fix dangling tail anchors in reflow on partially-filled lines (T-92)

`_LineReflow._addPart`'s post-loop block reparents anchors past the
source line's trimmed content onto whatever `_builder._result` was
active at that moment. When no further content lands in the builder
(non-wrapped lines, or the last logical line of a wrapped run),
`finish()` was emitting only when `_builder.isNotEmpty` — leaving
the empty result line with the reparented anchor unappended. The
anchor then pointed to a `BufferLine` that the reflow output never
included, `lines.replaceWith(reflowResult)` discarded it, and
`CellAnchor.attached` returned false. The selection controller's
`extent.attached` null-check then dropped the selection silently
on resize.

The fix adds a `_LineBuilder.hasAnchors` getter and uses it in
`finish()` so the builder line is also emitted when it's carrying
an anchor — even when otherwise empty. Trade-off: an extra trailing
line in the reflow output when (and only when) a tail anchor would
have dangled. `Buffer.resize` already pads the result to `newHeight`
afterward, so for the common case (resize fits inside view height)
the total ring length is unchanged; only when the result already
meets / exceeds `newHeight` does the buffer grow by one. Acceptable
in exchange for selections surviving a width change.

User-visible trigger paths:
- `SelectAllTextIntent` (Ctrl+A) creates an end anchor at
  `x = viewWidth` on the last buffer line — exactly the past-
  trimmed-length position. Resizing narrower while the selection
  was active dropped it.
- Mouse drag selections past the end of a partially-filled line
  hit the same shape.

Tests:
- The pre-existing `reflow anchors on the source line tail (past
  trimmedLength) get reparented` test was originally written to
  document the buggy behaviour ("anchor moves off the source onto
  a dangling builder line"). Updated to assert the post-fix
  contract: `out.contains(tail.line)` is true.
- New `SelectAllTextIntent-shaped end anchor survives shrink`
  regression test that mirrors the actual production trigger
  (anchor at `x = viewWidth` on a partially-filled line, narrower
  reflow).

reflow.dart 71/71 → 72/72 (the new getter is a one-liner). Project
coverage 54.62% unchanged within rounding.

