diff --git a/local/docs/IMPROVEMENT-PLAN.md b/local/docs/IMPROVEMENT-PLAN.md
index cbc6070bab..9399f2af4f 100644
--- a/local/docs/IMPROVEMENT-PLAN.md
+++ b/local/docs/IMPROVEMENT-PLAN.md
@@ -210,7 +210,11 @@ The `UsbHostController` trait provides HC-agnostic API but is not implemented by
 - Option A: Implement in xhcid and make ecmd/uhcid/ohcid use it
 - Option B: Remove the trait as dead code
 
-### 4.2 Add TRB encoding/decoding tests
+### 4.2 Add TRB encoding/decoding tests ✅ ENHANCED (2026-07-08)
+
+**File**: `xhci/trb.rs:539-660`
+
+Added 3 more TRB field tests (setup stage address, data pointer round-trip, completion status). Combined with existing 9 tests, the TRB test suite now has 12 tests total.
 
 **File**: `xhci/trb.rs`
 **Severity**: MEDIUM — critical for correctness