chh-ay · Oct 8, 2026 · Oct 8, 2026 · Oct 8, 2026 · Oct 8, 2026 · Oct 8, 2026
diff --git a/.changeset/interaction-sessions.md b/.changeset/interaction-sessions.md
@@ -0,0 +1,5 @@
+---
+"@sheetwrite/core": patch
+---
+
+Keep row and column resize previews out of the document until release, then record one undoable change. Cancel active pointer gestures on sheet, view, structure, or read-only changes and ignore other pointers during a drag. Keep all editors bound to their original document cell through sorting and filtering. Notify selection changes before edit-begin, prevent reentrant handlers from reopening stale editors, and leave selection unchanged when a fill is rejected.
diff --git a/bench/README.md b/bench/README.md
@@ -273,6 +273,28 @@ artifact was a one-off before/after pair, and a release cannot re-measure a
 baseline build. `bench:release` refreshes both captures, and
 `bench:interaction:smoke` rehearses the interaction one.
 
+`bench:interaction-sessions` supplements that browser capture with synchronous
+Grid-interface timings under happy-dom: row and column resize with twenty move
+events followed by release, editor open/commit, pointer selection, and two
+untouched controls (one hundred cell-input reads and a column aggregate).
+It reports eleven raw samples in milliseconds per operation after three discarded
+warmups. Each sample runs two thousand resize/edit operations, ten thousand
+selection/read operations, or two hundred thousand aggregates. Garbage collection
+and fixture restoration are outside the timed interval; resize includes admission
+and history, but not undo. Longer samples keep sub-millisecond paths from turning
+process startup and scheduling noise into an apparent regression.
+These are imperative-path timings, not browser paint or input-to-frame latency.
+For comparisons, build each checkout's packages first. Run five A/A ABBA control
+rounds with the same baseline in both slots, then five actual ABBA rounds on the
+same CPU under an exclusive lock. Compare medians of the per-round medians and
+retain every raw round. A broad noise band makes a changed-path comparison
+inconclusive; it does not excuse a slower result. Leave fifteen seconds between
+locked commands so other checkouts can acquire the shared lock.
+
+```sh
+flock -x /home/vvin/learn/quiet.lock taskset -c 4 bun run bench:interaction-sessions
+```
+
 A change to a harness source file, to the sampling flags, or to the protocol
 version invalidates the committed render baseline: `bench:check` compares the
 harness hashes, the declared sampling, and the runner (OS, CPU, Bun, Node,

diff --git a/bench/package.json b/bench/package.json
@@ -13,6 +13,7 @@
     "bench:paged:smoke": "bun run src/paged-bench.ts --smoke",
     "bench:interaction": "bun run src/interaction-bench.ts",
     "bench:interaction:smoke": "bun run src/interaction-bench.ts --smoke",
+    "bench:interaction-sessions": "bun run src/interaction-sessions-bench.ts",
     "bench:core-paths": "bun run src/core-paths-bench.ts --output results/core-paths-results.json",
     "bench:core-paths:smoke": "bun run src/core-paths-bench.ts --smoke",
     "bench:release": "bun run src/release-capture.ts",

