An upward capex revision would firm up already-elevated odds of a BOJ hike this month, reinforcing the yield differential story that has kept the yen from sliding further despite its recent softness. JGB yields, already at multi-decade highs, would likely extend gains on a stronger print, squeezing valuations across rate-sensitive pockets of the Nikkei even as exporters benefit from a firmer growth narrative. A miss on the revision would cut the other way: hike conviction would soften, yen weakness would likely resume, and equities could see a short-term relief bounce on reduced tightening risk. Either outcome keeps USD/JPY and Nikkei futures reactive through the release window.---Today's GDP revision is less about the headline number and more about whether it hands the BOJ enough cover to hike this month.Summary:Preliminary Q2 GDP showed 0.3% quarter-on-quarter growth, an annualised 1.1%, both below forecasts of 0.5% and 2% respectivelyCapital expenditure fell 1.2% in the preliminary read against expectations for a 0.4% risePrivate consumption was flat, the first such reading in eight quartersStrong corporate capex and profit data released last week points to a likely upward revision to today's figureMarkets currently price around an 80% chance of a BOJ rate hike at the September 17-18 meetingBenchmark 10-year JGB yields have climbed to a 30-year high near 2.925% as hike expectations buildJapan's Cabinet Office publishes its second estimate of second-quarter GDP today, a revision that carries more weight than usual given its proximity to the Bank of Japan's September policy meeting (September 17–18, 2026). The preliminary figure, released in mid-August, showed the economy expanding an annualised 1.1%, well below the 2% consensus, with quarter-on-quarter growth of 0.3% missing the 0.5% forecast. Weakness was concentrated in domestic demand, as capital expenditure fell 1.2% against expectations for a modest rise, and private consumption was flat for the first time in eight quarters.The case for an upgrade has strengthened since then. Corporate capex and profit survey data released last week showed firms lifting spending more than the preliminary GDP figures implied, and capex components have historically tended toward upward revision once fuller survey data becomes available. A meaningful lift to the capex figure would push the annualised growth rate closer to, or potentially above, the original 2% forecast that the preliminary print missed.The stakes for monetary policy are immediate. The BOJ meets on September 17 and 18, and overnight swaps currently imply roughly an 80% probability of a rate increase at that meeting, with some sources suggesting the central bank may consider a faster pace of tightening beyond that point. A stronger GDP revision, particularly one driven by business investment rather than one-off trade effects, would reinforce the case that the economy can absorb higher borrowing costs, giving the BOJ additional cover to proceed.Market reaction is likely to run through two channels. JGB yields, with the 10-year benchmark already at a 30-year high near 2.925%, would probably extend their climb on a stronger print, tightening financial conditions further and pressuring rate-sensitive sectors of the Nikkei even as exporters gain from the reinforced growth narrative. The yen, which has been trading defensively despite the hike odds already in the price, would likely find some support from a print that removes ambiguity around the BOJ's near-term path. A downside surprise would work in reverse, softening hike conviction, weighing on the yen again, and potentially offering equities a short-lived reprieve from tightening-related pressure. This article was written by Eamonn Sheridan at investinglive.com.