chore(vendor): import pi 0.85.1

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/packages/coding-agent/test/suite/regressions/7925-toolcall-start-metadata.test.ts

@@ -0,0 +1,43 @@
+import { fauxAssistantMessage, fauxToolCall } from "@earendil-works/pi-ai";
+import { afterEach, describe, expect, it } from "vitest";
+import { toJsonEvent } from "../../../src/modes/json-event.ts";
+import { createHarness, type Harness } from "../harness.ts";
+
+describe("regression #7925: tool-call metadata is available when streaming starts", () => {
+	let harness: Harness | undefined;
+
+	afterEach(() => {
+		harness?.cleanup();
+	});
+
+	it("includes the tool call id and name without cumulative snapshots", async () => {
+		harness = await createHarness();
+		harness.setResponses([
+			fauxAssistantMessage(
+				fauxToolCall("write", { path: "output.txt", content: "x".repeat(100) }, { id: "call_7925" }),
+				{ stopReason: "toolUse" },
+			),
+			fauxAssistantMessage("done"),
+		]);
+
+		await harness.session.prompt("write a file");
+
+		const update = harness
+			.eventsOfType("message_update")
+			.find((event) => event.assistantMessageEvent.type === "toolcall_start");
+		if (!update || update.message.role !== "assistant") {
+			throw new Error("Expected toolcall_start assistant update");
+		}
+
+		expect(toJsonEvent(update)).toEqual({
+			type: "message_update",
+			usage: update.message.usage,
+			assistantMessageEvent: {
+				type: "toolcall_start",
+				contentIndex: 0,
+				id: "call_7925",
+				toolName: "write",
+			},
+		});
+	});
+});