diff --git a/cmd/expedition-sim/main.go b/cmd/expedition-sim/main.go
new file mode 100644
index 0000000..0e36feb
--- /dev/null
+++ b/cmd/expedition-sim/main.go
@@ -0,0 +1,80 @@
+// expedition-sim drives synthetic players through expeditions for batch
+// analysis. Re-uses production plugin paths against a fresh sqlite DB so
+// outcomes mirror what live players hit.
+//
+// Usage: expedition-sim [-class fighter] [-level 5] [-zone goblin_warrens]
+//                       [-bank 1000] [-cap 200] [-data DIR]
+//
+// Defaults run one L5 fighter through goblin_warrens and print a JSON
+// SimResult to stdout. Per-room logs and matrix-mode batches land in a
+// follow-up; this binary is the scaffold the analysis stack hangs off.
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+
+	"gogobee/internal/plugin"
+
+	"maunium.net/go/mautrix/id"
+)
+
+func main() {
+	var (
+		class   = flag.String("class", "fighter", "DnD class id (fighter, mage, cleric, …)")
+		level   = flag.Int("level", 5, "character level")
+		zone    = flag.String("zone", "goblin_warrens", "zone id (see internal/plugin/dnd_zone_registry.go)")
+		bank    = flag.Float64("bank", 1000, "starting coin balance — must cover outfitting")
+		cap     = flag.Int("cap", 200, "max !expedition run invocations per expedition")
+		dataDir = flag.String("data", "", "data dir for the temp sqlite db (default: OS tempdir)")
+		userTag = flag.String("user", "@sim:expedition", "synthetic user id")
+	)
+	flag.Parse()
+
+	dir := *dataDir
+	if dir == "" {
+		var err error
+		dir, err = os.MkdirTemp("", "expedition-sim-")
+		if err != nil {
+			fail("mkdir temp:", err)
+		}
+		defer os.RemoveAll(dir)
+	}
+
+	runner, err := plugin.NewSimRunner(dir)
+	if err != nil {
+		fail("init runner:", err)
+	}
+	defer runner.Close()
+
+	uid := id.UserID(*userTag)
+	if _, err := runner.BuildCharacter(uid, plugin.DnDClass(*class), *level); err != nil {
+		fail("build character:", err)
+	}
+
+	runner.Euro.Credit(uid, *bank, "expedition-sim bankroll")
+
+	res, err := runner.RunExpedition(uid, plugin.ZoneID(*zone), *cap)
+	if err != nil {
+		// RunExpedition returns a partial result alongside the error so the
+		// outcome of a partial run is still observable.
+		if res != nil {
+			emit(res)
+		}
+		fail("run expedition:", err)
+	}
+	emit(res)
+}
+
+func emit(res *plugin.SimResult) {
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", "  ")
+	_ = enc.Encode(res)
+}
+
+func fail(args ...interface{}) {
+	fmt.Fprintln(os.Stderr, args...)
+	os.Exit(1)
+}
diff --git a/internal/plugin/expedition_sim.go b/internal/plugin/expedition_sim.go
new file mode 100644
index 0000000..19b6607
--- /dev/null
+++ b/internal/plugin/expedition_sim.go
@@ -0,0 +1,194 @@
+package plugin
+
+// Expedition sim runner — headless driver that walks expeditions through
+// the production plugin code paths against a temp sqlite DB. Used by
+// cmd/expedition-sim to generate batched corpora for H3/H4 analysis.
+//
+// SendDM is a no-op when AdventurePlugin.Client is nil, so the runner
+// reads ground truth from the DB rather than parsing transcripts. The
+// real-time day cycle (06:00/21:00 cron) is bypassed; expeditions are
+// driven to completion via repeated !expedition run cycles until the
+// autopilot stops or supplies drain.
+
+import (
+	"fmt"
+
+	"gogobee/internal/db"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// SimRunner owns a temp-DB AdventurePlugin + EuroPlugin pair and exposes
+// just enough surface to drive synthetic players end-to-end.
+type SimRunner struct {
+	P    *AdventurePlugin
+	Euro *EuroPlugin
+}
+
+// NewSimRunner initializes a fresh sqlite DB in dataDir and constructs
+// the plugin pair. dataDir should already exist and be writable; the
+// caller is responsible for cleanup. Re-init after a Close+new dataDir.
+func NewSimRunner(dataDir string) (*SimRunner, error) {
+	db.Close()
+	if err := db.Init(dataDir); err != nil {
+		return nil, fmt.Errorf("db init: %w", err)
+	}
+	euro := &EuroPlugin{}
+	p := &AdventurePlugin{euro: euro}
+	return &SimRunner{P: p, Euro: euro}, nil
+}
+
+// Close releases the shared sqlite handle. Safe to call multiple times.
+func (s *SimRunner) Close() {
+	db.Close()
+}
+
+// BuildCharacter persists a synthetic character at (class, level) under
+// uid, with adventure_character + dnd_character + spell-slot rows wired
+// up so handleDnDExpeditionCmd accepts them. Stats are class-flavored
+// but otherwise vanilla (no race/subclass perks, no equipment).
