fix(ai): default tool call arguments to empty object for Google providers

When Google providers return tool calls without an args field (common for
no-argument tools), the arguments field was undefined. This breaks
subsequent API calls that require tool_use.input to be present.

Now defaults to {} when args is missing.

Related: clawdbot/clawdbot#1509

packages/ai/src/providers/google-gemini-cli.ts

@@ -685,7 +685,7 @@ export const streamGoogleGeminiCli: StreamFunction<"google-gemini-cli", GoogleGe
 											type: "toolCall",
 											id: toolCallId,
 											name: part.functionCall.name || "",
-											arguments: part.functionCall.args as Record<string, unknown>,
+											arguments: (part.functionCall.args as Record<string, unknown>) ?? {},
 											...(part.thoughtSignature && { thoughtSignature: part.thoughtSignature }),
 										};
 

packages/ai/src/providers/google-vertex.ts

@@ -191,7 +191,7 @@ export const streamGoogleVertex: StreamFunction<"google-vertex", GoogleVertexOpt
 								type: "toolCall",
 								id: toolCallId,
 								name: part.functionCall.name || "",
-								arguments: part.functionCall.args as Record<string, any>,
+								arguments: (part.functionCall.args as Record<string, any>) ?? {},
 								...(part.thoughtSignature && { thoughtSignature: part.thoughtSignature }),
 							};
 

packages/ai/src/providers/google.ts

@@ -179,7 +179,7 @@ export const streamGoogle: StreamFunction<"google-generative-ai", GoogleOptions>
 								type: "toolCall",
 								id: toolCallId,
 								name: part.functionCall.name || "",
-								arguments: part.functionCall.args as Record<string, any>,
+								arguments: (part.functionCall.args as Record<string, any>) ?? {},
 								...(part.thoughtSignature && { thoughtSignature: part.thoughtSignature }),
 							};
 

packages/ai/test/google-tool-call-missing-args.test.ts

@@ -0,0 +1,105 @@
+import { Type } from "@sinclair/typebox";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { streamGoogleGeminiCli } from "../src/providers/google-gemini-cli.js";
+import type { Context, Model, ToolCall } from "../src/types.js";
+
+const emptySchema = Type.Object({});
+
+const originalFetch = global.fetch;
+
+afterEach(() => {
+	global.fetch = originalFetch;
+	vi.restoreAllMocks();
+});
+
+describe("google providers tool call missing args", () => {
+	it("defaults arguments to empty object when provider omits args field", async () => {
+		// Simulate a tool call response where args is missing (no-arg tool)
+		const sse = `${[
+			`data: ${JSON.stringify({
+				response: {
+					candidates: [
+						{
+							content: {
+								role: "model",
+								parts: [
+									{
+										functionCall: {
+											name: "get_status",
+											// args intentionally omitted
+										},
+									},
+								],
+							},
+							finishReason: "STOP",
+						},
+					],
+					usageMetadata: {
+						promptTokenCount: 10,
+						candidatesTokenCount: 5,
+						totalTokenCount: 15,
+					},
+				},
+			})}`,
+		].join("\n\n")}\n\n`;
+
+		const encoder = new TextEncoder();
+		const dataStream = new ReadableStream<Uint8Array>({
+			start(controller) {
+				controller.enqueue(encoder.encode(sse));
+				controller.close();
+			},
+		});
+
+		const fetchMock = vi.fn(async () => {
+			return new Response(dataStream, {
+				status: 200,
+				headers: { "content-type": "text/event-stream" },
+			});
+		});
+
+		global.fetch = fetchMock as typeof fetch;
+
+		const model: Model<"google-gemini-cli"> = {
+			id: "gemini-2.5-flash",
+			name: "Gemini 2.5 Flash",
+			api: "google-gemini-cli",
+			provider: "google-gemini-cli",
+			baseUrl: "https://cloudcode-pa.googleapis.com",
+			reasoning: false,
+			input: ["text"],
+			cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+			contextWindow: 128000,
+			maxTokens: 8192,
+		};
+
+		const context: Context = {
+			messages: [{ role: "user", content: "Check status", timestamp: Date.now() }],
+			tools: [
+				{
+					name: "get_status",
+					description: "Get current status",
+					parameters: emptySchema,
+				},
+			],
+		};
+
+		const stream = streamGoogleGeminiCli(model, context, {
+			apiKey: JSON.stringify({ token: "token", projectId: "project" }),
+		});
+
+		for await (const _ of stream) {
+			// consume stream
+		}
+
+		const result = await stream.result();
+
+		expect(result.stopReason).toBe("toolUse");
+		expect(result.content).toHaveLength(1);
+
+		const toolCall = result.content[0] as ToolCall;
+		expect(toolCall.type).toBe("toolCall");
+		expect(toolCall.name).toBe("get_status");
+		expect(toolCall.arguments).toEqual({});
+	});
+});