perf(serve): keep the ACP spawn channel out of Managed Runtime workers (#16235)

The worker sizes media responses with DAEMON_ACP_NDJSON_LIMITS, which
managed-tool-media imported from acp-bridge's spawnChannel. That module
pulls in the ACP SDK schemas, the acp-bridge status module and, through
it, core's package root, so every resident worker loaded about 1.5 MiB
of modules for one constant.

Define the constant in the dependency-free ndJsonStream module,
re-export it from spawnChannel, and import it from there. On Linux
x86_64 an idle worker drops from 91.0 to 79.6 MiB of private memory and
from 215 to 175 loaded modules.

packages/acp-bridge/src/ndJsonStream.ts

@@ -62,6 +62,18 @@ export interface NdJsonStreamLimits {
   queueSaturationGraceMs?: number;
 }
 
+/**
+ * The daemon's ACP channel limits. Kept in this dependency-free module so a
+ * Managed Runtime worker can size media responses without loading the whole
+ * spawn channel; `spawnChannel` re-exports it.
+ */
+export const DAEMON_ACP_NDJSON_LIMITS: Readonly<NdJsonStreamLimits> =
+  Object.freeze({
+    maxFrameBytes: 64 * 1024 * 1024,
+    maxQueuedMessages: 256,
+    maxQueuedBytes: 64 * 1024 * 1024,
+  });
+
 export type NdJsonInboundMessageValidator = (message: AnyMessage) => boolean;
 
 export class NdJsonFrameTooLargeError extends Error {

packages/acp-bridge/src/spawnChannel.test.ts

@@ -66,6 +66,7 @@ import {
   getAcpMemoryArgs,
   scrubChildEnv,
 } from './spawnChannel.js';
+import { DAEMON_ACP_NDJSON_LIMITS as LEAF_DAEMON_ACP_NDJSON_LIMITS } from './ndJsonStream.js';
 
 function createFakeChildProcess(): ChildProcess {
   const child = Object.assign(new EventEmitter(), {
@@ -597,6 +598,13 @@ describe('createSpawnChannelFactory env policy', () => {
     });
   });
 
+  it('re-exports the daemon limits that Managed Runtime workers read from the leaf module', () => {
+    // Workers import the limits from ndJsonStream so they do not load this
+    // module; both names must stay one object.
+    expect(DAEMON_ACP_NDJSON_LIMITS).toBe(LEAF_DAEMON_ACP_NDJSON_LIMITS);
+    expect(Object.isFrozen(LEAF_DAEMON_ACP_NDJSON_LIMITS)).toBe(true);
+  });
+
   it('keeps the default factory unbounded and validates opt-in limits early', () => {
     expect(DAEMON_ACP_NDJSON_LIMITS).toEqual({
       maxFrameBytes: 64 * 1024 * 1024,

packages/acp-bridge/src/spawnChannel.ts

@@ -26,6 +26,7 @@ import type { ChannelFactory } from './channel.js';
 import { markChannelFactoryForwardsChildEnv } from './child-env-forwarding.js';
 import { redactLogCredentials } from './logRedaction.js';
 import {
+  DAEMON_ACP_NDJSON_LIMITS,
   NdJsonQueueLimitError,
   ndJsonStream,
   type NdJsonMessageObservation,
@@ -43,12 +44,7 @@ import { estimateJsonStringBytes } from './json-string-bytes.js';
 import { detectAvailableMemoryMb } from './daemon-memory-budget.js';
 
 let cachedMemoryArgs: string[] | undefined;
-export const DAEMON_ACP_NDJSON_LIMITS: Readonly<NdJsonStreamLimits> =
-  Object.freeze({
-    maxFrameBytes: 64 * 1024 * 1024,
-    maxQueuedMessages: 256,
-    maxQueuedBytes: 64 * 1024 * 1024,
-  });
+export { DAEMON_ACP_NDJSON_LIMITS };
 
 const daemonClientParamValidators = new Map<
   string,

packages/cli/src/acp-integration/managed-tool-media.ts

@@ -4,8 +4,12 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { hasBoundedJsonStructure } from '@qwen-code/acp-bridge/ndJsonStream';
-import { DAEMON_ACP_NDJSON_LIMITS } from '@qwen-code/acp-bridge/spawnChannel';
+// The leaf module, not spawnChannel: that one loads about 1.5 MiB of modules
+// into every Managed Runtime worker for this one constant.
+import {
+  DAEMON_ACP_NDJSON_LIMITS,
+  hasBoundedJsonStructure,
+} from '@qwen-code/acp-bridge/ndJsonStream';
 
 // Leave room for the JSON-RPC/HTTP envelopes without changing ACP capacity.
 export const MAX_MANAGED_MEDIA_RESPONSE_BYTES =