Co-Authored-By: Claude <noreply@anthropic.com>

.pql/pql-plan.json

@@ -1,5 +1,5 @@
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       "file_path": "decisions/tooling.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "D-66",
@@ -649,7 +649,7 @@
       "status": "active",
       "date": "2026-05-06",
       "file_path": "decisions/testing.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-1",
@@ -658,7 +658,7 @@
       "title": "Authorisation granularity on the IPC socket",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-2",
@@ -667,7 +667,7 @@
       "title": "Back-pressure on event streams",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-3",
@@ -676,7 +676,7 @@
       "title": "Event persistence + audit/undo",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-4",
@@ -685,7 +685,7 @@
       "title": "`.canvas` schema compatibility with Obsidian",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-5",
@@ -694,7 +694,7 @@
       "title": "IPC wire-format stability + `schema_version:`",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-6",
@@ -703,7 +703,7 @@
       "title": "Window chrome — native frame vs frameless custom",
       "status": "resolved",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-7",
@@ -712,7 +712,7 @@
       "title": "macOS app bundle signing / notarisation",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-8",
@@ -721,7 +721,7 @@
       "title": "Extension API shape — widgets, subcommands, both?",
       "status": "open",
       "file_path": "decisions/questions-extensions.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-9",
@@ -730,7 +730,7 @@
       "title": "Lua runtime vendoring",
       "status": "open",
       "file_path": "decisions/questions-extensions.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-10",
@@ -739,7 +739,7 @@
       "title": "Extension manifest `schema_version:`",
       "status": "open",
       "file_path": "decisions/questions-extensions.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-11",
@@ -748,7 +748,7 @@
       "title": "Coverage gates — hard thresholds vs soft reporting",
       "status": "open",
       "file_path": "decisions/questions-testing.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-12",
@@ -757,7 +757,7 @@
       "title": "Screen-reader automation (axe-core via Playwright)",
       "status": "open",
       "file_path": "decisions/questions-testing.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-13",
@@ -766,7 +766,7 @@
       "title": "Web production-mode a11y",
       "status": "open",
       "file_path": "decisions/questions-accessibility.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-14",
@@ -775,7 +775,7 @@
       "title": "i18n plurals / gender / date-format tooling",
       "status": "open",
       "file_path": "decisions/questions-accessibility.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-15",
@@ -784,7 +784,7 @@
       "title": "Editor tab — full LSP vs tree-sitter-only highlight",
       "status": "open",
       "file_path": "decisions/questions-process.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-16",
@@ -793,7 +793,7 @@
       "title": "`tree-sitter-dart` grammar maintenance",
       "status": "open",
       "file_path": "decisions/questions-process.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-17",
@@ -802,7 +802,7 @@
       "title": "Icon set growth",
       "status": "open",
       "file_path": "decisions/questions-process.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-18",
@@ -811,7 +811,7 @@
       "title": "Theme hot-reload in release builds",
       "status": "open",
       "file_path": "decisions/questions-process.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-19",
@@ -820,7 +820,7 @@
       "title": "(withdrawn)",
       "status": "resolved",
       "file_path": "decisions/questions-process.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-20",
@@ -829,7 +829,7 @@
       "title": "Kernel DB service — namespaced SQL access?",
       "status": "open",
       "file_path": "decisions/questions-process.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-21",
@@ -838,7 +838,7 @@
       "title": "Pql absorbs planning vs keeps separate",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-22",
@@ -847,7 +847,7 @@
       "title": "Ticket persistence strategy",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-23",
@@ -856,7 +856,7 @@
       "title": "SSH-remote development — run clide against a remote workspace",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-25",
@@ -865,7 +865,7 @@
       "title": "Body text face — mono everywhere vs Josefin Sans UI + mono code",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-26",
@@ -874,7 +874,7 @@
       "title": "Small screen layout (\u003c 1000px)",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-27",
@@ -883,7 +883,7 @@
       "title": "Two-editor split",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-28",
@@ -892,7 +892,7 @@
       "title": "Terminal strip scope — shell only or logs/errors/tests",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-29",
@@ -901,7 +901,7 @@
       "title": "Branch picker location",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-30",
@@ -910,7 +910,7 @@
       "title": "Focus behavior when editor is dirty and viewer is peeked",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "Q-31",
