fix(app): stabilize native composer sizing after edits (#4946)

* fix(app): stabilize native composer sizing after edits

* test(app): verify workspace composer space after keyboard dismissal

* test(app): start the hold-to-delete regression mid-draft

From the end of the draft the pre-fix input also returns to baseline. Placing the cursor
eight lines into the draft before the first hold-delete leaves the old build at the
capped height with the placeholder visible, and the fixed build at one line.

packages/app/e2e/mobile/composer-keyboard/android.sh

@@ -17,6 +17,7 @@ DAEMON_HOME="${PASEO_COMPOSER_KEYBOARD_DAEMON_HOME:-${REPO_ROOT}/.dev/composer-e
 SERVER_ID="${PASEO_COMPOSER_KEYBOARD_SERVER_ID:-}"
 MESSAGE=$'keyboard invariant line one\nline two\nline three\nline four'
 LONG_MESSAGE="$(node -e 'process.stdout.write(Array.from({ length: 180 }, (_, index) => `line${index + 1}`).join(" "))')"
+BLANK_LINE_DRAFT="$(node -e 'process.stdout.write("\n".repeat(22) + "ddjdj")')"
 AGENT_TITLE="Keyboard dismiss QA $(date +%s)"
 
 if [[ -z "${SERVER_ID}" ]]; then
@@ -280,6 +281,35 @@ node "${ASSERT}" xml-composer-contained \
   "${ARTIFACTS_DIR}/long-draft-keyboard-open.xml" \
   "$(read_ime_top)" \
   "${display_density}"
+# Emptying a capped blank-line draft with Gboard's hold-to-delete must return the input to
+# its baseline height. Fabric only re-measures the Android input when its text prop changes,
+# so the editing input renders again after every edit
+# (packages/app/src/components/ui/text-input/text-input.native.tsx). The sequence mirrors the
+# report: grow to the cap, close and reopen the keyboard, hold delete from the middle of the
+# draft, jump to the end, hold delete again. The first hold-delete must start mid-draft: from
+# the end, the pre-fix input also returns to baseline. Backspace sits on Gboard's third key
+# row on the paseo-api35 layout.
+adb shell ime set "${HELPER_IME}" >/dev/null
+ad fill 'editable=true' "${BLANK_LINE_DRAFT}" --settle
+open_gboard "${input_x}" "${input_y}"
+adb shell input keyevent BACK
+wait_for_ime false
+open_gboard "${input_x}" "${input_y}"
+adb shell input keycombination 113 122
+adb shell input keyevent 20 20 20 20 20 20 20 20
+screen_width="$(adb shell wm size | sed -n 's/.*: \([0-9]*\)x.*/\1/p' | tail -1)"
+backspace_x="$((screen_width - 85))"
+backspace_y="$(($(read_ime_top) + 507))"
+adb shell input swipe "${backspace_x}" "${backspace_y}" "${backspace_x}" "${backspace_y}" 8000
+adb shell input keycombination 113 123
+adb shell input swipe "${backspace_x}" "${backspace_y}" "${backspace_x}" "${backspace_y}" 12000
+adb shell ime set "${HELPER_IME}" >/dev/null
+ad wait 'label="Message, @files, /commands"' 10000
+snapshot_json "${ARTIFACTS_DIR}/after-hold-delete.json"
+node "${ASSERT}" same-input-height \
+  "${ARTIFACTS_DIR}/baseline.json" \
+  "${ARTIFACTS_DIR}/after-hold-delete.json"
+
 adb shell ime set "${HELPER_IME}" >/dev/null
 ad fill 'editable=true' "${MESSAGE}" --settle
 open_gboard "${input_x}" "${input_y}"
@@ -362,4 +392,13 @@ node "${ASSERT}" xml-composer-contained \
   "$(read_ime_top)" \
   "${display_density}"
 
+adb shell input keyevent BACK
+wait_for_ime false
+adb shell ime set "${HELPER_IME}" >/dev/null
+snapshot_json "${ARTIFACTS_DIR}/new-workspace-long-draft-keyboard-closed.json"
+capture_screen "${ARTIFACTS_DIR}/new-workspace-long-draft-keyboard-closed.png"
+node "${ASSERT}" same-input-height \
+  "${ARTIFACTS_DIR}/new-workspace-long-draft.json" \
+  "${ARTIFACTS_DIR}/new-workspace-long-draft-keyboard-closed.json"
+
 echo "Composer keyboard invariants passed"

packages/app/e2e/mobile/composer-keyboard/assert-composer-keyboard.mjs

@@ -103,7 +103,9 @@ if (command === "xml-composer-contained") {
     readInputHeight(firstPath),
     readInputHeight(secondPath),
   ]);
-  if (firstHeight !== secondHeight) {
+  // Yoga rounds each edge to physical pixels; moving the same-sized input can
+  // change its reported height by one pixel when its origin is fractional.
+  if (Math.abs(firstHeight - secondHeight) > 1) {
     throw new Error(`Composer height drifted from ${firstHeight} to ${secondHeight}`);
   }
 } else if (command === "has-exact-text") {