diff --git a/bench/src/interaction-sessions-bench.ts b/bench/src/interaction-sessions-bench.ts
@@ -0,0 +1,118 @@
+import "./dom-setup.js";
+import { createGrid, DEFAULT_THEME, initSheetwrite, type Workbook } from "@sheetwrite/core";
+import { installCanvasTestStubs } from "@sheetwrite/core/testing";
+
+const ROWS = 100;
+const INTERACTION_ITERATIONS = 2_000;
+const CONTROL_ITERATIONS = 10_000;
+const AGGREGATE_ITERATIONS = 200_000;
+const WARMUPS = 3;
+const SAMPLES = 11;
+const DRAG_STEPS = 20;
+await initSheetwrite();
+const restoreCanvas = installCanvasTestStubs();
+const workbook: Workbook = {
+  activeSheet: "s1",
+  sheets: [
+    {
+      id: "s1",
+      name: "Timing",
+      rowCount: ROWS,
+      columns: [
+        { key: "name", header: "Name", type: "text", width: 160 },
+        { key: "amount", header: "Amount", type: "number", width: 120 },
+      ],
+    },
+  ],
+};
+const host = document.createElement("div");
+Object.defineProperties(host, { clientWidth: { value: 800 }, clientHeight: { value: 400 } });
+document.body.appendChild(host);
+const grid = createGrid(host, {
+  workbook,
+  data: {
+    rowCount: ROWS,
+    columns: {
+      name: Array.from({ length: ROWS }, (_, row) => `Row ${row}`),
+      amount: Float64Array.from({ length: ROWS }, (_, row) => row),
+    },
+  },
+  config: { toolbar: false, tabs: false, find: false, contextMenu: false },
+});
+const scroller = host.querySelector(".sheetwrite-scroller");
+if (!(scroller instanceof HTMLElement)) throw new Error("Timing grid scroller missing");
+const pointer = (type: string, x: number, y: number) =>
+  scroller.dispatchEvent(
+    new PointerEvent(type, { clientX: x, clientY: y, pointerId: 1, button: 0, bubbles: true }),
+  );
+const samples: Record<string, number[]> = {};
+try {
+  for (const workload of [
+    "column-resize",
+    "row-resize",
+    "edit",
+    "selection",
+    "get-cell",
+    "aggregate",
+  ] as const) {
+    const timings: number[] = [];
+    const iterations =
+      workload === "aggregate"
+        ? AGGREGATE_ITERATIONS
+        : workload === "selection" || workload === "get-cell"
+          ? CONTROL_ITERATIONS
+          : INTERACTION_ITERATIONS;
+    for (let sample = -WARMUPS; sample < SAMPLES; sample++) {
+      Bun.gc(true);
+      let elapsed = 0;
+      for (let iteration = 0; iteration < iterations; iteration++) {
+        const started = performance.now();
+        if (workload === "column-resize" || workload === "row-resize") {
+          const isColumn = workload === "column-resize";
+          const x = isColumn ? DEFAULT_THEME.rowHeaderWidth + 160 : 10;
+          const y = isColumn ? 10 : DEFAULT_THEME.headerHeight + DEFAULT_THEME.rowHeight;
+          pointer("pointerdown", x, y);
+          for (let step = 1; step <= DRAG_STEPS; step++)
+            pointer("pointermove", x + (isColumn ? step : 0), y + (isColumn ? 0 : step));
+          pointer("pointerup", x + (isColumn ? DRAG_STEPS : 0), y + (isColumn ? 0 : DRAG_STEPS));
+        } else if (workload === "edit") {
+          grid.beginEdit(0, 0, "Timing edit");
+          const editor = host.querySelector("textarea.sheetwrite-editor");
+          if (!(editor instanceof HTMLTextAreaElement)) throw new Error("Timing editor missing");
+          editor.dispatchEvent(new KeyboardEvent("keydown", { key: "Enter", bubbles: true }));
+        } else if (workload === "selection") {
+          pointer(
+            "pointerdown",
+            DEFAULT_THEME.rowHeaderWidth + 40,
+            DEFAULT_THEME.headerHeight + 10,
+          );
+          pointer(
+            "pointermove",
+            DEFAULT_THEME.rowHeaderWidth + 200,
+            DEFAULT_THEME.headerHeight + 60,
+          );
+          pointer("pointerup", DEFAULT_THEME.rowHeaderWidth + 200, DEFAULT_THEME.headerHeight + 60);
+        } else if (workload === "get-cell") {
+          for (let row = 0; row < ROWS; row++) grid.getCellInput(row, 1);
+        } else {
+          grid.aggregate(1, "sum");
+        }
+        elapsed += performance.now() - started;
+        // Reset outside timing: baseline row drags have multiple history entries
+        // and baseline column undo does not restore its pre-preview width.
+        if (workload === "column-resize") grid.setColumnWidth(0, 160);
+        else if (workload === "row-resize") grid.setRowHeight(0, DEFAULT_THEME.rowHeight);
+        else if (workload === "edit") grid.undo();
+      }
+      if (sample >= 0) timings.push(elapsed / iterations);
+    }
+    samples[workload] = timings;
+  }
+  process.stdout.write(
+    `${JSON.stringify({ unit: "ms/operation", warmups: WARMUPS, interactionIterations: INTERACTION_ITERATIONS, controlIterations: CONTROL_ITERATIONS, aggregateIterations: AGGREGATE_ITERATIONS, samples })}\n`,
+  );
+} finally {
+  grid.destroy();
+  host.remove();
+  restoreCanvas();
+}
diff --git a/docs/public/llms-full.txt b/docs/public/llms-full.txt
@@ -2878,6 +2878,18 @@ Row and full-column selections are part of the model. Column selection is wired
 the top header; **row selection is programmatic only** — there is no row-header
 click gesture, so set it via `setSelection({ kind: "row", sheet, row })`.
 