@@ -919,7 +919,7 @@
       "title": "XWayland fallback for frameless — proper Wayland protocol needed",
       "status": "open",
       "file_path": "decisions/questions-architecture.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-2",
@@ -929,7 +929,7 @@
       "status": "active",
       "date": "2026-04-20",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-3",
@@ -939,7 +939,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-4",
@@ -949,7 +949,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-5",
@@ -959,7 +959,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-6",
@@ -969,7 +969,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-7",
@@ -979,7 +979,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-8",
@@ -989,7 +989,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-9",
@@ -999,7 +999,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-10",
@@ -1009,7 +1009,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-11",
@@ -1019,7 +1019,7 @@
       "status": "active",
       "date": "2026-04-21",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     },
     {
       "id": "R-12",
@@ -1029,7 +1029,7 @@
       "status": "active",
       "date": "2026-04-22",
       "file_path": "decisions/rejected.md",
-      "synced_at": "2026-05-06 22:01:32"
+      "synced_at": "2026-05-07 05:57:38"
     }
   ],
   "decision_refs": [
@@ -2791,6 +2791,16 @@
       "decision_ref": "D-66",
       "created_at": "2026-05-06 20:49:47",
       "updated_at": "2026-05-06 20:50:32"
+    },
+    {
+      "id": "T-92",
+      "type": "bug",
+      "title": "reflow tail-anchor reparenting can dangle on partially-filled lines",
+      "description": "**File:** `lib/src/terminal/src/core/reflow.dart` (`_LineReflow._addPart`).\n\n**Bug:** Anchors whose x-coordinate sits past the source line's `trimmedLength` get reparented onto whatever `_builder._result` is active at that moment. After the main reparenting loop has run with `lineFilled` on the final iteration, `_builder.take()` has already moved the filled line into `_lines` and reset `_result` to a fresh empty `BufferLine`. The post-loop block (lines 144-150 in the current source) then reparents the tail anchor onto that fresh empty line. If no further content lands in the builder before `finish()` exits — which is the case whenever the post-loop block fires on a non-wrapped logical line — the empty builder line is never appended to `_lines`, and the anchor ends up pointing to a `BufferLine` that the reflow result never includes.\n\n**Trigger paths in production code:**\n\n1. `SelectAllTextIntent` (`lib/src/terminal/src/ui/shortcut/actions.dart:60-63`) creates the end anchor at `x = terminal.viewWidth`. That is *exactly* the past-trimmedLength position for every partially-filled line in the buffer. Any user who Ctrl+A's and then resizes the terminal narrower hits the bug for every short line in the scrollback.\n2. `selectCharacters` / mouse drag selection (`lib/src/terminal/src/ui/render.dart:286-298`) — anchors are clamped to `[0, viewWidth-1]` but can sit past `trimmedLength` on a partially-filled line. Drag past content end + resize narrower trips the bug.\n3. `selectWord` (`render.dart:264-275`) — `getWordBoundary` walks until a separator OR `viewWidth`, so the end anchor of a near-edge word can land at `x = viewWidth` and trip the bug on resize.\n\n**Symptom:** selection extents lose track of content after a width change. Visible highlight stops moving with the underlying selection, or extents disappear off the rendered buffer entirely. No exception is thrown — the dangling anchor still has a valid `BufferLine` reference, it just isn't on a line in the visible buffer.\n\n**Acceptance:**\n- New unit test in `test/terminal/core/core_test.dart` (or a sibling) that:\n  - Constructs a partially-filled source line and an anchor past `trimmedLength`,\n  - Runs reflow shrink,\n  - Asserts the anchor's owning line is *in the reflow output list*, not dangling.\n- The existing widget-level select-all behaviour still works on resize: a Ctrl+A across the buffer followed by a narrower resize keeps the selection's end anchor pointing to a line in the reflowed result.\n- No regression in the existing reflow tests (the tail-clamp cases, wide-char boundaries, multi-line wrapped runs).\n\n**Investigation notes (do not skip):**\n\nThe fix is conceptually small — the reparented tail anchor must land on a line that gets emitted. Two candidate shapes:\n\n- **Skip the reparent entirely.** Anchors past `trimmedLength` arguably shouldn't survive a shrink that drops their column. Risk: callers expect every anchor on the source to be reparented somewhere; silently disposing them changes semantics.\n- **Force `finish()` to flush the builder line.** Whenever the tail-anchor branch fired during `_addPart`, set a flag, and have `finish()` emit the builder line even if `isEmpty`. Risk: empty trailing lines start showing up in the reflow result, which would break callers that assume reflow returns only content lines (resize loop in `Buffer.resize` pads to viewport height after, so an extra empty might be benign there but worth checking).\n\nDon't pick one without re-reading the full reflow flow + every caller of `reflow()`. The selection round-trip is also tested at the widget layer indirectly — verify `make test-a11y` still passes after the change.\n\n**Surfaced from:** T-91 test sweep (commit 3196c49). The 100% coverage on reflow.dart was achieved by exercising this branch but explicitly *not* asserting on the resulting line being in the output — see the test comment.\n\n**Cross-references:** T-91 (epic parent for the test sweep that found this), T-89 (coverage epic), the test in `test/terminal/core/core_test.dart` group `reflow` named \"anchors on the source line tail (past trimmedLength) get reparented\" documents the current (buggy) behaviour.\n",
