diff --git a/CHANGELOG.md b/CHANGELOG.md
index b280eb6..cfdd794 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,9 @@ versioned release tag yet, so entries are organized as pre-alpha snapshots.
 - Inventory lifecycle guards for issue #219 now clear body carry, equipped
   items, and temporary run loot on body death, preserve account stash through
   reinhabitation, and reject inventory mutations while the current body is dead.
+- Inventory validation coverage now asserts rejected slot equips, full body
+  carry capacity, and denied model inventory intents do not partially mutate
+  inventory state.
 - Inventory and equipment design refinements covering custody lifecycle states,
   hostile / monster / boss body loadout rules, alpha starter item definitions,
   starter body loadouts, first reward tables, compact AI inventory context, and
diff --git a/backend/nakama/tests/supabase_custom_auth.test.mjs b/backend/nakama/tests/supabase_custom_auth.test.mjs
index 04efcc8..376dc0e 100644
--- a/backend/nakama/tests/supabase_custom_auth.test.mjs
+++ b/backend/nakama/tests/supabase_custom_auth.test.mjs
@@ -1567,6 +1567,30 @@ assert.equal(salvagedBlade.inventory.materials.length, 1);
 assert.equal(salvagedBlade.inventory.materials[0].item_def_id, "material.relay_scrap.common");
 assert.equal(salvagedBlade.inventory.materials[0].quantity, 5);
 
+const offHandStaff = JSON.parse(inventoryHarness.registeredRpcs.get("secondspawn_inventory_pickup")(
+  { userId: "inventory-user", env: {} },
+  inventoryHarness.logger,
+  inventoryHarness.nk,
+  JSON.stringify({ drop_id: "drop.relay_staff", idempotency_key: "slot-guard-staff" })
+));
+const slotGuardSnapshot = JSON.stringify(offHandStaff.inventory);
+assert.throws(
+  () => inventoryHarness.registeredRpcs.get("secondspawn_inventory_equip")(
+    { userId: "inventory-user", env: {} },
+    inventoryHarness.logger,
+    inventoryHarness.nk,
+    JSON.stringify({ item_instance_id: offHandStaff.item.item_instance_id, slot_id: "off_hand" })
+  ),
+  /item cannot be equipped/
+);
+const inventoryAfterRejectedSlotEquip = JSON.parse(inventoryHarness.registeredRpcs.get("secondspawn_inventory_get")(
+  { userId: "inventory-user", env: {} },
+  inventoryHarness.logger,
+  inventoryHarness.nk,
+  ""
+));
+assert.equal(JSON.stringify(inventoryAfterRejectedSlotEquip.inventory), slotGuardSnapshot);
+
 assert.throws(
   () => inventoryHarness.registeredRpcs.get("secondspawn_inventory_stash_move")(
     { userId: "inventory-user", env: {} },
@@ -1591,6 +1615,71 @@ assert.ok(inventoryLedger.entries.some((entry) => entry.category === "inventory"
 assert.ok(inventoryLedger.entries.some((entry) => entry.category === "inventory" && entry.kind === "inventory_unequip"));
 assert.ok(inventoryLedger.entries.some((entry) => entry.category === "inventory" && entry.kind === "inventory_salvage"));
 
+const slotConflictHarness = createRuntimeHarness(module);
+slotConflictHarness.registeredRpcs.get("secondspawn_profile_get")(
+  { userId: "slot-conflict-user", env: {} },
+  slotConflictHarness.logger,
+  slotConflictHarness.nk,
+  ""
+);
+const slotConflictBlade = JSON.parse(slotConflictHarness.registeredRpcs.get("secondspawn_inventory_pickup")(
+  { userId: "slot-conflict-user", env: {} },
+  slotConflictHarness.logger,
+  slotConflictHarness.nk,
+  JSON.stringify({ drop_id: "drop.training_blade", idempotency_key: "slot-conflict-blade" })
+));
+JSON.parse(slotConflictHarness.registeredRpcs.get("secondspawn_inventory_equip")(
