Index transcripts

- Move .pi/specs/ files into specs/ (healing, factions, merged magical-objects)
- Move src/*.allium files into specs/ (levels, changing-level)
- Delete .pi/specs/ directory
- Document specs/ convention in AGENTS.md

.pi/extensions/yak-mode-gate.ts

@@ -0,0 +1,20 @@
+import type { ExtensionAPI } from '@earendil-works/pi-coding-agent';
+import { isToolCallEventType } from '@earendil-works/pi-coding-agent';
+
+export default function (pi: ExtensionAPI) {
+  pi.on('tool_call', async (event, ctx) => {
+    if (!isToolCallEventType('bash', event)) return;
+
+    const cmd = event.input.command || '';
+    const isYxCommand = cmd.includes('yx ');
+
+    // Allow yaks in interactive mode, block in print mode (sub-agents)
+    if (isYxCommand && ctx.mode === 'print') {
+      return {
+        block: true,
+        reason:
+          'yx commands are disabled in print mode. Sub-agents must focus on domain work only.',
+      };
+    }
+  });
+}

.pi/skills/yak-tasks/SKILL.md

@@ -0,0 +1,88 @@
+---
+name: yak-tasks
+description: Orchestrate sub-agents using yx task tracking. Use when delegating work to sub-agents, tracking task progress, or marking tasks complete. For breaking down problems into tasks, use /skill:problem-breakdown first.
+---
+
+# Yak Task Orchestration
+
+Coordinate sub-agent work using the `yx` CLI. The main agent creates tasks and delegates to sub-agents; sub-agents execute domain work without yx CLI access.
+
+## Workflow
+
+1. **Break down** → `/skill:problem-breakdown` (creates yaks with context)
+2. **Delegate** → sub-agents run on yaks via `pi -p` (blocked from yx CLI)
+3. **Track** → `yx list` / `yx show <task-id>`
+4. **Verify** → run `npm run checks` after sub-agent work
+5. **Complete** → `yx done <task-id>`
+
+## Running Sub-Agents
+
+Sub-agents execute in print mode and are **hard-blocked from using `yx` commands** (see `.pi/extensions/yak-mode-gate.ts`). They receive:
+
+- The yak's `.context.md` (task description)
+- `AGENTS.md` (project conventions)
+- Domain files to work on
+- No yx CLI access
+
+```bash
+# Run a sub-agent on a specific yak
+# The sub-agent reads the yak context and executes the work
+pi -p "Work on yak: <task-name>. Read .yaks/<task-id>/.context.md for details."
+```
+
+## Tracking Progress
+
+```bash
+# List all yaks with hierarchy
+yx list
+
+# Show yak details
+yx show <task-id>
+
+# Check state directly
+cat .yaks/<task-id>/.state
+```
+
+States:
+
+- `pending` — not yet started
+- `in-progress` — being worked on
+- `done` — completed
+
+## Marking Tasks Complete
+
+```bash
+yx done <task-id>
+```
+
+Always verify before marking done:
+
+```bash
+# 1. Check state
+cat .yaks/<task-id>/.state
+
+# 2. Review what was done
+cat .yaks/<task-id>/.context.md
+
+# 3. Run project checks
+npm run checks
+```
+
+## Sub-Agent Communication
+
+Sub-agents can read yak state files directly (no yx CLI needed):
+
+```bash
+cat .yaks/<task-id>/.name    # task name
+cat .yaks/<task-id>/.state   # current state
+cat .yaks/<task-id>/.context.md  # task description
+cat .yaks/<task-id>/.created.json  # creation metadata
+```
+
+## Best Practices
+
+- **Delegate after breakdown** — run `/skill:problem-breakdown` first to create structured yaks
+- **Verify before marking done** — always run `npm run checks` to catch sub-agent errors
+- **Review context** — read `.context.md` to understand what the sub-agent was supposed to do
+- **Keep yaks focused** — each yak should be a single file operation or one method implementation
+- **Use hierarchy** — parent yaks block children; fix leaves first

.pi/specs/story-4-magical-objects.allium

@@ -1,174 +0,0 @@
--- allium: 3
-
--- allium: magical-objects
-
-------------------------------------------------------------
--- External Entities
-------------------------------------------------------------
-
-external entity Character {
-    name: String
-    health: Health
-    status: alive | dead
-    level: Level
-    factions: Set<Faction>
-}
-
-external entity Health {
-    value: Integer
-}
-
-external entity Level {
-    value: Integer
-}
-
-external entity Faction {
-    name: String
-}
-
-------------------------------------------------------------
--- Entities and Variants
-------------------------------------------------------------
-
-entity MagicalWeapon {
-    health: Health
-    maxHealth: Integer
-    status: alive | destroyed
-    damage: Integer
-    owner: Character
-}
-
-entity HealingObject {
-    health: Health
-    maxHealth: Integer
-    status: alive | destroyed
-}
-
-------------------------------------------------------------
--- Rules
-------------------------------------------------------------
-
-rule WeaponDealsDamage {
-    when: MagicalWeapon.dealsDamage(weapon, target, attacker)
-    requires: weapon.status = alive
-    requires: attacker = weapon.owner
-    requires: attacker.status = alive
-    ensures: target.health.value = max(0, target.health.value - weapon.damage)
-    ensures: weapon.health.value = weapon.health.value - 1
-    ensures:
-        if weapon.health.value - 1 = 0:
-            weapon.status = destroyed
-        else:
-            weapon.status = alive
-    ensures:
-        if max(0, target.health.value - weapon.damage) = 0:
-            target.status = dead
-        else:
-            target.status = alive
-}
-
-rule DeadCannotUseWeapon {
-    when: MagicalWeapon.dealsDamage(weapon, target, attacker)
-    requires: attacker.status = dead
-    ensures:
-        target.health.value = target.health.value
-        weapon.health.value = weapon.health.value
-        weapon.status = weapon.status
-        target.status = target.status
-}
-
-rule NonOwnerCannotUseWeapon {
-    when: MagicalWeapon.dealsDamage(weapon, target, attacker)
-    requires: attacker != weapon.owner
-    ensures:
-        target.health.value = target.health.value
-        weapon.health.value = weapon.health.value
-        weapon.status = weapon.status
-        target.status = target.status
-}
-
-rule DestroyedWeaponCannotDealDamage {
-    when: MagicalWeapon.dealsDamage(weapon, target, attacker)
-    requires: weapon.status = destroyed
-    ensures:
-        target.health.value = target.health.value
-        weapon.health.value = weapon.health.value
-        weapon.status = weapon.status
-        target.status = target.status
-}
-
-rule HealingObjectHealsCharacter {
-    when: HealingObject.healsCharacter(object, character, amount)
-    requires: object.status = alive
-    requires: character.status = alive
-    ensures: healAmount = min(amount, object.maxHealth - object.health.value)
-    ensures: character.health.value = character.health.value + healAmount
-    ensures: object.health.value = object.health.value - healAmount
-    ensures:
-        if object.health.value - healAmount = 0:
-            object.status = destroyed
-        else:
-            object.status = alive
-}
-
-rule DeadCannotUseHealingObject {
-    when: HealingObject.healsCharacter(object, character, amount)
-    requires: character.status = dead
-    ensures:
-        character.health.value = character.health.value
-        object.health.value = object.health.value
-        object.status = object.status
-}
-
-rule DestroyedHealingObjectCannotHeal {
-    when: HealingObject.healsCharacter(object, character, amount)
-    requires: object.status = destroyed
-    ensures:
-        character.health.value = character.health.value
-        object.health.value = object.health.value
-        object.status = object.status
-}
-
-------------------------------------------------------------
--- Invariants
-------------------------------------------------------------
-
-invariant WeaponHealthNeverNegative {
-    for w in MagicalWeapons:
-        w.health.value >= 0
-}
-
-invariant WeaponDestroyedAtZeroHealth {
-    for w in MagicalWeapons:
-        w.health.value = 0 implies w.status = destroyed
-}
-
-invariant WeaponMaxHealthNeverExceeded {
-    for w in MagicalWeapons:
-        w.health.value <= w.maxHealth
-}
-
-invariant HealingObjectHealthNeverNegative {
-    for h in HealingObjects:
-        h.health.value >= 0
-}
-
-invariant HealingObjectDestroyedAtZeroHealth {
-    for h in HealingObjects:
-        h.health.value = 0 implies h.status = destroyed
-}
-
-invariant HealingObjectMaxHealthNeverExceeded {
-    for h in HealingObjects:
-        h.health.value <= h.maxHealth
-}
-
-invariant HealingObjectCannotDealDamage {
-    for h in HealingObjects:
-        not h.dealsDamage(_, _)
-}
-
-invariant WeaponCannotHeal {
-    for w in MagicalWeapons:
-        not w.healsCharacter(_, _)
-}

