LatticeworkTHE EVIDENCE DESK
Decision record· ADD · Q2 2026

Baupost Group increased AMZN by 20%. Was it still actionable?

The filing established that Baupost Group increased AMZN shares by 20.0%. It did not reveal transaction dates, execution prices, or the manager's reason for the change.

Share𝕏in

Latticework verdict

Context, not a trade alert

High-conviction increase. Low timing precision.

A 16.5% reported portfolio weight makes this increase material. Pattern: sustained build. But the disclosed change could have occurred anywhere in the quarter and was published 44 days after quarter end, making it 44–134 days old at disclosure. Use it to investigate the thesis, not to copy an entry or exit.

Inspect the original SEC filing ↗See the disclosure delay ↓

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Reported shares
+20.0%
+625,100
Portfolio weight
16.5%
from 12.7%
Quarter-end value
$892M
not purchase cost
Signal age
44–134d
when disclosed

What the clock tells us

Apr 1, 2026

Change window opens

The net change could begin here—or later.

Jun 30, 2026

Quarter-end snapshot

The filing measures shares and fair value on this date.

Aug 13, 2026

Public disclosure

The snapshot arrived 44 days after quarter end.

The filing does not identify transaction dates inside the Apr 1, 2026–Jun 30, 2026 change window.

What we know

  • Shares: 3,118,754 → 3,743,854, a net increase of 625,100.
  • Weight: AMZN moved from 12.7% to 16.5% of Baupost Group's reported long U.S. equity book.
  • Pattern: Reported shares rose in 3 consecutive observed quarters. Reported weight path: 2022Q3 0.5% → 2022Q4 1.4% → 2023Q2 2.2% → 2025Q4 9.3% → 2026Q1 12.7% → 2026Q2 16.5%.
  • Valuation snapshot: the filing implies $238.34 per share at quarter end. That is reported fair value, not Baupost Group's entry price.

Decision test

Meaningful?Yes
Large share change and material book weight. Pattern: sustained build.
Timely?No
The information was 44–134 days old at publication.
Corroborated?Mixed
8 material buy/add and 8 trim/exit signals across the cohort.
Copyable?No
No trade dates, cost basis, rationale, or manager-specific constraints.

Source versions and follow-through

What was recorded, and when?

First registered 2026-09-07 · source version 1, recorded 2026-09-07. The source filing was public on 2026-08-13; registration here happened separately.

Prospective observation · tracking

This version's clock begins at the first shared market close strictly after 2026-09-07. The filing date alone cannot backdate a selection. Earlier post-filing returns remain in the retrospective tracker below.

-2.1% stock · 0.7% SPY · -2.9 percentage points vs SPY · 2026-09-08–2026-10-02 (19 closes).

Inspect source versions and corrections (1)

  1. Version 1 · 2026-09-07

    First prospective registration; earlier filing returns remain retrospective.

    ADD · 12.70% before → 16.48% after.

    Original SEC source ↗

    Source snapshot SHA-256 8fc209fc2bc89af4f78aa9478ba9f1000e444b16991be60d7e9edc21b012844c

30 dated prospective observations retained. Source changes restart the revised claim's clock; previous versions and observations stay in the registry.

Download the source and observation registry

Registration versions are retained in this project's history, not certified by an independent timestamp authority. This is an editorial sample with overlapping stocks, not a prediction or a manager portfolio backtest.

Retrospective outcome tracker · tracking

What happened after disclosure?

35 sessions · through Oct 2, 2026

Measured from the first shared market close after the SEC filing—not from the manager's unknown entry or exit price.

AMZN
-4.2%
SPY
-0.6%
Vs SPY
-3.6%

The disclosed direction is not supported so far.

Early performance can reverse. This is observation, not a verdict on the manager or the security.

The cohort did not move as one

Tracked managers disclosed 8 material buy/add signals and 8 trim/exit signals in AMZN. Quarter-end cohort ownership moved from 35 to 32. This was disagreement, not consensus.

Source trail and limits

Original SEC filing ↗Full Q2 2026 diff →AMZN researchBaupost Group portfolio →Outcome prices ↗
  • A 13F reports quarter-end holdings, not transaction dates or execution prices.
  • The net share change may represent multiple purchases and sales during the quarter.
  • Portfolio weight covers Baupost Group's disclosed long U.S. 13F book, not its full assets or exposures.
  • Quarter-end value per share is reported fair value divided by shares; it is not the manager's cost basis.

SEC accession 0001061768-26-000010 · CUSIP 023135106

Primary-source research, not investment advice.