+Only the pointer that began a drag can change it. Switching sheets, changing
+sheet structure or the sorted/filtered view, or losing pointer capture ends the
+gesture; a later pointer release cannot apply it to a different sheet or view.
+
+## Resizing
+
+Drag a column-header boundary or a row-header boundary to preview its size.
+The preview changes geometry only: the document and undo history remain intact
+until release. Release submits one undoable size change. Cancellation, capture
+loss, or a rejected change restores the document's size. Turning read-only on
+ends an active resize without committing.
+
 ## Keyboard navigation
 
 When the grid is focused and not editing:
@@ -2947,6 +2959,19 @@ Commit and navigation keys:
 While the IME is composing, keystrokes belong to the composition and are not
 treated as navigation. Editing emits `edit-begin` and `edit-commit` events.
 
+`beginEdit` closes the previous editor, selects the requested cell, and emits
+`selection` when that changes the selection, then emits `edit-begin` before
+opening the editor. A synchronous handler can replace or cancel the request
+without the old editor reopening.
+Successful completion emits `change`, then `edit-commit`, then the navigation's
+`selection` event; rejected completion does not emit `edit-commit` or navigate.
+Event addresses remain view coordinates.
+
+Stock, validation, and custom editors retain the underlying document cell while
+sorting or filtering changes its visible position. Completion writes that same
+cell, not whichever row now occupies the old position. If the cell leaves the
+view, or sheet structure changes, the editor is cancelled.
+
 ## Clipboard interoperability
 
 Copy and cut always produce injection-hardened TSV and, where the browser exposes

diff --git a/docs/src/content/docs/api/core/create-grid.md b/docs/src/content/docs/api/core/create-grid.md
@@ -8,7 +8,7 @@ description: "Creates and mounts an imperative Grid in the supplied host element
 Creates and mounts an imperative Grid in the supplied host element.
 
 <dl class="api-metadata" data-pagefind-ignore>
-<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L347"><code>packages/core/src/grid.ts#L347</code></a></dd></div>
+<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L341"><code>packages/core/src/grid.ts#L341</code></a></dd></div>
 </dl>
 
 ## Declaration

diff --git a/docs/src/content/docs/api/core/default-theme.md b/docs/src/content/docs/api/core/default-theme.md
@@ -8,7 +8,7 @@ description: "Default canvas theme used before CSS and explicit theme overrides.
 Default canvas theme used before CSS and explicit theme overrides.
 
