Preview a Berkshire holdings watchlist

TL;DR

Berkshire's reported Apple holding value rose 6.44% between December 2025 and June 2026, while its share count stayed at 227,917,808. Higher dollar value did not mean it bought more shares. The guide previews a holdings watchlist tied to Berkshire's manager CIK and delayed public filings. Validation passed, but no list was saved or refreshed. Review the draft and verify an actual refresh before treating the watchlist as maintained.

Higher holding value did not mean Berkshire bought more Apple

The two original 13F tables have the same Apple share count. Reported value rose 6.44%; share change was 0%. This is a concrete counterexample to treating higher reported dollar holdings as a purchase signal.

Sum distinct manager rows for the same issuer/class before comparing periods. The later filing was accepted August 14 at 16:05:04; the retained NexusTrade snapshot uses August 15 as its public-availability boundary. The June 30 holding was not public on June 30. This covers disclosed 13F positions, not Berkshire's complete current portfolio, trade dates or cost basis.

Preview the exact maintained-list definition

The copied draft explains the source and notification choices and requests validation. Inspect all returned issues before saving or starting maintenance.

Define the maintained list separately from the source observation

The template follows holdings publicly available from manager CIK 0001067983. The retained October 10 snapshot contains 29 positions and $299,253,556,246 reported value. The producer preview validated; it was not saved, deployed or refreshed in that recorded example.

1. Evidence result

   A source record and a valid configuration establish what can be followed. They do not establish a maintained list's contents or investment performance.

2. After creation

   Verify the returned producer and list identity, compare as-of contents with source availability, and inspect the first actual refresh before treating the list as maintained.

Start with the public filing, not a manager’s name

This example follows Berkshire manager CIK 1067983 with a 365-day availability window. It uses the latest complete publicly available equity book. A company name search can find the wrong filer; the manager CIK binds the source.

What the public product actually shows

Read on October 10, 2026: Berkshire’s June 30, 2026 filing has an August 15 availability boundary in this NexusTrade snapshot; the original SEC filing date is August 14. NexusTrade shows 29 reported positions worth $299,253,556,246. Apple accounts for $65,950,296,923, American Express $51,282,319,275 and Coca-Cola $32,508,000,000. Values are reported US dollars; share amounts are a different field.

These are delayed reported positions, not a live brokerage account. The 29 positions are not necessarily 29 companies or 29 managed-list members: share classes and eligibility matter. The public page records one effective filing, no unresolved ticker positions and no put/call positions for this snapshot.

Preview the complete producer before saving

Copy this entire JSON into watchlist-draft.json. The strategy wrapper is name plus action; UpdateWatchlist takes no condition because it refreshes on each portfolio tick. initialValue is zero because this portfolio maintains a research list rather than allocating capital. The output starts with in-app membership alerts enabled, email off and Aurora briefs off.

In your connected MCP client, call build_portfolio with this exact object. Continue only when valid is true and issues is empty. Both published examples passed that real preview. build_portfolio saves nothing and does not invoke a text model; its validation receipt is not a quote for maintaining a deployed portfolio. Review account limits and any displayed plan or compute charge before activation.

{
  "name": "Public guide preview - institutional watchlist",
  "initialValue": 0,
  "strategies": [
    {
      "name": "Maintain berkshire-equities",
      "action": {
        "type": "UpdateWatchlist",
        "watchlistKey": "berkshire-equities",
        "source": {
          "type": "InstitutionalHoldings",
          "managerCik": "1067983",
          "windowDays": 365
        },
        "output": {
          "name": "Berkshire disclosed equities",
          "purpose": "Review the latest complete public equity filing; compare reporting and availability dates.",
          "alertSettings": {
            "onChange": true,
            "inApp": true,
            "email": false,
            "briefCadence": "never"
          }
        }
      }
    }
  ],
  "supportsCrypto": false,
  "alertsEnabled": false
}

Save once, then read the saved draft

Install the Python SDK and configure its documented account authentication first. This code saves the complete JSON as a chat draft and reads it back. Keep the same idempotency key when recovering an uncertain response; change the key only for a deliberately new draft. Saving does not create a running managed list.

import json
from pathlib import Path
from nexustrade import NexusTradeClient

client = NexusTradeClient.from_environment()
# Copy this complete JSON unchanged into watchlist-draft.json.
draft = json.loads(Path("watchlist-draft.json").read_text())
# Saving creates a chat draft, not a running paper producer.
saved = client.create_portfolio(
    draft, idempotency_key="managed-institutional-guide-v1"
)
chat_id = saved["portfolioId"]
readback = client.get_portfolio(chat_id)
assert readback["type"] == "chat"
assert readback["isActive"] is False
assert readback["strategies"][0]["action"]["source"] == draft["strategies"][0]["action"]["source"]
print(json.dumps(readback, indent=2))
# Stop here. Review the saved draft before deciding to deploy.

Start maintenance only after reviewing the draft

No successful membership refresh recorded yet is an unconfirmed output, not a completed empty list. Portfolio needs attention or Portfolio status unavailable means inspect the producer. Coverage failure blocks new allocation rather than claiming a partial book is complete. The guide’s validation run stopped before saving or activation; these are instructions for your explicitly chosen continuation.

Review changes, pause safely and recover

A later DynamicRebalance consumer can use the committed list, but it introduces allocation rules and needs its own review. Backtests keep membership within the historical run; they do not publish the account’s durable watchlist. Subsequent edits to the list name, purpose and notifications remain authoritative.

Recorded illustrations

Continue exploring