AGENTS.md

@@ -16,7 +16,7 @@ An implementation of the RPG Combat rules engine. There are six user stories des
 
 This project combines three practices:
 
-1. **Allium** (`.allium` specs) — formal behavioural specifications that capture _what_ the system does
+1. **Allium** (`.allium` specs) — formal behavioural specifications that capture _what_ the system does. All specs live in [specs/](specs/) — one file per story/domain area.
 2. **fast-check** — property-based testing that verifies those properties hold across thousands of random inputs
 3. **"I can't believe it's not Haskell"** — TypeScript with ADTs, value objects, and immutability
 

README.md

@@ -51,13 +51,13 @@ The TypeScript implementation embraces functional patterns:
 
 All five user stories are implemented and verified:
 
-| Story | Topic | Status |
-|-------|-------|--------|
-| 1 | Character Creation & Damage | ✅ Done |
-| 2 | Levels | ✅ Done |
-| 3 | Factions | ✅ Done |
-| 4 | Magical Objects | ✅ Done |
-| 5 | Changing Level | ✅ Done |
+| Story | Topic                       | Status  |
+| ----- | --------------------------- | ------- |
+| 1     | Character Creation & Damage | ✅ Done |
+| 2     | Levels                      | ✅ Done |
+| 3     | Factions                    | ✅ Done |
+| 4     | Magical Objects             | ✅ Done |
+| 5     | Changing Level              | ✅ Done |
 
 **70 tests passing** across 6 spec files.
 
@@ -85,7 +85,9 @@ Two custom extensions were developed for this project:
 
 ### The Transcript Archive
 
-Every session is exported as an HTML transcript in the `transcripts/` directory — over 20 sessions documenting the full journey from first requirements review through horizontal refactoring. These are the project's most valuable artifacts.
+Every session is exported as an HTML transcript in the `transcripts/` directory — 28 sessions documenting the full journey from first requirements review through horizontal refactoring. See the [full transcript index](transcripts/index.md) for a chronological list.
+
+These are the project's most valuable artifacts.
 
 ## Build & Test
 

eslint.config.js

@@ -1,6 +1,7 @@
 import js from '@eslint/js';
 import tseslint from 'typescript-eslint';
 import prettier from 'eslint-config-prettier';
+import noPrimitiveValue from './eslint/no-primitive-value-properties.js';
 
 export default tseslint.config(
   { ignores: ['dist', 'node_modules', 'coverage', 'allium-main'] },
@@ -17,9 +18,17 @@ export default tseslint.config(
         tsconfigRootDir: import.meta.dirname,
       },
     },
+    plugins: {
+      rpg: {
+        rules: {
+          'no-primitive-value-properties': noPrimitiveValue,
+        },
+      },
+    },
     rules: {
       '@typescript-eslint/switch-exhaustiveness-check': 'warn',
       '@typescript-eslint/no-unnecessary-condition': 'warn',
+      'rpg/no-primitive-value-properties': 'warn',
     },
   },
 

eslint/no-primitive-value-properties.js

@@ -0,0 +1,145 @@
+import { readdirSync } from 'node:fs';
+import { join, parse } from 'node:path';
+
+const VALUE_OBJECTS_DIR = join(import.meta.dirname, '..', 'src', 'value-objects');
+
+function discoverValueObjects() {
+  const files = readdirSync(VALUE_OBJECTS_DIR).filter((f) => f.endsWith('.ts') && f !== 'index.ts');
+  return files.map((f) => parse(f).name);
+}
+
+const VALUE_OBJECTS = discoverValueObjects();
+
+function buildPropertyMap() {
+  const map = {};
+  for (const name of VALUE_OBJECTS) {
+    const propertyName = name.charAt(0).toLowerCase() + name.slice(1);
+    map[propertyName] = name;
+  }
+  return map;
+}
+
+const PROPERTY_MAP = buildPropertyMap();
+
+/** Map ESLint AST type names to the primitive keyword string. */
+const PRIMITIVE_TYPE_MAP = {
+  TSNumberKeyword: 'number',
+  TSStringKeyword: 'string',
+  TSBooleanKeyword: 'boolean',
+};
+
+function isPrimitiveType(typeNode) {
+  if (!typeNode) return false;
+  const keyword = PRIMITIVE_TYPE_MAP[typeNode.type];
+  return keyword !== undefined;
+}
+
+function getPrimitiveKeyword(typeNode) {
+  if (!typeNode) return null;
+  return PRIMITIVE_TYPE_MAP[typeNode.type] || null;
+}
+
+function getParamName(param) {
+  if (param.type === 'TSParameterProperty') {
+    return getParamName(param.parameter);
+  }
+  if (param.type === 'Identifier') {
+    return param.name;
+  }
+  return null;
+}
+
+export default {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'Warn when primitive types are used in class properties or constructor parameters that should be value objects',
+      recommended: false,
+    },
+    schema: [
+      {
+        type: 'object',
+        properties: {
+          includeConstructorParams: { type: 'boolean', default: true },
+          includeProperties: { type: 'boolean', default: true },
+        },
+        additionalProperties: false,
+      },
+    ],
+    messages: {
+      primitiveProperty:
+        'Use value object "{{valueObject}}" instead of primitive "{{primitive}}" for property "{{propertyName}}". Available: {{available}}',
+      primitiveParam:
+        'Use value object "{{valueObject}}" instead of primitive "{{primitive}}" for parameter "{{paramName}}". Available: {{available}}',
+    },
+  },
+
+  create(context) {
+    const options = context.options[0] || {};
+    const includeConstructorParams = options.includeConstructorParams !== false;
+    const includeProperties = options.includeProperties !== false;
+
+    function reportPrimitive(node, propName, primitiveType, messageId) {
+      const valueObject = PROPERTY_MAP[propName];
+      if (valueObject) {
+        context.report({
+          node,
+          messageId,
+          data: {
+            valueObject,
+            primitive: primitiveType,
+            propertyName: propName,
+            paramName: propName,
+            available: VALUE_OBJECTS.join(', '),
+          },
+        });
+      }
+    }
+
+    return {
+      ClassProperty(node) {
+        if (!includeProperties) return;
+        if (!node.typeAnnotation) return;
+
+        const typeNode = node.typeAnnotation.typeAnnotation;
+        if (!isPrimitiveType(typeNode)) return;
+
+        reportPrimitive(node, node.key.name, getPrimitiveKeyword(typeNode), 'primitiveProperty');
+      },
+
+      PropertyDefinition(node) {
+        if (!includeProperties) return;
+        if (!node.typeAnnotation) return;
+
+        const typeNode = node.typeAnnotation.typeAnnotation;
+        if (!isPrimitiveType(typeNode)) return;
+
+        reportPrimitive(node, node.key.name, getPrimitiveKeyword(typeNode), 'primitiveProperty');
+      },
+
+      MethodDefinition(node) {
+        if (!includeConstructorParams) return;
+        if (node.key.name !== 'constructor') return;
+        if (!node.value.params) return;
+
+        for (const param of node.value.params) {
+          let paramName = null;
+          let typeNode = null;
+
+          if (param.type === 'TSParameterProperty') {
+            paramName = getParamName(param.parameter);
+            typeNode = param.parameter.typeAnnotation?.typeAnnotation;
+          } else if (param.type === 'Identifier') {
+            paramName = param.name;
+            typeNode = param.typeAnnotation?.typeAnnotation;
+          }
+
+          if (!paramName || !typeNode || !isPrimitiveType(typeNode)) continue;
+
+          reportPrimitive(param, paramName, getPrimitiveKeyword(typeNode), 'primitiveParam');
+        }
+      },
+    };
+  },
+};

