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fix: auto-enable accessibility defaults on simulator boot (#290)
On iOS 26+ fresh simulators, AccessibilityEnabled and ApplicationAccessibilityEnabled default to 0, which prevents accessibility hierarchy queries from returning any elements. Enable both flags via xcrun simctl spawn defaults write after boot_sim and build_run_sim boot the simulator. The check is idempotent (reads first, writes only if needed) and failures are logged but never propagated to avoid blocking boot.
1 parent b6f49dd commit c33e842

6 files changed

Lines changed: 248 additions & 1 deletion

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‎CHANGELOG.md‎

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# Changelog
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## [Unreleased]
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### Fixed
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- Fixed `snapshot_ui` returning empty accessibility hierarchy on iOS 26+ simulators by auto-enabling accessibility defaults at simulator boot ([#290](https://github.com/getsentry/XcodeBuildMCP/issues/290)).
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## [2.3.2]
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### Fixed

‎src/mcp/tools/simulator/__tests__/boot_sim.test.ts‎

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@@ -142,7 +142,8 @@ describe('boot_sim tool', () => {
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await boot_simLogic({ simulatorId: 'test-uuid-123' }, mockExecutor);
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expect(calls).toHaveLength(1);
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// First call is the boot command; subsequent calls are from ensureSimulatorAccessibility
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expect(calls.length).toBeGreaterThanOrEqual(1);
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expect(calls[0]).toEqual({
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command: ['xcrun', 'simctl', 'boot', 'test-uuid-123'],
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description: 'Boot Simulator',

‎src/mcp/tools/simulator/boot_sim.ts‎

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@@ -7,6 +7,7 @@ import {
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createSessionAwareTool,
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getSessionAwareToolSchemaShape,
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} from '../../../utils/typed-tool-factory.ts';
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import { ensureSimulatorAccessibility } from '../../../utils/simulator-accessibility.ts';
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const baseSchemaObject = z.object({
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simulatorId: z
@@ -59,6 +60,9 @@ export async function boot_simLogic(
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};
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}
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// Ensure accessibility defaults are enabled (required for UI hierarchy on iOS 26+)
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await ensureSimulatorAccessibility(params.simulatorId, executor);
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return {
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content: [
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{

‎src/mcp/tools/simulator/build_run_sim.ts‎

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@@ -22,6 +22,7 @@ import { determineSimulatorUuid } from '../../../utils/simulator-utils.ts';
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import { nullifyEmptyStrings } from '../../../utils/schema-helpers.ts';
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import { inferPlatform } from '../../../utils/infer-platform.ts';
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import { constructDestinationString } from '../../../utils/xcode.ts';
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import { ensureSimulatorAccessibility } from '../../../utils/simulator-accessibility.ts';
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// Unified schema: XOR between projectPath and workspacePath, and XOR between simulatorId and simulatorName
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const baseOptions = {
@@ -346,6 +347,9 @@ export async function build_run_simLogic(
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} else {
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log('info', `Simulator ${simulatorId} is already booted`);
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}
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// Ensure accessibility defaults are enabled (required for UI hierarchy on iOS 26+)
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await ensureSimulatorAccessibility(simulatorId, executor);
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} catch (error) {
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const errorMessage = error instanceof Error ? error.message : String(error);
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log('error', `Error checking/booting simulator: ${errorMessage}`);

