diff --git a/internal/db/migrate_test.go b/internal/db/migrate_test.go
index 24ae244..5804a49 100644
--- a/internal/db/migrate_test.go
+++ b/internal/db/migrate_test.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"errors"
+	"slices"
 	"testing"
 )
 
@@ -41,6 +42,20 @@ func registeredMigrations(t *testing.T, ctx context.Context, db *sql.DB) []strin
 	return ids
 }
 
+// upMigrationIDs returns the ids of the embedded up-migrations in apply order.
+func upMigrationIDs(t *testing.T) []string {
+	t.Helper()
+	migs, err := loadMigrations()
+	if err != nil {
+		t.Fatalf("loadMigrations: %v", err)
+	}
+	ids := make([]string, len(migs))
+	for i, m := range migs {
+		ids[i] = m.id
+	}
+	return ids
+}
+
 // appMetaExists reports whether the app_meta table is present.
 func appMetaExists(t *testing.T, ctx context.Context, db *sql.DB) bool {
 	t.Helper()
@@ -60,15 +75,16 @@ func TestMigrateUp_FirstApply_正常(t *testing.T) {
 		t.Fatalf("MigrateUp first call: %v", err)
 	}
 
+	// Applies every embedded up-migration, in order.
 	ids := registeredMigrations(t, ctx, db)
-	if len(ids) != 1 || ids[0] != "0001_init" {
-		t.Fatalf("schema_migrations = %v, want exactly [0001_init]", ids)
+	if want := upMigrationIDs(t); !slices.Equal(ids, want) {
+		t.Fatalf("schema_migrations = %v, want %v", ids, want)
 	}
 	if !appMetaExists(t, ctx, db) {
 		t.Fatal("app_meta table should exist after MigrateUp")
 	}
 
-	// applied_at must be recorded on the single row.
+	// applied_at must be recorded on the first migration row.
 	var appliedAt string
 	if err := db.QueryRowContext(ctx, "SELECT applied_at FROM schema_migrations WHERE id = ?", "0001_init").Scan(&appliedAt); err != nil {
 		t.Fatalf("read applied_at: %v", err)
@@ -87,13 +103,14 @@ func TestMigrateUp_Idempotent_正常(t *testing.T) {
 		t.Fatalf("MigrateUp first call: %v", err)
 	}
 
-	// Second call must not re-execute or duplicate the record.
+	// Second call must not re-execute or duplicate the records.
 	if err := MigrateUp(ctx, db, testLogger()); err != nil {
 		t.Fatalf("MigrateUp second call: %v", err)
 	}
+	want := upMigrationIDs(t)
 	ids := registeredMigrations(t, ctx, db)
-	if len(ids) != 1 {
-		t.Fatalf("schema_migrations rows = %d, want 1 (idempotent), ids=%v", len(ids), ids)
+	if !slices.Equal(ids, want) {
+		t.Fatalf("idempotent: schema_migrations = %v, want %v", ids, want)
 	}
 	if !appMetaExists(t, ctx, db) {
 		t.Fatal("app_meta should still exist after idempotent re-run")
@@ -105,16 +122,17 @@ func TestMigrateDown_ThenReUp_正常(t *testing.T) {
 	ctx := context.Background()
 	db := openMemory(t)
 
+	want := upMigrationIDs(t)
 	if err := MigrateUp(ctx, db, testLogger()); err != nil {
 		t.Fatalf("MigrateUp: %v", err)
 	}
 
-	// Roll back the single applied migration.
-	if err := MigrateDown(ctx, db, 1, testLogger()); err != nil {
-		t.Fatalf("MigrateDown: %v", err)
+	// Roll back every applied migration.
+	if err := MigrateDown(ctx, db, len(want), testLogger()); err != nil {
+		t.Fatalf("MigrateDown(all): %v", err)
 	}
 	if appMetaExists(t, ctx, db) {
-		t.Fatal("app_meta should be dropped after MigrateDown")
+		t.Fatal("app_meta should be dropped after MigrateDown(all)")
 	}
 	if ids := registeredMigrations(t, ctx, db); len(ids) != 0 {
 		t.Fatalf("schema_migrations should be empty after rollback, got %v", ids)
@@ -127,8 +145,8 @@ func TestMigrateDown_ThenReUp_正常(t *testing.T) {
 	if !appMetaExists(t, ctx, db) {
 		t.Fatal("app_meta should exist again after re-MigrateUp")
 	}
-	if ids := registeredMigrations(t, ctx, db); len(ids) != 1 || ids[0] != "0001_init" {
-		t.Fatalf("schema_migrations = %v, want exactly [0001_init]", ids)
+	if ids := registeredMigrations(t, ctx, db); !slices.Equal(ids, want) {
+		t.Fatalf("schema_migrations = %v, want %v", ids, want)
 	}
 }
 
diff --git a/internal/db/migrations/0002_memory.down.sql b/internal/db/migrations/0002_memory.down.sql
new file mode 100644
index 0000000..5466a55
--- /dev/null
+++ b/internal/db/migrations/0002_memory.down.sql
@@ -0,0 +1 @@
+DROP TABLE IF EXISTS memory_items;
diff --git a/internal/db/migrations/0002_memory.up.sql b/internal/db/migrations/0002_memory.up.sql
new file mode 100644
index 0000000..81fe218
--- /dev/null
+++ b/internal/db/migrations/0002_memory.up.sql
@@ -0,0 +1,21 @@
+-- M2: long-term memory items (DevDocs/design/03 §0/§3).
+-- Canonical schema reference; internal/runtime/memory reuses this table.
+CREATE TABLE IF NOT EXISTS memory_items (
+    id                  TEXT PRIMARY KEY,
+    persona_id          TEXT NOT NULL,
+    role_id             TEXT NOT NULL DEFAULT '',
+    scope               TEXT NOT NULL,
+    kind                TEXT NOT NULL,
+    content             TEXT NOT NULL,
+    tags                TEXT NOT NULL DEFAULT '[]',
+    confidence          REAL NOT NULL DEFAULT 1.0,
+    source_conversation TEXT NOT NULL DEFAULT '',
+    created_at          TEXT NOT NULL,
+    updated_at          TEXT NOT NULL,
+    decay_weight        REAL NOT NULL DEFAULT 1.0
+);
+
+CREATE INDEX IF NOT EXISTS idx_memory_items_persona_id
+    ON memory_items (persona_id);
+CREATE INDEX IF NOT EXISTS idx_memory_items_persona_id_created_at
+    ON memory_items (persona_id, created_at);