fix(ai): ignore unknown anthropic sse events

closes #3708

packages/ai/test/anthropic-sse-parsing.test.ts

@@ -13,6 +13,61 @@ function createSseResponse(events: Array<{ event: string; data: string }>): Resp
 	});
 }
 
+const minimalAnthropicEvents = [
+	{
+		event: "message_start",
+		data: JSON.stringify({
+			type: "message_start",
+			message: {
+				id: "msg_test",
+				usage: {
+					input_tokens: 12,
+					output_tokens: 0,
+					cache_read_input_tokens: 0,
+					cache_creation_input_tokens: 0,
+				},
+			},
+		}),
+	},
+	{
+		event: "content_block_start",
+		data: JSON.stringify({
+			type: "content_block_start",
+			index: 0,
+			content_block: { type: "text", text: "" },
+		}),
+	},
+	{
+		event: "content_block_delta",
+		data: JSON.stringify({
+			type: "content_block_delta",
+			index: 0,
+			delta: { type: "text_delta", text: "Hello" },
+		}),
+	},
+	{
+		event: "content_block_stop",
+		data: JSON.stringify({ type: "content_block_stop", index: 0 }),
+	},
+	{
+		event: "message_delta",
+		data: JSON.stringify({
+			type: "message_delta",
+			delta: { stop_reason: "end_turn" },
+			usage: {
+				input_tokens: 12,
+				output_tokens: 5,
+				cache_read_input_tokens: 0,
+				cache_creation_input_tokens: 0,
+			},
+		}),
+	},
+	{
+		event: "message_stop",
+		data: JSON.stringify({ type: "message_stop" }),
+	},
+];
+
 function createFakeAnthropicClient(response: Response): Anthropic {
 	return {
 		messages: {
@@ -110,4 +165,25 @@ describe("Anthropic raw SSE parsing", () => {
 			text: "col1\tcol2",
 		});
 	});
+
+	it("ignores unknown SSE events after message_stop", async () => {
+		const model = getModel("anthropic", "claude-haiku-4-5");
+		const context: Context = {
+			messages: [{ role: "user", content: "Say hello.", timestamp: Date.now() }],
+		};
+		const response = createSseResponse([
+			...minimalAnthropicEvents,
+			{ event: "done", data: "[DONE]" },
+			{ event: "proxy.stats", data: "not json" },
+		]);
+
+		const stream = streamAnthropic(model, context, {
+			client: createFakeAnthropicClient(response),
+		});
+		const result = await stream.result();
+
+		expect(result.stopReason).toBe("stop");
+		expect(result.errorMessage).toBeUndefined();
+		expect(result.content).toEqual([{ type: "text", text: "Hello" }]);
+	});
 });