diff --git a/src/web/public/terminal-ui.js b/src/web/public/terminal-ui.js
index 4dfa7364..17b934cc 100644
--- a/src/web/public/terminal-ui.js
+++ b/src/web/public/terminal-ui.js
@@ -1428,8 +1428,11 @@ Object.assign(CodemanApp.prototype, {
         // frame — this observer only ever measured Pane A's container, so
         // without this call Pane B never learned about a window resize, an
         // Alt+B sidebar toggle, or a tab-rail drag, and its PTY silently
-        // stayed at whatever size it was last dragged to.
-        this._forEachTile?.((tile) => tile.fit());
+        // stayed at whatever size it was last dragged to. Grid tiles are left
+        // out: the grid's own observer (tile-grid.js _scheduleTileGridRefit)
+        // refits every one of them on the same resize, and a second fit here
+        // only re-measured six panes to send nothing.
+        this._forEachTile?.((tile) => tile.fit(), { grid: false });
       }, 300); // Trailing-edge: only fire after 300ms of no resize events
     };
 
diff --git a/test/tile-grid-park-guards.test.ts b/test/tile-grid-park-guards.test.ts
index b995ce60..d7a21b65 100644
--- a/test/tile-grid-park-guards.test.ts
+++ b/test/tile-grid-park-guards.test.ts
@@ -29,6 +29,8 @@
  * tile-grid.js in one `vm` context, with the shared fake DOM and fake
  * TerminalTile (test/mocks/tile-grid-vm.ts). Port: N/A.
  */
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import {
   FakeTile,
@@ -357,6 +359,22 @@ describe('panes and fonts while the grid is open', () => {
     expect(pane.sessionId).toBe('s-a');
   });
 
+  it("the main terminal's window-resize timer leaves grid tiles to the grid's own observer", () => {
+    // A window resize fires both: the grid's ResizeObserver refits every tile
+    // (tile-grid.js _scheduleTileGridRefit) and the main terminal's trailing
+    // timer used to refit them again, twelve fit() calls for six tiles and
+    // nothing more sent (measured). The timer lives inside initTerminal(), so
+    // this reads its source; the split's Pane B is still refitted there.
+    const src = readFileSync(resolve(import.meta.dirname, '../src/web/public/terminal-ui.js'), 'utf8');
+    const start = src.indexOf('const throttledResize = () => {');
+    const end = src.indexOf("window.addEventListener('resize', throttledResize)", start);
+    expect(start).toBeGreaterThan(-1);
+    expect(end).toBeGreaterThan(start);
+    const calls = src.slice(start, end).match(/this\._forEachTile\?\.\([^;]*;/g) ?? [];
+    expect(calls).toHaveLength(1);
+    expect(calls[0]).toContain('{ grid: false }');
+  });
+
   it('_forEachTile reaches every grid tile; { grid: false } skips them', () => {
     const app = appWithGrid(true);
     const seen: string[] = [];