9' {
+		idx := int(trimmed[0] - '1')
+		if idx >= 0 && idx < len(subs) {
+			return subs[idx].ID, true
+		}
+	}
+	// Name match: case-insensitive, ignore spaces/underscores.
+	norm := normalizeSubclassName(trimmed)
+	for _, s := range subs {
+		if normalizeSubclassName(string(s.ID)) == norm ||
+			normalizeSubclassName(s.Display) == norm {
+			return s.ID, true
+		}
+	}
+	return "", false
+}
+
+func normalizeSubclassName(s string) string {
+	s = strings.ToLower(s)
+	s = strings.ReplaceAll(s, " ", "")
+	s = strings.ReplaceAll(s, "_", "")
+	s = strings.ReplaceAll(s, "-", "")
+	return s
+}
+
+// renderSubclassPrompt builds the "Choose your path" message for the
+// player's class. Used by !subclass with no args and by the L5 level-up
+// DM cue.
+func renderSubclassPrompt(class DnDClass) string {
+	subs := subclassesForClass(class)
+	if len(subs) == 0 {
+		return "" // unreachable for any registered class
+	}
+	ci, _ := classInfo(class)
+	var b strings.Builder
+	b.WriteString("⚔️ **Choose your path** — ")
+	b.WriteString(ci.Display)
+	b.WriteString(" subclass\n\n")
+	for i, s := range subs {
+		b.WriteString("  ")
+		b.WriteString(string(rune('1' + i)))
+		b.WriteString(". **")
+		b.WriteString(s.Display)
+		b.WriteString("** — ")
+		b.WriteString(s.Tagline)
+		b.WriteString("\n")
+	}
+	b.WriteString("\nReply: `!subclass <name or number>` (e.g. `!subclass 1` or `!subclass champion`).")
+	return b.String()
+}
+
+// allSubclassIDs — used by tests/audits to walk every subclass.
+func allSubclassIDs() []DnDSubclass {
+	ids := make([]DnDSubclass, 0, len(dndSubclassRegistry))
+	for _, s := range dndSubclassRegistry {
+		ids = append(ids, s.ID)
+	}
+	sort.Slice(ids, func(i, j int) bool { return ids[i] < ids[j] })
+	return ids
+}
diff --git a/internal/plugin/dnd_subclass_cmd.go b/internal/plugin/dnd_subclass_cmd.go
new file mode 100644
index 0000000..11d4703
--- /dev/null
+++ b/internal/plugin/dnd_subclass_cmd.go
@@ -0,0 +1,145 @@
+package plugin
+
+import (
+	"fmt"
+	"strings"
+	"time"
+)
+
+// !subclass — Phase 10 SUB1.
+//
+// Usage:
+//
+//	!subclass                  → show selection prompt for player's class
+//	!subclass <name|number>    → choose / change subclass
+//
+// Rules:
+//   - L<5: blocked with hint message.
+//   - First selection (Subclass == ""): free, no cooldown.
+//   - Subsequent change: 30-day cooldown + 500-coin cost. Same surface
+//     command — no separate `respec` subcommand. The full-character-wipe
+//     `!respec` command is unchanged.
+//
+// Mechanical effects of L5/7/10/15 subclass abilities arrive in SUB2/SUB3.
+
+const (
+	dndSubclassMinLevel       = 5
+	dndSubclassRespecCost     = 500
+	dndSubclassRespecCooldown = 30 * 24 * time.Hour
+)
+
+func (p *AdventurePlugin) handleDnDSubclassCmd(ctx MessageContext, args string) error {
+	userMu := p.advUserLock(ctx.Sender)
+	userMu.Lock()
+	defer userMu.Unlock()
+
+	c, err := LoadDnDCharacter(ctx.Sender)
+	if err != nil {
+		return p.SendDM(ctx.Sender, "Couldn't load your character: "+err.Error())
+	}
+	if c == nil || c.PendingSetup {
+		return p.SendDM(ctx.Sender,
+			"No Adv 2.0 character yet — run `!setup` (or just enter combat and we'll auto-build one).")
