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/shared/model-bridge-contracts.test.ts

@@ -1,8 +1,10 @@
 import { describe, expect, it } from 'vitest'
+import { canonicalJson } from './agent-protocol/canonical'
 import {
   MODEL_BRIDGE_LIMITS,
   MODEL_BRIDGE_PROTOCOL,
   ModelBridgeCodecError,
+  ModelBridgeMessageBuffer,
   createModelBridgeRequestMessage,
   decodeModelBridgeMessage,
   digestModelBridgeRequest,
@@ -46,6 +48,31 @@ const request = {
 } as const
 
 describe('model bridge contracts and codec', () => {
+  it('preserves released v1 canonical bytes and accepts a released single-frame message immediately', async () => {
+    const message = await createModelBridgeRequestMessage({ identity, policy, request })
+    const released = Buffer.from(canonicalJson(message))
+    expect(Buffer.from(await encodeModelBridgeMessage(message))).toEqual(released)
+    const buffer = new ModelBridgeMessageBuffer()
+    await expect(decodeModelBridgeMessage(buffer.push(released)!)).resolves.toEqual(message)
+    await expect(decodeModelBridgeMessage(Buffer.concat([released, Buffer.from('\n')]))).rejects.toMatchObject({ code: 'invalid-message' })
+  })
+
+  it('reassembles v1 across arbitrary frame boundaries including escaped strings and resets for the ACK', async () => {
+    const message = modelBridgeErrorMessageSchema.parse({
+      protocol: MODEL_BRIDGE_PROTOCOL, kind: 'error', identity,
+      requestDigest: await digestModelBridgeRequest(request),
+      error: { code: 'test', message: 'nested { [ \\"quoted\\" ] } and \\ slash', retryable: false, poisoned: false, outcomeUnknown: false }
+    })
+    const bytes = await encodeModelBridgeMessage(message)
+    const buffer = new ModelBridgeMessageBuffer()
+    for (let index = 0; index < bytes.length - 1; index += 1) {
+      expect(buffer.push(bytes.subarray(index, index + 1))).toBeUndefined()
+    }
+    await expect(decodeModelBridgeMessage(buffer.push(bytes.subarray(-1))!)).resolves.toEqual(message)
+    const ack = { protocol: MODEL_BRIDGE_PROTOCOL, kind: 'response-delivered', identity, requestDigest: message.requestDigest }
+    await expect(decodeModelBridgeMessage(buffer.push(await encodeModelBridgeMessage(ack))!)).resolves.toEqual(ack)
+  })
+
   it('round trips one bounded request message with an exact digest', async () => {
     const message = await createModelBridgeRequestMessage({
       identity,
@@ -226,4 +253,4 @@ describe('model bridge contracts and codec', () => {
       })
     ).rejects.toThrow()
   })
-})
+})