+  { userId: "slot-conflict-user", env: {} },
+  slotConflictHarness.logger,
+  slotConflictHarness.nk,
+  JSON.stringify({ item_instance_id: slotConflictBlade.item.item_instance_id, slot_id: "main_hand" })
+));
+const slotConflictStaff = JSON.parse(slotConflictHarness.registeredRpcs.get("secondspawn_inventory_pickup")(
+  { userId: "slot-conflict-user", env: {} },
+  slotConflictHarness.logger,
+  slotConflictHarness.nk,
+  JSON.stringify({ drop_id: "drop.relay_staff", idempotency_key: "slot-conflict-staff" })
+));
+const resolvedSlotConflict = JSON.parse(slotConflictHarness.registeredRpcs.get("secondspawn_inventory_equip")(
+  { userId: "slot-conflict-user", env: {} },
+  slotConflictHarness.logger,
+  slotConflictHarness.nk,
+  JSON.stringify({ item_instance_id: slotConflictStaff.item.item_instance_id, slot_id: "main_hand" })
+));
+assert.equal(resolvedSlotConflict.inventory.equipment.items.length, 1);
+assert.equal(resolvedSlotConflict.inventory.equipment.items[0].item_def_id, "weapon.relay_staff.common");
+assert.equal(resolvedSlotConflict.inventory.body_carry.items.length, 1);
+assert.equal(resolvedSlotConflict.inventory.body_carry.items[0].item_def_id, "weapon.relay_blade.common");
+assert.equal(resolvedSlotConflict.inventory.body_carry.items[0].slot_id, "");
+
+const fullInventoryHarness = createRuntimeHarness(module);
+fullInventoryHarness.registeredRpcs.get("secondspawn_profile_get")(
+  { userId: "full-inventory-user", env: {} },
+  fullInventoryHarness.logger,
+  fullInventoryHarness.nk,
+  ""
+);
+JSON.parse(fullInventoryHarness.registeredRpcs.get("secondspawn_inventory_pickup")(
+  { userId: "full-inventory-user", env: {} },
+  fullInventoryHarness.logger,
+  fullInventoryHarness.nk,
+  JSON.stringify({ drop_id: "drop.training_blade", idempotency_key: "full-capacity-blade" })
+));
+const fullInventoryState = fullInventoryHarness.storage.get(storageKey("full-inventory-user", "secondspawn_inventory", "state"));
+fullInventoryState.value.body_carry.capacity = 1;
+const fullInventorySnapshot = JSON.stringify(fullInventoryState.value);
+assert.throws(
+  () => fullInventoryHarness.registeredRpcs.get("secondspawn_inventory_pickup")(
+    { userId: "full-inventory-user", env: {} },
+    fullInventoryHarness.logger,
+    fullInventoryHarness.nk,
+    JSON.stringify({ drop_id: "drop.relay_staff", idempotency_key: "full-capacity-staff" })
+  ),
+  /body carry inventory is full/
+);
+const fullInventoryAfterRejectedPickup = fullInventoryHarness.storage.get(storageKey("full-inventory-user", "secondspawn_inventory", "state"));
+assert.equal(JSON.stringify(fullInventoryAfterRejectedPickup.value), fullInventorySnapshot);
+
 const inventoryDeathHarness = createRuntimeHarness(module);
 inventoryDeathHarness.registeredRpcs.get("secondspawn_profile_get")(
   { userId: "inventory-death-user", env: {} },
@@ -2915,6 +3004,64 @@ assert.ok(promptTraces.traces[0].prompt_components.knowledge_pack_ids.includes("
 assert.deepEqual(promptTraces.traces[0].prompt_components.inventory_summary.current_loadout, ["Relay Blade"]);
 assert.equal(JSON.stringify(promptTraces.traces[0].prompt_components.inventory_summary).includes(modelBladeId), false);
 
+const inventoryIntentDeniedHarness = createRuntimeHarness(module);
+JSON.parse(inventoryIntentDeniedHarness.registeredRpcs.get("secondspawn_inventory_pickup")(
+  { userId: "inventory-intent-denied-user", env: {} },
+  inventoryIntentDeniedHarness.logger,
