Do a visible-only scroll reflow when the only pending layout is held

evidence/held-layout-scroll-20261006/README.md

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+# Held layout requests during scrolling
+
+Screen previously chose full layout whenever `_layout_widgets` was nonempty.
+After a layout during a mutation, that same mapping intentionally retains
+requests below the held roots. Compositor already preserves those roots' exact
+committed geometry in both full and visible arrangement. Retained requests
+therefore forced repeated full layout without being allowed to change their
+subtree.
+
+Screen now owns the existing hold classification in `_held_layout_requests`.
+Scroll takes the original visible traversal when every pending member is held.
+Requests outside the hold, including promoted auto-size ancestors, still force
+full layout. The full-layout branch uses that same classification to retain
+requests after arrangement. Release makes those requests actionable again.
+An empty request mapping needs no mutation-root acquisition.
+
+No placement, mutation-root, damage, callback, resize or renderer owner was
+replaced. The original visible traversal still acquires retained reader paths;
+Compositor still preserves exact held hit/paint geometry. No persistent state,
+cache, timer, Toad change or publication exemption was added.
+
+## Confirmation
+
+The existing real App control now performs two scroll layouts while a mounted
+child is held, verifies exact geometry/hits and pending requests, then admits an
+outside request and verifies full layout. Original release applies the mount.
+The original cut-cell, callback and overlap assertions remain. That control and
+the inline/translucent controls passed: **3 passed in 0.57s**. The final empty
+request shortcut was subsequently exercised by the source App below.
+
+One original Toad sidebar source App completed with 508 widgets / 10 tabs,
+exit zero and empty stderr. First-display medians were 35.1ms / 40.1ms, with a
+112.1ms left maximum. This ordinary layout check does not measure the changed
+held-scroll path or establish a reliable speed improvement.
+
+Source: `before.json` parses native 249, Toad 288 and Core 324 modules with zero
+omissions; `after.json` contains the native decision/consumer sites. Arbitrary
+external dynamic mutation of private layout state remains outside this audit.
+
+Raw App output and profiles remain under
+`/home/ts/.cache/agent-scratch/held-layout-scroll-20261006/`.
+The supplied live scroll profile identifies full/visible arrangement activity;
+its transition groups do not establish call counts, CPU durations or which
+pending layout requests caused any particular pass.
+
+This is a source/native-framework qualification. Installed saved scrolling,
+writer-gap reduction and overall smoothness remain unqualified. No provider,
+package, artifact, public-owner or recorder operation occurred.

evidence/held-layout-scroll-20261006/RESULT.json

@@ -0,0 +1,22 @@
+{
+  "source_head": "21e5620866fbf960ac7d39fd7f659bfa56c89fdd",
+  "controls": "3 passed in 0.57s",
+  "app": {
+    "exit": 0,
+    "stderr_bytes": 0,
+    "widgets": 508,
+    "tabs": 10,
+    "boundary": "source headless App _display, not terminal pixels or held-scroll latency"
+  },
+  "keepers": {
+    "src/textual/screen.py": "66ca0546457c22de6bdd9165a0e4c0a4b6a1294ad09ac5136f188a521729f6b2",
+    "tests/test_batch_paint_admission.py": "b002872170751bfea8cc99847574ac0df019c538191fe71c4f1fac71db745a0d",
+    "evidence/held-layout-scroll-20261006/before.json": "b17233b81c922f4a0f7652e603ee188d393f4a53421562a770cdac8f29ddeffa",
+    "evidence/held-layout-scroll-20261006/after.json": "9937a6bcc505cd48a2e5c0e1cbbe0c17272e9fd05d44bf438609202323e63466",
+    "evidence/held-layout-scroll-20261006/controls.log": "a2781fcf8f9c65bdb27d0edf589ab8df478ce510960a3dcee3c456a717c0f5ed",
+    "/home/ts/.cache/agent-scratch/held-layout-scroll-20261006/app.stdout.log": "518cc08803afbfecc92913c0e6953f19c9638d7c5ea57446ca58f3430fac1b8e",
+    "/home/ts/.cache/agent-scratch/held-layout-scroll-20261006/app.stderr.log": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+  },
+  "installed": false,
+  "reliable_latency_improvement": false
+}

evidence/held-layout-scroll-20261006/after.json

@@ -0,0 +1,174 @@
+{
+  "modules": 249,
+  "omissions": [],
+  "sites": [
+    [
+      "src/textual/_compositor.py",
+      873,
+      "_layout_mutation_roots",
+      "Attribute"
+    ],
+    [
+      "src/textual/_compositor.py",
+      1309,
+      "_layout_mutation_roots",
+      "Attribute"
+    ],
+    [
+      "src/textual/_compositor.py",
+      1292,
+      "_layout_mutation_roots",
+      "Attribute"
+    ],
+    [
+      "src/textual/app.py",
+      3850,
+      "_refresh_layout",
+      "Attribute"
+    ],
+    [
+      "src/textual/layouts/stream.py",
+      58,
+      "_layout_widgets",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1220,
+      "_layout_mutation_roots",
+      "FunctionDef"
+    ],
+    [
+      "src/textual/screen.py",
+      1419,
+      "_held_layout_requests",
+      "FunctionDef"
+    ],
+    [
+      "src/textual/screen.py",
+      1432,
+      "_refresh_layout",
+      "FunctionDef"
+    ],
+    [
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+      "_layout_widgets",
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+    ],
+    [
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+    ],
+    [
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+      "Attribute"
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+    [
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+    [
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+    [
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+    ],
+    [
+      "src/textual/screen.py",
+      1445,
+      "_held_layout_requests",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1485,
+      "_held_layout_requests",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1548,
+      "_layout_widgets",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1589,
+      "_layout_widgets",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1642,
+      "_refresh_layout",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1315,
+      "_refresh_layout",
+      "Attribute"
+    ],
+    [
+      "src/textual/screen.py",
+      1591,
+      "_layout_widgets",
+      "Attribute"
+    ],
+    [
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+    [
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+    [
+      "src/textual/screen.py",
+      1451,
+      "_layout_widgets",
+      "Attribute"
+    ]
+  ]
+}