+      "status": "in_progress",
+      "priority": "high",
+      "created_at": "2026-05-07 05:51:48",
+      "updated_at": "2026-05-07 05:56:47"
     }
   ],
   "ticket_deps": null,
@@ -4429,6 +4439,19 @@
       "old_value": "backlog",
       "new_value": "in_progress",
       "changed_at": "2026-05-06 20:50:32"
+    },
+    {
+      "ticket_id": "T-92",
+      "field": "description",
+      "new_value": "**File:** `lib/src/terminal/src/core/reflow.dart` (`_LineReflow._addPart`).\n\n**Bug:** Anchors whose x-coordinate sits past the source line's `trimmedLength` get reparented onto whatever `_builder._result` is active at that moment. After the main reparenting loop has run with `lineFilled` on the final iteration, `_builder.take()` has already moved the filled line into `_lines` and reset `_result` to a fresh empty `BufferLine`. The post-loop block (lines 144-150 in the current source) then reparents the tail anchor onto that fresh empty line. If no further content lands in the builder before `finish()` exits — which is the case whenever the post-loop block fires on a non-wrapped logical line — the empty builder line is never appended to `_lines`, and the anchor ends up pointing to a `BufferLine` that the reflow result never includes.\n\n**Trigger paths in production code:**\n\n1. `SelectAllTextIntent` (`lib/src/terminal/src/ui/shortcut/actions.dart:60-63`) creates the end anchor at `x = terminal.viewWidth`. That is *exactly* the past-trimmedLength position for every partially-filled line in the buffer. Any user who Ctrl+A's and then resizes the terminal narrower hits the bug for every short line in the scrollback.\n2. `selectCharacters` / mouse drag selection (`lib/src/terminal/src/ui/render.dart:286-298`) — anchors are clamped to `[0, viewWidth-1]` but can sit past `trimmedLength` on a partially-filled line. Drag past content end + resize narrower trips the bug.\n3. `selectWord` (`render.dart:264-275`) — `getWordBoundary` walks until a separator OR `viewWidth`, so the end anchor of a near-edge word can land at `x = viewWidth` and trip the bug on resize.\n\n**Symptom:** selection extents lose track of content after a width change. Visible highlight stops moving with the underlying selection, or extents disappear off the rendered buffer entirely. No exception is thrown — the dangling anchor still has a valid `BufferLine` reference, it just isn't on a line in the visible buffer.\n\n**Acceptance:**\n- New unit test in `test/terminal/core/core_test.dart` (or a sibling) that:\n  - Constructs a partially-filled source line and an anchor past `trimmedLength`,\n  - Runs reflow shrink,\n  - Asserts the anchor's owning line is *in the reflow output list*, not dangling.\n- The existing widget-level select-all behaviour still works on resize: a Ctrl+A across the buffer followed by a narrower resize keeps the selection's end anchor pointing to a line in the reflowed result.\n- No regression in the existing reflow tests (the tail-clamp cases, wide-char boundaries, multi-line wrapped runs).\n\n**Investigation notes (do not skip):**\n\nThe fix is conceptually small — the reparented tail anchor must land on a line that gets emitted. Two candidate shapes:\n\n- **Skip the reparent entirely.** Anchors past `trimmedLength` arguably shouldn't survive a shrink that drops their column. Risk: callers expect every anchor on the source to be reparented somewhere; silently disposing them changes semantics.\n- **Force `finish()` to flush the builder line.** Whenever the tail-anchor branch fired during `_addPart`, set a flag, and have `finish()` emit the builder line even if `isEmpty`. Risk: empty trailing lines start showing up in the reflow result, which would break callers that assume reflow returns only content lines (resize loop in `Buffer.resize` pads to viewport height after, so an extra empty might be benign there but worth checking).\n\nDon't pick one without re-reading the full reflow flow + every caller of `reflow()`. The selection round-trip is also tested at the widget layer indirectly — verify `make test-a11y` still passes after the change.\n\n**Surfaced from:** T-91 test sweep (commit 3196c49). The 100% coverage on reflow.dart was achieved by exercising this branch but explicitly *not* asserting on the resulting line being in the output — see the test comment.\n\n**Cross-references:** T-91 (epic parent for the test sweep that found this), T-89 (coverage epic), the test in `test/terminal/core/core_test.dart` group `reflow` named \"anchors on the source line tail (past trimmedLength) get reparented\" documents the current (buggy) behaviour.\n",
+      "changed_at": "2026-05-07 05:52:26"
+    },
+    {
+      "ticket_id": "T-92",
+      "field": "status",
+      "old_value": "backlog",
+      "new_value": "in_progress",
+      "changed_at": "2026-05-07 05:56:47"
     }
   ]
 }