+  inventoryIntentDeniedHarness.nk,
+  JSON.stringify({ drop_id: "drop.training_blade", idempotency_key: "intent-denied-blade" })
+));
+const inventoryIntentBefore = JSON.stringify(inventoryIntentDeniedHarness.storage.get(
+  storageKey("inventory-intent-denied-user", "secondspawn_inventory", "state")
+).value);
+inventoryIntentDeniedHarness.nk.httpRequest = () => ({
+  code: 200,
+  body: JSON.stringify({
+    choices: [{
+      message: {
+        content: JSON.stringify({
+          action: "inventory_pickup",
+          drop_id: "drop.relay_staff",
+          reason: "model tried to mutate inventory directly",
+          confidence: 0.8
+        })
+      }
+    }]
+  })
+});
+const inventoryIntentDeniedDecision = JSON.parse(inventoryIntentDeniedHarness.registeredRpcs.get("secondspawn_agent_decide")(
+  {
+    userId: "inventory-intent-denied-user",
+    env: {
+      DOS_AI_API_KEY: "dos-ai-test-key",
+      DOS_AI_BASE_URL: "https://api.dos.ai/v1",
+      AGENT_DECISION_MODEL: "dos-ai"
+    }
+  },
+  inventoryIntentDeniedHarness.logger,
+  inventoryIntentDeniedHarness.nk,
+  JSON.stringify({
+    world_snapshot: {
+      position: { x: 2, z: 3 },
+      body_time_seconds: 3600
+    },
+    allowed: ["say", "stop"]
+  })
+));
+assert.equal(inventoryIntentDeniedDecision.source, "fallback");
+assert.equal(inventoryIntentDeniedDecision.source_reason, "dos_ai_validate_error");
+const inventoryIntentAfter = JSON.stringify(inventoryIntentDeniedHarness.storage.get(
+  storageKey("inventory-intent-denied-user", "secondspawn_inventory", "state")
+).value);
+assert.equal(inventoryIntentAfter, inventoryIntentBefore);
+assert.ok(inventoryIntentDeniedHarness.structuredLogs().some((log) => {
+  return log.event === "secondspawn.ai_decision" &&
+    log.owner_id === "inventory-intent-denied-user" &&
+    log.source === "fallback" &&
+    log.source_reason === "dos_ai_validate_error" &&
+    log.validation_result === "action is not allowed";
+}));
+
 const repeatedSpeechHarness = createRuntimeHarness(module);
 repeatedSpeechHarness.nk.httpRequest = () => ({
   code: 200,
diff --git a/docs/design/45-inventory-and-equipment-system.md b/docs/design/45-inventory-and-equipment-system.md
index d408239..726c044 100644
--- a/docs/design/45-inventory-and-equipment-system.md
+++ b/docs/design/45-inventory-and-equipment-system.md
@@ -951,11 +951,11 @@ Cut line for all three packets:
 - [x] Add inventory mutation ledger rows.
 - [x] Add RPCs for get, pickup, equip, unequip, stash move, salvage, use, and
       run loot claim.
-- [ ] Add unit tests for slot conflicts, full inventory, body death loss,
-      account stash survival, and LLM intent denial. Body death loss, account
-      stash survival, and post-error no-mutation checks are now covered; track
-      remaining slot/full-capacity and LLM denial coverage in
-      [#219](https://github.com/DOS/Second-Spawn/issues/219).
+- [x] Add unit tests for slot conflicts, full inventory, body death loss,
+      account stash survival, and LLM intent denial. Covered cases include
+      rejected slot equip, full body carry, body death loss, account stash
+      survival, denied model inventory intent, and post-error no-mutation
+      checks.
 - [ ] Add custody lifecycle transition guards for world drop, run loot, body
       carry, body equip, Yard storage, account stash, entitlement, destroyed,
       and recoverable wreck states. Dead-body mutation guards now cover the