fix(app): stabilize native terminal rendering

Scale custom glyph paths in measured cell coordinates so box-drawing runs fill their cells on Android. Debounce daemon resize claims at the terminal pane boundary so keyboard layout animation sends only the settled dimensions.

packages/app/src/components/terminal-pane.tsx

@@ -53,6 +53,10 @@ import { useSessionStore } from "@/stores/session-store";
 import { toXtermTheme } from "@/utils/to-xterm-theme";
 import TerminalEmulator, { type TerminalEmulatorHandle } from "./terminal-emulator";
 import { TerminalFloatingCopyAction, TerminalPasteAction } from "./terminal-copy-paste-actions";
+import {
+  createTerminalResizeDebouncer,
+  type TerminalResizeRequest,
+} from "./terminal-resize-debouncer";
 import { useIsCompactFormFactor } from "@/constants/layout";
 import { isNative } from "@/constants/platform";
 import {
@@ -85,6 +89,7 @@ interface TerminalPaneProps {
 }
 
 const TERMINAL_REFIT_DELAYS_MS = [0, 48, 144, 320];
+const TERMINAL_RESIZE_DEBOUNCE_MS = 100;
 
 const MODIFIER_LABELS = {
   ctrl: "Ctrl",
@@ -759,52 +764,70 @@ export function TerminalPane({
     ],
   );
 
-  const handleTerminalResize = useStableEvent(
-    (input: { rows: number; cols: number; shouldClaim: boolean; forceClaim?: boolean }) => {
-      const { rows, cols } = input;
-      if (rows <= 0 || cols <= 0) {
-        return;
-      }
-      const normalizedRows = Math.floor(rows);
-      const normalizedCols = Math.floor(cols);
-      const nextSize = { rows: normalizedRows, cols: normalizedCols };
-      measuredTerminalSizeRef.current = nextSize;
-      const claim = resolveTerminalResizeClaim({
-        size: nextSize,
-        previousSentSize: lastSentTerminalSizeRef.current,
-        shouldClaim: input.shouldClaim,
-        forceClaim: input.forceClaim ?? false,
-        supportsTerminalSizeOwnership,
-        readiness: {
-          isWorkspaceFocused: isTerminalActive,
-          isPaneFocused,
-          isAppActivelyVisible,
-          isClientReady: client !== null,
-          isConnected,
-          isRendererReady: rendererReadyStreamKey === terminalStreamKey,
-        },
+  const sendTerminalResize = useStableEvent((input: TerminalResizeRequest) => {
+    const nextSize = { rows: input.rows, cols: input.cols };
+    const claim = resolveTerminalResizeClaim({
+      size: nextSize,
+      previousSentSize: lastSentTerminalSizeRef.current,
+      shouldClaim: input.shouldClaim,
+      forceClaim: input.forceClaim ?? false,
+      supportsTerminalSizeOwnership,
+      readiness: {
+        isWorkspaceFocused: isTerminalActive,
+        isPaneFocused,
+        isAppActivelyVisible,
+        isClientReady: client !== null,
+        isConnected,
+        isRendererReady: rendererReadyStreamKey === terminalStreamKey,
+      },
+    });
+    let sent = false;
+    if (client && terminalId && claim.shouldSend) {
+      lastSentTerminalSizeRef.current = nextSize;
+      client.sendTerminalInput(terminalId, {
+        type: "resize",
+        rows: input.rows,
+        cols: input.cols,
+        intent: claim.intent,
       });
-      let sent = false;
-      if (client && terminalId && claim.shouldSend) {
-        lastSentTerminalSizeRef.current = nextSize;
-        client.sendTerminalInput(terminalId, {
-          type: "resize",
-          rows: normalizedRows,
-          cols: normalizedCols,
-          intent: claim.intent,
-        });
-        sent = true;
-      }
-      const requestedKey = paneFocusResizeClaimRef.current.requestedKey;
-      if (requestedKey && claim.intent === "claim") {
-        paneFocusResizeClaimRef.current = settleFocusClaim(paneFocusResizeClaimRef.current, {
-          key: requestedKey,
-          sent,
-        });
-      }
-    },
+      sent = true;
+    }
+    const requestedKey = paneFocusResizeClaimRef.current.requestedKey;
+    if (requestedKey && claim.intent === "claim") {
+      paneFocusResizeClaimRef.current = settleFocusClaim(paneFocusResizeClaimRef.current, {
+        key: requestedKey,
+        sent,
+      });
+    }
+  });
+
+  const terminalResizeDebouncer = useMemo(
+    () =>
+      createTerminalResizeDebouncer({
+        delayMs: TERMINAL_RESIZE_DEBOUNCE_MS,
+        emit: sendTerminalResize,
+      }),
+    [sendTerminalResize],
   );
 
