Stellar Bancorp's Q1 2026 10-Q filed April 28 confirms all three regulatory approvals for the pending Prosperity Bancshares merger (closes ~July 1, 2026; 0.3803 PB shares + $11.36 cash). STEL trades at $37.59 against deal value $37.79 — a 0.5% spread, 2.94% annualized, below T-bill. STEL itself is uninvestable. The interest is what PB inherits.

What the filing says

Buried in a footnote table, troubled-loan modification flow per ASU 2022-02:

A single quarter exceeded entire FY2025 by 4.1× with composition rotating from C&I-dominant to pure CRE term extensions. Modifications-to-keep-accruing reveal management's view about which loans are curable with a 6-month runway. STEL is running 4× their FY2025 annual rate. The cohort matures around September-October 2026, after the merger closes.

Headline metrics above this signal looked clean: NIM expanded 4bps to 4.24% TE (cost of interest-bearing liabilities -49bps), net income $27.0M (+9.3% YoY), CET1 13.97%. NPAs simultaneously climbed: $60.0M → $70.1M (+16.7% QoQ); NPL/loans 0.72% → 0.80%; substandard $176.8M → $192.0M (+$15M); ACL/NPL coverage fell from 159% to 141% as reserves did not keep pace.

What the market thinks

PB at $69.48 trades like a quality Texas community bank executing a routine acquisition (P/E 12.15, 1Y +5%, 5.6% short interest); implied probability of post-merger reserve catch-up ≈25-30%. CFR (the discipline name, ACL/NPL 342% → 399%) at $143.44, +25.7% 1Y, P/E 14.45, zero short — partly priced. HOMB at $27.05, -0.5% 1Y, 6.3% short — soft tape, market sees something but has not generalized. FFIN is the swing: P/E 17.76 with 7.5% short interest. Q1 2026 10-Q files in 2-15 days and disambiguates whether the FFIN bears are reading the same signal.

Why the gap exists

ASU 2022-02 added the modification disclosure in 2023; it is not in legacy bank models. Sell-side reads NPA/NPL ratios; few decompose modification flow by composition and asset class. PB has been releasing reserves through FY2025 (ACL/NPL coverage 464% → 243%) on organic NPL migration of +85%. PB's diligence is presumably complete, but the public-facing reserve-discipline asymmetry has not been priced. Combined-entity Q3 2026 will be the first 10-Q where Day-1 CECL marks plus ongoing portfolio CECL flow into a single P&L visible to non-management readers.

Risks (ranked)

1. Peer prints flat May 1-15. Six TX peer 10-Qs file in 2-15 days (CFR, FFIN, PB, HOMB, VBTX, CADE). If they show no mod-flow rotation, STEL is idio. ≈25-30% probability.
2. Day-1 CECL absorbs through goodwill. Acquisition accounting can route credit shock through balance sheet rather than P&L. Provision stays clean even if portfolio quality has impaired.
3. KRE rally on rate cuts. Low-quality regional banks rally hardest in flight-from-quality rotations.
4. CFR-specific surprise. Long-leg blowup risk; CFR Q1 2026 10-Q is the first test.

Catalysts

• May 1-15, 2026 — Peer Q1 2026 10-Qs file. Disambiguates idio vs sector mod-flow signal.
• May 27, 2026 — STEL shareholder vote (near-certain).
• ~July 1, 2026 — Merger close; Day-1 CECL mark recognized.
• September-October 2026 — STEL CRE term-extension cohort matures.
• Late October / early November 2026 — PB Q3 2026 10-Q, first full post-merger quarter.

What would change our mind

• Three or more peer 10-Qs show flat or declining mod flow with no C&I→CRE rotation.
• PB Q1 2026 10-Q reverses reserve-release pattern (ACL/NPL coverage builds back above 300%).
• CFR Q1 2026 shows mod-flow rotation similar to STEL.
• HOMB's $91.4M concentrated TX relationship resolves favorably.

Evidence