fix: remove avoidable model runtime limits

Preserve long histories and parsed attachments, expose paged process and Subagent output, isolate MCP discovery failures, and expand browser snapshots and knowledge result selection. Remove fixed Harness output and updated remote Runtime duration limits.

Keep released Agent profile and v1 bridge compatibility while enabling larger framed exchanges and optional limits for updated peers. Document remote coverage requirements and real-model boundary validation.

Release note: Long model tasks can retain more context and continue reading complete tool output; remote execution preserves compatibility with released Agents. Updated remote limits require an updated Agent and Runtime bundle.

src/main/remote-agent/main-model-bridge-session.ts

@@ -1,7 +1,9 @@
 import { isDeepStrictEqual } from 'node:util'
+import { AGENT_PROTOCOL_LIMITS } from '../../shared/agent-protocol/contracts'
 import {
   MODEL_BRIDGE_LIMITS,
   MODEL_BRIDGE_PROTOCOL,
+  ModelBridgeMessageBuffer,
   decodeModelBridgeMessage,
   encodeModelBridgeMessage,
   modelBridgeErrorMessageSchema,
@@ -22,7 +24,6 @@ import {
   type MainModelBridgePoison
 } from './main-model-bridge-dispatcher'
 
-const DEFAULT_REQUEST_TIMEOUT_MS = 180_000
 const DEFAULT_CLOSE_TIMEOUT_MS = 2_000
 
 export type MainModelBridgeSessionIdentity = {
@@ -73,7 +74,7 @@ export class MainModelBridgeSession {
   readonly #onDelivered: MainModelBridgeDelivered
   readonly #finalizePrompt: MainModelBridgeFinalizePrompt
   readonly #poisonCallback: MainModelBridgePoison
-  readonly #requestTimeoutMs: number
+  readonly #requestTimeoutMs: number | undefined
   readonly #closeTimeoutMs: number
   readonly #lifetime = new AbortController()
   readonly #closedResolve: (
@@ -100,10 +101,9 @@ export class MainModelBridgeSession {
     this.#onDelivered = options.onDelivered
     this.#finalizePrompt = options.finalizePrompt
     this.#poisonCallback = options.poison
-    this.#requestTimeoutMs = boundedTimeout(
-      options.requestTimeoutMs,
-      DEFAULT_REQUEST_TIMEOUT_MS
-    )
+    this.#requestTimeoutMs = options.requestTimeoutMs === undefined
+      ? undefined
+      : boundedTimeout(options.requestTimeoutMs, options.requestTimeoutMs)
     this.#closeTimeoutMs = boundedTimeout(
       options.closeTimeoutMs,
       DEFAULT_CLOSE_TIMEOUT_MS
@@ -173,7 +173,7 @@ export class MainModelBridgeSession {
 
         this.#active = { request, phase: 'dispatching' }
         const controller = new AbortController()
-        const timeout = setTimeout(() => {
+        const timeout = this.#requestTimeoutMs === undefined ? undefined : setTimeout(() => {
           controller.abort(
             new DOMException(
               'Remote model bridge request timed out',
@@ -181,7 +181,7 @@ export class MainModelBridgeSession {
             )
           )
         }, this.#requestTimeoutMs)
-        timeout.unref?.()
+        timeout?.unref?.()
         const abort = (): void => controller.abort(this.#lifetime.signal.reason)
         this.#lifetime.signal.addEventListener('abort', abort, {
           once: true
@@ -302,25 +302,33 @@ export class MainModelBridgeSession {
     expectedIdentity?: ModelBridgeIdentity,
     expectedRequestDigest?: string
   ) {
-    const frame = await this.#channel.receive(this.#lifetime.signal)
-    if (expectedIdentity === undefined) {
-      this.#receivingRequest = true
-    }
-    try {
-      this.#assertCurrent()
-      const message = await decodeModelBridgeMessage(frame.payload, {
-        expectedIdentity,
-        expectedRequestDigest,
-        maximumMessageBytes: MODEL_BRIDGE_LIMITS.maximumMessageBytes
-      })
-      await frame.consume()
+    const buffer = new ModelBridgeMessageBuffer()
+    while (true) {
+      const frame = await this.#channel.receive(this.#lifetime.signal)
       if (expectedIdentity === undefined) {
-        this.#receivingRequest = false
+        this.#receivingRequest = true
+      }
+      try {
+        this.#assertCurrent()
+        const payload = buffer.push(frame.payload)
+        if (payload === undefined) {
+          await frame.consume()
+          continue
+        }
+        const message = await decodeModelBridgeMessage(payload, {
+          expectedIdentity,
+          expectedRequestDigest,
+          maximumMessageBytes: MODEL_BRIDGE_LIMITS.maximumMessageBytes
+        })
+        await frame.consume()
+        if (expectedIdentity === undefined) {
+          this.#receivingRequest = false
+        }
+        return message
+      } catch (error) {
+        await frame.consume().catch(() => undefined)
+        throw error
       }
-      return message
-    } catch (error) {
-      await frame.consume().catch(() => undefined)
-      throw error
     }
   }
 
@@ -369,7 +377,13 @@ export class MainModelBridgeSession {
   ): Promise<void> {
     const payload = await encodeModelBridgeMessage(message)
     this.#assertCurrent()
-    await this.#channel.send(payload, signal)
+    for (let offset = 0; offset < payload.byteLength; offset += AGENT_PROTOCOL_LIMITS.maximumBlobFrameBytes) {
+      this.#assertCurrent()
+      await this.#channel.send(
+        payload.subarray(offset, offset + AGENT_PROTOCOL_LIMITS.maximumBlobFrameBytes),
+        signal
+      )
+    }
   }
 
   #assertCurrent(): void {
@@ -529,7 +543,7 @@ function boundedTimeout(
   if (
     !Number.isSafeInteger(timeout) ||
     timeout < 1 ||
-    timeout > 300_000
+    timeout > 0x7fff_ffff
   ) {
     throw new RangeError('Model bridge timeout is invalid')
   }