fix(runtime): guard pi stream setup failures

tests/unit/pi-safe-stream.test.ts

@@ -0,0 +1,94 @@
+import {
+  createAssistantMessageEventStream,
+  type AssistantMessage,
+  type AssistantMessageEvent,
+  type Context,
+  type Model,
+} from "@mariozechner/pi-ai";
+import { describe, expect, it } from "vitest";
+import { createSafePiStream } from "../../src/main/worker/runtime/pi-safe-stream";
+
+function createModel(): Model<"openai-responses"> {
+  return {
+    id: "mock",
+    name: "mock",
+    api: "openai-responses",
+    provider: "openai",
+    baseUrl: "https://example.invalid",
+    reasoning: false,
+    input: ["text"],
+    cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+    contextWindow: 8192,
+    maxTokens: 2048,
+  };
+}
+
+function createAssistantMessage(): AssistantMessage {
+  return {
+    role: "assistant",
+    content: [{ type: "text", text: "done" }],
+    api: "openai-responses",
+    provider: "openai",
+    model: "mock",
+    usage: {
+      input: 1,
+      output: 1,
+      cacheRead: 0,
+      cacheWrite: 0,
+      totalTokens: 2,
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+    },
+    stopReason: "stop",
+    timestamp: Date.now(),
+  };
+}
+
+const emptyContext: Context = { messages: [] };
+
+describe("pi safe stream", () => {
+  it("forwards successful stream events", async () => {
+    const safeStream = createSafePiStream(() => {
+      const stream = createAssistantMessageEventStream();
+      queueMicrotask(() => {
+        const message = createAssistantMessage();
+        stream.push({ type: "done", reason: "stop", message });
+        stream.end(message);
+      });
+      return stream;
+    });
+
+    const stream = safeStream(createModel(), emptyContext);
+    const events: AssistantMessageEvent[] = [];
+    for await (const event of stream) {
+      events.push(event);
+    }
+
+    expect(events.map((event) => event.type)).toEqual(["done"]);
+    await expect(stream.result()).resolves.toMatchObject({ stopReason: "stop" });
+  });
+
+  it("turns rejected stream setup into an error event", async () => {
+    const safeStream = createSafePiStream(async () => {
+      throw new Error("stream setup failed");
+    });
+
+    const stream = safeStream(createModel(), emptyContext);
+    const events: AssistantMessageEvent[] = [];
+    for await (const event of stream) {
+      events.push(event);
+    }
+    const result = await stream.result();
+
+    expect(events).toHaveLength(1);
+    expect(events[0]).toMatchObject({
+      type: "error",
+      reason: "error",
+      error: {
+        stopReason: "error",
+        errorMessage: "stream setup failed",
+      },
+    });
+    expect(result.stopReason).toBe("error");
+    expect(result.errorMessage).toBe("stream setup failed");
+  });
+});