+  useEffect(
+    () => () => terminalResizeDebouncer.cancel(),
+    [terminalResizeDebouncer, terminalStreamKey],
+  );
+
+  const handleTerminalResize = useStableEvent((input: TerminalResizeRequest) => {
+    if (input.rows <= 0 || input.cols <= 0) {
+      return;
+    }
+    const nextResize = {
+      ...input,
+      rows: Math.floor(input.rows),
+      cols: Math.floor(input.cols),
+    };
+    measuredTerminalSizeRef.current = { rows: nextResize.rows, cols: nextResize.cols };
+    terminalResizeDebouncer.schedule(nextResize);
+  });
+
   const handleTerminalKey = useCallback(
     async (input: { key: string; ctrl: boolean; shift: boolean; alt: boolean; meta: boolean }) => {
       sendTerminalKey(input);

packages/app/src/components/terminal-resize-debouncer.test.ts

@@ -0,0 +1,68 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { createTerminalResizeDebouncer } from "./terminal-resize-debouncer";
+
+describe("terminal resize debouncer", () => {
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("emits only the latest size after resize callbacks settle", () => {
+    vi.useFakeTimers();
+    const emitted: Array<{
+      rows: number;
+      cols: number;
+      shouldClaim: boolean;
+      forceClaim?: boolean;
+    }> = [];
+    const debouncer = createTerminalResizeDebouncer({
+      delayMs: 100,
+      emit: (resize) => emitted.push(resize),
+    });
+
+    debouncer.schedule({ rows: 40, cols: 100, shouldClaim: false });
+    vi.advanceTimersByTime(50);
+    debouncer.schedule({ rows: 35, cols: 100, shouldClaim: false });
+    vi.advanceTimersByTime(99);
+
+    expect(emitted).toEqual([]);
+
+    vi.advanceTimersByTime(1);
+
+    expect(emitted).toEqual([{ rows: 35, cols: 100, shouldClaim: false }]);
+  });
+
+  it("preserves a claim while taking the latest dimensions", () => {
+    vi.useFakeTimers();
+    const emitted: Array<{
+      rows: number;
+      cols: number;
+      shouldClaim: boolean;
+      forceClaim?: boolean;
+    }> = [];
+    const debouncer = createTerminalResizeDebouncer({
+      delayMs: 100,
+      emit: (resize) => emitted.push(resize),
+    });
+
+    debouncer.schedule({ rows: 40, cols: 100, shouldClaim: true, forceClaim: true });
+    debouncer.schedule({ rows: 35, cols: 100, shouldClaim: false });
+    vi.runAllTimers();
+
+    expect(emitted).toEqual([{ rows: 35, cols: 100, shouldClaim: true, forceClaim: true }]);
+  });
+
+  it("cancels a pending resize", () => {
+    vi.useFakeTimers();
+    const emitted: unknown[] = [];
+    const debouncer = createTerminalResizeDebouncer({
+      delayMs: 100,
+      emit: (resize) => emitted.push(resize),
+    });
+
+    debouncer.schedule({ rows: 40, cols: 100, shouldClaim: false });
+    debouncer.cancel();
+    vi.runAllTimers();
+
+    expect(emitted).toEqual([]);
+  });
+});

