Senator Investment Group LP ATI — ATI INC

Ownership history in Senator Investment Group LP  ·  9 quarters on record

AI Ownership Summary

Senator Investment Group LP reported ATI INC (ATI) in 9 quarterly 13F filings from 2024 Q1 through 2026 Q1. Peak portfolio weight reached 3.35% in 2025 Q1. The latest visible filing shows ATI at 0.97% of the fund.

This page tracks quarterly shares, estimated market value, portfolio weight, filing dates, and disclosure-aligned stock prices directly from SEC EDGAR 13F filings.

What this ATI ownership page tells you

This page is designed to answer the real investor question behind a 13F filing: how meaningful was Senator Investment Group LP's position in ATI INC, and how did that conviction change over time? You can read the holding window, peak weight, latest reported size, disclosure timing, and quarter-by-quarter changes without piecing the story together from raw SEC rows.

Freshest filing
Latest Reported Filing
2026 Q1

ATI was reported at 0.97% of portfolio in the most recent visible filing.

High-water mark
Peak Conviction
3.35% in 2025 Q1

Peak weight helps separate a token disclosure from a real conviction holding the fund genuinely cared about.

Time in book
Holding Window
2024 Q1 to 2026 Q1

Longer holding windows often tell a very different story from short-lived tactical trades or one-quarter experiments.

Decision context
Why It Matters
Position size beats headlines

Knowing that a fund owned a stock is useful. Knowing whether it was a 0.20% placeholder or a true high-conviction position is where the signal actually starts.

ATI stock page Senator Investment Group LP fund profile Senator Investment Group LP full holdings
How Senator Investment Group LP held ATI — position size vs. price
% of Fund (quarterly)    ATI price (quarter-end, indexed to 100)    SPY (indexed to 100)    QQQ (indexed to 100)
📋 Quarterly Holdings History 9 quarters  ▾
Quarter Action Sold % After 3M Timing Shares Change Chg % % of Fund Mkt Value Filed Price (Filed)
2026 Q1 REDUCED — — — 145,000 -180,000 -55.4% 0.97% $21.1M 2026-05-13 $164.83
2025 Q4 UNCHANGED — — — 325,000 — 0% 1.50% $37.3M 2026-02-13 $143.93
2025 Q3 REDUCED 56.7% +43.4% ❌ 325,000 -425,000 -56.7% 0.98% $26.4M 2025-11-14 $99.37
2025 Q2 REDUCED 38.1% -8.2% ✅ 750,000 -462,500 -38.1% 2.50% $64.8M 2025-08-13 $75.32
2025 Q1 ADDED — — — 1,212,500 +493,944 +68.7% 3.35% $63.1M 2025-05-14 $75.07
2024 Q4 ADDED — — — 718,556 +28,556 +4.1% 1.16% $39.5M 2025-02-13 $61.23
2024 Q3 REDUCED 22.6% -18.0% ✅ 690,000 -201,138 -22.6% 2.19% $46.2M 2024-11-13 $58.37
2024 Q2 ADDED — — — 891,138 +558,138 +167.6% 2.41% $49.4M 2024-08-20 $63.41
2024 Q1 INITIATED — — — 333,000 — — 0.78% $17.0M 2024-05-14 $60.36

🏢 Other funds also holding ATI

As of 2026 Q1 — sorted by position size

DENDUR CAPITAL LP 3Y 13.68% Square Wave Capital, LLC 12.89% FACT Capital, LP 3Y 9.97% Mountaineer Partners Management, LLC 3Y 7Y 6.63% H Squared Management LP 4.85% BOWEN HANES & CO INC 3Y 7Y 3.69% Expect Equity LLC 3.62% Candelo Capital Management LP 3.38% KLCM Advisors, Inc. 3Y 7Y 3.23% S SQUARED TECHNOLOGY, LLC 3Y 7Y 3.03%

FAQ About Senator Investment Group LP and ATI

These are the practical questions this page is built to answer before you even open the full history table.

How long has Senator Investment Group LP reported owning ATI?

Senator Investment Group LP reported ATI across 9 quarterly 13F filings, from 2024 Q1 through 2026 Q1.

What was the largest reported ATI position in Senator Investment Group LP's portfolio?

The largest reported portfolio weight for ATI was 3.35% in 2025 Q1.

What is the latest reported ATI position on this page?

The most recent filing on this page is 2026 Q1, when Senator Investment Group LP reported 145,000 shares, equal to 0.97% of portfolio, with an estimated market value of $21.1M.

What does the chart on this ATI ownership page compare?

The chart compares Senator Investment Group LP's quarterly ATI portfolio weight with the stock's indexed share price, so you can see whether the fund was building, trimming, or holding the position as price moved.

How well did Senator Investment Group LP time their ATI position?

Based on 13F filing dates vs. subsequent ATI price moves, Senator Investment Group LP correctly timed 3 out of 7 reported position changes (43%). The annualised alpha on ATI relative to SPY over the holding period was +37.2%.

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