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.ts

@@ -33,6 +33,8 @@ export const MODEL_BRIDGE_LIMITS = {
 } as const
 
 export const MODEL_BRIDGE_PROTOCOL = 'goodbuddy-model-bridge-v1' as const
+export const MODEL_BRIDGE_OPTIONAL_LIMITS_CAPABILITY =
+  'runtime/model-bridge-optional-limits' as const
 
 export const modelBridgeModelProtocolSchema = z.enum([
   'anthropic-messages',
@@ -131,12 +133,13 @@ export const agentPromptModelProfileSchema = z
       .strict(),
     limits: z
       .object({
-        maximumOutputTokens: z.number().int().min(1).max(1_000_000),
+        maximumOutputTokens: z.number().int().positive().safe().optional(),
         requestTimeoutMilliseconds: z
           .number()
           .int()
           .min(1)
-          .max(300_000)
+          .max(0x7fff_ffff)
+          .optional()
       })
       .strict()
   })
@@ -385,6 +388,45 @@ export type ModelBridgeDecodeOptions = {
   maximumMessageBytes?: number
 }
 
+// Keep the released v1 bytes unchanged, including for single-frame peers.
+export class ModelBridgeMessageBuffer {
+  #chunks: Uint8Array[] = []
+  #bytes = 0
+  #depth = 0
+  #inString = false
+  #escaped = false
+
+  push(chunk: Uint8Array): Uint8Array | undefined {
+    this.#bytes += chunk.byteLength
+    if (this.#bytes > MODEL_BRIDGE_LIMITS.maximumMessageBytes) {
+      this.clear()
+      throw new ModelBridgeCodecError('oversized', 'Model bridge message exceeds its byte limit')
+    }
+    this.#chunks.push(chunk)
+    for (const byte of chunk) {
+      if (this.#inString) {
+        if (this.#escaped) this.#escaped = false
+        else if (byte === 92) this.#escaped = true
+        else if (byte === 34) this.#inString = false
+      } else if (byte === 34) this.#inString = true
+      else if (byte === 123 || byte === 91) this.#depth += 1
+      else if (byte === 125 || byte === 93) this.#depth -= 1
+    }
+    if (this.#inString || this.#depth > 0) return undefined
+    const payload = Buffer.concat(this.#chunks, this.#bytes)
+    this.clear()
+    return payload
+  }
+
+  clear(): void {
+    this.#chunks = []
+    this.#bytes = 0
+    this.#depth = 0
+    this.#inString = false
+    this.#escaped = false
+  }
+}
+
 export async function decodeModelBridgeMessage(
   input: Uint8Array,
   options: ModelBridgeDecodeOptions = {}