packages/app/src/components/ui/text-input/text-input.native.tsx

@@ -1,4 +1,11 @@
-import React, { forwardRef, useCallback, useImperativeHandle, useRef, useState } from "react";
+import React, {
+  forwardRef,
+  useCallback,
+  useImperativeHandle,
+  useRef,
+  useReducer,
+  useState,
+} from "react";
 import { TextInput } from "react-native";
 import { BottomSheetTextInput } from "@gorhom/bottom-sheet";
 import PasteInput, {
@@ -46,6 +53,12 @@ export const EditingTextInput = forwardRef<EditingTextInputHandle, EditingTextIn
     // once the view is attached.
     const isAwaitingReplacementRef = useRef(false);
     const [replacement, setReplacement] = useState({ revision: 0, autoFocus: false });
+    // Fabric re-measures the Android input when its `text` prop changes. A native edit only
+    // refreshes a cached spannable, and batched IME deletes (Gboard hold-to-delete) leave the
+    // measured height at the previous content, so an emptied draft keeps several lines. Render
+    // again after every edit so `defaultValue` carries the current text and the input is
+    // re-measured. Only this leaf renders; the composer stays isolated from typing.
+    const [, bumpTextRevision] = useReducer((revision: number) => revision + 1, 0);
 
     const assignInputRef = useCallback((input: NativeInput | null) => {
       inputRef.current = input;
@@ -107,6 +120,7 @@ export const EditingTextInput = forwardRef<EditingTextInputHandle, EditingTextIn
       (nextText: string) => {
         textRef.current = nextText;
         onChangeText?.(nextText);
+        bumpTextRevision();
       },
       [onChangeText],
     );

packages/app/src/composer/draft/workspace-tab.tsx

@@ -630,7 +630,7 @@ export function WorkspaceDraftAgentTab({
     [composerState.agentControls, handleDropdownCloseFocus, isSubmitting],
   );
   return (
-    <ComposerViewport style={styles.container} bottomInset={insets.bottom}>
+    <ComposerViewport style={styles.container} bottomInset={insets.bottom} keyboardReserve="retain">
       <FileDropZone style={styles.container}>
         <View style={styles.contentContainer}>
           {isSubmitting && draftAgent ? (

packages/app/src/composer/input/input.tsx

@@ -1961,9 +1961,13 @@ const styles = StyleSheet.create((theme: Theme) => ({
     color: theme.colors.foreground,
     fontSize: theme.fontSize.content,
     fontWeight: theme.fontWeight.normal,
-    lineHeight: theme.fontSize.content * 1.4,
+    // No lineHeight on native. React Native applies it as a span over the text, and an
+    // empty trailing line is laid out from the font's own metrics on some devices, so
+    // the input jumps when the first character lands on a new line. The font's natural
+    // line box is the same for every line. Web keeps the CSS value.
     ...(isWeb
       ? ({
+          lineHeight: theme.fontSize.content * 1.4,
           outlineStyle: "none",
           outlineWidth: 0,
           outlineColor: "transparent",

packages/app/src/composer/viewport/capacity.test.ts

@@ -2,37 +2,47 @@ import { describe, expect, it } from "vitest";
 import { resolveComposerCapacity, updateComposerCapacity } from "./capacity";
 
 describe("composer viewport", () => {
-  it("preserves the editing capacity when the keyboard closes", () => {
+  it("preserves the editing capacity when the keyboard closes on a docked composer", () => {
     const viewport = { height: 582, bottomInset: 24, centered: false };
-    const open = updateComposerCapacity(undefined, { ...viewport, keyboardShift: 308 });
-    const closed = updateComposerCapacity(open, { ...viewport, keyboardShift: 0 });
+    const open = updateComposerCapacity(undefined, { ...viewport, keyboardShift: 308 }, "retain");
+    const closed = updateComposerCapacity(open, { ...viewport, keyboardShift: 0 }, "retain");
     expect(open.capacity).toBe(245);
     expect(closed.capacity).toBe(open.capacity);
-    expect(updateComposerCapacity(closed, { ...viewport, keyboardShift: 250 }).capacity).toBe(303);
+    expect(
+      updateComposerCapacity(closed, { ...viewport, keyboardShift: 250 }, "retain").capacity,
+    ).toBe(303);
+  });
+
+  it("releases the whole viewport when the keyboard closes on a form", () => {
+    const viewport = { height: 582, bottomInset: 24, centered: false };
+    const open = updateComposerCapacity(undefined, { ...viewport, keyboardShift: 308 }, "release");
+    const closed = updateComposerCapacity(open, { ...viewport, keyboardShift: 0 }, "release");
+    expect(open.capacity).toBe(245);
+    expect(closed.capacity).toBe(553);
+    expect(
+      updateComposerCapacity(closed, { ...viewport, keyboardShift: 308 }, "release").capacity,
+    ).toBe(245);
   });
 
