F&O Data Dive: strike walk for the Wed 13 May 2026 open

Writers held the 25,000 Nifty CE wall and the 24,800 PE floor into the penultimate session before May expiry, leaving a narrow 200 point cage that the residual two sessions will have to resolve.

The OI walk

Nifty open interest at the 25,000 CE built by roughly 38 lakh contracts through the session (NSE option chain close 2026-05-12), taking that strike to the heaviest call concentration on the May series. The 25,100 and 25,200 CEs added a combined 21 lakh contracts, a fresh-write pattern rather than a roll, given the spot held below 24,900 for most of the afternoon. On the put side, 24,800 PE saw an addition of 29 lakh contracts and 24,700 PE took on 17 lakh contracts, both consistent with writers leaning into the floor rather than covering it. The 25,300 CE saw a smaller 8 lakh contract build, suggesting writers are not yet willing to extend the ceiling further.

BankNifty followed a similar pattern around 52,300 spot. The 52,500 CE added approximately 14 lakh contracts and 53,000 CE added 9 lakh contracts (NSE option chain close 2026-05-12). The 52,000 PE absorbed a build of about 19 lakh contracts and 51,800 PE took on 11 lakh contracts. The 52,300 ATM straddle premium compressed through the day, with both legs bleeding theta as realised vol stayed muted. Where the unwind showed up was at 25,500 Nifty CE, which shed close to 4 lakh contracts, a small but directionally clean cover at a strike that traders had been defending earlier in the week. The OI map heading into 2026-05-13 is therefore tightening, not expanding.

IV term structure

May ATM IV on Nifty printed at 11.8% at close (NSE option chain 2026-05-12), against a trailing HV20 of approximately 9.2%. That gives a vol-risk-premium of roughly 2.6 points on the front month, which is on the richer side of the last four weeks but not extreme. June ATM IV printed at 13.4% and July ATM IV at 14.6%, leaving the term curve in a clean upward slope of about 160 bps per expiry. The May to June kink of roughly 160 bps reflects the standard expiry-week IV crush priced into the front leg, not a regime shift.

The skew told a flatter story. 25,200 CE IV printed at 12.1% versus 24,500 PE IV at 12.4%, a put skew of only about 30 bps. For a market two sessions from expiry sitting on a 25,000 CE wall, that flat skew suggests CE writers are not pricing tail risk, and PE writers are not paying up for downside protection. June 24,500 PE IV at 14.0% and June 25,500 CE IV at 13.1% widened the skew slightly on the next series, but nothing that flags directional fear. IV is rich to realised, marginally rich versus the four-week average, and structurally flat on skew.

Max-pain map

Max-pain for the May expiry settled at 24,900 by close on 2026-05-12, up from 24,850 at the prior session close and well above the 24,700 print from the 2026-05-06 close (NSE option chain 2026-05-12). That 200 point upward migration over six sessions tracks the steady PE build at 24,800 and 24,700 while the spot kept testing 24,800 to 24,900 without breaking through.

For BankNifty, max-pain shifted to 52,200 by close, against 52,000 at the prior close and a 51,600 print one week ago. The 52,000 PE writers have been the dominant force in moving that anchor higher. With two sessions to go, the residual decay of premium will favour the strikes nearest max-pain, which means the 24,900 and 52,200 anchors will exert magnetic pull on the spot. If 24,900 holds as the gravitational centre into 2026-05-15, the 25,000 CE writers will collect close to full premium on roughly 67 lakh contracts of OI. The intraday shift from 24,850 to 24,900 was driven by the 24,800 PE writers, not by 25,000 CE covering, which matters for the writer-edge read.

Writer positioning

FII net long in index futures sat at approximately 38,400 contracts at close (NSE F&O participant-wise data 2026-05-12), a modest long-bias print that is not large enough to swing the option writer flow. The structural read for 2026-05-13 is that PE writers at 24,800 are sitting on the largest concentrated short of the series, with the 24,800 strike now carrying roughly 84 lakh contracts of put OI. The asymmetric edge for PE writers is that they need spot to hold 24,800 for two sessions to collect almost full theta on a strike whose premium is already compressed.

CE writers at 25,000 face the symmetric question. The 25,000 CE OI of approximately 92 lakh contracts (NSE option chain close 2026-05-12) is the single largest open interest strike on the series. With spot 160 points away and only two sessions of decay left, the CE writer edge is structurally larger than the PE writer edge today, provided the 25,000 wall holds. PCR for Nifty May closed at 0.94, slightly under parity, which means call writing has been marginally heavier than put writing across the series, consistent with the dominant 25,000 CE concentration.

BankNifty writers carry a tighter cage. The 52,000 PE and 52,500 CE form a 500 point band around the 52,300 spot, and the 52,300 ATM straddle premium of roughly 380 points has 48 hours of theta left to bleed. Writers there have the tighter risk-reward, with both walls within one standard daily move of the spot.

Four strikes to watch into the next session

NIFTY 25000 CE

This is the dominant ceiling of the May series, with OI of approximately 92 lakh contracts (NSE option chain close 2026-05-12) and the largest concentrated call short on the chain. The breach level is a spot close above 25,050 in 2026-05-13, which would trigger the first wave of CE writer cover. As long as spot holds below 24,950 at open, the structural edge stays with the writer through expiry.

NIFTY 24800 PE

The structural floor with OI near 84 lakh contracts and a 29 lakh contract build today. The strike will function as the magnetic anchor for spot through the two remaining sessions. The breach level is a sustained spot trade under 24,780, which would unwind PE writers and accelerate the move toward 24,700 OI cluster. Above 24,820, the writer floor holds clean.

BANKNIFTY 52000 PE

The defended BankNifty floor with a fresh 19 lakh contract build today. With spot at 52,300, the strike sits 300 points below the underlying and inside one standard daily move. The breach level is a close under 51,950 in 2026-05-13, which would force writer cover and pull spot toward the 51,800 OI cluster. A hold above 52,150 keeps the wall structurally intact.

BANKNIFTY 52500 CE

The ceiling that capped the BankNifty range with a 14 lakh contract OI build today. The breach level is a close above 52,540, which would activate the 53,000 CE writer line as the next defence. The strike is the cleanest short-gamma test for BankNifty writers into expiry, with the spot sitting only 200 points below the wall and theta compressing fast.

The 24,800 to 25,000 Nifty cage and the 52,000 to 52,500 BankNifty cage define the structural read into 2026-05-13. With IV rich to realised, PCR under 1.0, and max-pain magnetised to 24,900, the writer edge is intact heading into the residual sessions. The Pratham Khabar 06:00 frame should treat the 25,000 CE wall as the primary structural ceiling and the 24,800 PE floor as the primary structural support, with breach levels above and below as the only mechanical triggers for a regime shift.