fix(ENG-12540): prevent unhandled rejection cascade on ONNX load failure

specs/onnx-classifier.spec.ts

@@ -79,6 +79,34 @@ describe.skipIf(!!process.env.CI)('OnnxClassifier', () => {
   });
 });
 
+describe('#OnnxClassifier load failure', () => {
+	it('does not emit unhandledRejection when model fails to load', async () => {
+		// arrange
+		const unhandledRejections: unknown[] = [];
+		const handler = (reason: unknown) => unhandledRejections.push(reason);
+		process.on('unhandledRejection', handler);
+
+		try {
+			const badClassifier = new OnnxClassifier('/nonexistent/path/to/model');
+
+			// act
+			try {
+				await badClassifier.loadModel();
+			} catch {
+				// Expected — model doesn't exist
+			}
+
+			// Allow microtasks to flush (unhandled rejections are reported asynchronously)
+			await new Promise((r) => setTimeout(r, 100));
+		} finally {
+			process.removeListener('unhandledRejection', handler);
+		}
+
+		// assert
+		expect(unhandledRejections).toHaveLength(0);
+	});
+});
+
 describe.skipIf(!!process.env.CI)('Tier2Classifier ONNX mode', () => {
   let classifier: Tier2Classifier;
 

src/classifiers/onnx-classifier.ts

@@ -187,7 +187,9 @@ export class OnnxClassifier {
 				_sessionCache.set(modelPath, { session, OrtTensor, tokenizer });
 			})();
 			_loadingPromises.set(this.modelPath, inFlight);
-			void inFlight.finally(() => _loadingPromises.delete(this.modelPath));
+			// Swallow .finally() rejection — the actual error propagates via `await inFlight` below.
+			// Without this, a rejected inFlight produces an unhandled rejection from the .finally() chain.
+			inFlight.finally(() => _loadingPromises.delete(this.modelPath)).catch(() => {});
 		}
 
 		await inFlight;