diff --git a/FABRIC-3.5.md b/FABRIC-3.5.md
index e50a1b1e..389e448b 100644
--- a/FABRIC-3.5.md
+++ b/FABRIC-3.5.md
@@ -4515,3 +4515,108 @@ left implicit.
 - ⬜ **B1/B2/B3 (items 27, 32, §XXXII.5.1)** — the Phase 3 blockers, tracked in both documents.
   **§XXXII.5.1, the delivery hand-off, is the last genuine design question in the reshuffle.**
 - Design work continues **here**; execution is tracked **there**.
+
+---
+
+## XLIII. B3 SETTLED: the target drains its own queue, at its own outermost checkpoint
+
+The last genuine design question in the reshuffle (§XXXII.5.1, Phase 3 blocker B3). **Settled,
+and once again the mechanism already exists — built for the structurally identical problem and
+corrected twice in the field.**
+
+### XLIII.1 — What the hand-off has to satisfy
+
+Delivery must cause the payload to **execute inside the target** — `messaging.4th` block 5041:
+"Payload is FORTH text, executed by the receiver, same as every other message here." But
+§XXXII retired the pump, so **kernel-Hermes may not `VM-EXEC` into anyone.** The payload must
+therefore wait somewhere the target consumes under its own power, at a moment when doing so is
+safe.
+
+"Safe" is the hard part: interpreting a payload while the target is mid-word, mid-unwind, or
+running nested inside someone else's dispatch is the reentrancy class this codebase has been
+bitten by repeatedly (§XX, §XXVIII.2).
+
+### XLIII.2 — The safe-boundary machinery is already there
+
+Traced 2026-09-19 in `vm_core.c`:
+
+- **`sk_vm_at_outermost_interpret()`** — `return g_vm_interpret_depth <= 1;` (`:1164`), with
+  `g_vm_interpret_depth` incremented and decremented by `vm_interpret()` itself (`:1173`,
+  `:1206`).
+- **A per-word checkpoint** in `execute_colon_word()` (`:946`), gated on that predicate.
+- **A defer-don't-lose discipline**, in the checkpoint's own words (`:925-935`): if a word is
+  "executing nested inside a `VM-EXEC`/`VM-CALL` dispatch… `vm` here **does not own the
+  physical stack it's currently running on**," so acting would corrupt the enclosing VM's call
+  chain. It is therefore **"left pending… so the next checkpoint at the outermost frame picks
+  it up instead of losing it."**
+- And it runs **before** the error/abort/exit-colon checks, "deliberately, so a switch never
+  happens mid-unwind" — acting only when the word left the VM "in a clean, resumable state."
+
+**That is the exact predicate, the exact placement, and the exact deferral semantics delivery
+needs.** It exists because the switcher needed to answer the same question — *when is it safe to
+act on this VM?* — and it has already been corrected twice in the field (2026-09-13 ×2,
+2026-09-14).
+
+### XLIII.3 — RULING
+
+> **Kernel-Hermes enqueues the payload onto the target's own pending queue and publishes the
+> fact. It dispatches nothing. The target drains its own queue, in its own context, at its own
+> outermost interpret checkpoint — the same checkpoint, the same `sk_vm_at_outermost_interpret()`
+> gate, and the same defer-if-nested discipline the switcher already uses.**
+
+**One published fact, two independent consumers** — which is precisely the shape §XV.3 and
+§XXXII established:
+
+| Consumer | Uses the fact for |
+|---|---|
+| **The switcher** | eligibility — whether to resume this VM (§XXXII) |
+| **The target VM itself** | drain — whether to interpret a pending payload at its next safe boundary |
+
+**Neither dispatches into anyone.** Kernel-Hermes publishes; the switcher moves control; the VM
+does its own work. Three roles, no overlap, no second owner of anything.
