diff --git a/packages/ai/src/api/google-generative-ai.ts b/packages/ai/src/api/google-generative-ai.ts
index b29244752..ceed2f347 100644
--- a/packages/ai/src/api/google-generative-ai.ts
+++ b/packages/ai/src/api/google-generative-ai.ts
@@ -212,6 +212,7 @@ export const stream: StreamFunction<"google-generative-ai", GoogleOptions> = (
 				}
 
 				if (candidate?.finishReason) {
+					output.rawStopReason = candidate.finishReason;
 					output.stopReason = mapStopReason(candidate.finishReason);
 					if (output.content.some((b) => b.type === "toolCall")) {
 						output.stopReason = "toolUse";
@@ -266,7 +267,10 @@ export const stream: StreamFunction<"google-generative-ai", GoogleOptions> = (
 				throw new Error("Google stream ended without a finish reason");
 			}
 			if (output.stopReason === "aborted" || output.stopReason === "error") {
-				throw new Error("An unknown error occurred");
+				const errorMessage = output.rawStopReason
+					? `Gemini stopped with ${output.rawStopReason}`
+					: "An unknown error occurred";
+				throw new Error(errorMessage);
 			}
 
 			stream.push({ type: "done", reason: output.stopReason, message: output });
diff --git a/packages/ai/src/api/google-vertex.ts b/packages/ai/src/api/google-vertex.ts
index dbef8c2f1..864ffe2c6 100644
--- a/packages/ai/src/api/google-vertex.ts
+++ b/packages/ai/src/api/google-vertex.ts
@@ -229,6 +229,7 @@ export const stream: StreamFunction<"google-vertex", GoogleVertexOptions> = (
 				}
 
 				if (candidate?.finishReason) {
+					output.rawStopReason = candidate.finishReason;
 					output.stopReason = mapStopReason(candidate.finishReason);
 					if (output.content.some((b) => b.type === "toolCall")) {
 						output.stopReason = "toolUse";
@@ -283,7 +284,10 @@ export const stream: StreamFunction<"google-vertex", GoogleVertexOptions> = (
 				throw new Error("Google Vertex stream ended without a finish reason");
 			}
 			if (output.stopReason === "aborted" || output.stopReason === "error") {
-				throw new Error("An unknown error occurred");
+				const errorMessage = output.rawStopReason
+					? `Gemini stopped with ${output.rawStopReason}`
+					: "An unknown error occurred";
+				throw new Error(errorMessage);
 			}
 
 			stream.push({ type: "done", reason: output.stopReason, message: output });
diff --git a/packages/ai/src/types.ts b/packages/ai/src/types.ts
index 98cd9d22b..26470a458 100644
--- a/packages/ai/src/types.ts
+++ b/packages/ai/src/types.ts
@@ -408,6 +408,7 @@ export interface AssistantMessage {
 	usage: Usage;
 	stopReason: StopReason;
 	errorMessage?: string;
+	rawStopReason?: string;
 	timestamp: number; // Unix timestamp in milliseconds
 }
 
diff --git a/packages/ai/test/google-raw-stop-reason.test.ts b/packages/ai/test/google-raw-stop-reason.test.ts
new file mode 100644
index 000000000..005d389e6
--- /dev/null
+++ b/packages/ai/test/google-raw-stop-reason.test.ts
@@ -0,0 +1,106 @@
+import { describe, expect, it, vi } from "vitest";
+
+const googleGenAiMock = vi.hoisted(() => ({
+	finishReason: "MALFORMED_FUNCTION_CALL",
+}));
+
+vi.mock("@google/genai", () => {
+	class GoogleGenAI {
+		models = {
+			generateContentStream: async function* () {
+				yield {
+					responseId: "google-response-id",
+					candidates: [
+						{
+							finishReason: googleGenAiMock.finishReason,
+						},
+					],
+					usageMetadata: {
+						promptTokenCount: 1,
+						candidatesTokenCount: 0,
+						totalTokenCount: 1,
+					},
+				};
+			},
+		};
+	}
+
+	return {
+		FinishReason: {
+			STOP: "STOP",
+			MAX_TOKENS: "MAX_TOKENS",
+			BLOCKLIST: "BLOCKLIST",
+			PROHIBITED_CONTENT: "PROHIBITED_CONTENT",
+			SPII: "SPII",
+			SAFETY: "SAFETY",
+			IMAGE_SAFETY: "IMAGE_SAFETY",
+			IMAGE_PROHIBITED_CONTENT: "IMAGE_PROHIBITED_CONTENT",
+			IMAGE_RECITATION: "IMAGE_RECITATION",
+			IMAGE_OTHER: "IMAGE_OTHER",
+			RECITATION: "RECITATION",
+			FINISH_REASON_UNSPECIFIED: "FINISH_REASON_UNSPECIFIED",
+			OTHER: "OTHER",
+			LANGUAGE: "LANGUAGE",
+			MALFORMED_FUNCTION_CALL: "MALFORMED_FUNCTION_CALL",
+			UNEXPECTED_TOOL_CALL: "UNEXPECTED_TOOL_CALL",
+			NO_IMAGE: "NO_IMAGE",
+		},
+		FunctionCallingConfigMode: {
+			AUTO: "AUTO",
+			NONE: "NONE",
+			ANY: "ANY",
+			VALIDATED: "VALIDATED",
+		},
+		GoogleGenAI,
+		ResourceScope: {
+			COLLECTION: "COLLECTION",
+		},
+		ThinkingLevel: {
+			THINKING_LEVEL_UNSPECIFIED: "THINKING_LEVEL_UNSPECIFIED",
+			MINIMAL: "MINIMAL",
+			LOW: "LOW",
+			MEDIUM: "MEDIUM",
+			HIGH: "HIGH",
+		},
+	};
+});
+
+import { stream as streamGoogleGenerativeAi } from "../src/api/google-generative-ai.ts";
+import { stream as streamGoogleVertex } from "../src/api/google-vertex.ts";
+import { getModel } from "../src/compat.ts";
+import type { Context } from "../src/types.ts";
+
+const context: Context = {
+	messages: [{ role: "user", content: "hello", timestamp: Date.now() }],
+};
+
+describe("Google raw stop reasons", () => {
+	it("preserves raw Gemini finish reasons for Google Generative AI errors", async () => {
+		googleGenAiMock.finishReason = "MALFORMED_FUNCTION_CALL";
+
+		const stream = streamGoogleGenerativeAi(getModel("google", "gemini-2.5-flash"), context, {
+			apiKey: "test-api-key",
+		});
+
+		const message = await stream.result();
+
+		expect(message.stopReason).toBe("error");
+		expect(message.rawStopReason).toBe("MALFORMED_FUNCTION_CALL");
+		expect(message.errorMessage).toBe("Gemini stopped with MALFORMED_FUNCTION_CALL");
+	});
+
+	it("preserves raw Gemini finish reasons for Google Vertex errors", async () => {
+		googleGenAiMock.finishReason = "SAFETY";
+
+		const stream = streamGoogleVertex(getModel("google-vertex", "gemini-3-flash-preview"), context, {
+			project: "test-project",
+			location: "us-central1",
+		});
+
+		const message = await stream.result();
+
+		expect(message.stopReason).toBe("error");
+		expect(message.rawStopReason).toBe("SAFETY");
+		expect(message.errorMessage).toBe("Gemini stopped with SAFETY");
+	});
+});