forgot to mention the story

src/Character.ts

@@ -5,7 +5,7 @@
  * State is encapsulated in a CharacterState record type.
  */
 import { Health } from './Health.ts';
-import type { Level } from './Level.ts';
+import { Level } from './Level.ts';
 import type { Status } from './Status.ts';
 import { StatusAlive, StatusDead } from './Status.ts';
 import { CharacterState } from './CharacterState.ts';
@@ -81,4 +81,21 @@ export class Character {
       new CharacterState(target.name, newHealth, newStatus, target.level, target.factions),
     );
   }
+
+  /**
+   * Heal self by the given amount. Returns a new Character with updated state.
+   * Dead characters cannot heal. Healing is capped at max health for level.
+   */
+  healSelf(amount: number): Character {
+    // Dead characters cannot heal
+    if (this.status.kind === 'dead') return this;
+    // Negative heal is invalid
+    if (amount < 0) throw new Error(`Heal amount must be non-negative, got ${amount}`);
+    // Increase health, capped at level-based maximum
+    const maxHealth = Level.maxHealthForLevel(this.level.value);
+    const newHealth = this.health.add(amount, maxHealth);
+    return new Character(
+      new CharacterState(this.name, newHealth, this.status, this.level, this.factions),
+    );
+  }
 }

src/Health.ts

@@ -26,4 +26,9 @@ export class Health {
   sub(amount: number): Health {
     return Health.create(Math.max(0, this.#value - amount));
   }
+
+  /** Add healing — capped at the given maximum. */
+  add(amount: number, max: number): Health {
+    return Health.create(Math.min(this.#value + amount, max));
+  }
 }