specs/changing-level.allium

@@ -0,0 +1,120 @@
+-- allium: 3
+
+-- allium: changing-level
+
+------------------------------------------------------------
+-- Value Types
+------------------------------------------------------------
+
+value Faction {
+    name: String
+}
+
+value Health {
+    value: Integer
+    requires: value >= 0
+}
+
+value Level {
+    value: Integer
+    requires: value >= 1 and value <= 10
+}
+
+value Damage {
+    value: Integer
+    requires: value >= 0
+}
+
+------------------------------------------------------------
+-- Enumerations
+------------------------------------------------------------
+
+enum Status {
+    alive | dead
+}
+
+------------------------------------------------------------
+-- Entities
+------------------------------------------------------------
+
+entity Character {
+    name: String
+    health: Health
+    status: Status
+    level: Level
+    factions: Set<Faction>
+    totalDamageTaken: Damage
+    factionsJoined: Set<Faction>
+}
+
+------------------------------------------------------------
+-- Rules
+------------------------------------------------------------
+
+rule DamageIsAccumulated {
+    when: Character.dealDamage(attacker, target, damage)
+    requires: target.status = alive
+    ensures: target.totalDamageTaken.value = old(target.totalDamageTaken.value) + damage.value
+}
+
+rule LevelUpFromDamage {
+    when: Character.dealDamage(attacker, target, damage)
+    requires: target.status = alive
+    requires: old(target.totalDamageTaken.value) + damage.value >= 1000 * (target.level.value + 1) * (target.level.value + 2) / 2
+    ensures: target.level.value = target.level.value + 1
+    ensures: target.totalDamageTaken.value = old(target.totalDamageTaken.value) + damage.value
+}
+
+rule LevelUpFromFaction {
+    when: Character.joinFaction(character, faction)
+    requires: character.status = alive
+    requires: old(character.factionsJoined.size) + 1 >= 3 * (character.level.value + 1)
+    ensures: character.level.value = character.level.value + 1
+    ensures: character.factionsJoined = old(character.factionsJoined) + {faction}
+}
+
+rule MaxLevelCappedOnDamage {
+    when: Character.dealDamage(attacker, target, damage)
+    requires: target.status = alive
+    requires: target.level.value = 10
+    ensures: target.level.value = 10
+}
+
+rule MaxLevelCappedOnFaction {
+    when: Character.joinFaction(character, faction)
+    requires: character.status = alive
+    requires: character.level.value = 10
+    ensures: character.level.value = 10
+}
+
+rule DeadCannotLevelUpFromDamage {
+    when: Character.dealDamage(attacker, target, damage)
+    requires: target.status = dead
+    ensures: target.level.value = old(target.level.value)
+    ensures: target.totalDamageTaken.value = old(target.totalDamageTaken.value)
+}
+
+rule DeadCannotLevelUpFromFaction {
+    when: Character.joinFaction(character, faction)
+    requires: character.status = dead
+    ensures: character.level.value = old(character.level.value)
+}
+
+------------------------------------------------------------
+-- Invariants
+------------------------------------------------------------
+
+invariant LevelBounded {
+    for c in Characters:
+        c.level.value >= 1 and c.level.value <= 10
+}
+
+invariant DamageTotalNonNegative {
+    for c in Characters:
+        c.totalDamageTaken.value >= 0
+}
+
+invariant FactionsJoinedNonNegative {
+    for c in Characters:
+        c.factionsJoined.size >= 0
+}

specs/factions.allium

@@ -6,9 +6,22 @@
 -- Value Types
 ------------------------------------------------------------
 
-type Faction {
+value Faction {
     name: String
-    requires: trimmed(name).length > 0
+}
+
+value Health {
+    value: Integer
+    requires: value >= 0
+}
+
+value Level {
+    value: Integer
+    requires: value >= 1 and value <= 10
+}
+
+enum Status {
+    alive | dead
 }
 
 ------------------------------------------------------------
@@ -18,7 +31,7 @@ type Faction {
 entity Character {
     name: String
     health: Health
-    status: alive | dead
+    status: Status
     level: Level
     factions: Set<Faction>
 }
@@ -83,12 +96,7 @@ rule DeadCannotLeaveFaction {
 invariant FactionsAlwaysValid {
     for c in Characters:
         for f in c.factions:
-            f.name.trim().length > 0
-}
-
-invariant AllyRelationIsSymmetric {
-    for a in Characters, b in Characters:
-        a.isAllyOf(b) implies b.isAllyOf(a)
+            f.name.length > 0
 }
 
 invariant SelfNotAlly {

specs/magical-objects.allium

@@ -0,0 +1,189 @@
+-- allium: 3
+-- allium: magical-objects
+
+------------------------------------------------------------
+-- Value Types
+------------------------------------------------------------
+
+value Health {
+    value: Integer
+    requires: value >= 0
+}
+
+value Faction {
+    name: String
+}
+
+value Level {
+    value: Integer
+    requires: value >= 1 and value <= 10
+}
+
+------------------------------------------------------------
+-- Enumerations
+------------------------------------------------------------
+
+enum Status {
+    alive | destroyed
+}
+
+------------------------------------------------------------
+-- Entities
+------------------------------------------------------------
+
+entity Character {
+    name: String
+    health: Health
+    status: Status
+    level: Level
+    factions: Set<Faction>
+}
+
+entity MagicalObject {
+    health: Health
+    maxHealth: Integer
+    status: Status
+}
+
+entity HealingObject {
+    health: Health
+    maxHealth: Integer
+    status: Status
+}
+
+entity MagicalWeapon {
+    health: Health
+    maxHealth: Integer
+    status: Status
+    damage: Integer
+    owner: Character
+}
+
+------------------------------------------------------------
+-- Rules
+------------------------------------------------------------
+
+rule HealingObjectHealsCharacter {
+    when: CharacterUsesHealingObject(character, object, amount)
+
+    requires: object.status = alive
+    requires: character.status = alive
+    requires: amount >= 0
+
+    ensures:
+        character.health.value = character.health.value + min(amount, object.health.value, Level.maxHealthForLevel(character.level) - character.health.value)
+        object.health.value = object.health.value - min(amount, object.health.value, Level.maxHealthForLevel(character.level) - character.health.value)
+        if object.health.value = 0:
+            object.status = destroyed
+        else:
+            object.status = alive
+}
+
+rule HealingObjectDestroyedCannotHeal {
+    when: CharacterUsesHealingObject(character, object, amount)
+
+    requires: object.status = destroyed
+
+    ensures:
+        character.health.value = character.health.value
+        object.health.value = object.health.value
+}
+
+rule DeadCannotUseHealingObject {
+    when: CharacterUsesHealingObject(character, object, amount)
+
+    requires: character.status = dead
+
+    ensures:
+        character.health.value = character.health.value
+        object.health.value = object.health.value
+}
+
+rule HealingObjectZeroHealIsNoOp {
+    when: CharacterUsesHealingObject(character, object, amount)
+
+    requires: object.status = alive
+    requires: character.status = alive
+    requires: amount >= 0
+    requires: min(amount, object.health.value, Level.maxHealthForLevel(character.level) - character.health.value) = 0
+
+    ensures:
+        character.health.value = character.health.value
+        object.health.value = object.health.value
+}
+
+rule MagicalWeaponDealsDamage {
+    when: CharacterUsesWeapon(owner, weapon, target)
+
+    requires: weapon.status = alive
+    requires: owner.status = alive
+    requires: owner = weapon.owner
+
+    ensures:
+        target.health.value = max(0, target.health.value - weapon.damage)
+        weapon.health.value = weapon.health.value - 1
+        if weapon.health.value = 0:
+            weapon.status = destroyed
+        else:
+            weapon.status = alive
+}
+
+rule DeadCannotUseWeapon {
+    when: CharacterUsesWeapon(owner, weapon, target)
+
+    requires: owner.status = dead
+
+    ensures:
+        target.health.value = target.health.value
+        weapon.health.value = weapon.health.value
+        weapon.status = weapon.status
+        target.status = target.status
+}
+
+rule NonOwnerCannotUseWeapon {
+    when: CharacterUsesWeapon(thief, weapon, target)
+
+    requires: thief != weapon.owner
+
+    ensures:
+        target.health.value = target.health.value
+        weapon.health.value = weapon.health.value
+        weapon.status = weapon.status
+        target.status = target.status
+}
+
+rule WeaponDestroyedCannotDealDamage {
+    when: CharacterUsesWeapon(owner, weapon, target)
+
+    requires: weapon.status = destroyed
+
+    ensures:
+        target.health.value = target.health.value
+        weapon.health.value = weapon.health.value
+        weapon.status = weapon.status
+        target.status = target.status
+}
+
+------------------------------------------------------------
+-- Invariants
+------------------------------------------------------------
+
+invariant MagicalObjectHealthNonNegative {
+    for m in MagicalObjects:
+        m.health.value >= 0
+}
+
+invariant MagicalObjectHealthNeverExceedsMax {
+    for m in MagicalObjects:
+        m.health.value <= m.maxHealth
+}
+
+invariant MagicalObjectDestroyedAtZeroHealth {
+    for m in MagicalObjects:
+        m.health.value = 0 implies m.status = destroyed
+}
+
+invariant MagicalObjectAliveAtPositiveHealth {
+    for m in MagicalObjects:
+        m.health.value > 0 implies m.status = alive
+}