+	}
+	if c.Level < dndSubclassMinLevel {
+		return p.SendDM(ctx.Sender, fmt.Sprintf(
+			"Subclass selection unlocks at **Level %d**. You're currently L%d.",
+			dndSubclassMinLevel, c.Level))
+	}
+	if len(subclassesForClass(c.Class)) == 0 {
+		return p.SendDM(ctx.Sender, "Your class has no subclasses registered yet.")
+	}
+
+	args = strings.TrimSpace(args)
+
+	// Bare `!subclass` → prompt or current.
+	if args == "" {
+		if c.Subclass == "" {
+			return p.SendDM(ctx.Sender, renderSubclassPrompt(c.Class))
+		}
+		info, _ := subclassInfo(c.Subclass)
+		var b strings.Builder
+		b.WriteString(fmt.Sprintf("**Current subclass:** %s — _%s_\n\n", info.Display, info.Tagline))
+		b.WriteString(fmt.Sprintf(
+			"To change: `!subclass <name>` — costs **%d euros**, **%d-day** cooldown.\n",
+			dndSubclassRespecCost, int(dndSubclassRespecCooldown/(24*time.Hour))))
+		return p.SendDM(ctx.Sender, b.String())
+	}
+
+	// `!subclass <name|number>` → set or change.
+	chosen, ok := resolveSubclassInput(c.Class, args)
+	if !ok {
+		var b strings.Builder
+		b.WriteString("Unknown subclass for your class. Options:\n\n")
+		b.WriteString(renderSubclassPrompt(c.Class))
+		return p.SendDM(ctx.Sender, b.String())
+	}
+
+	// First selection — free.
+	if c.Subclass == "" {
+		return p.applySubclassChoice(ctx, c, chosen, false)
+	}
+
+	// Same subclass already chosen — no-op.
+	if c.Subclass == chosen {
+		info, _ := subclassInfo(chosen)
+		return p.SendDM(ctx.Sender, fmt.Sprintf(
+			"You're already a **%s**. No change made.", info.Display))
+	}
+
+	// Change — gated by cooldown + cost.
+	if c.LastSubclassRespecAt != nil {
+		elapsed := time.Since(*c.LastSubclassRespecAt)
+		if elapsed < dndSubclassRespecCooldown {
+			return p.SendDM(ctx.Sender, fmt.Sprintf(
+				"Subclass change is on cooldown — %s remaining.",
+				formatRespecDuration(dndSubclassRespecCooldown-elapsed)))
+		}
+	}
+	if p.euro == nil || p.euro.GetBalance(ctx.Sender) < float64(dndSubclassRespecCost) {
+		return p.SendDM(ctx.Sender, fmt.Sprintf(
+			"Changing subclass costs **%d euros** — you don't have enough.",
+			dndSubclassRespecCost))
+	}
+	return p.applySubclassChoice(ctx, c, chosen, true)
+}
+
+// applySubclassChoice writes the new subclass to the character and (if
+// charged) debits the cost. Saves before debiting (audit pattern from
+// !respec): if the save fails the player keeps their euros.
+func (p *AdventurePlugin) applySubclassChoice(
+	ctx MessageContext, c *DnDCharacter, chosen DnDSubclass, charged bool,
+) error {
+	prev := c.Subclass
+	c.Subclass = chosen
+	if charged {
+		now := time.Now().UTC()
+		c.LastSubclassRespecAt = &now
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		return p.SendDM(ctx.Sender, "Couldn't save subclass choice: "+err.Error())
+	}
+	if charged {
+		// Debit last; race vs. balance change is rare and strictly safer
+		// to favor the player than risk taking euros without applying the
+		// change (matches the !respec ordering).
+		// Race vs. balance change is rare; if Debit fails the save
+		// already landed. Mirrors the !respec ordering in dnd_setup.go.
