fix(nodes): preserve falsy event payloads

src/gateway/node-registry.test.ts

@@ -493,8 +493,16 @@ describe("gateway/node-registry", () => {
     const frames: string[] = [];
     registry.register(makeClient("conn-1", "node-1", frames), {});
     const payload = serializeEventPayload({ foo: "bar" });
+    const nullPayload = serializeEventPayload(null);
+    const falsePayload = serializeEventPayload(false);
+    const zeroPayload = serializeEventPayload(0);
+    const emptyStringPayload = serializeEventPayload("");
 
     expect(registry.sendEventRaw("node-1", "chat", payload)).toBe(true);
+    expect(registry.sendEventRaw("node-1", "nullish", nullPayload)).toBe(true);
+    expect(registry.sendEventRaw("node-1", "flag", falsePayload)).toBe(true);
+    expect(registry.sendEventRaw("node-1", "count", zeroPayload)).toBe(true);
+    expect(registry.sendEventRaw("node-1", "empty", emptyStringPayload)).toBe(true);
     expect(registry.sendEventRaw("missing-node", "chat", payload)).toBe(false);
     expect(registry.sendEventRaw("node-1", "heartbeat", null)).toBe(true);
     expect(
@@ -514,6 +522,10 @@ describe("gateway/node-registry", () => {
 
     expect(frames).toEqual([
       '{"type":"event","event":"chat","payload":{"foo":"bar"}}',
+      '{"type":"event","event":"nullish","payload":null}',
+      '{"type":"event","event":"flag","payload":false}',
+      '{"type":"event","event":"count","payload":0}',
+      '{"type":"event","event":"empty","payload":""}',
       '{"type":"event","event":"heartbeat"}',
     ]);
   });

src/gateway/node-registry.ts

@@ -88,7 +88,7 @@ export type SerializedEventPayload = {
 };
 
 export function serializeEventPayload(payload: unknown): SerializedEventPayload | null {
-  if (!payload) {
+  if (payload === undefined) {
     return null;
   }
   const json = JSON.stringify(payload);

src/node-host/invoke.sanitize-env.test.ts

@@ -2,7 +2,7 @@ import { describe, expect, it } from "vitest";
 import { parseWindowsCodePage } from "../infra/windows-encoding.js";
 import { withEnv } from "../test-utils/env.js";
 import { decodeCapturedOutputBuffer, sanitizeEnv } from "./invoke.js";
-import { buildNodeInvokeResultParams } from "./runner.js";
+import { buildNodeEventParams, buildNodeInvokeResultParams } from "./runner.js";
 
 describe("node-host sanitizeEnv", () => {
   it("ignores PATH overrides", () => {
@@ -121,3 +121,28 @@ describe("buildNodeInvokeResultParams", () => {
     expect(params.payload).toEqual({ reason: "bad" });
   });
 });
+
+describe("buildNodeEventParams", () => {
+  it("serializes explicit falsy event payloads", () => {
+    expect(buildNodeEventParams("node.test", undefined)).toEqual({
+      event: "node.test",
+      payloadJSON: null,
+    });
+    expect(buildNodeEventParams("node.test", null)).toEqual({
+      event: "node.test",
+      payloadJSON: "null",
+    });
+    expect(buildNodeEventParams("node.test", false)).toEqual({
+      event: "node.test",
+      payloadJSON: "false",
+    });
+    expect(buildNodeEventParams("node.test", 0)).toEqual({
+      event: "node.test",
+      payloadJSON: "0",
+    });
+    expect(buildNodeEventParams("node.test", "")).toEqual({
+      event: "node.test",
+      payloadJSON: '""',
+    });
+  });
+});

src/node-host/invoke.ts

@@ -618,12 +618,20 @@ export function buildNodeInvokeResultParams(
   return params;
 }
 
+export function buildNodeEventParams(
+  event: string,
+  payload: unknown,
+): { event: string; payloadJSON: string | null } {
+  const payloadJSON = payload === undefined ? undefined : JSON.stringify(payload);
+  return {
+    event,
+    payloadJSON: typeof payloadJSON === "string" ? payloadJSON : null,
+  };
+}
+
 async function sendNodeEvent(client: GatewayClient, event: string, payload: unknown) {
   try {
-    await client.request("node.event", {
-      event,
-      payloadJSON: payload ? JSON.stringify(payload) : null,
-    });
+    await client.request("node.event", buildNodeEventParams(event, payload));
   } catch {
     // ignore: node events are best-effort
   }

src/node-host/runner.ts

@@ -28,6 +28,7 @@ import {
 } from "./plugin-node-host.js";
 
 export { buildNodeInvokeResultParams };
+export { buildNodeEventParams } from "./invoke.js";
 
 type NodeHostRunOptions = {
   gatewayHost: string;