+
+### XLIII.4 — This is §XX's proven-safe pattern, generalized to the whole fleet
+
+`FABRIC-3.md` §XX already established the safe shape, for Hera specifically. With the pump
+skipping her, she drains her own queue via "a plain word dispatch **in her own dictionary**, not
+a `VM-EXEC` dispatch into anyone else's input buffer — **no reentrancy risk.**"
+
+**The pump's defect was never draining; it was draining *from outside*.** Hera was special-cased
+into safety. Retire the pump (§XXXII) and **every VM does what Hera already does** — the special
+case disappears by becoming universal. That is a relocation of a proven pattern, not an
+invention, and it keeps this document's scope discipline intact at the last design question.
+
+### XLIII.5 — Recursive drain is prevented for free
+
+Interpreting a payload calls `vm_interpret()`, which **increments `g_vm_interpret_depth`** — so
+any checkpoint reached *during* the drain sees `depth > 1` and will not drain again. **The same
+counter that defines the safe boundary also makes the drain non-reentrant**, with no flag, no
+lock and no new state.
+
+### XLIII.6 — Three constraints, named rather than discovered later
+
+1. **`INPUT_BUFFER_SIZE` is 1025** — 1024 content bytes plus NUL, and `.claude/CLAUDE.md` calls
+   this non-negotiable because `vm_interpret()` is the shared dispatch path for both REPL lines
+   and `LOAD`ed block content. **A payload above 1024 bytes cannot be interpreted in one
+   drain.** Today's `MSG-PADDR`/`MSG-PLEN` are out-of-line and carry no such bound. **Kernel-
+   Hermes needs either a payload bound at send time or a chunking story — decide at build time,
+   do not discover it at Stage C.**
+2. **Starvation is possible and bounded.** A VM in a tight loop never returns to outermost
+   depth, so never drains. The switcher can still preempt it, but preemption does not create a
+   boundary — the VM must still reach one. **This is the switcher's existing risk, not a new
+   one**, and it should be recorded as shared rather than solved twice.
+3. **Drain one message per checkpoint, not all.** Draining the whole queue at one boundary runs
+   unbounded work in a single checkpoint — the §XXII wall pattern in miniature. One per
+   checkpoint is bounded and fair. **Recommended, not ruled.**
+
+### XLIII.7 — Punch list
+
+- ✅ **B3 — SETTLED** (§XLIII): the target drains its own queue at its own outermost checkpoint;
+  kernel-Hermes publishes and never dispatches.
+- ⬜ **Item 44, NEW** — payload bound or chunking, against `INPUT_BUFFER_SIZE` 1025
+  (§XLIII.6.1). **Decide before Phase 3.**
+- ⬜ **B1 (item 27)** and **B2 (item 32)** remain — both are rulings, not designs.
+
+**Phase 3's design blocker is cleared. What remains before it is buildable are two decisions,
+neither of which requires further investigation:** channels (one membership or negotiation), and
+the switch-slot ceiling. **The reshuffle has no undesigned mechanism left.**
diff --git a/FABRIC-3.6.md b/FABRIC-3.6.md
index f7e3acce..23239bd0 100644
--- a/FABRIC-3.6.md
+++ b/FABRIC-3.6.md
@@ -135,8 +135,11 @@ one message type owned by exactly one layer, no message shared.
       recommends the latter; unruled.)
 - [ ] **B2** — **Item 32**: `SK_SWITCH_MAX_SLOTS` is 16 and §XXXII made the switcher the sole
       mover of control. Constant bump or table redesign?
-- [ ] **B3** — **§XXXII.5.1**: the delivery hand-off is undesigned. **The last genuine design
-      question, and on the critical path.**
+- [x] **B3** — **CLEARED 2026-09-19 by `FABRIC-3.5.md` §XLIII**: the target drains its own
+      queue at its own outermost interpret checkpoint; kernel-Hermes publishes and never
+      dispatches. Reuses `sk_vm_at_outermost_interpret()` and the Stage 3 checkpoint.
+- [ ] **B4** — **Item 44**: payload bound or chunking against `INPUT_BUFFER_SIZE` 1025
+      (§XLIII.6.1). Decide before Phase 3.
 
 ## Phase 4 — Category B strip