+		_ = p.euro.Debit(ctx.Sender, float64(dndSubclassRespecCost), "dnd subclass change")
+	}
+
+	info, _ := subclassInfo(chosen)
+	var b strings.Builder
+	if prev == "" {
+		b.WriteString(fmt.Sprintf("🎯 **Subclass selected: %s**\n\n", info.Display))
+	} else {
+		prevInfo, _ := subclassInfo(prev)
+		b.WriteString(fmt.Sprintf("🎯 **Subclass changed: %s → %s**\n\n",
+			prevInfo.Display, info.Display))
+		b.WriteString(fmt.Sprintf("_%d euros spent. Cooldown: %dd before next change._\n\n",
+			dndSubclassRespecCost, int(dndSubclassRespecCooldown/(24*time.Hour))))
+	}
+	b.WriteString("_" + info.Flavor + "_\n\n")
+	b.WriteString("_(Mechanical L5/7/10/15 subclass abilities land in upcoming phases.)_")
+	return p.SendDM(ctx.Sender, b.String())
+}
diff --git a/internal/plugin/dnd_subclass_test.go b/internal/plugin/dnd_subclass_test.go
new file mode 100644
index 0000000..4d50800
--- /dev/null
+++ b/internal/plugin/dnd_subclass_test.go
@@ -0,0 +1,357 @@
+package plugin
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// Phase 10 SUB1 — subclass selection.
+
+// ── Registry sanity ──────────────────────────────────────────────────────
+
+func TestSubclassRegistry_FifteenEntriesThreePerClass(t *testing.T) {
+	if got := len(dndSubclassRegistry); got != 15 {
+		t.Fatalf("registry size: got %d, want 15", got)
+	}
+	perClass := map[DnDClass]int{}
+	for _, s := range dndSubclassRegistry {
+		perClass[s.Class]++
+		if s.ID == "" || s.Display == "" || s.Tagline == "" || s.Flavor == "" {
+			t.Errorf("incomplete entry: %+v", s)
+		}
+	}
+	for _, cls := range []DnDClass{ClassFighter, ClassRogue, ClassMage, ClassCleric, ClassRanger} {
+		if perClass[cls] != 3 {
+			t.Errorf("%s: %d subclasses, want 3", cls, perClass[cls])
+		}
+	}
+}
+
+func TestSubclassRegistry_UniqueIDs(t *testing.T) {
+	seen := map[DnDSubclass]bool{}
+	for _, s := range dndSubclassRegistry {
+		if seen[s.ID] {
+			t.Errorf("duplicate subclass id: %s", s.ID)
+		}
+		seen[s.ID] = true
+	}
+}
+
+// ── resolveSubclassInput ─────────────────────────────────────────────────
+
+func TestResolveSubclassInput_ByNumber(t *testing.T) {
+	got, ok := resolveSubclassInput(ClassFighter, "1")
+	if !ok || got != SubclassChampion {
+		t.Errorf("Fighter '1' = (%q, %v), want (champion, true)", got, ok)
+	}
+	got, ok = resolveSubclassInput(ClassFighter, "3")
+	if !ok || got != SubclassBerserker {
+		t.Errorf("Fighter '3' = (%q, %v), want (berserker, true)", got, ok)
+	}
+	if _, ok := resolveSubclassInput(ClassFighter, "4"); ok {
+		t.Error("Fighter '4' should be invalid")
+	}
+}
+
+func TestResolveSubclassInput_ByNameAndDisplay(t *testing.T) {
+	cases := []struct {
+		class DnDClass
+		input string
+		want  DnDSubclass
+	}{
+		{ClassFighter, "champion", SubclassChampion},
+		{ClassFighter, "Champion", SubclassChampion},
+		{ClassFighter, "Battle Master", SubclassBattleMaster},
+		{ClassFighter, "battlemaster", SubclassBattleMaster},
+		{ClassFighter, "battle_master", SubclassBattleMaster},
+		{ClassRogue, "Arcane Trickster", SubclassArcaneTrickster},
+		{ClassMage, "necromancy", SubclassNecromancy},
+		{ClassCleric, "life domain", SubclassLifeDomain},
+		{ClassRanger, "Gloom-Stalker", SubclassGloomStalker},
+	}
+	for _, tc := range cases {
+		got, ok := resolveSubclassInput(tc.class, tc.input)
+		if !ok || got != tc.want {
+			t.Errorf("%s/%q: got (%q,%v), want (%q,true)", tc.class, tc.input, got, ok, tc.want)
+		}
+	}
+}
+
+func TestResolveSubclassInput_WrongClass(t *testing.T) {
+	// "champion" belongs to Fighter — should not resolve for Rogue.