src/changing-level.spec.ts

@@ -0,0 +1,131 @@
+import fc from 'fast-check';
+import { describe, it, expect } from 'vitest';
+import { Character } from './characters/Character.ts';
+import { Level } from './value-objects/Level.ts';
+import { Damage } from './value-objects/Damage.ts';
+import { Faction } from './factions/Faction.ts';
+
+describe('ChangingLevel', () => {
+  describe('MaxLevelCappedOnDamage (example)', () => {
+    it('L10 takes 99999 damage → stays L10', () => {
+      const attacker = Character.create({ name: 'dragons', level: Level.create(1) });
+      const target = Character.create({ name: 'hero', level: Level.create(10) });
+      const result = attacker.dealDamage(target, Damage.create(99999));
+      expect(result.level.value).toBe(10);
+    });
+  });
+
+  describe('MaxLevelCappedOnFaction (example)', () => {
+    it('L10 joins 100 factions → stays L10', () => {
+      const hero = Character.create({ name: 'hero', level: Level.create(10) });
+      let char = hero;
+      for (let i = 0; i < 100; i++) {
+        char = char.joinFaction(Faction.create(`faction-${i}`));
+      }
+      expect(char.level.value).toBe(10);
+    });
+  });
+
+  describe('DeadCannotLevelUpFromDamage (example)', () => {
+    it('dead char takes 1000 damage → stays same level', () => {
+      const attacker = Character.create({ name: 'attacker', level: Level.create(1) });
+      const target = Character.create({ name: 'hero', level: Level.create(1) });
+      const dead = attacker.dealDamage(target, Damage.create(10000));
+      const result = attacker.dealDamage(dead, Damage.create(1000));
+      expect(result.level.value).toBe(1);
+    });
+  });
+
+  describe('DeadCannotLevelUpFromFaction (example)', () => {
+    it('dead char joins 5 factions → stays same level', () => {
+      const attacker = Character.create({ name: 'attacker', level: Level.create(1) });
+      const target = Character.create({ name: 'hero', level: Level.create(1) });
+      const dead = attacker.dealDamage(target, Damage.create(10000));
+      let char = dead;
+      for (let i = 0; i < 5; i++) {
+        char = char.joinFaction(Faction.create(`faction-${i}`));
+      }
+      expect(char.level.value).toBe(1);
+    });
+  });
+
+  describe('LevelUpFromDamage (property)', () => {
+    it('property: cumulative damage triggers level-up at threshold', () => {
+      fc.assert(
+        fc.property(
+          fc.integer({ min: 1, max: 9 }),
+          fc.integer({ min: 1, max: 500 }),
+          fc.integer({ min: 1, max: 500 }),
+          (level, dmg1, dmg2) => {
+            const currentLevel = Level.create(level);
+            const threshold = Level.damageThresholdForLevel(level + 1);
+            const total = dmg1 + dmg2;
+
+            // Only test when total meets threshold AND target survives
+            // Target starts with 1000 health, needs health > total after damage
+            if (total >= threshold && total < 1000) {
+              const attacker = Character.create({ name: 'a', level: Level.create(1) });
+              const target = Character.create({ name: 't', level: currentLevel });
+              const afterFirst = attacker.dealDamage(target, Damage.create(dmg1));
+              const afterSecond = attacker.dealDamage(afterFirst, Damage.create(dmg2));
+              const expectedLevel = Math.min(10, level + 1);
+              return afterSecond.level.value === expectedLevel;
+            }
+            return true; // skip non-applicable cases
+          },
+        ),
+      );
+    });
+  });
+
+  describe('LevelUpFromFaction (property)', () => {
+    it('property: faction count triggers level-up at thresholds', () => {
+      fc.assert(
+        fc.property(
+          fc.integer({ min: 1, max: 9 }),
+          fc.integer({ min: 1, max: 30 }),
+          (level, totalFactions) => {
+            // Compute expected level: how many thresholds are crossed?
+            let currentLevel = level;
+            for (let f = 1; f <= totalFactions; f++) {
+              if (f >= 3 * (currentLevel + 1) && currentLevel < 10) {
+                currentLevel++;
+              }
+            }
+
+            const hero = Character.create({ name: 'hero', level: Level.create(level) });
+            let char = hero;
+            for (let i = 0; i < totalFactions; i++) {
+              char = char.joinFaction(Faction.create(`faction-${i}`));
+            }
+            return char.level.value === currentLevel;
+          },
+        ),
+      );
+    });
+  });
+
+  describe('DamageAccumulation (property)', () => {
+    it('property: totalDamageTaken accumulates across multiple damage events', () => {
+      fc.assert(
+        fc.property(
+          fc.array(fc.integer({ min: 1, max: 200 }), { minLength: 2, maxLength: 10 }),
+          (damageEvents) => {
+            const expectedTotal = damageEvents.reduce((sum, d) => sum + d, 0);
+            // Ensure target survives: total damage must be < 1000 (starting health)
+            if (expectedTotal >= 1000) return true;
+
+            const attacker = Character.create({ name: 'a', level: Level.create(1) });
+            const target = Character.create({ name: 't', level: Level.create(1) });
+
+            let current = target;
+            for (const dmg of damageEvents) {
+              current = attacker.dealDamage(current, Damage.create(dmg));
+            }
+            return current.totalDamageTaken.value === expectedTotal;
+          },
+        ),
+      );
+    });
+  });
+});

src/characters/Character.ts

@@ -6,6 +6,7 @@
  */
 import { Health } from '../value-objects/Health.ts';
 import { Level } from '../value-objects/Level.ts';
+import { Damage } from '../value-objects/Damage.ts';
 import type { Status } from '../value-objects/Status.ts';
 import { StatusAlive, StatusDead } from '../value-objects/Status.ts';
 import type { CharacterState } from './CharacterState.ts';
@@ -48,6 +49,8 @@ export class Character {
       status: StatusAlive,
       level,
       factions: new Set(),
+      totalDamageTaken: Damage.create(0),
+      factionsJoined: new Set(),
     };
     return new Character(state);
   }
@@ -60,6 +63,8 @@ export class Character {
       status: StatusAlive,
       level,
       factions: new Set(),
+      totalDamageTaken: Damage.create(0),
+      factionsJoined: new Set(),
     };
     return new Character(state);
   }
@@ -77,6 +82,8 @@ export class Character {
       status,
       level,
       factions: new Set(),
+      totalDamageTaken: Damage.create(0),
+      factionsJoined: new Set(),
     };
     return new Character(state);
   }
@@ -101,6 +108,14 @@ export class Character {
     return this.#state.factions;
   }
 
+  get totalDamageTaken(): Damage {
+    return this.#state.totalDamageTaken;
+  }
+
+  get factionsJoined(): ReadonlySet<Faction> {
+    return this.#state.factionsJoined;
+  }
+
   /**
    * Check if this character is an ally of another.
    * Two characters are allies if they share at least one faction.
@@ -122,12 +137,24 @@ export class Character {
     if (this.status.kind === 'dead') return this;
     const newFactions = new Set(this.#state.factions);
     newFactions.add(faction);
+
+    const newFactionsJoined = new Set(this.#state.factionsJoined);
+    newFactionsJoined.add(faction);
+
+    // Level-up from faction count
+    let newLevel = this.level;
+    if (newFactionsJoined.size >= 3 * (newLevel.value + 1)) {
+      newLevel = Level.create(Math.min(10, newLevel.value + 1));
+    }
+
     return new Character({
       name: this.name,
       health: this.health,
       status: this.status,
-      level: this.level,
+      level: newLevel,
       factions: newFactions,
+      totalDamageTaken: this.totalDamageTaken,
+      factionsJoined: newFactionsJoined,
     });
   }
 
