diff --git a/server/src/industry/__tests__/inventionValidator.test.ts b/server/src/industry/__tests__/inventionValidator.test.ts
new file mode 100644
index 0000000..f5a357a
--- /dev/null
+++ b/server/src/industry/__tests__/inventionValidator.test.ts
@@ -0,0 +1,111 @@
+import { describe, it, expect } from 'vitest';
+import { validateInvention, type RawInvention } from '../inventionValidator.js';
+import { ItemRegistry } from '../itemRegistry.js';
+
+function createTestRegistry(): ItemRegistry {
+  return ItemRegistry.createDefault(); // has log, stone, water, wooden_axe, hammer
+}
+
+describe('validateInvention', () => {
+  it('accepts a valid crafted item', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: 'rope',
+      description: 'Twisted plant fibers',
+      category: 'material',
+      inputs: [{ itemId: 'log', quantity: 2 }],
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(true);
+    expect(result.itemId).toBe('rope');
+  });
+
+  it('rejects when input itemId does not exist', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: 'magic wand',
+      description: 'A wand',
+      category: 'tool',
+      inputs: [{ itemId: 'unicorn_horn', quantity: 1 }],
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(false);
+    expect(result.error).toContain('unicorn_horn');
+  });
+
+  it('rejects duplicate item name (case-insensitive)', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: 'Log',
+      description: 'Another log',
+      category: 'resource',
+      inputs: [],
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(false);
+    expect(result.error).toContain('already exists');
+  });
+
+  it('rejects invalid category', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: 'potion',
+      description: 'A potion',
+      category: 'magic' as any,
+      inputs: [{ itemId: 'water', quantity: 1 }],
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(false);
+    expect(result.error).toContain('category');
+  });
+
+  it('rejects missing name', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: '',
+      description: 'No name',
+      category: 'material',
+      inputs: [{ itemId: 'log', quantity: 1 }],
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(false);
+  });
+
+  it('generates a snake_case itemId from name', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: 'Fishing Rod',
+      description: 'A rod for catching fish',
+      category: 'tool',
+      inputs: [{ itemId: 'log', quantity: 2 }],
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(true);
+    expect(result.itemId).toBe('fishing_rod');
+  });
+
+  it('accepts a structure invention with workshopType', () => {
+    const registry = createTestRegistry();
+    const raw: RawInvention = {
+      name: 'kiln',
+      description: 'A stone furnace',
+      category: 'structure',
+      inputs: [{ itemId: 'stone', quantity: 5 }],
+      workshopType: 'kiln',
+    };
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(true);
+    expect(result.workshopType).toBe('kiln');
+  });
+
+  it('rejects if inputs array is missing', () => {
+    const registry = createTestRegistry();
+    const raw = {
+      name: 'thing',
+      description: 'A thing',
+      category: 'material',
+    } as any;
+    const result = validateInvention(raw, registry);
+    expect(result.valid).toBe(false);
+  });
+});
diff --git a/server/src/industry/inventionValidator.ts b/server/src/industry/inventionValidator.ts
new file mode 100644
index 0000000..2fac6e2
--- /dev/null
+++ b/server/src/industry/inventionValidator.ts
@@ -0,0 +1,78 @@
+import type { ItemRegistry } from './itemRegistry.js';
+
+export interface RawInvention {
+  name: string;
+  description: string;
+  category: string;
+  inputs: { itemId: string; quantity: number }[];
+  workshopType?: string | null;
+  toolRequired?: string | null;
+}
+
+export interface ValidationResult {
+  valid: boolean;
+  error?: string;
+  itemId?: string;
+  workshopType?: string;
+}
+
+const VALID_CATEGORIES = ['resource', 'tool', 'material', 'structure'];
+
+function toSnakeCase(name: string): string {
+  return name.toLowerCase().trim().replace(/\s+/g, '_').replace(/[^a-z0-9_]/g, '');
+}
+
+export function validateInvention(raw: RawInvention, registry: ItemRegistry): ValidationResult {
+  // Check name exists
+  if (!raw.name || typeof raw.name !== 'string' || raw.name.trim().length === 0) {
+    return { valid: false, error: 'Missing or empty name' };
+  }
+
+  // Check description exists
+  if (!raw.description || typeof raw.description !== 'string') {
+    return { valid: false, error: 'Missing description' };
+  }
+
+  // Check category is valid
+  if (!VALID_CATEGORIES.includes(raw.category)) {
+    return { valid: false, error: `Invalid category '${raw.category}'; must be one of: ${VALID_CATEGORIES.join(', ')}` };
+  }
+
+  // Check inputs is array
+  if (!Array.isArray(raw.inputs)) {
+    return { valid: false, error: 'Missing or invalid inputs array' };
+  }
+
+  // Check all input itemIds exist in registry
+  for (const input of raw.inputs) {
+    if (!registry.get(input.itemId)) {
+      return { valid: false, error: `Unknown input item '${input.itemId}'` };
+    }
+    if (typeof input.quantity !== 'number' || input.quantity < 1) {
+      return { valid: false, error: `Invalid quantity for '${input.itemId}'` };
+    }
+  }
+
+  // Generate itemId
+  const itemId = toSnakeCase(raw.name);
+  if (!itemId) {
+    return { valid: false, error: 'Name produces empty itemId' };
+  }
+
+  // Check for name collision (case-insensitive via itemId and existing names)
+  const existingItems = registry.getAll();
+  if (existingItems.some(item => item.id === itemId || item.name.toLowerCase() === raw.name.toLowerCase().trim())) {
+    return { valid: false, error: `Item '${raw.name}' already exists` };
+  }
+
+  // Check toolRequired exists if specified
+  if (raw.toolRequired && !registry.get(raw.toolRequired)) {
+    return { valid: false, error: `Unknown toolRequired '${raw.toolRequired}'` };
+  }
+
+  return {
+    valid: true,
+    itemId,
+    workshopType: raw.workshopType ?? undefined,
+  };
+}