diff --git a/ebox-layer.el b/ebox-layer.el
index ecfff2b..f7facc0 100644
--- a/ebox-layer.el
+++ b/ebox-layer.el
@@ -190,7 +190,7 @@ the fact once for its spatial root.")
     (car matches)))
 
 (defun ebox-layer--absolute-origin (node host bounds width height layer-width layer-height)
-  "Resolve NODE's origin in HOST's BASE, or nil for an invisible anchor.
+  "Resolve NODE's origin in HOST, or nil for an invisible anchor.
 BOUNDS is the already resolved anchor rectangle, or nil.
 WIDTH and HEIGHT bound the host; LAYER-WIDTH and LAYER-HEIGHT bound the panel."
   (let ((x (ebox-layer--offset node :left host width))
diff --git a/ebox-layout.el b/ebox-layout.el
index 7ca7bab..2c9c489 100644
--- a/ebox-layout.el
+++ b/ebox-layout.el
@@ -1570,8 +1570,10 @@ the separate unwrapped measurement keeps that resolution non-recursive."
       (cond
        ((and (eq (ebox-get props :width) 'max-content)
              (not (memq (ebox--box-layout-kind props) '(normal column))))
+        ;; This is an unbounded *visible* formatting context, not necessarily
+        ;; an intrinsic-size probe.  Preserve the caller's measurement mode;
+        ;; suppressing paint here would discard positioned descendants.
         (let ((ebox-viewport-width nil)
-              (ebox--intrinsic-layout-measurement t)
               (ebox--inline-auto-width-intrinsic-p nil))
           (funcall function)))
        (content-viewport
diff --git a/ebox-native-reflow.el b/ebox-native-reflow.el
index 8963748..6e05463 100644
--- a/ebox-native-reflow.el
+++ b/ebox-native-reflow.el
@@ -18,6 +18,8 @@
 (require 'ebox-runtime-index)
 (require 'ebox-size)
 
+(defvar ebox-incremental--render-portals-p)
+
 (declare-function ebox-string-height "ebox" (string))
 (declare-function ebox-surface--retained-property-value-equal-p
                   "ebox-surface" (left right))
diff --git a/ebox-render-context.el b/ebox-render-context.el
index 396fb66..7de8270 100644
--- a/ebox-render-context.el
+++ b/ebox-render-context.el
@@ -9,6 +9,10 @@
 
 (require 'cl-lib)
 
+(defvar ebox-layer--active-p)
+(defvar ebox-incremental--render-portals-p)
+(defvar ebox--render-source-index)
+
 (declare-function ebox-interaction--refresh-hover! "ebox-interaction"
                   (string start end &optional face))
 
@@ -266,6 +270,16 @@ including strings returned from a render-cache hit."
                 (ebox--css-size-context-active-p t)
                 (ebox--render-runtime-revision
                  (plist-get ,render-state :runtime-revision))
+                (ebox--render-source-index
+                 (plist-get ,render-state :source-index))
+                (ebox-layer--active-p
+                 (if (plist-member ,render-state :layered-p)
+                     (plist-get ,render-state :layered-p)
+                   'unknown))
+                (ebox-incremental--render-portals-p
+                 (if (plist-member ,render-state :root-portals-p)
+                     (plist-get ,render-state :root-portals-p)
+                   'unknown))
                 (ebox--surface-materialization-active t)
                 (ebox--render-cache-table
                  (plist-get ,render-state :render-cache))
diff --git a/ebox-state-contract.el b/ebox-state-contract.el
index 32793c5..2c32ef1 100644
--- a/ebox-state-contract.el
+++ b/ebox-state-contract.el
@@ -301,6 +301,9 @@ rather than relying on an implicit default.")
     (:symbol ebox--box-content-empty-width
      :reason dynamic-scalar-result
      :evidence numeric-inline-extent-returned-with-one-content-materialization)
+    (:symbol ebox-layer--portals
+     :reason dynamically-bound-render-collection
+     :evidence let-bound-per-spatial-root-and-discarded-with-the-candidate-render)
     (:symbol ebox--string-pixel-width-cache-ring-index
      :reason numeric-eviction-cursor
      :evidence value-is-an-integer-ring-position)
diff --git a/ebox-surface.el b/ebox-surface.el
index 24b110b..a434d5b 100644
--- a/ebox-surface.el
+++ b/ebox-surface.el
@@ -24,6 +24,7 @@
 (require 'tp)
 