@@ -147,6 +174,8 @@ export class Character {
       status: this.status,
       level: this.level,
       factions: newFactions,
+      totalDamageTaken: this.totalDamageTaken,
+      factionsJoined: this.factionsJoined,
     });
   }
 
@@ -169,6 +198,8 @@ export class Character {
       status: ally.status,
       level: ally.level,
       factions: ally.factions,
+      totalDamageTaken: ally.totalDamageTaken,
+      factionsJoined: ally.factionsJoined,
     });
   }
 
@@ -176,34 +207,46 @@ export class Character {
    * Deal damage to another character. Returns a new Character with updated state.
    * Does not mutate the attacker or the original target reference.
    */
-  dealDamage(target: Character, damage: number): Character {
+  dealDamage(target: Character, damage: Damage): Character {
     // Self-damage is forbidden — use reference equality, not name
     if (this === target) return target;
     // Allies cannot deal damage to each other
     if (this.isAllyOf(target)) return target;
     // Dead characters cannot take damage
     if (target.status.kind === 'dead') return target;
-    // Negative damage is invalid
-    if (damage < 0) throw new Error(`Damage must be non-negative, got ${damage}`);
     // Level-based damage modifier
     const levelDiff = this.level.diff(target.level); // = this.level - target.level
-    let actualDamage = damage;
+    let actualDamage = damage.value;
     if (levelDiff <= -5) {
       // Target is ≥5 levels above → damage reduced by 50%
-      actualDamage = Math.floor(damage * 0.5);
+      actualDamage = Math.floor(damage.value * 0.5);
     } else if (levelDiff >= 5) {
       // Target is ≥5 levels below → damage increased by 50%
-      actualDamage = Math.floor(damage * 1.5);
+      actualDamage = Math.floor(damage.value * 1.5);
     }
     // Reduce health by the (possibly modified) damage amount
     const newHealth = target.health.sub(actualDamage);
     const newStatus = newHealth.value === 0 ? StatusDead : StatusAlive;
+
+    // Level-up from cumulative damage
+    let newLevel = target.level;
+    const newTotalDamage = target.totalDamageTaken.add(Damage.create(actualDamage));
+
+    if (newStatus.kind === 'alive') {
+      const threshold = Level.damageThresholdForLevel(newLevel.value + 1);
+      if (newTotalDamage.value >= threshold) {
+        newLevel = Level.create(Math.min(10, newLevel.value + 1));
+      }
+    }
+
     return new Character({
       name: target.name,
       health: newHealth,
       status: newStatus,
-      level: target.level,
+      level: newLevel,
       factions: target.factions,
+      totalDamageTaken: newTotalDamage,
+      factionsJoined: target.factionsJoined,
     });
   }
 
@@ -225,6 +268,8 @@ export class Character {
       status: this.status,
       level: this.level,
       factions: this.factions,
+      totalDamageTaken: this.totalDamageTaken,
+      factionsJoined: this.factionsJoined,
     });
   }
 

src/characters/CharacterState.ts

@@ -8,6 +8,7 @@ import type { Health } from '../value-objects/Health.ts';
 import type { Level } from '../value-objects/Level.ts';
 import type { Status } from '../value-objects/Status.ts';
 import type { Faction } from '../factions/Faction.ts';
+import type { Damage } from '../value-objects/Damage.ts';
 
 export type CharacterState = {
   readonly name: string;
@@ -15,4 +16,6 @@ export type CharacterState = {
   readonly status: Status;
   readonly level: Level;
   readonly factions: ReadonlySet<Faction>;
+  readonly totalDamageTaken: Damage;
+  readonly factionsJoined: ReadonlySet<Faction>;
 };

src/damage-and-health.spec.ts

@@ -2,6 +2,7 @@ import fc from 'fast-check';
 import { describe, it } from 'vitest';
 import { Character } from './characters/Character.ts';
 import { Level } from './value-objects/Level.ts';
+import { Damage } from './value-objects/Damage.ts';
 
 describe('DamageAndHealth', () => {
   describe('DamageReducesHealth', () => {
@@ -18,7 +19,7 @@ describe('DamageAndHealth', () => {
               health,
             });
             const expected = Math.max(0, health - damage);
-            const result = attacker.dealDamage(target, damage);
+            const result = attacker.dealDamage(target, Damage.create(damage));
             return result.health.value === expected;
           },
         ),
@@ -39,7 +40,7 @@ describe('DamageAndHealth', () => {
               level: Level.create(1),
               health,
             });
-            const result = attacker.dealDamage(target, damage);
+            const result = attacker.dealDamage(target, Damage.create(damage));
             return result.health.value >= 0;
           },
         ),
@@ -60,7 +61,7 @@ describe('DamageAndHealth', () => {
               level: Level.create(1),
               health,
             });
-            const result = attacker.dealDamage(target, damage);
+            const result = attacker.dealDamage(target, Damage.create(damage));
             const expected = Math.max(0, health - damage);
             if (expected === 0) {
               return result.status.kind === 'dead';
@@ -82,7 +83,7 @@ describe('DamageAndHealth', () => {
             const c = Character.createWithHealth({ name: 'hero', level: Level.create(1), health });
             const healthBefore = c.health.value;
             const statusBefore = c.status.kind;
-            const result = c.dealDamage(c, damage);
+            const result = c.dealDamage(c, Damage.create(damage));
             // Should return the same reference
             return (
               result === c &&
@@ -102,11 +103,11 @@ describe('DamageAndHealth', () => {
           const attacker = Character.create({ name: 'attacker', level: Level.create(1) });
           const target = Character.create({ name: 'target', level: Level.create(1) });
           // Kill the target first — capture the returned (dead) character
-          const deadTarget = attacker.dealDamage(target, 10000);
+          const deadTarget = attacker.dealDamage(target, Damage.create(10000));
           const healthBefore = deadTarget.health.value;
           const statusBefore = deadTarget.status.kind;
           // Then try to deal more damage to the dead character
-          const result = attacker.dealDamage(deadTarget, damage);
+          const result = attacker.dealDamage(deadTarget, Damage.create(damage));
           return (
             result === deadTarget &&
             result.health.value === healthBefore &&
@@ -118,14 +119,12 @@ describe('DamageAndHealth', () => {
   });
 
   describe('NegativeDamageForbidden', () => {
-    it('property: negative damage throws an error', () => {
+    it('property: negative damage throws an error via Damage.create', () => {
       fc.assert(
         fc.property(fc.integer({ min: -10000, max: -1 }), (negativeDamage) => {
-          const attacker = Character.create({ name: 'attacker', level: Level.create(1) });
-          const target = Character.create({ name: 'target', level: Level.create(1) });
           let threw = false;
           try {
-            attacker.dealDamage(target, negativeDamage);
+            Damage.create(negativeDamage);
           } catch {
             threw = true;
           }

src/factions.spec.ts

@@ -3,6 +3,7 @@ import { describe, it } from 'vitest';
 import { Character } from './characters/Character.ts';
 import { Faction } from './factions/Faction.ts';
 import { Level } from './value-objects/Level.ts';
+import { Damage } from './value-objects/Damage.ts';
 