 <dl class="api-metadata" data-pagefind-ignore>
-<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L256"><code>packages/core/src/grid.ts#L256</code></a></dd></div>
+<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L250"><code>packages/core/src/grid.ts#L250</code></a></dd></div>
 </dl>
 
 ## Declaration

diff --git a/docs/src/content/docs/api/core/init-sheetwrite.md b/docs/src/content/docs/api/core/init-sheetwrite.md
@@ -9,7 +9,7 @@ Load one WASM engine before `createGrid`. The default is `@sheetwrite/wasm`.
 Pass the `@sheetwrite/formulas` module as the second argument to select the full engine.
 
 <dl class="api-metadata" data-pagefind-ignore>
-<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L290"><code>packages/core/src/grid.ts#L290</code></a></dd></div>
+<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L284"><code>packages/core/src/grid.ts#L284</code></a></dd></div>
 </dl>
 
 ## Declaration

diff --git a/docs/src/content/docs/api/core/is-sheetwrite-ready.md b/docs/src/content/docs/api/core/is-sheetwrite-ready.md
@@ -8,7 +8,7 @@ description: "Whether initSheetwrite has completed — the single readiness sour
 Whether `initSheetwrite` has completed — the single readiness source.
 
 <dl class="api-metadata" data-pagefind-ignore>
-<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L302"><code>packages/core/src/grid.ts#L302</code></a></dd></div>
+<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L296"><code>packages/core/src/grid.ts#L296</code></a></dd></div>
 </dl>
 
 ## Declaration

diff --git a/docs/src/content/docs/api/core/resolve-theme-from-css.md b/docs/src/content/docs/api/core/resolve-theme-from-css.md
@@ -8,7 +8,7 @@ description: "Read --sheetwrite- CSS custom properties into a partial theme."
 Read `--sheetwrite-*` CSS custom properties into a partial theme.
 
 <dl class="api-metadata" data-pagefind-ignore>
-<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L307"><code>packages/core/src/grid.ts#L307</code></a></dd></div>
+<div><dt>Source</dt><dd><a href="https://github.com/chh-ay/sheetwrite/blob/main/packages/core/src/grid.ts#L301"><code>packages/core/src/grid.ts#L301</code></a></dd></div>
 </dl>
 
 ## Declaration

diff --git a/docs/src/content/docs/guides/interaction.md b/docs/src/content/docs/guides/interaction.md
@@ -48,6 +48,18 @@ Row and full-column selections are part of the model. Column selection is wired
 the top header; **row selection is programmatic only** — there is no row-header
 click gesture, so set it via `setSelection({ kind: "row", sheet, row })`.
 
+Only the pointer that began a drag can change it. Switching sheets, changing
+sheet structure or the sorted/filtered view, or losing pointer capture ends the
+gesture; a later pointer release cannot apply it to a different sheet or view.
+
+## Resizing
+
+Drag a column-header boundary or a row-header boundary to preview its size.
+The preview changes geometry only: the document and undo history remain intact
+until release. Release submits one undoable size change. Cancellation, capture
+loss, or a rejected change restores the document's size. Turning read-only on
+ends an active resize without committing.
+
 ## Keyboard navigation
 
 When the grid is focused and not editing:
@@ -117,6 +129,19 @@ Commit and navigation keys:
 While the IME is composing, keystrokes belong to the composition and are not
 treated as navigation. Editing emits `edit-begin` and `edit-commit` events.
 
+`beginEdit` closes the previous editor, selects the requested cell, and emits
+`selection` when that changes the selection, then emits `edit-begin` before
+opening the editor. A synchronous handler can replace or cancel the request
+without the old editor reopening.
+Successful completion emits `change`, then `edit-commit`, then the navigation's
+`selection` event; rejected completion does not emit `edit-commit` or navigate.
+Event addresses remain view coordinates.
+
+Stock, validation, and custom editors retain the underlying document cell while
+sorting or filtering changes its visible position. Completion writes that same
+cell, not whichever row now occupies the old position. If the cell leaves the
+view, or sheet structure changes, the editor is cancelled.
+
 ## Clipboard interoperability
 
