U.S. spot bitcoin ETFs absorbed $2.4 billion in net inflows during the week ending Sept. 25, the largest weekly haul since October 2025 and enough to flip year-to-date flows positive for 2026, according to The Block's analysis of SoSoValue data.

The 12 publicly traded products had sat roughly $5.8 billion in the red as recently as July 13. Last week's surge left the cohort about $934.1 million in the green for the year. Year-to-date flows turned positive on Tuesday.

The prior larger week ended Oct. 10, 2025, when bitcoin ETFs drew $2.7 billion as the asset reached a then-record price of $126,296.

What drove the reversal?

Bloomberg ETF analyst Eric Balchunas pointed to macro drivers in a Wednesday post on X, tying the "$4.6b tsunami of cash" to the Treasury Department's plan to increase buybacks of long-dated bonds.

Nate Geraci, president of NovaDius Wealth Management, wrote in a Saturday post that the bitcoin funds have taken in $5.3 billion since the Treasury first announced the buybacks. "Monday's $1bil inflow was 9th largest ever," Geraci said.

How were the daily flows distributed?

Monday carried the bulk of the week's inflow. The 12 funds absorbed $999.0 million on day one, their largest daily inflow since Oct. 6, 2025 and the ninth-largest single session since the products launched in January 2024.

Inflows then declined every session afterward: $714.7 million Tuesday, $347.0 million Wednesday, $190.6 million Thursday and $134.5 million Friday. Friday marked the funds' seventh straight day of inflows, a $3.0 billion streak that began Sept. 17.

Which issuers led?

BlackRock's IBIT, the AUM frontrunner, drew $1.2 billion for the week. That marked its second-largest weekly total since October 2025, behind only the $1.3 billion it absorbed in the week ending Aug. 21.

Fidelity's FBTC added $701.7 million, its strongest week since the week of Sept. 8, 2025. Ark and 21Shares' ARKB took in $294.7 million, almost all on Monday.

Morgan Stanley's MSBT logged $203.3 million, its biggest week since its April launch. The fund's prior weekly high was $71.1 million, set in mid-April.

What is the state of the market now?

Cumulative net inflows since the products' January 2024 launch stand at $57.6 billion, with net assets totaling $108.4 billion as of Friday. Weekly trading volume fell to $15.0 billion from $16.2 billion the prior week, per The Block.

Ether funds also recover

Spot ether ETFs drew $689.9 million over the same stretch, reversing the prior week's $140.0 million in outflows.

BlackRock's ETHA led with $326.2 million, followed by Fidelity's FETH at $174.0 million and Grayscale's Ethereum Mini Trust at $100.3 million. BlackRock's ETHB added $47.5 million, including $31.9 million on Friday.

The ether funds' weekly total was the largest since the week ending Aug. 28, when they absorbed $824.4 million. Year-to-date inflows now sit at roughly $1.6 billion, with $17.8 billion in net assets and $13.9 billion in cumulative inflows since launch. Ether ETF trading volume dropped to $4.8 billion from $6.9 billion the prior week.

Solana and other altcoin funds

U.S. spot Solana ETFs pulled in $86.7 million on Friday, their largest single day since the products launched in late October 2025. Bitwise's BSOL accounted for $55.7 million of that figure.

The Solana cohort drew $188.2 million for the week, second only to its $199.2 million launch week. Combined assets reached a record $1.5 billion on Friday, up from $1.2 billion a week earlier. BSOL holds roughly 71% of that total.

Spot XRP ETFs added $75.6 million for the week. Grayscale's Zcash fund, ZCSH, briefly topped $1.0 billion in net assets on Thursday.

What happens next?

The next test for sustained momentum is the month-end portfolio rebalancing window and the next round of Treasury buyback data, both due in the week ahead.