diff --git a/server/src/llm/__tests__/openRouterClient.test.ts b/server/src/llm/__tests__/openRouterClient.test.ts
new file mode 100644
index 0000000..860864d
--- /dev/null
+++ b/server/src/llm/__tests__/openRouterClient.test.ts
@@ -0,0 +1,129 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { createOpenRouterClient } from '../openRouterClient.js';
+import type { LlmConfig } from '../../config/llmConfig.js';
+
+const mockConfig: LlmConfig = {
+  apiKey: 'test-key',
+  model: 'arcee-ai/trinity-large-preview:free',
+  maxTokens: 200,
+  temperature: 0.8,
+  requestsPerMinute: 60,
+  timeoutMs: 5000,
+  enabled: true,
+};
+
+describe('openRouterClient', () => {
+  let originalFetch: typeof globalThis.fetch;
+
+  beforeEach(() => {
+    originalFetch = globalThis.fetch;
+  });
+
+  afterEach(() => {
+    globalThis.fetch = originalFetch;
+  });
+
+  it('sends correct request to OpenRouter API', async () => {
+    globalThis.fetch = vi.fn().mockResolvedValue({
+      ok: true,
+      json: () => Promise.resolve({
+        choices: [{ message: { content: 'Hello world' } }],
+      }),
+    });
+
+    const client = createOpenRouterClient(mockConfig);
+    const result = await client.complete({
+      system: 'You are helpful.',
+      user: 'Say hello.',
+    });
+
+    expect(result).toBe('Hello world');
+    expect(globalThis.fetch).toHaveBeenCalledWith(
+      'https://openrouter.ai/api/v1/chat/completions',
+      expect.objectContaining({
+        method: 'POST',
+        headers: expect.objectContaining({
+          'Authorization': 'Bearer test-key',
+          'Content-Type': 'application/json',
+        }),
+      }),
+    );
+
+    const body = JSON.parse(
+      (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0][1].body,
+    );
+    expect(body.model).toBe('arcee-ai/trinity-large-preview:free');
+    expect(body.max_tokens).toBe(200);
+    expect(body.temperature).toBe(0.8);
+    expect(body.messages).toEqual([
+      { role: 'system', content: 'You are helpful.' },
+      { role: 'user', content: 'Say hello.' },
+    ]);
+  });
+
+  it('returns null on HTTP error', async () => {
+    globalThis.fetch = vi.fn().mockResolvedValue({
+      ok: false,
+      status: 429,
+      statusText: 'Too Many Requests',
+    });
+
+    const client = createOpenRouterClient(mockConfig);
+    const result = await client.complete({
+      system: 'sys',
+      user: 'usr',
+    });
+
+    expect(result).toBeNull();
+  });
+
+  it('returns null on network error', async () => {
+    globalThis.fetch = vi.fn().mockRejectedValue(new Error('Network error'));
+
+    const client = createOpenRouterClient(mockConfig);
+    const result = await client.complete({
+      system: 'sys',
+      user: 'usr',
+    });
+
+    expect(result).toBeNull();
+  });
+
+  it('returns null when response has no choices', async () => {
+    globalThis.fetch = vi.fn().mockResolvedValue({
+      ok: true,
+      json: () => Promise.resolve({ choices: [] }),
+    });
+
+    const client = createOpenRouterClient(mockConfig);
+    const result = await client.complete({
+      system: 'sys',
+      user: 'usr',
+    });
+
+    expect(result).toBeNull();
+  });
+
+  it('allows per-request maxTokens and temperature override', async () => {
+    globalThis.fetch = vi.fn().mockResolvedValue({
+      ok: true,
+      json: () => Promise.resolve({
+        choices: [{ message: { content: 'ok' } }],
+      }),
+    });
+
+    const client = createOpenRouterClient(mockConfig);
+    await client.complete({
+      system: 'sys',
+      user: 'usr',
+      maxTokens: 50,
+      temperature: 0.2,
+    });
+
+    const body = JSON.parse(
+      (globalThis.fetch as ReturnType<typeof vi.fn>).mock.calls[0][1].body,
+    );
+    expect(body.max_tokens).toBe(50);
+    expect(body.temperature).toBe(0.2);
+  });
+});
diff --git a/server/src/llm/openRouterClient.ts b/server/src/llm/openRouterClient.ts
new file mode 100644
index 0000000..4050b88
--- /dev/null
+++ b/server/src/llm/openRouterClient.ts
@@ -0,0 +1,51 @@
+import type { LlmConfig } from '../config/llmConfig.js';
+import type { RenderedPrompt } from './promptTemplate.js';
+
+const OPENROUTER_URL = 'https://openrouter.ai/api/v1/chat/completions';
+
+export interface CompletionRequest extends RenderedPrompt {
+  maxTokens?: number;
+  temperature?: number;
+}
+
+export interface OpenRouterClient {
+  complete(request: CompletionRequest): Promise<string | null>;
+}
+
+export function createOpenRouterClient(config: LlmConfig): OpenRouterClient {
+  return {
+    async complete(request: CompletionRequest): Promise<string | null> {
+      try {
+        const response = await fetch(OPENROUTER_URL, {
+          method: 'POST',
+          signal: AbortSignal.timeout(config.timeoutMs),
+          headers: {
+            'Authorization': `Bearer ${config.apiKey}`,
+            'Content-Type': 'application/json',
+          },
+          body: JSON.stringify({
+            model: config.model,
+            max_tokens: request.maxTokens ?? config.maxTokens,
+            temperature: request.temperature ?? config.temperature,
+            messages: [
+              { role: 'system', content: request.system },
+              { role: 'user', content: request.user },
+            ],
+          }),
+        });
+
+        if (!response.ok) {
+          console.warn(`OpenRouter API error: ${response.status} ${response.statusText}`);
+          return null;
+        }
+
+        const data = await response.json();
+        const content = data?.choices?.[0]?.message?.content;
+        return content ?? null;
+      } catch (error) {
+        console.warn('OpenRouter request failed:', (error as Error).message);
+        return null;
+      }
+    },
+  };
+}