+	if _, ok := resolveSubclassInput(ClassRogue, "champion"); ok {
+		t.Error("champion should not resolve under Rogue")
+	}
+}
+
+// ── renderSubclassPrompt ─────────────────────────────────────────────────
+
+func TestRenderSubclassPrompt_ContainsAllThree(t *testing.T) {
+	got := renderSubclassPrompt(ClassMage)
+	for _, want := range []string{"Evocation", "Abjuration", "Necromancy", "Mage"} {
+		if !strings.Contains(got, want) {
+			t.Errorf("prompt missing %q:\n%s", want, got)
+		}
+	}
+}
+
+// ── !subclass command flow ───────────────────────────────────────────────
+
+func subclassTestCharacter(t *testing.T, uid id.UserID, level int) *DnDCharacter {
+	t.Helper()
+	if err := createAdvCharacter(uid, "subclass"); err != nil {
+		t.Fatal(err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceHuman, Class: ClassFighter, Level: level,
+		STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 16,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	return c
+}
+
+func TestSubclass_BlockedBelowLevel5(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_low:example")
+	subclassTestCharacter(t, uid, 4)
+	p := &AdventurePlugin{euro: &EuroPlugin{}}
+	// Should not error, just send a "level" message; we rely on the row
+	// staying empty.
+	if err := p.handleDnDSubclassCmd(MessageContext{Sender: uid}, "champion"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Subclass != "" {
+		t.Errorf("subclass set despite L4: %q", got.Subclass)
+	}
+}
+
+func TestSubclass_FirstSelectionFreeAndPersists(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_first:example")
+	subclassTestCharacter(t, uid, 5)
+	euro := &EuroPlugin{}
+	euro.ensureBalance(uid)
+	bal := euro.GetBalance(uid)
+	p := &AdventurePlugin{euro: euro}
+
+	if err := p.handleDnDSubclassCmd(MessageContext{Sender: uid}, "champion"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Subclass != SubclassChampion {
+		t.Errorf("subclass = %q, want champion", got.Subclass)
+	}
+	if got.LastSubclassRespecAt != nil {
+		t.Errorf("first selection should not set cooldown timestamp")
+	}
+	if euro.GetBalance(uid) != bal {
+		t.Errorf("first selection should be free; balance %.0f → %.0f", bal, euro.GetBalance(uid))
+	}
+}
+
+func TestSubclass_SameChoiceIsNoop(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_same:example")
+	c := subclassTestCharacter(t, uid, 5)
+	c.Subclass = SubclassChampion
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	euro := &EuroPlugin{}
+	euro.ensureBalance(uid)
+	euro.Credit(uid, 10000, "test")
+	bal := euro.GetBalance(uid)
+	p := &AdventurePlugin{euro: euro}
+
+	if err := p.handleDnDSubclassCmd(MessageContext{Sender: uid}, "champion"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.LastSubclassRespecAt != nil {
+		t.Error("same-choice no-op should not set cooldown")
+	}
+	if euro.GetBalance(uid) != bal {
+		t.Error("same-choice no-op should not debit")
+	}
+}
+
+func TestSubclass_ChangeChargesAndSetsCooldown(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_change:example")
+	c := subclassTestCharacter(t, uid, 6)
+	c.Subclass = SubclassChampion
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	euro := &EuroPlugin{}
+	euro.ensureBalance(uid)
+	euro.Credit(uid, 10000, "test")
