Fix: Correctly use context model for moderation (#26)

* Correctly use context model for moderation
* Address copilot comments

Author: steven10a

src/__tests__/unit/checks/moderation-secret-keys.test.ts

@@ -67,6 +67,86 @@ describe('moderation guardrail', () => {
     expect(result.tripwireTriggered).toBe(false);
     expect(result.info?.error).toBe('Moderation API call failed');
   });
+
+  it('uses context client when available', async () => {
+    // Track whether context client was used
+    let contextClientUsed = false;
+    const contextCreateMock = vi.fn().mockImplementation(async () => {
+      contextClientUsed = true;
+      return {
+        results: [
+          {
+            categories: {
+              [Category.HATE]: false,
+              [Category.VIOLENCE]: false,
+            },
+          },
+        ],
+      };
+    });
+
+    // Create a context with a guardrailLlm client
+    // We need to import OpenAI to create a proper instance
+    const OpenAI = (await import('openai')).default;
+    const contextClient = new OpenAI({ apiKey: 'test-context-key' });
+    contextClient.moderations = {
+      create: contextCreateMock,
+    } as unknown as typeof contextClient.moderations;
+
+    const ctx = { guardrailLlm: contextClient };
+    const cfg = ModerationConfig.parse({ categories: [Category.HATE] });
+    const result = await moderationCheck(ctx, 'test text', cfg);
+
+    // Verify the context client was used
+    expect(contextClientUsed).toBe(true);
+    expect(contextCreateMock).toHaveBeenCalledWith({
+      model: 'omni-moderation-latest',
+      input: 'test text',
+      safety_identifier: 'openai-guardrails-js',
+    });
+    expect(result.tripwireTriggered).toBe(false);
+  });
+
+  it('falls back to default client for third-party providers', async () => {
+    // Track whether fallback client was used
+    let fallbackUsed = false;
+    
+    // The default mock from vi.mock will be used for the fallback
+    createMock.mockImplementation(async () => {
+      fallbackUsed = true;
+      return {
+        results: [
+          {
+            categories: {
+              [Category.HATE]: false,
+            },
+          },
+        ],
+      };
+    });
+
+    // Create a context client that simulates a third-party provider
+    // When moderation is called, it should raise a 404 error
+    const contextCreateMock = vi.fn().mockRejectedValue({
+      status: 404,
+      message: '404 page not found',
+    });
+
+    const OpenAI = (await import('openai')).default;
+    const thirdPartyClient = new OpenAI({ apiKey: 'third-party-key', baseURL: 'https://localhost:8080/v1' });
+    thirdPartyClient.moderations = {
+      create: contextCreateMock,
+    } as unknown as typeof thirdPartyClient.moderations;
+
+    const ctx = { guardrailLlm: thirdPartyClient };
+    const cfg = ModerationConfig.parse({ categories: [Category.HATE] });
+    const result = await moderationCheck(ctx, 'test text', cfg);
+
+    // Verify the fallback client was used (not the third-party one)
+    expect(contextCreateMock).toHaveBeenCalled();
+    expect(fallbackUsed).toBe(true);
+    expect(result.tripwireTriggered).toBe(false);
+  });
 });
 
 describe('secret key guardrail', () => {

src/checks/moderation.ts

@@ -156,7 +156,6 @@ export const moderationCheck: CheckFn<ModerationContext, string, ModerationConfi
       try {
         resp = await callModerationAPI(client, data);
       } catch (error) {
-        
         // Moderation endpoint doesn't exist on this provider (e.g., third-party)
         // Fall back to the OpenAI client
         if (isNotFoundError(error)) {