CHANGELOG.md

@@ -47,6 +47,15 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Fixed
 
+- Terminal selections no longer silently disappear when the terminal is
+  resized narrower. Reflow's tail-anchor handler used to reparent
+  anchors past the source's trimmed-content range onto a builder line
+  that was never emitted, leaving them detached from the visible
+  buffer; the selection controller's `extent.attached` check then
+  returned null and the highlight vanished. Common trigger paths:
+  Ctrl+A (select-all) followed by a width change, and mouse drag
+  selections that extended past the end of a partially-filled line
+  (T-92).
 - `BufferLine.removeCells` / `insertCells` / `dispose` no longer skip
   anchors due to concurrent list modification during iteration —
   surfaced by unit tests added under T-91. Anchors disposed inside

lib/src/terminal/src/core/reflow.dart

@@ -18,6 +18,15 @@ class _LineBuilder {
 
   bool get isNotEmpty => _length != 0;
 
+  /// True when the result line carries at least one CellAnchor. Used by
+  /// [_LineReflow.finish] to flush an otherwise-empty trailing line when
+  /// the tail-anchor branch in `_addPart` reparented an anchor onto it
+  /// — without this guard the anchor would point to a `BufferLine` that
+  /// reflow never emits, the selection controller's `extent.attached`
+  /// check would fail, and the selection would silently vanish on resize
+  /// (T-92).
+  bool get hasAnchors => _result.anchors.isNotEmpty;
+
   /// Adds a range of cells from [src] to the builder. Anchors within the range
   /// will be reparented to the new line returned by [take].
   void add(BufferLine src, int start, int length) {
@@ -152,7 +161,11 @@ class _LineReflow {
 
   /// Finalizes the reflow operation and returns the result.
   List<BufferLine> finish() {
-    if (_builder.isNotEmpty) {
+    // Emit the trailing builder line if it has content OR if it's
+    // carrying an anchor. The latter keeps tail-anchored selections
+    // (e.g. SelectAllTextIntent's end anchor at x=viewWidth) attached
+    // to a line that's actually in the reflow output (T-92).
+    if (_builder.isNotEmpty || _builder.hasAnchors) {
       _lines.add(_builder.take(wrapped: _lines.isNotEmpty));
     }
 

test/terminal/core/core_test.dart

@@ -354,17 +354,30 @@ void main() {
       expect(out[0].getCodePoint(3), 0);
     });
 
-    test('anchors on the source line tail (past trimmedLength) get reparented', () {
-      // The post-loop branch in `_addPart` reparents anchors whose x sits
-      // beyond the trimmed-content range — the empty tail of an over-wide
-      // source line. The anchor moves off the source onto whichever
-      // builder line was active at the time, regardless of whether that
-      // builder line ends up emitted — so the only contract we can rely
-      // on is that the anchor no longer points to the source.
+    test('anchors on the source line tail (past trimmedLength) land on a line in the result (T-92)', () {
+      // The post-loop tail-anchor branch in `_addPart` reparents the
+      // anchor onto the active builder line. The fix in T-92 makes
+      // `finish()` emit that builder line when it has anchors, even if
+      // it's otherwise empty — so the anchor's `line` is guaranteed to
+      // be in the reflow result and stays attached after replaceWith.
       final src = line(12, 'abcdefgh'); // width 12, content 8
       final tail = src.createAnchor(10); // past trimmedLength (8)
-      reflow(ring([src]), 12, 4);
-      expect(tail.line, isNot(equals(src)));
+      final out = reflow(ring([src]), 12, 4);
+      expect(tail.line, isNotNull);
+      expect(out.contains(tail.line), isTrue);
+    });
+
+    test('SelectAllTextIntent-shaped end anchor survives shrink (T-92 regression)', () {
+      // Models the actual bug path: SelectAllTextIntent (actions.dart)
+      // creates an end anchor at x = viewWidth on the last buffer line.
+      // Resizing narrower must not silently drop the selection.
+      final src = line(12, 'short');
+      final endAnchor = src.createAnchor(12); // viewWidth, past trimmedLength
+      final out = reflow(ring([src]), 12, 4);
+      expect(out.contains(endAnchor.line), isTrue,
+          reason: 'end anchor must land on a line that survives '
+              'lines.replaceWith — otherwise selection.attached is false '
+              'and the selection silently vanishes after resize.');
     });
 
     test('inner wide-char clamp during _addPart leaves the wide cell to the next iteration', () {