 (defvar ebox-region-types)
+(declare-function ebox--runtime-node-ids "ebox" (node))
 (defvar ebox--region-id-counter)
 (defvar ebox--runtime-node-id-counter)
 (defvar ebox--region-box-table)
diff --git a/ebox.el b/ebox.el
index 914e67e..0f54221 100644
--- a/ebox.el
+++ b/ebox.el
@@ -3854,6 +3854,8 @@ Defaults to the current buffer."
     :text-align :vertical-align
     :overflow :wrap-mode
      :scroll-offset :visibility)
+   (cl-loop for (property _value) on ebox-style--box-runtime-defaults by #'cddr
+            collect property)
    ebox-style--item-projection-properties)
   "Longhand box properties accepted by `ebox-region-update'.")
 
diff --git a/tests/ebox-layer-publication-tests.el b/tests/ebox-layer-publication-tests.el
index 044048e..d87cfdf 100644
--- a/tests/ebox-layer-publication-tests.el
+++ b/tests/ebox-layer-publication-tests.el
@@ -42,6 +42,27 @@
             (plist-get (ebox-surface-buffer-snapshot (current-buffer))
                        :input))))))
 
+(ert-deftest ebox-layer-publication-updates-every-placement-property ()
+  "Each layer declaration reaches the mounted runtime through a region update."
+  (dolist (properties '((:position relative) (:left (ch 2)) (:top (lh 1))
+                        (:z-index -1) (:layer root) (:anchor "lower")
+                        (:placement top-end)))
+    (ert-info ((format "Update %S" properties))
+      (ebox-layer-publication-test--with-buffer
+        (ebox-render-to-buffer
+         (current-buffer) (ebox-layer-publication-test--input nil t))
+        (let* ((handle (ebox-region-resolve (current-buffer) "upper"))
+               (region-id (cdr (ebox-selector--region-target handle)))
+               (revision (ebox-surface-buffer-revision (current-buffer))))
+          (should (apply #'ebox-region-update handle properties))
+          (should (> (ebox-surface-buffer-revision (current-buffer)) revision))
+          (should (equal (plist-get
+                          (ebox--buffer-region-render-owner-node
+                           (current-buffer) region-id)
+                          (car properties))
+                         (cadr properties)))
+          (ebox-layer-publication-test--assert-fresh-render))))))
+
 (ert-deftest ebox-layer-publication-hidden-updates-reveal-current-input ()
   "Hidden content and paint updates survive without painting over upper text."
   (ebox-layer-publication-test--with-buffer
diff --git a/tests/ebox-layer-tests.el b/tests/ebox-layer-tests.el
index 7a64de2..51301f9 100644
--- a/tests/ebox-layer-tests.el
+++ b/tests/ebox-layer-tests.el
@@ -77,5 +77,88 @@
                             :width (ch 6) "HIDDEN")))))
     (should (equal (substring-no-properties output) "LATEST"))))
 
