Bitcoin Trust Rides a Rally, But Shorts Are Quietly Rebuilding

BTC — the Grayscale Bitcoin Mini Trust — has had a strong week. The price climbed nearly 7% to $36.12. Over the past month, it's up more than 21%. That momentum is real. But the short-side data shows a different current running beneath the surface.

Short interest has risen sharply even as the price climbed. Estimated shares short jumped 27% over the past week, reaching about 0.51% of the float. That absolute level is modest — shorts are not crowded here in any conventional sense. But the direction is notable. A month ago, short interest was tracking lower. It bottomed mid-April around 400,000 shares and has since rebuilt steadily. The most recent daily reading showed another 13% single-day increase. Shorts are not fleeing the rally — they're leaning into it.

The lending market offers little friction to this activity. Availability is extremely loose. Only about 7% of the borrowable pool is currently in use — far below the 52-week peak of 97%. That means new short positions face no meaningful constraints on the borrow side. Cost to borrow confirms the same picture: it's running at just 0.55% annually. That's essentially free, well within the range it has traded all year with no meaningful spike. Bears can initiate or add without paying a premium.

Options positioning reinforces the bullish read — at least for now. The put/call ratio is 0.25, slightly below its 20-day average and well off the 52-week high of 0.46 reached during the April volatility. The z-score is marginally negative, meaning the options market is no more defensive than usual. Call flow continues to dominate, consistent with the momentum tone in the underlying price. The ORTEX short score is a modest 28 — drifting slowly higher over the past two weeks but nowhere near distressed territory.

What to watch is the divergence between price momentum and the short-interest rebuild. The two are running in opposite directions. If the trust continues rising, those short positions will face mark-to-market pressure. If the rally stalls, the rebuilt short interest could weigh on the price quickly — especially given how easily new positions can be added in an unconstrained borrow market.