packages/app/src/components/terminal-resize-debouncer.ts

@@ -0,0 +1,47 @@
+export interface TerminalResizeRequest {
+  rows: number;
+  cols: number;
+  shouldClaim: boolean;
+  forceClaim?: boolean;
+}
+
+export function createTerminalResizeDebouncer(input: {
+  delayMs: number;
+  emit: (resize: TerminalResizeRequest) => void;
+}): {
+  schedule: (resize: TerminalResizeRequest) => void;
+  cancel: () => void;
+} {
+  let timeout: ReturnType<typeof setTimeout> | null = null;
+  let pending: TerminalResizeRequest | null = null;
+
+  const cancel = () => {
+    if (timeout !== null) {
+      clearTimeout(timeout);
+      timeout = null;
+    }
+    pending = null;
+  };
+
+  return {
+    schedule: (resize) => {
+      pending = {
+        ...resize,
+        shouldClaim: (pending?.shouldClaim ?? false) || resize.shouldClaim,
+        forceClaim: (pending?.forceClaim ?? false) || resize.forceClaim || undefined,
+      };
+      if (timeout !== null) {
+        clearTimeout(timeout);
+      }
+      timeout = setTimeout(() => {
+        timeout = null;
+        const resizeToEmit = pending;
+        pending = null;
+        if (resizeToEmit) {
+          input.emit(resizeToEmit);
+        }
+      }, input.delayMs);
+    },
+    cancel,
+  };
+}

packages/app/src/terminal/native-renderer/terminal-grid-metrics.test.ts

@@ -1,12 +1,23 @@
 import { describe, expect, it } from "vitest";
 
 import {
+  resolveTerminalCustomGlyphCellTransform,
   resolveTerminalGridMetricsMeasurement,
   resolveMeasuredTerminalCellMetrics,
   resolveTerminalCursorOffset,
 } from "./terminal-grid-metrics";
 
 describe("native terminal grid metrics", () => {
+  it("places each normalized custom glyph in run viewport coordinates", () => {
+    expect(
+      resolveTerminalCustomGlyphCellTransform({
+        cellOffset: 57,
+        cellWidth: 7.4,
+        cellHeight: 16.2,
+      }),
+    ).toBe("matrix(7.4 0 0 16.2 421.8 0)");
+  });
+
   it("preserves fractional measured cell width for horizontal layout", () => {
     expect(
       resolveMeasuredTerminalCellMetrics({

packages/app/src/terminal/native-renderer/terminal-grid-metrics.ts

@@ -21,6 +21,19 @@ export interface TerminalCursorOffset {
   y: number;
 }
 
+export interface TerminalCustomGlyphCellTransformInput {
+  cellOffset: number;
+  cellWidth: number;
+  cellHeight: number;
+}
+
+export function resolveTerminalCustomGlyphCellTransform(
+  input: TerminalCustomGlyphCellTransformInput,
+): string {
+  const translateX = input.cellOffset * input.cellWidth;
+  return `matrix(${input.cellWidth} 0 0 ${input.cellHeight} ${translateX} 0)`;
+}
+
 export function resolveMeasuredTerminalCellMetrics(
   input: TerminalGridCellMetricsInput,
 ): TerminalGridCellMetrics {

packages/app/src/terminal/native-renderer/terminal-grid-view.native.tsx

@@ -22,6 +22,7 @@ import { resolveNativeTerminalFontFamily } from "./font.native";
 import type { TerminalViewportState } from "./headless-terminal-state";
 import {
   resolveMeasuredTerminalCellMetrics,
+  resolveTerminalCustomGlyphCellTransform,
   resolveTerminalGridMetricsMeasurement,
   resolveTerminalCursorOffset,
   type TerminalGridCellMetrics,
@@ -192,7 +193,7 @@ function TerminalGridCustomGlyphRun({
         pointerEvents="none"
         preserveAspectRatio="none"
         style={styles.customGlyphSvg}
-        viewBox={`0 0 ${run.cellCount} 1`}
+        viewBox={`0 0 ${run.cellCount * cellWidth} ${cellHeight}`}
         width={run.cellCount * cellWidth}
       >
         <G fill="none" stroke={run.foregroundColor}>
@@ -204,7 +205,11 @@ function TerminalGridCustomGlyphRun({
                 strokeLinecap="butt"
                 strokeLinejoin="miter"
                 strokeWidth={cell.glyph.strokeWidth}
-                transform={`translate(${cell.offset} 0)`}
+                transform={resolveTerminalCustomGlyphCellTransform({
+                  cellOffset: cell.offset,
+                  cellWidth,
+                  cellHeight,
+                })}
                 vectorEffect="non-scaling-stroke"
               />
             ) : null,