+	startBal := euro.GetBalance(uid)
+	p := &AdventurePlugin{euro: euro}
+
+	if err := p.handleDnDSubclassCmd(MessageContext{Sender: uid}, "berserker"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Subclass != SubclassBerserker {
+		t.Errorf("subclass = %q, want berserker", got.Subclass)
+	}
+	if got.LastSubclassRespecAt == nil {
+		t.Error("cooldown timestamp not set after charged change")
+	}
+	if delta := startBal - euro.GetBalance(uid); delta < float64(dndSubclassRespecCost) {
+		t.Errorf("debited %.0f, want at least %d", delta, dndSubclassRespecCost)
+	}
+}
+
+func TestSubclass_ChangeBlockedByCooldown(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_cd:example")
+	c := subclassTestCharacter(t, uid, 6)
+	c.Subclass = SubclassChampion
+	now := time.Now().UTC().Add(-1 * time.Hour) // 1h ago — well inside 30d
+	c.LastSubclassRespecAt = &now
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	euro := &EuroPlugin{}
+	euro.ensureBalance(uid)
+	euro.Credit(uid, 10000, "test")
+	bal := euro.GetBalance(uid)
+	p := &AdventurePlugin{euro: euro}
+
+	if err := p.handleDnDSubclassCmd(MessageContext{Sender: uid}, "berserker"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Subclass != SubclassChampion {
+		t.Errorf("subclass changed despite cooldown: %q", got.Subclass)
+	}
+	if euro.GetBalance(uid) != bal {
+		t.Error("cooldown-blocked change should not debit")
+	}
+}
+
+func TestSubclass_ChangeBlockedByInsufficientFunds(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_broke:example")
+	c := subclassTestCharacter(t, uid, 6)
+	c.Subclass = SubclassChampion
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	euro := &EuroPlugin{}
+	euro.ensureBalance(uid)
+	// No credit — balance ~0.
+	p := &AdventurePlugin{euro: euro}
+
+	if err := p.handleDnDSubclassCmd(MessageContext{Sender: uid}, "berserker"); err != nil {
+		t.Fatal(err)
+	}
+	got, _ := LoadDnDCharacter(uid)
+	if got.Subclass != SubclassChampion {
+		t.Errorf("subclass changed despite insufficient funds: %q", got.Subclass)
+	}
+}
+
+// ── level-up DM cue ──────────────────────────────────────────────────────
+
+func TestBuildLevelUpMessage_PromptsAtL5WhenUnchosen(t *testing.T) {
+	c := &DnDCharacter{
+		UserID: "@x:example", Race: RaceHuman, Class: ClassFighter,
+		Level: 5, HPMax: 40,
+	}
+	msg := buildLevelUpMessage(c, []LevelUpEvent{{NewLevel: 5, HPGain: 7}}, "")
+	if !strings.Contains(msg, "Choose your path") {
+		t.Errorf("L5 level-up missing subclass prompt:\n%s", msg)
+	}
+	if !strings.Contains(msg, "Champion") {
+		t.Errorf("L5 prompt should list Champion:\n%s", msg)
+	}
+}
+
+func TestBuildLevelUpMessage_NoPromptIfAlreadyChosen(t *testing.T) {
+	c := &DnDCharacter{
+		UserID: "@x:example", Race: RaceHuman, Class: ClassFighter,
+		Level: 6, HPMax: 47, Subclass: SubclassChampion,
+	}
+	msg := buildLevelUpMessage(c, []LevelUpEvent{{NewLevel: 6, HPGain: 7}}, "")
+	if strings.Contains(msg, "Choose your path") {
+		t.Errorf("L6 level-up should not re-prompt:\n%s", msg)
+	}
+}
+
+func TestBuildLevelUpMessage_NoPromptBelowL5(t *testing.T) {
+	c := &DnDCharacter{
+		UserID: "@x:example", Race: RaceHuman, Class: ClassFighter,
+		Level: 4, HPMax: 33,
+	}
+	msg := buildLevelUpMessage(c, []LevelUpEvent{{NewLevel: 4, HPGain: 7}}, "")