 describe('Factions', () => {
   const hero = () => Character.create({ name: 'hero', level: Level.create(1) });
@@ -189,7 +190,7 @@ describe('Factions', () => {
           (factionName) => {
             const attacker = Character.create({ name: 'attacker', level: Level.create(1) });
             const hero = Character.create({ name: 'hero', level: Level.create(1) });
-            const deadHero = attacker.dealDamage(hero, 10000);
+            const deadHero = attacker.dealDamage(hero, Damage.create(10000));
             const f = Faction.create(factionName);
             const result = deadHero.joinFaction(f);
             return result === deadHero && result.factions.size === 0;
@@ -209,7 +210,7 @@ describe('Factions', () => {
             const hero = Character.create({ name: 'hero', level: Level.create(1) });
             const f = Faction.create(factionName);
             const withFaction = hero.joinFaction(f);
-            const deadHero = attacker.dealDamage(withFaction, 10000);
+            const deadHero = attacker.dealDamage(withFaction, Damage.create(10000));
             const result = deadHero.leaveFaction(f);
             return result === deadHero && result.factions.has(f);
           },
@@ -302,7 +303,7 @@ describe('Factions', () => {
           const target = ally().joinFaction(faction);
           const healthBefore = target.health.value;
           const statusBefore = target.status.kind;
-          const result = attacker.dealDamage(target, 500);
+          const result = attacker.dealDamage(target, Damage.create(500));
           return result.health.value === healthBefore && result.status.kind === statusBefore;
         }),
       );
@@ -314,7 +315,7 @@ describe('Factions', () => {
           const faction = Faction.create('guard');
           const attacker = hero().joinFaction(faction);
           const target = ally().joinFaction(faction);
-          const result = attacker.dealDamage(target, 500);
+          const result = attacker.dealDamage(target, Damage.create(500));
           return result === target;
         }),
       );
@@ -326,7 +327,7 @@ describe('Factions', () => {
           const attacker = hero();
           const target = enemy();
           const healthBefore = target.health.value;
-          const result = attacker.dealDamage(target, 100);
+          const result = attacker.dealDamage(target, Damage.create(100));
           return result.health.value === healthBefore - 100;
         }),
       );
@@ -414,7 +415,7 @@ describe('Factions', () => {
           const target = ally().joinFaction(faction);
           // Kill the target with a non-ally attacker
           const killer = enemy();
-          const deadTarget = killer.dealDamage(target, 10000);
+          const deadTarget = killer.dealDamage(target, Damage.create(10000));
           const healthBefore = deadTarget.health.value;
           const statusBefore = deadTarget.status.kind;
           const result = healer.healAlly(deadTarget, 500);

src/healing.spec.ts

@@ -2,6 +2,7 @@ import fc from 'fast-check';
 import { describe, it } from 'vitest';
 import { Character } from './characters/Character.ts';
 import { Level } from './value-objects/Level.ts';
+import { Damage } from './value-objects/Damage.ts';
 
 describe('Healing', () => {
   describe('SelfHealIncreasesHealth', () => {
@@ -88,7 +89,7 @@ describe('Healing', () => {
           const attacker = Character.create({ name: 'attacker', level: Level.create(1) });
           const hero = Character.create({ name: 'hero', level: Level.create(1) });
           // Kill the hero first using a different attacker
-          const deadHero = attacker.dealDamage(hero, 10000);
+          const deadHero = attacker.dealDamage(hero, Damage.create(10000));
           const healthBefore = deadHero.health.value;
           const statusBefore = deadHero.status.kind;
           // Try to heal the dead character

src/levels.spec.ts

@@ -2,6 +2,7 @@ import fc from 'fast-check';
 import { describe, it } from 'vitest';
 import { Character } from './characters/Character.ts';
 import { Level } from './value-objects/Level.ts';
+import { Damage } from './value-objects/Damage.ts';
 
 describe('Levels', () => {
   describe('CloseLevelNoModifier', () => {
@@ -21,7 +22,7 @@ describe('Levels', () => {
               level: Level.create(targetLevel),
               health: 1000,
             });
-            const result = attacker.dealDamage(target, baseDamage);
+            const result = attacker.dealDamage(target, Damage.create(baseDamage));
             return result.health.value === Math.max(0, 1000 - baseDamage);
           },
         ),
@@ -47,7 +48,7 @@ describe('Levels', () => {
               health: 1000,
             });
             const expectedDamage = Math.floor(baseDamage * 0.5);
-            const result = attacker.dealDamage(target, baseDamage);
+            const result = attacker.dealDamage(target, Damage.create(baseDamage));
             return result.health.value === Math.max(0, 1000 - expectedDamage);
           },
         ),
@@ -66,7 +67,7 @@ describe('Levels', () => {
             health: 1000,
           });
           const expectedDamage = Math.floor(oddDamage * 0.5);
-          const result = attacker.dealDamage(target, oddDamage);
+          const result = attacker.dealDamage(target, Damage.create(oddDamage));
           return result.health.value === Math.max(0, 1000 - expectedDamage);
         }),
       );
@@ -91,7 +92,7 @@ describe('Levels', () => {
               health: 1000,
             });
             const expectedDamage = Math.floor(baseDamage * 1.5);
-            const result = attacker.dealDamage(target, baseDamage);
+            const result = attacker.dealDamage(target, Damage.create(baseDamage));
             return result.health.value === Math.max(0, 1000 - expectedDamage);
           },
         ),
@@ -111,7 +112,7 @@ describe('Levels', () => {
             health: 1000,
           });
           const expectedDamage = Math.floor(damage * 0.5);
-          const result = attacker.dealDamage(target, damage);
+          const result = attacker.dealDamage(target, Damage.create(damage));
           return result.health.value === Math.max(0, 1000 - expectedDamage);
         }),
       );
@@ -128,7 +129,7 @@ describe('Levels', () => {
             health: 1000,
           });
           const expectedDamage = Math.floor(damage * 1.5);
-          const result = attacker.dealDamage(target, damage);
+          const result = attacker.dealDamage(target, Damage.create(damage));
           return result.health.value === Math.max(0, 1000 - expectedDamage);
         }),
       );
@@ -144,7 +145,7 @@ describe('Levels', () => {
             level: Level.create(5),
             health: 1000,
           });
-          const result = attacker.dealDamage(target, damage);
+          const result = attacker.dealDamage(target, Damage.create(damage));
           return result.health.value === Math.max(0, 1000 - damage);
         }),
       );
@@ -160,7 +161,7 @@ describe('Levels', () => {
             level: Level.create(1),
             health: 1000,
           });
-          const result = attacker.dealDamage(target, damage);
+          const result = attacker.dealDamage(target, Damage.create(damage));
           return result.health.value === Math.max(0, 1000 - damage);
         }),
       );

src/magical-objects.spec.ts

@@ -2,6 +2,7 @@ import fc from 'fast-check';
 import { describe, it } from 'vitest';
 import { Character } from './characters/Character.ts';
 import { Level } from './value-objects/Level.ts';
+import { Damage } from './value-objects/Damage.ts';
 import { MagicalWeapon } from './magical-objects/MagicalWeapon.ts';
 import { HealingObject } from './magical-objects/HealingObject.ts';
 
