PROSPERITY BANCSHARES, INC.® COMPLETES MERGER WITH STELLAR BANCORP, INC.

Prosperity Bancshares completed its merger with Stellar effective July 1, 2026, issuing 0.3803 shares of PB stock plus $11.36 cash for each Stellar share. Stellar’s 52 banking offices will operate under the Stellar Bank name until operational integration in March 2027, after which customers can use Prosperity Bank’s full service centers. Deal terms and board/management changes suggest a modest positive for the combined franchise, with likely limited near-term price impact outside of the involved banks.

Analysis

The cleanest takeaway is that PB has turned a strategic uncertainty into an execution story. In the near term, that usually supports multiple expansion only if the market believes the deal is modestly accretive and the integration burden is contained; otherwise the stock can still drift because bank M&A gets penalized when tangible book dilution is visible before synergies are realized. The key variable over the next 1-2 quarters is not headline scale, but whether deposit costs, core fee retention, and operating expenses stabilize fast enough to offset purchase-accounting noise.

Second-order, the bigger competitive effect is in Texas branch density. A larger PB can be more aggressive on commercial deposit pricing and treasury services in Houston/Dallas, which pressures smaller regional lenders that compete on relationship banking rather than product breadth; that is more relevant to names with overlapping footprints than to asset-sensitive lenders elsewhere. The integration window through March 2027 matters: until conversion risk passes, the market will likely assign a discount for customer attrition and systems risk, so any rally ahead of the first combined-quarter print may be fragile.

Contrarian view: consensus may be too focused on the obvious expense synergies and underestimating how much of the value comes from avoiding deposit runoff. If management preserves low-cost core deposits, PB can defend ROE even in a slower loan-growth tape; if not, this becomes just another scale deal with delayed payback. What would falsify the bullish case is a pro forma efficiency ratio that fails to improve by the first post-close reporting cycle, or evidence that deposit betas reprice higher than expected as the combined franchise is digested.

Key Decisions for Investors

• Long PB on weakness over the next 1-3 weeks; use the first post-close trading window before the next earnings print to establish size. Risk/reward is attractive only if the market is still discounting integration risk more than 12 months of synergy potential; reduce if pro forma expense run-rate does not improve by the first combined quarter.
• Pair trade: long PB / short KRE for 1-3 months as a cleaner way to express idiosyncratic integration upside while hedging sector beta. This works if PB can show stable deposits and fee income while the broader regional bank tape remains range-bound.
• Watch-list, not a buy: TBBK and other Texas-leaning regionals with similar commercial deposit gathering. If PB starts competing aggressively on pricing, expect margin pressure to spill over into nearby franchises; that would be a relative short only if deposit costs in the region start rising faster than loan yields.
• Set a hard alert on the first combined earnings release: if tangible book dilution is greater than expected or the efficiency ratio fails to inflect lower, fade the post-close enthusiasm and trim PB exposure.