+(ert-deftest ebox-layer-max-content-row-paints-positioned-descendants ()
+  (let ((output (ebox-layer-test--render
+                 '(row :width max-content
+                       (box :width (ch 4) :height (lh 1)
+                            (box "ABCD")
+                            (box :position absolute :left (ch 1)
+                                 :width (ch 2) "XX"))))))
+    (should (equal (substring-no-properties output) "AXXD"))))
+
+(ert-deftest ebox-layer-anchor-dependency-resolves-before-paint-order ()
+  (let ((output (ebox-layer-test--render
+                 '(box :width (ch 10) :height (lh 4)
+                       (box "0123456789\nabcdefghij\nABCDEFGHIJ\n0123456789")
+                       (box :position absolute :anchor parent-panel :width (ch 4)
+                            :z-index 2 "MENU")
+                       (box :id parent-panel :position absolute :left (ch 2)
+                            :top (lh 1) :width (ch 4) :z-index 1 "BASE")))))
+    (should (equal (substring-no-properties output)
+                   "0123456789\nabBASEghij\nABMENUGHIJ\n0123456789"))))
+
+(ert-deftest ebox-layer-anchor-cycles-are-rejected ()
+  (should-error
+   (ebox-layer-test--render
+    '(box :width (ch 10) :height (lh 4)
+          (box :id a :position absolute :anchor b "A")
+          (box :id b :position absolute :anchor a "B")))))
+
+(ert-deftest ebox-layer-absolute-margins-do-not-cover-underlay ()
+  (let ((output (ebox-layer-test--render
+                 '(box :width (ch 8) :height (lh 3)
+                       (box "abcdefgh\nABCDEFGH\n01234567")
+                       (box :position absolute :width (ch 4) :height (lh 1)
+                            :margin ((lh 1) (ch 1)) :background-color "red"
+                            "TOP!")))))
+    (should (equal (substring-no-properties output)
+                   "abcdefgh\nATOP!FGH\n01234567"))))
+
+(ert-deftest ebox-layer-absolute-keeps-all-flow-layout-sizes ()
+  (dolist (tag '(box row column flex grid))
+    (let* ((form `(,tag :width (ch 8)
+                       (box :width (ch 8) :height (lh 1) "abcdefgh")
+                       (box :position absolute :left (ch 2)
+                            :width (ch 2) :height (lh 9) "XX")))
+           (output (ebox-layer-test--render form)))
+      (ert-info ((format "Layout %s" tag))
+        (should (= (length (ebox-string-lines output)) 1))
+        (should (equal (substring-no-properties output) "abXXefgh"))))))
+
+(ert-deftest ebox-layer-root-projection-inside-an-absolute-panel ()
+  (let ((output (ebox-layer-test--render
+                 '(box :width (ch 10) :height (lh 4)
+                       (box "0123456789\nabcdefghij\nABCDEFGHIJ\n0123456789")
+                       (box :position absolute :left (ch 2) :top (lh 1)
+                            :width (ch 4) :height (lh 1)
+                            (box :id trigger "BASE")
+                            (box :position absolute :layer root :anchor trigger
+                                 :width (ch 4) :height (lh 1) "MENU"))))))
+    (should (equal (substring-no-properties output)
+                   "0123456789\nabBASEghij\nABMENUGHIJ\n0123456789"))))
+
+(ert-deftest ebox-layer-native-to-layer-transition-keeps-composition ()
+  (skip-unless (and (fboundp 'ebox-native-reflow-layout-ready-p)
+                    (ebox-native-reflow-layout-ready-p)))
+  (let ((ebox-viewport-width 80) (ebox-viewport-height 10)
+        (ebox-runtime-idle-prewarm nil)
+        (ebox-runtime-idle-reflow-cache-prewarm nil))
+    (with-temp-buffer
+      (ebox-render-to-buffer
+       (current-buffer)
+       (ebox-build '(column :width (px 8) :height (lh 2)
+                           (box :id "lower" :width (px 8) :height (lh 1) "LOWER001")
+                           (box :id "upper" :width (px 8) :height (lh 1) "UPPER001"))))
+      (should (eq (plist-get (ebox--buffer-render-state (current-buffer))
+                             :projection-kind) 'native-frame))
+      (should (ebox-region-update "upper" :position 'absolute))
+      (should (plist-get (ebox--buffer-render-state (current-buffer)) :layered-p))
+      (should-not (string-match-p "LOWER001" (buffer-string)))
+      (should (string-match-p "UPPER001" (buffer-string)))
+      (ebox-region-update "lower" :content "LOWER002")
+      (ebox-region-update "upper" :visibility 'hidden)
+      (should (string-match-p "LOWER002" (buffer-string)))
+      (should-not (string-match-p "UPPER001" (buffer-string))))))
+
 (provide 'ebox-layer-tests)
 ;;; ebox-layer-tests.el ends here
diff --git a/tests/ebox-m0a-inventory-fixture.el b/tests/ebox-m0a-inventory-fixture.el
index 4c9afcd..326eb5b 100644
--- a/tests/ebox-m0a-inventory-fixture.el
+++ b/tests/ebox-m0a-inventory-fixture.el
@@ -25,6 +25,9 @@
     (:storage (:state-key :content-index)
      :why address-scalar-not-a-store :owner ebox-surface
      :evidence plist-key-holds-a-numeric-content-address)
+    (:storage (:state-key :z-index)
+     :why paint-order-scalar-not-a-store :owner ebox-layer
+     :evidence style-schema-requires-an-integer-used-only-for-layer-ordering)
     (:storage (:state-key :max-jobs)
      :why native-limit-not-a-store :owner ebox-native-reflow
      :evidence plist-key-holds-a-numeric-capacity)
diff --git a/tests/ebox-package-tests.el b/tests/ebox-package-tests.el
index 25f0836..7ae9182 100644
--- a/tests/ebox-package-tests.el
+++ b/tests/ebox-package-tests.el
@@ -162,7 +162,8 @@
             "ebox-node-factory.el"
             "ebox-child-range.el"
             "ebox-tree.el" "ebox-measure.el"
-            "ebox-fragment.el" "ebox-render-context.el" "ebox-layout.el"
+            "ebox-fragment.el" "ebox-render-context.el" "ebox-composite.el"
+            "ebox-layer.el" "ebox-layout.el"
             "ebox-flex.el" "ebox-grid.el" "ebox-canonical.el"
             "ebox-buffer-backend.el" "ebox-patch-plan.el"
             "ebox-incremental.el"