diff --git a/packages/ai/src/providers/openai-completions.ts b/packages/ai/src/providers/openai-completions.ts
index ffe4e28e..f2d36e7c 100644
--- a/packages/ai/src/providers/openai-completions.ts
+++ b/packages/ai/src/providers/openai-completions.ts
@@ -575,6 +575,10 @@ function buildParams(
 		prompt_cache_retention: cacheRetention === "long" && compat.supportsLongCacheRetention ? "24h" : undefined,
 	};
 
+	if (isOpenRouterImageGenerationModel(model)) {
+		Reflect.set(params, "modalities", ["image"]);
+	}
+
 	if (compat.supportsUsageInStreaming !== false) {
 		(params as any).stream_options = { include_usage: true };
 	}
diff --git a/packages/ai/test/openai-completions-image-output.test.ts b/packages/ai/test/openai-completions-image-output.test.ts
index 2cf1b7fb..745305c4 100644
--- a/packages/ai/test/openai-completions-image-output.test.ts
+++ b/packages/ai/test/openai-completions-image-output.test.ts
@@ -92,8 +92,9 @@ describe("openai-completions image output", () => {
 			data: "ZmFrZS1wbmc=",
 		});
 
-		const params = mockState.lastParams as { stream?: boolean; stream_options?: unknown };
+		const params = mockState.lastParams as { stream?: boolean; stream_options?: unknown; modalities?: string[] };
 		expect(params.stream).toBe(false);
 		expect("stream_options" in (params as object)).toBe(false);
+		expect(params.modalities).toEqual(["image"]);
 	});
 });