@@ -38,7 +39,7 @@ describe('Magical Objects', () => {
             const target = Character.create({ name: 'goblin', level: Level.create(1) });
             const weapon = MagicalWeapon.create({ damage, maxHealth: weaponHP, owner: attacker });
             const result = attacker.useWeapon(weapon, target);
-            return result.weapon.health === weaponHP - 1;
+            return result.weapon.health.value === weaponHP - 1;
           },
         ),
       );
@@ -85,12 +86,12 @@ describe('Magical Objects', () => {
             const weapon = MagicalWeapon.create({ damage, maxHealth: weaponHP, owner: attacker });
             // Kill the attacker using a separate killer
             const killer = Character.create({ name: 'boss', level: Level.create(1) });
-            const deadAttacker = killer.dealDamage(attacker, 10000);
-            const weaponHPBefore = weapon.health;
+            const deadAttacker = killer.dealDamage(attacker, Damage.create(10000));
+            const weaponHPBefore = weapon.health.value;
             const targetHealthBefore = target.health.value;
             const result = deadAttacker.useWeapon(weapon, target);
             return (
-              result.weapon.health === weaponHPBefore &&
+              result.weapon.health.value === weaponHPBefore &&
               result.target.health.value === targetHealthBefore
             );
           },
@@ -110,11 +111,11 @@ describe('Magical Objects', () => {
             const thief = Character.create({ name: 'thief', level: Level.create(1) });
             const target = Character.create({ name: 'goblin', level: Level.create(1) });
             const weapon = MagicalWeapon.create({ damage, maxHealth: weaponHP, owner });
-            const weaponHPBefore = weapon.health;
+            const weaponHPBefore = weapon.health.value;
             const targetHealthBefore = target.health.value;
             const result = thief.useWeapon(weapon, target);
             return (
-              result.weapon.health === weaponHPBefore &&
+              result.weapon.health.value === weaponHPBefore &&
               result.target.health.value === targetHealthBefore
             );
           },
@@ -136,7 +137,9 @@ describe('Magical Objects', () => {
           const targetHealthBefore = firstUse.target.health.value;
           // Try to use again on the destroyed weapon
           const result = owner.useWeapon(destroyedWeapon, firstUse.target);
-          return result.weapon.health === 0 && result.target.health.value === targetHealthBefore;
+          return (
+            result.weapon.health.value === 0 && result.target.health.value === targetHealthBefore
+          );
         }),
       );
     });
@@ -203,7 +206,7 @@ describe('Magical Objects', () => {
             });
             const object = HealingObject.create({ maxHealth: objectHP, currentHealth: objectHP });
             const result = character.useHealingObject(object, healAmount);
-            return result.object.health === objectHP - healAmount;
+            return result.object.health.value === objectHP - healAmount;
           },
         ),
       );
@@ -254,12 +257,12 @@ describe('Magical Objects', () => {
           const object = HealingObject.create({ maxHealth: objectHP, currentHealth: objectHP });
           // Kill the character using a separate killer
           const killer = Character.create({ name: 'boss', level: Level.create(1) });
-          const deadCharacter = killer.dealDamage(character, 10000);
-          const objectHPBefore = object.health;
+          const deadCharacter = killer.dealDamage(character, Damage.create(10000));
+          const objectHPBefore = object.health.value;
           const characterHealthBefore = deadCharacter.health.value;
           const result = deadCharacter.useHealingObject(object, 100);
           return (
-            result.object.health === objectHPBefore &&
+            result.object.health.value === objectHPBefore &&
             result.character.health.value === characterHealthBefore
           );
         }),
@@ -287,7 +290,8 @@ describe('Magical Objects', () => {
           // Try to use again on the destroyed object
           const result = healedCharacter.useHealingObject(destroyedObject, 100);
           return (
-            result.object.health === 0 && result.character.health.value === characterHealthBefore
+            result.object.health.value === 0 &&
+            result.character.health.value === characterHealthBefore
           );
         }),
       );
@@ -305,7 +309,7 @@ describe('Magical Objects', () => {
             const target = Character.create({ name: 'goblin', level: Level.create(1) });
             const weapon = MagicalWeapon.create({ damage, maxHealth: weaponHP, owner: attacker });
             const result = attacker.useWeapon(weapon, target);
-            return result.weapon.health >= 0;
+            return result.weapon.health.value >= 0;
           },
         ),
       );
@@ -320,7 +324,7 @@ describe('Magical Objects', () => {
             const character = Character.create({ name: 'hero', level: Level.create(1) });
             const object = HealingObject.create({ maxHealth: objectHP, currentHealth: objectHP });
             const result = character.useHealingObject(object, healAmount);
-            return result.object.health >= 0;
+            return result.object.health.value >= 0;
           },
         ),
       );
@@ -336,7 +340,7 @@ describe('Magical Objects', () => {
             const target = Character.create({ name: 'goblin', level: Level.create(1) });
             const weapon = MagicalWeapon.create({ damage, maxHealth: weaponHP, owner: attacker });
             const result = attacker.useWeapon(weapon, target);
-            return result.weapon.health <= weaponHP;
+            return result.weapon.health.value <= weaponHP;
           },
         ),
       );
@@ -351,7 +355,7 @@ describe('Magical Objects', () => {
             const character = Character.create({ name: 'hero', level: Level.create(1) });
             const object = HealingObject.create({ maxHealth: objectHP, currentHealth: objectHP });
             const result = character.useHealingObject(object, healAmount);
-            return result.object.health <= objectHP;
+            return result.object.health.value <= objectHP;
           },
         ),
       );

src/magical-objects/HealingObject.ts

@@ -7,14 +7,15 @@
  */
 
 import { Character } from '../characters/Character.ts';
+import { Health } from '../value-objects/Health.ts';
 import { Level } from '../value-objects/Level.ts';
 import { MagicalObject } from './MagicalObject.ts';
 import type { Healer } from './magical-object-types.ts';
 
 export class HealingObject extends MagicalObject implements Healer {
   private constructor(
-    health: number,
-    maxHealth: number,
+    health: Health,
+    maxHealth: Health,
     status: { readonly kind: 'alive' } | { readonly kind: 'destroyed' },
   ) {
     super(health, maxHealth, status);
@@ -32,7 +33,7 @@ export class HealingObject extends MagicalObject implements Healer {
     if (currentHealth > maxHealth) throw new Error('CurrentHealth cannot exceed maxHealth');
     const status =
       currentHealth === 0 ? { kind: 'destroyed' as const } : { kind: 'alive' as const };
-    return new HealingObject(currentHealth, maxHealth, status);
+    return new HealingObject(Health.create(currentHealth), Health.create(maxHealth), status);
   }
 
   /** Use this object to heal a character. Returns updated object and character. */
@@ -44,7 +45,7 @@ export class HealingObject extends MagicalObject implements Healer {
     // Negative amount is invalid
     if (amount < 0) throw new Error('Heal amount must be non-negative');
     // Calculate actual heal amount: min of requested, object remaining, character headroom
-    const objectRemaining = this.health;
+    const objectRemaining = this.health.value;
     const characterMax = Level.maxHealthForLevel(character.level.value);
     const characterHeadroom = characterMax - character.health.value;
     const actualHeal = Math.min(amount, objectRemaining, characterHeadroom);
@@ -53,7 +54,7 @@ export class HealingObject extends MagicalObject implements Healer {
       return { object: this, character };
     }
     // Create updated object
-    const newObjectHealth = this.health - actualHeal;
+    const newObjectHealth = this.health.value - actualHeal;
     const newObjectStatus =
       newObjectHealth === 0 ? { kind: 'destroyed' as const } : { kind: 'alive' as const };
     // Create updated character
@@ -64,7 +65,7 @@ export class HealingObject extends MagicalObject implements Healer {
       health: newCharacterHealth,
     });
     return {
-      object: new HealingObject(newObjectHealth, this.maxHealth, newObjectStatus),
+      object: new HealingObject(Health.create(newObjectHealth), this.maxHealth, newObjectStatus),
       character: newCharacter,
     };
   }

src/magical-objects/MagicalObject.ts

@@ -7,24 +7,26 @@
  * - Status derived from health (0 = destroyed, > 0 = alive)
  */
 
+import { Health } from '../value-objects/Health.ts';
+
 export type MagicalObjectStatus = { readonly kind: 'alive' } | { readonly kind: 'destroyed' };
 
 export class MagicalObject {
-  readonly #health: number;
-  readonly #maxHealth: number;
+  readonly #health: Health;
+  readonly #maxHealth: Health;
   readonly #status: MagicalObjectStatus;
 
-  protected constructor(health: number, maxHealth: number, status: MagicalObjectStatus) {
+  protected constructor(health: Health, maxHealth: Health, status: MagicalObjectStatus) {
     this.#health = health;
     this.#maxHealth = maxHealth;
     this.#status = status;
   }
 
-  get health(): number {
+  get health(): Health {
     return this.#health;
   }
 
-  get maxHealth(): number {
+  get maxHealth(): Health {
     return this.#maxHealth;
   }
 
@@ -35,7 +37,7 @@ export class MagicalObject {
   /** Create a destroyed object (health = 0). */
   static createDestroyed(maxHealth: number): MagicalObject {
     if (maxHealth < 0) throw new Error('MaxHealth cannot be negative');
-    return new MagicalObject(0, maxHealth, { kind: 'destroyed' });
+    return new MagicalObject(Health.create(0), Health.create(maxHealth), { kind: 'destroyed' });
   }
 
