diff --git a/local/docs/IRQ-AND-LOWLEVEL-CONTROLLERS-ENHANCEMENT-PLAN.md b/local/docs/IRQ-AND-LOWLEVEL-CONTROLLERS-ENHANCEMENT-PLAN.md
index 349d00cbd5..ae04e53e80 100644
--- a/local/docs/IRQ-AND-LOWLEVEL-CONTROLLERS-ENHANCEMENT-PLAN.md
+++ b/local/docs/IRQ-AND-LOWLEVEL-CONTROLLERS-ENHANCEMENT-PLAN.md
@@ -571,6 +571,37 @@ Why third:
 
 This improves reliability without changing the underlying architecture.
 
+### Shared-IRQ re-arm bug class — FIXED (2026-07-20)
+
+A systematic driver bug class was found and fixed across the base driver tree:
+the kernel masks the IRQ line when it delivers an interrupt and only re-arms it
+on the userspace write-back (irq scheme `write` → `acknowledge()` →
+`pic_unmask()`/`ioapic_unmask()`). Drivers that acked only when the interrupt
+was their own wedged the line permanently on the first foreign interrupt on a
+shared INTx line — every later interrupt for the device was silently lost.
+
+This is exactly the "works in QEMU (dedicated MSI/INTx), wedges on real
+hardware (shared INTx)" failure signature that P1/P6 hardware validation was
+expected to hunt.
+
+Fixed (always ack, tick/process only when ours, device-level status cleared
+before re-arm so no interrupt storm):
+
+- `ahcid` (`ad40fffd`, from the UAS workstream)
+- `e1000d`, `ihdad`, `vboxd`, `xhcid` (`92924224`)
+- `sb16d`, `ac97d`, `rtl8139d`, `rtl8168d`, `ixgbed`, `ihdgd` (`28afc1fe`)
+
+Audited, NOT affected:
+
+- `ided` — already acked unconditionally
+- `nvmed` — the shared `executor` crate acks unconditionally for INTx; MSI
+  vectors are never shared so every delivery is ours by construction
+- `virtio-core` consumers — MSI-X only, same reasoning
+- `ps2d` — does not use the irq scheme fd path
+
+Both fix commits verified with `cargo check -Z build-std --target
+x86_64-unknown-redox` for every touched crate — clean, no new warnings.
+
 ## Priority 4 — input/controller runtime proof
 
 Goal: continue turning the existing input substrate into a well-proven low-level controller path.
diff --git a/local/sources/base b/local/sources/base
index fb421083e0..28afc1fefd 160000
--- a/local/sources/base
+++ b/local/sources/base
@@ -1 +1 @@
-Subproject commit fb421083e0bfa3b8f7ab25f923d087de5f0e117f
+Subproject commit 28afc1fefdd1cd90dc117be735c7103b1fa1e56d