+	if strings.Contains(msg, "Choose your path") {
+		t.Errorf("L4 should not prompt:\n%s", msg)
+	}
+}
+
+// ── sheet display ────────────────────────────────────────────────────────
+
+func TestSheet_ShowsSubclassWhenChosen(t *testing.T) {
+	c := &DnDCharacter{
+		UserID: "@x:example", Race: RaceHuman, Class: ClassFighter,
+		Level: 7, HPMax: 50, HPCurrent: 50, ArmorClass: 16,
+		STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+		Subclass: SubclassBattleMaster,
+	}
+	out := renderDnDSheet(c, nil, nil, nil)
+	if !strings.Contains(out, "Battle Master") {
+		t.Errorf("sheet missing subclass name:\n%s", out)
+	}
+}
+
+func TestSheet_PromptsWhenUnchosenAtL5(t *testing.T) {
+	c := &DnDCharacter{
+		UserID: "@x:example", Race: RaceHuman, Class: ClassFighter,
+		Level: 5, HPMax: 40, HPCurrent: 40, ArmorClass: 16,
+		STR: 16, DEX: 12, CON: 14, INT: 8, WIS: 10, CHA: 10,
+	}
+	out := renderDnDSheet(c, nil, nil, nil)
+	if !strings.Contains(out, "!subclass") {
+		t.Errorf("sheet should nudge `!subclass` when unchosen at L5:\n%s", out)
+	}
+}
+
+// ── schema migration round-trip ──────────────────────────────────────────
+
+func TestSubclass_SchemaRoundTrip(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@subclass_rt:example")
+	if err := createAdvCharacter(uid, "rt"); err != nil {
+		t.Fatal(err)
+	}
+	now := time.Now().UTC().Truncate(time.Second)
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceElf, Class: ClassMage, Level: 7,
+		STR: 8, DEX: 14, CON: 12, INT: 17, WIS: 12, CHA: 10,
+		HPMax: 30, HPCurrent: 30, ArmorClass: 12,
+		Subclass: SubclassEvocation, LastSubclassRespecAt: &now,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	got, err := LoadDnDCharacter(uid)
+	if err != nil || got == nil {
+		t.Fatalf("load: %v %v", got, err)
+	}
+	if got.Subclass != SubclassEvocation {
+		t.Errorf("subclass roundtrip: got %q, want evocation", got.Subclass)
+	}
+	if got.LastSubclassRespecAt == nil || !got.LastSubclassRespecAt.Equal(now) {
+		t.Errorf("LastSubclassRespecAt roundtrip: got %v, want %v", got.LastSubclassRespecAt, now)
+	}
+}
diff --git a/internal/plugin/dnd_xp.go b/internal/plugin/dnd_xp.go
index bd701ef..60ec8f2 100644
--- a/internal/plugin/dnd_xp.go
+++ b/internal/plugin/dnd_xp.go
@@ -189,13 +189,18 @@ func buildLevelUpMessage(c *DnDCharacter, events []LevelUpEvent, flavor string)
 		}
 	}
 
-	// Subclass selection cue: design doc specs a prompt at L5. Mechanics
-	// arrive in a future phase; for now the level-up DM mentions it so the
-	// player isn't surprised when it lands.
-	for _, ev := range events {
-		if ev.NewLevel == 5 {
-			b.WriteString("\n🎯 _Subclass selection unlocks at L5 — coming in a future update._")
-			break
+	// Phase 10 — subclass selection cue. Fires when the player crosses L5
+	// without already having a subclass (rare path: a multi-level grant
+	// that crosses L5 keeps prompting until they pick). Existing-subclass
+	// cases stay quiet on later level-ups.
+	if c.Subclass == "" && c.Level >= dndSubclassMinLevel {
+		for _, ev := range events {
+			if ev.NewLevel >= dndSubclassMinLevel {
+				b.WriteString("\n🎯 ")
+				b.WriteString(renderSubclassPrompt(c.Class))
+				b.WriteString("\n")
+				break
+			}
 		}
 	}
 	return b.String()