+func (s *SimRunner) BuildCharacter(uid id.UserID, class DnDClass, level int) (*DnDCharacter, error) {
+	if err := createAdvCharacter(uid, "sim_"+string(class)); err != nil {
+		return nil, fmt.Errorf("createAdvCharacter: %w", err)
+	}
+	c := &DnDCharacter{
+		UserID: uid,
+		Race:   RaceHuman,
+		Class:  class,
+		Level:  level,
+	}
+	applyClassBaselineStats(c)
+	conMod := abilityModifier(c.CON)
+	c.HPMax = computeMaxHP(c.Class, conMod, level)
+	c.HPCurrent = c.HPMax
+	c.ArmorClass = computeAC(c.Class, abilityModifier(c.DEX))
+	c.ShortRestCharges = level
+	if err := SaveDnDCharacter(c); err != nil {
+		return nil, fmt.Errorf("SaveDnDCharacter: %w", err)
+	}
+	if pool := slotsForClassLevel(class, level); len(pool) > 0 {
+		if err := setSpellSlotsForLevel(uid, class, level); err != nil {
+			return nil, fmt.Errorf("setSpellSlotsForLevel: %w", err)
+		}
+	}
+	return c, nil
+}
+
+// applyClassBaselineStats sets ability scores that put each class in
+// its expected role band — martials prioritize STR/CON, casters their
+// casting stat. Values mirror the array choices in the class-balance
+// harness so sim numbers stay comparable.
+func applyClassBaselineStats(c *DnDCharacter) {
+	switch c.Class {
+	case ClassFighter, ClassPaladin:
+		c.STR, c.DEX, c.CON, c.INT, c.WIS, c.CHA = 16, 13, 15, 8, 12, 10
+	case ClassRogue, ClassRanger:
+		c.STR, c.DEX, c.CON, c.INT, c.WIS, c.CHA = 10, 16, 14, 12, 13, 8
+	case ClassMage, ClassSorcerer:
+		c.STR, c.DEX, c.CON, c.INT, c.WIS, c.CHA = 8, 14, 13, 16, 12, 10
+	case ClassCleric, ClassDruid:
+		c.STR, c.DEX, c.CON, c.INT, c.WIS, c.CHA = 12, 10, 14, 8, 16, 13
+	case ClassBard, ClassWarlock:
+		c.STR, c.DEX, c.CON, c.INT, c.WIS, c.CHA = 8, 13, 14, 10, 12, 16
+	default:
+		c.STR, c.DEX, c.CON, c.INT, c.WIS, c.CHA = 12, 12, 12, 12, 12, 12
+	}
+}
+
+// SimResult is the per-expedition summary the runner emits. The
+// per-room log lives in the dnd_expedition_log table for now; later
+// phases can extract a structured slice here.
+type SimResult struct {
+	UserID    string
+	Class     string
+	Level     int
+	Zone      string
+	Outcome   string // "extracted" | "abandoned" | "tpk" | "halted" | "ongoing"
+	Rooms     int
+	StartHP   int
+	EndHP     int
+	StartCoin float64
+	EndCoin   float64
+	SUStart   float32
+	SUEnd     float32
+	DaysAtEnd int
+}
+
+// RunExpedition starts an expedition for uid in zoneID and loops
+// !expedition run until the autopilot stops advancing rooms. runCap
+// bounds the total !expedition run invocations as a safety net against
+// runaway loops (each invocation walks up to autopilotRoomCap rooms).
+//
+// Pre-state: uid must own a synthetic character via BuildCharacter and
+// have a coin balance sufficient for outfitting (caller's responsibility).
+func (s *SimRunner) RunExpedition(uid id.UserID, zoneID ZoneID, runCap int) (*SimResult, error) {
+	c, err := LoadDnDCharacter(uid)
+	if err != nil || c == nil {
+		return nil, fmt.Errorf("LoadDnDCharacter: %w", err)
+	}
+	res := &SimResult{
+		UserID:    string(uid),
+		Class:     string(c.Class),
+		Level:     c.Level,
+		Zone:      string(zoneID),
+		StartHP:   c.HPCurrent,
+		StartCoin: s.Euro.GetBalance(uid),
+	}
+
+	ctx := MessageContext{Sender: uid}
+	if err := s.P.handleDnDExpeditionCmd(ctx, "start "+string(zoneID)); err != nil {
+		return res, fmt.Errorf("expedition start: %w", err)
+	}
+	exp, _ := getActiveExpedition(uid)
+	if exp == nil {
+		res.Outcome = "halted"
+		return res, fmt.Errorf("expedition did not persist after start")
+	}
+	res.SUStart = exp.Supplies.Current
+
+	priorRoom := -1
+	stalls := 0
+	for i := 0; i < runCap; i++ {
+		if err := s.P.handleDnDExpeditionCmd(ctx, "run"); err != nil {
+			return res, fmt.Errorf("expedition run iter %d: %w", i, err)
+		}
+		cur, _ := getActiveExpedition(uid)
+		if cur == nil {
+			// Expedition closed (extracted, TPK, abandoned).
+			res.Outcome = "extracted"
+			break
+		}
+		run, _ := getActiveZoneRun(uid)
+		room := -1
+		if run != nil {
+			room = run.CurrentRoom
+		}
+		if room == priorRoom {
+			stalls++
+			if stalls >= 2 {
+				// Two consecutive runs with no room advance — autopilot
+				// has stopped (HP/SU/threshold). Sim mode bails so we
+				// can record the halt rather than loop forever.
+				res.Outcome = "halted"
+				break
+			}
+		} else {
+			stalls = 0
+			priorRoom = room
+		}
+		res.Rooms++
+	}
+	if res.Outcome == "" {
+		res.Outcome = "ongoing"
+	}
+
+	if c2, _ := LoadDnDCharacter(uid); c2 != nil {
+		res.EndHP = c2.HPCurrent
+	}
+	res.EndCoin = s.Euro.GetBalance(uid)
+	if exp2, _ := getActiveExpedition(uid); exp2 != nil {
+		res.SUEnd = exp2.Supplies.Current
+		res.DaysAtEnd = exp2.CurrentDay
+	}
+	return res, nil
+}