   /** Check if this object is alive. */

src/magical-objects/MagicalWeapon.ts

@@ -6,18 +6,20 @@
  * - Damage is non-negative
  */
 import { Character } from '../characters/Character.ts';
+import { Health } from '../value-objects/Health.ts';
+import { Damage } from '../value-objects/Damage.ts';
 import { MagicalObject } from './MagicalObject.ts';
 import type { DamageDealer } from './magical-object-types.ts';
 
 export class MagicalWeapon extends MagicalObject implements DamageDealer {
-  readonly #damage: number;
+  readonly #damage: Damage;
   readonly #owner: Character;
 
   private constructor(
-    health: number,
-    maxHealth: number,
+    health: Health,
+    maxHealth: Health,
     status: { readonly kind: 'alive' } | { readonly kind: 'destroyed' },
-    damage: number,
+    damage: Damage,
     owner: Character,
   ) {
     super(health, maxHealth, status);
@@ -35,11 +37,16 @@ export class MagicalWeapon extends MagicalObject implements DamageDealer {
     owner: Character;
   }): MagicalWeapon {
     if (maxHealth < 0) throw new Error('MaxHealth cannot be negative');
-    if (damage < 0) throw new Error('Damage cannot be negative');
-    return new MagicalWeapon(maxHealth, maxHealth, { kind: 'alive' }, damage, owner);
+    return new MagicalWeapon(
+      Health.create(maxHealth),
+      Health.create(maxHealth),
+      { kind: 'alive' },
+      Damage.create(damage),
+      owner,
+    );
   }
 
-  get damage(): number {
+  get damage(): Damage {
     return this.#damage;
   }
 
@@ -54,7 +61,7 @@ export class MagicalWeapon extends MagicalObject implements DamageDealer {
       return { weapon: this, target };
     }
     // Deal fixed damage
-    const newTargetHealth = Math.max(0, target.health.value - this.#damage);
+    const newTargetHealth = Math.max(0, target.health.value - this.#damage.value);
     const newTargetStatus = newTargetHealth === 0 ? { kind: 'dead' as const } : target.status;
     const newTarget = Character.createWithHealthAndStatus({
       name: target.name,
@@ -63,12 +70,12 @@ export class MagicalWeapon extends MagicalObject implements DamageDealer {
       status: newTargetStatus,
     });
     // Reduce weapon health by 1
-    const newWeaponHealth = this.health - 1;
+    const newWeaponHealth = this.health.value - 1;
     const newWeaponStatus =
       newWeaponHealth === 0 ? { kind: 'destroyed' as const } : { kind: 'alive' as const };
     return {
       weapon: new MagicalWeapon(
-        newWeaponHealth,
+        Health.create(newWeaponHealth),
         this.maxHealth,
         newWeaponStatus,
         this.#damage,

src/magical-objects/magical-object-types.ts

@@ -6,19 +6,20 @@
  * so Character can depend on abstractions rather than concrete classes.
  */
 import type { Character } from '../characters/Character.ts';
+import type { Health } from '../value-objects/Health.ts';
 import type { MagicalObjectStatus } from './MagicalObject.ts';
 
 /** A magical object that deals damage — from Character's point of view */
 export interface DamageDealer {
   readonly owner: Character;
-  readonly health: number;
+  readonly health: Health;
   readonly status: MagicalObjectStatus;
   use(target: Character): { weapon: DamageDealer; target: Character };
 }
 
 /** A magical object that heals — from Character's point of view */
 export interface Healer {
-  readonly health: number;
+  readonly health: Health;
   readonly status: MagicalObjectStatus;
   heal(character: Character, amount: number): { object: Healer; character: Character };
 }

src/value-objects/Damage.ts

@@ -0,0 +1,26 @@
+/**
+ * Damage value object — non-negative, immutable.
+ *
+ * Invariant enforced at construction: n >= 0
+ */
+export class Damage {
+  readonly #value: number;
+
+  private constructor(n: number) {
+    this.#value = n;
+  }
+
+  static create(n: number): Damage {
+    if (n < 0) throw new Error(`Damage must be non-negative, got ${n}`);
+    return new Damage(n);
+  }
+
+  get value(): number {
+    return this.#value;
+  }
+
+  /** Add another damage amount — cumulative damage is still a Damage. */
+  add(other: Damage): Damage {
+    return Damage.create(this.#value + other.value);
+  }
+}

src/value-objects/Level.ts

@@ -31,4 +31,12 @@ export class Level {
   diff(target: Level): number {
     return this.value - target.value;
   }
+
+  /** Damage threshold to reach the given level.
+   *  Level 1→2: 1000, Level 2→3: 3000, Level 3→4: 6000, etc.
+   *  Formula: 1000 * N * (N+1) / 2
+   */
+  static damageThresholdForLevel(level: number): number {
+    return (1000 * level * (level + 1)) / 2;
+  }
 }

transcripts/index.md

@@ -0,0 +1,34 @@
+# Transcript Archive
+
+Chronological list of all session transcripts from the RPG Combat project.
+
+| Date | Transcript |
+| ---- | ---------- |
+| 2026-06-12 20:20 | [Card, Conversation & Confirmation](card-conversation-confirmation.html) |
+| 2026-06-12 20:20 | [Install Allium](install-allium.html) |
+| 2026-06-12 20:20 | [Review User Stories](review-user-stories.md) |
+| 2026-06-12 23:02 | [Clear and Export](clear-and-export.html) |
+| 2026-06-12 23:02 | [Refactor Story 1](refactor-story-1.html) |
+| 2026-06-12 23:02 | [Story 1 — Process Improvement](story1-process-improvement.md) |
+| 2026-06-13 15:42 | [YAGNI in AGENTS.md](yagni-in-agents-md.html) |
+| 2026-06-13 15:51 | [Story 2 — Refactored](story-2-refactored.html) |
+| 2026-06-13 16:06 | [Forgot to Mention the Story](forgot-to-mention-the-story.html) |
+| 2026-06-13 22:03 | [Forgot to Commit](forgot-to-commit.html) |
+| 2026-06-13 22:03 | [Story 2 (re?) — Done](story-2-(re?)-done.html) |
+| 2026-06-13 22:20 | [Story 4 — Built](story-4-built.html) |
+| 2026-06-13 22:32 | [Found Out Story 3 Is Not Done](found-out-story-3-is-not-done.html) |
+| 2026-06-14 10:48 | [Break Down Horizontal Refactoring into Yaks](break-down-horizontal-refactoring-into-yaks.html) |
+| 2026-06-14 10:48 | [Create Task Breakdown with Yaks Skill](create-task-breakdown-with-yaks-skill.html) |
+| 2026-06-14 10:48 | [Fixed Character Implementation (Maybe)](fixed-character-implementation-maybe.html) |
+| 2026-06-14 10:51 | [Resolved Circular Dependency](resolved-circular-dependency.html) |
+| 2026-06-14 12:01 | [Break Down the Refactoring Yaks](break-down-the-refactoring-yaks.html) |
+| 2026-06-14 12:01 | [Break Yaks Down into Phases](break-yaks-down-into-phases.html) |
+| 2026-06-14 12:01 | [Yaks Were Not Marked S-Done](yaks-were-not-marked-s-done.html) |
+| 2026-06-14 12:47 | [Create Yak Run Skill](create-yak-run-skill.html) |
+| 2026-06-14 12:47 | [ESLint Rule Against Value Objects and Yaks to Refactor](eslint-rule-against-value-objects-and-yaks-to-refactor.html) |
+| 2026-06-14 12:47 | [Generate README](generate-readme.html) |
+| 2026-06-14 12:47 | [Yaks Work for Horizontal Refactoring](yaks-work-for-horizontal-refactoring.html) |
+| 2026-06-14 14:26 | [Refactor: Replace Number Health with Health Value Object in MagicalObject](refactor:-replace-number-health-with-Health-value-object-in-MagicalObject.html) |
+| 2026-06-14 14:26 | [Story 4 Also Done — Spec and Story Needed to Be Put Straight](story-4-also-done,-spec-and-story-needed-to-be-put-straight.html) |
+| 2026-06-15 08:09 | [Last Story Done](last-story-done.html) |
+| 2026-06-15 09:36 | [Wrap Up](wrap-up.html) |

user-stories.md

@@ -50,6 +50,7 @@ This is a description of the business rules we should support in the game engine
    - Healing Magical Objects cannot deal Damage
 
 3. Characters can deal Damage by using a Magical Weapon.
+   - A Character can only use a Magical Weapon they own
    - These Magical Objects deal a fixed amount of damage when they are used
    - The amount of damage is fixed at the time the weapon is created
    - Every time the weapon is used, the Health is reduced by 1