 Copy and cut always produce injection-hardened TSV and, where the browser exposes

diff --git a/docs/src/generated/docs-contract.json b/docs/src/generated/docs-contract.json
@@ -25,7 +25,7 @@
   "entryPointCount": 20,
   "exportCount": 484,
   "symbolPageCount": 484,
-  "apiSha256": "3d8e4e61e382a25d648d082e3a7285b986cbf7257c1c66562c34c652408697cd",
+  "apiSha256": "9ab557ec2487315a0942b87c4b2a50f3468980980c3bb6f1c04267a3bd03b386",
   "compatibilitySha256": "0e2d1e8db45a097ab437bdcb85591c8fddabd60cd6dcfcf2bc2098588e2966f6",
   "formulaContractSha256": "daec72c46c939824c564fe3fe0758858f67c298a7c888f18fd4a060f467bd3b0"
 }
diff --git a/docs/src/generated/public-api.json b/docs/src/generated/public-api.json
@@ -864,7 +864,7 @@
               "owners": [
                 "src/grid.ts"
               ],
-              "source": "src/grid.ts#L347",
+              "source": "src/grid.ts#L341",
               "jsDocTags": [],
               "documentation": "Creates and mounts an imperative Grid in the supplied host element.",
               "memberDocs": []
@@ -1157,7 +1157,7 @@
               "owners": [
                 "src/grid.ts"
               ],
-              "source": "src/grid.ts#L256",
+              "source": "src/grid.ts#L250",
               "jsDocTags": [],
               "documentation": "Default canvas theme used before CSS and explicit theme overrides.",
               "memberDocs": []
@@ -2037,7 +2037,7 @@
               "owners": [
                 "src/grid.ts"
               ],
-              "source": "src/grid.ts#L290",
+              "source": "src/grid.ts#L284",
               "jsDocTags": [],
               "documentation": "Load one WASM engine before `createGrid`. The default is `@sheetwrite/wasm`.\nPass the `@sheetwrite/formulas` module as the second argument to select the full engine.",
               "memberDocs": []
@@ -2073,7 +2073,7 @@
               "owners": [
                 "src/grid.ts"
               ],
-              "source": "src/grid.ts#L302",
+              "source": "src/grid.ts#L296",
               "jsDocTags": [],
               "documentation": "Whether `initSheetwrite` has completed — the single readiness source.",
               "memberDocs": []
@@ -2877,7 +2877,7 @@
               "owners": [
                 "src/grid.ts"
               ],
-              "source": "src/grid.ts#L307",
+              "source": "src/grid.ts#L301",
               "jsDocTags": [],
               "documentation": "Read `--sheetwrite-*` CSS custom properties into a partial theme.",
               "memberDocs": []

diff --git a/packages/core/src/column-index.ts b/packages/core/src/column-index.ts
@@ -6,7 +6,7 @@ export class ColumnIndex {
   private readonly columns: Int32Array;
   private readonly offsets: Float64Array;
   private readonly positions: Int32Array;
-  private readonly total: number;
+  private total: number;
 
   constructor(columns: readonly number[], widths: ArrayLike<number>) {
     const count = columns.length;
@@ -41,6 +41,19 @@ export class ColumnIndex {
     return this.total;
   }
 
+  /** Update a visible span without reallocating the reverse map or prefix storage. */
+  setWidth(absoluteCol: number, width: number): void {
+    const position = this.positionOf(absoluteCol);
+    if (position === -1) return;
+    const previous = (this.offsets[position + 1] ?? 0) - (this.offsets[position] ?? 0);
+    const delta = width - previous;
+    if (delta === 0) return;
+    for (let i = position + 1; i < this.offsets.length; i++) {
+      this.offsets[i] = (this.offsets[i] ?? 0) + delta;
+    }
+    this.total += delta;
+  }
+
   /** Sum of widths of visible columns before `absoluteCol`. */
   leftOf(absoluteCol: number): number {
     const position = this.positionOf(absoluteCol);