   it("remeasures the viewport without forgetting the keyboard reservation", () => {
-    const open = updateComposerCapacity(undefined, {
-      height: 582,
-      bottomInset: 24,
-      centered: false,
-      keyboardShift: 308,
-    });
+    const open = updateComposerCapacity(
+      undefined,
+      { height: 582, bottomInset: 24, centered: false, keyboardShift: 308 },
+      "retain",
+    );
     expect(
-      updateComposerCapacity(open, {
-        height: 650,
-        bottomInset: 24,
-        centered: false,
-        keyboardShift: 0,
-      }).capacity,
+      updateComposerCapacity(
+        open,
+        { height: 650, bottomInset: 24, centered: false, keyboardShift: 0 },
+        "retain",
+      ).capacity,
     ).toBe(313);
     expect(
-      updateComposerCapacity(open, {
-        height: 0,
-        bottomInset: 24,
-        centered: false,
-        keyboardShift: 0,
-      }),
+      updateComposerCapacity(
+        open,
+        { height: 0, bottomInset: 24, centered: false, keyboardShift: 0 },
+        "retain",
+      ),
     ).toEqual(open);
   });
   it("leaves five points below the header for a bottom-anchored composer", () => {

packages/app/src/composer/viewport/capacity.ts

@@ -10,6 +10,14 @@ export interface ComposerCapacity {
   capacity: number;
 }
 
+/**
+ * What the closed keyboard leaves behind. A docked chat composer retains its last
+ * editing reservation so a capped draft does not expand over the stream. A form
+ * that scrolls inside the constrained space releases it so the whole form is
+ * visible again once the keyboard is gone.
+ */
+export type KeyboardReservePolicy = "retain" | "release";
+
 export function resolveComposerCapacity(input: ComposerGeometry): number {
   "worklet";
   // A centered form grows upward by half its height. Reserve both halves so
@@ -22,13 +30,15 @@ export function resolveComposerCapacity(input: ComposerGeometry): number {
 export function updateComposerCapacity(
   previous: ComposerCapacity | undefined,
   input: ComposerGeometry,
+  policy: KeyboardReservePolicy,
 ): ComposerCapacity {
   "worklet";
   if (input.height <= 0 && previous) return previous;
-  // Closing the keyboard moves the composer; it does not enlarge its editing
-  // capacity. A subsequent keyboard opening supplies the next reservation.
+  // A subsequent keyboard opening always supplies the next reservation.
   const keyboardReserve =
-    input.keyboardShift > 0 ? input.keyboardShift : (previous?.keyboardReserve ?? 0);
+    input.keyboardShift > 0 || policy === "release"
+      ? input.keyboardShift
+      : (previous?.keyboardReserve ?? 0);
   return {
     keyboardReserve,
     capacity: resolveComposerCapacity({ ...input, keyboardShift: keyboardReserve }),

packages/app/src/composer/viewport/index.native.tsx

@@ -8,13 +8,18 @@ import Animated, {
   type SharedValue,
 } from "react-native-reanimated";
 import { useKeyboardShift } from "@/hooks/keyboard-shift-context";
-import { updateComposerCapacity, type ComposerCapacity } from "./capacity";
+import {
+  updateComposerCapacity,
+  type ComposerCapacity,
+  type KeyboardReservePolicy,
+} from "./capacity";
 
 const ViewportCapacity = createContext<SharedValue<number | undefined> | null>(null);
 
 interface ComposerViewportProps extends ViewProps {
   bottomInset?: number;
   centered?: boolean;
+  keyboardReserve?: KeyboardReservePolicy;
 }
 
 /** Measure the stationary space below the header, outside keyboard translation. */
@@ -23,6 +28,7 @@ export function ComposerViewport({
   onLayout,
   bottomInset = 0,
   centered = false,
+  keyboardReserve = "release",
   ...props
 }: ComposerViewportProps) {
   const measuredHeight = useSharedValue(0);
@@ -37,8 +43,9 @@ export function ComposerViewport({
     }),
     (geometry) => {
       if (geometry.height <= 0) return;
-      sizing.value = updateComposerCapacity(sizing.value, geometry);
+      sizing.value = updateComposerCapacity(sizing.value, geometry, keyboardReserve);
     },
+    [keyboardReserve],
   );
   const capacity = useDerivedValue(() => sizing.value?.capacity);
   const measureViewport = useCallback(

packages/app/src/composer/viewport/index.tsx

@@ -3,11 +3,13 @@ import { View, type ViewProps } from "react-native";
 interface ComposerViewportProps extends ViewProps {
   bottomInset?: number;
   centered?: boolean;
+  keyboardReserve?: "retain" | "release";
 }
 
 export function ComposerViewport({
   bottomInset: _bottomInset,
   centered: _centered,
+  keyboardReserve: _keyboardReserve,
   ...props
 }: ComposerViewportProps) {
   return <View {...props} />;

packages/app/src/panels/agent-panel.tsx

@@ -1280,7 +1280,7 @@ const ChatAgentReadyContent = memo(function ChatAgentReadyContent({
       setText={agentInputDraft.replaceText}
       onRewindComplete={handleRewindComplete}
     >
-      <ComposerViewport style={styles.root}>
+      <ComposerViewport style={styles.root} keyboardReserve="retain">
         <DockedChatSurface disabled={isArchivingCurrentAgent}>
           {contentContainer}