feat(stream): make SSE maxEventSize configurable end-to-end

packages/appkit/src/plugin/plugin.ts

@@ -251,7 +251,7 @@ export abstract class Plugin<
       config.name ??
       (this.constructor as { manifest?: { name: string } }).manifest?.name ??
       "plugin";
-    this.streamManager = new StreamManager();
+    this.streamManager = new StreamManager(config.streamConfig);
     this.app = new AppManager();
     this.devFileReader = DevFileReader.getInstance();
     this.context = (config as Record<string, unknown>).context as

packages/appkit/src/plugin/tests/plugin.test.ts

@@ -261,6 +261,19 @@ describe("Plugin", () => {
       expect(AppManager).toHaveBeenCalledTimes(1);
       expect(StreamManager).toHaveBeenCalledTimes(1);
     });
+
+    test("should forward streamConfig to the StreamManager", () => {
+      const streamConfig = { maxEventSize: 20 * 1024 * 1024 };
+      new TestPlugin({ ...config, streamConfig });
+
+      expect(StreamManager).toHaveBeenCalledWith(streamConfig);
+    });
+
+    test("should construct the StreamManager with defaults when no streamConfig", () => {
+      new TestPlugin(config);
+
+      expect(StreamManager).toHaveBeenCalledWith(undefined);
+    });
   });
 
   describe("setup", () => {

packages/shared/src/plugin.ts

@@ -1,6 +1,7 @@
 import type express from "express";
 import type { JSONSchema7 } from "json-schema";
 
+import type { StreamConfig } from "./execute";
 import type {
   DiscoveryDescriptor,
   PluginManifest as GeneratedPluginManifest,
@@ -72,6 +73,14 @@ export interface BasePluginConfig {
    * @default true for all telemetry types
    */
   telemetry?: TelemetryOptions;
+
+  /**
+   * SSE stream configuration for this plugin's `executeStream()` calls (buffer
+   * sizes, `maxEventSize`, TTL, heartbeat). Sets the plugin's StreamManager
+   * defaults; a per-call `stream` config still overrides these. Use it to raise
+   * `maxEventSize` above the 5 MiB default when a stream emits larger events.
+   */
+  streamConfig?: StreamConfig;
 }
 
 export type TelemetryOptions =