‎src/utils/__tests__/simulator-accessibility.test.ts‎

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@@ -0,0 +1,141 @@
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import { describe, it, expect } from 'vitest';
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import {
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createMockExecutor,
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createCommandMatchingMockExecutor,
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createMockCommandResponse,
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} from '../../test-utils/mock-executors.ts';
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import type { CommandExecutor } from '../execution/index.ts';
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import { ensureSimulatorAccessibility } from '../simulator-accessibility.ts';
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const SIM_UUID = '12345678-1234-4234-8234-123456789012';
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describe('ensureSimulatorAccessibility', () => {
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it('should enable accessibility when currently disabled', async () => {
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const executorCalls: string[][] = [];
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const mockExecutor = createCommandMatchingMockExecutor({
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'defaults read': { output: '0' },
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'defaults write': { success: true, output: '' },
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});
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const trackingExecutor: CommandExecutor = async (...args) => {
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executorCalls.push(args[0] as string[]);
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return mockExecutor(...args);
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};
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await ensureSimulatorAccessibility(SIM_UUID, trackingExecutor);
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expect(executorCalls).toHaveLength(3);
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expect(executorCalls[0].join(' ')).toContain('defaults read');
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expect(executorCalls[1].join(' ')).toContain('AccessibilityEnabled');
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expect(executorCalls[1].join(' ')).toContain('defaults write');
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expect(executorCalls[2].join(' ')).toContain('ApplicationAccessibilityEnabled');
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expect(executorCalls[2].join(' ')).toContain('defaults write');
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});
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it('should skip writes when accessibility is already enabled', async () => {
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const executorCalls: string[][] = [];
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const mockExecutor = createMockExecutor({
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success: true,
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output: '1',
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});
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const trackingExecutor: CommandExecutor = async (...args) => {
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executorCalls.push(args[0] as string[]);
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return mockExecutor(...args);
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};
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await ensureSimulatorAccessibility(SIM_UUID, trackingExecutor);
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// Only the read command should have been called
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expect(executorCalls).toHaveLength(1);
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expect(executorCalls[0].join(' ')).toContain('defaults read');
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});
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it('should not throw when read command fails', async () => {
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const mockExecutor = createCommandMatchingMockExecutor({
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'defaults read': { success: false, output: '', error: 'Domain does not exist' },
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'AccessibilityEnabled -bool': { success: false, error: 'write failed' },
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});
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// Should not throw
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await ensureSimulatorAccessibility(SIM_UUID, mockExecutor);
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});
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it('should not throw when executor throws', async () => {
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const mockExecutor = createMockExecutor(new Error('spawn failed'));
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// Should not throw
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await ensureSimulatorAccessibility(SIM_UUID, mockExecutor);
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});
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it('should stop if first write fails', async () => {
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const executorCalls: string[][] = [];
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const callCount = { n: 0 };
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const mockExecutor: CommandExecutor = async (command, ...rest) => {
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const cmd = (command as string[]).join(' ');
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executorCalls.push(command as string[]);
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callCount.n++;
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if (cmd.includes('defaults read')) {
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return createMockCommandResponse({ success: true, output: '0' });
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}
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if (cmd.includes('defaults write') && callCount.n === 2) {
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return createMockCommandResponse({ success: false, error: 'write failed' });
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}
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return createMockCommandResponse({ success: true, output: '' });
85+
};
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await ensureSimulatorAccessibility(SIM_UUID, mockExecutor);
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// read + first write only (second write should not happen)
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expect(executorCalls).toHaveLength(2);
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});
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it('should pass correct simctl spawn commands', async () => {
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const executorCalls: string[][] = [];
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const mockExecutor: CommandExecutor = async (command) => {
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const cmd = (command as string[]).join(' ');
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executorCalls.push(command as string[]);
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if (cmd.includes('defaults read')) {
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return createMockCommandResponse({ success: true, output: '0' });
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}
101+
return createMockCommandResponse({ success: true, output: '' });
102+
};
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104+
await ensureSimulatorAccessibility(SIM_UUID, mockExecutor);
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106+
expect(executorCalls[0]).toEqual([
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'xcrun',
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'simctl',
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'spawn',
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SIM_UUID,
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'defaults',
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'read',
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'com.apple.Accessibility',
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'AccessibilityEnabled',
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]);
116+
expect(executorCalls[1]).toEqual([
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'xcrun',
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'simctl',
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'spawn',
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SIM_UUID,
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'defaults',
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'write',
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'com.apple.Accessibility',
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'AccessibilityEnabled',
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'-bool',
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'true',
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]);
128+
expect(executorCalls[2]).toEqual([
129+
'xcrun',
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'simctl',
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'spawn',
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SIM_UUID,
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'defaults',
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'write',
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'com.apple.Accessibility',
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'ApplicationAccessibilityEnabled',
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'-bool',
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'true',
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]);
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});
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});

‎src/utils/simulator-accessibility.ts‎

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import type { CommandExecutor } from './execution/index.ts';
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import { log } from './logging/index.ts';
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const LOG_PREFIX = '[Simulator]';
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/**
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* Ensure accessibility defaults are enabled on a simulator.
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* On iOS 26+ fresh simulators, AccessibilityEnabled and ApplicationAccessibilityEnabled
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* default to 0, which prevents accessibility hierarchy queries from returning any elements.
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*
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* This is safe to call on any simulator — it checks the current value first and
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* only writes if needed. The write is idempotent and persists until device erasure.
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*
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* Failures are logged but never propagated — accessibility setup should not block boot.
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*/
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export async function ensureSimulatorAccessibility(
17+
simulatorId: string,
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executor: CommandExecutor,
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): Promise<void> {
20+
try {
21+
const readResult = await executor(
22+
[
23+
'xcrun',
24+
'simctl',
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'spawn',
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simulatorId,
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'defaults',
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'read',
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'com.apple.Accessibility',
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'AccessibilityEnabled',
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],
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`${LOG_PREFIX}: read accessibility defaults`,
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);
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35+
if (readResult.output?.trim() === '1') {
36+
return; // already enabled
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}
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39+
const writeA11y = await executor(
40+
[
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'xcrun',
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'simctl',
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'spawn',
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simulatorId,
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'defaults',
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'write',
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'com.apple.Accessibility',
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'AccessibilityEnabled',
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'-bool',
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'true',
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],
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`${LOG_PREFIX}: enable AccessibilityEnabled`,
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);
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if (!writeA11y.success) {
56+
log('warn', `${LOG_PREFIX}: Failed to enable AccessibilityEnabled: ${writeA11y.error}`);
57+
return;
58+
}
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60+
const writeAppA11y = await executor(
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[
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'xcrun',
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'simctl',
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'spawn',
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simulatorId,
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'defaults',
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'write',
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'com.apple.Accessibility',
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'ApplicationAccessibilityEnabled',
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'-bool',
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'true',
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],
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`${LOG_PREFIX}: enable ApplicationAccessibilityEnabled`,
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);
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if (!writeAppA11y.success) {
77+
log(
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'warn',
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`${LOG_PREFIX}: Failed to enable ApplicationAccessibilityEnabled: ${writeAppA11y.error}`,
80+
);
81+
return;
82+
}
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84+
log('info', `${LOG_PREFIX}: Accessibility defaults enabled for simulator ${simulatorId}`);
85+
} catch (error) {
86+
log(
87+
'warn',
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`${LOG_PREFIX}: Failed to check/enable accessibility defaults: ${error instanceof Error ? error.message : String(error)}`,
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);
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}
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}

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