diff --git a/packages/desktop/scripts/ensure-node-pty-exec.mjs b/packages/desktop/scripts/ensure-node-pty-exec.mjs
index a09270092..0b2e32285 100644
--- a/packages/desktop/scripts/ensure-node-pty-exec.mjs
+++ b/packages/desktop/scripts/ensure-node-pty-exec.mjs
@@ -1,21 +1,16 @@
 #!/usr/bin/env node
 import { chmodSync, existsSync, readdirSync, statSync } from 'node:fs';
-import { join } from 'node:path';
+import { createRequire } from 'node:module';
+import { dirname, join } from 'node:path';
 
 const SHIPPED_ARCH = 'darwin-arm64';
 
-const prebuildsDirFor = (resourcesDir) =>
-  join(resourcesDir, 'app.asar.unpacked', 'node_modules', 'node-pty', 'prebuilds');
-
-export function ensureNodePtySpawnHelperExecutable(resourcesDir) {
-  const prebuildsDir = prebuildsDirFor(resourcesDir);
+function chmodSpawnHelpersUnderPrebuilds(prebuildsDir, remediation) {
   const requiredHelper = join(prebuildsDir, SHIPPED_ARCH, 'spawn-helper');
   if (!existsSync(requiredHelper)) {
     throw new Error(
       `[ensure-node-pty-exec] node-pty ${SHIPPED_ARCH} spawn-helper missing at ${requiredHelper}. ` +
-        `Confirm node-pty is a desktop dependency and the '**/node-pty/prebuilds/**' asarUnpack ` +
-        `rule in electron-builder.yml unpacked it — without an executable spawn-helper on the real ` +
-        `filesystem, pty.fork() fails at runtime with "posix_spawnp failed".`,
+        remediation,
     );
   }
 
@@ -29,3 +24,41 @@ export function ensureNodePtySpawnHelperExecutable(resourcesDir) {
   }
   return chmodded;
 }
+
+function resolveNodePtyDir() {
+  const require = createRequire(import.meta.url);
+  return dirname(require.resolve('node-pty/package.json'));
+}
+
+export function ensureNodePtySpawnHelperExecutable(resourcesDir) {
+  const prebuildsDir = join(
+    resourcesDir,
+    'app.asar.unpacked',
+    'node_modules',
+    'node-pty',
+    'prebuilds',
+  );
+  return chmodSpawnHelpersUnderPrebuilds(
+    prebuildsDir,
+    `Confirm node-pty is a desktop dependency and the '**/node-pty/prebuilds/**' asarUnpack ` +
+      `rule in electron-builder.yml unpacked it — without an executable spawn-helper on the real ` +
+      `filesystem, pty.fork() fails at runtime with "posix_spawnp failed".`,
+  );
+}
+
+export function ensureNodePtySpawnHelperExecutableInNodeModules(nodePtyDir = resolveNodePtyDir()) {
+  return chmodSpawnHelpersUnderPrebuilds(
+    join(nodePtyDir, 'prebuilds'),
+    `Confirm node-pty is installed (it is a desktop dependency) and 'bun install' did not run ` +
+      `with --ignore-scripts — without an executable spawn-helper, pty.fork() fails at runtime ` +
+      `with "posix_spawnp failed" and the in-app terminal cannot spawn a shell.`,
+  );
+}
+
+export function ensureNodePtySpawnHelperExecutableInNodeModulesSafe(nodePtyDir) {
+  try {
+    return { ok: true, chmodded: ensureNodePtySpawnHelperExecutableInNodeModules(nodePtyDir) };
+  } catch (err) {
+    return { ok: false, error: err instanceof Error ? err : new Error(String(err)) };
+  }
+}
diff --git a/packages/desktop/scripts/postinstall.mjs b/packages/desktop/scripts/postinstall.mjs
index c4815004a..1daaba9e4 100644
--- a/packages/desktop/scripts/postinstall.mjs
+++ b/packages/desktop/scripts/postinstall.mjs
@@ -1,5 +1,17 @@
 #!/usr/bin/env node
 import { spawn } from 'node:child_process';
+import { ensureNodePtySpawnHelperExecutableInNodeModulesSafe } from './ensure-node-pty-exec.mjs';
+
+const spawnHelper = ensureNodePtySpawnHelperExecutableInNodeModulesSafe();
+if (spawnHelper.ok) {
+  console.log(
+    `[desktop postinstall] node-pty spawn-helper marked executable (${spawnHelper.chmodded.length} file(s))`,
+  );
+} else {
+  console.warn(
+    `[desktop postinstall] could not make node-pty spawn-helper executable: ${spawnHelper.error.message}`,
+  );
+}
 
 if (process.env.ELECTRON_SKIP_REBUILD === '1') {
   console.log(
diff --git a/packages/desktop/tests/unit/ensure-node-pty-exec.test.ts b/packages/desktop/tests/unit/ensure-node-pty-exec.test.ts
index 2ffad50cc..36573c9a5 100644
--- a/packages/desktop/tests/unit/ensure-node-pty-exec.test.ts
+++ b/packages/desktop/tests/unit/ensure-node-pty-exec.test.ts
@@ -2,7 +2,11 @@ import { afterEach, describe, expect, test } from 'bun:test';
 import { chmodSync, mkdirSync, mkdtempSync, rmSync, statSync, writeFileSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { join } from 'node:path';
-import { ensureNodePtySpawnHelperExecutable } from '../../scripts/ensure-node-pty-exec.mjs';
+import {
+  ensureNodePtySpawnHelperExecutable,
+  ensureNodePtySpawnHelperExecutableInNodeModules,
+  ensureNodePtySpawnHelperExecutableInNodeModulesSafe,
+} from '../../scripts/ensure-node-pty-exec.mjs';
 
 const tmpRoots: string[] = [];
 
@@ -67,3 +71,72 @@ describe('ensureNodePtySpawnHelperExecutable', () => {
     );
   });
 });
+
+function nodeModulesHelperPath(nodePtyDir: string, arch: string): string {
+  return join(nodePtyDir, 'prebuilds', arch, 'spawn-helper');
+}
+
+function makeNodeModulesFixture(archDirs: string[]): string {
+  const root = mkdtempSync(join(tmpdir(), 'ok-nodepty-dev-exec-'));
+  tmpRoots.push(root);
+  const nodePtyDir = join(root, 'node_modules', 'node-pty');
+  for (const arch of archDirs) {
+    const helper = nodeModulesHelperPath(nodePtyDir, arch);
+    mkdirSync(join(helper, '..'), { recursive: true });
+    writeFileSync(helper, 'fake-mach-o');
+    chmodSync(helper, 0o644);
+  }
+  return nodePtyDir;
+}
+
+describe('ensureNodePtySpawnHelperExecutableInNodeModules', () => {
+  test('promotes the shipped darwin-arm64 spawn-helper from 0644 to executable 0755', () => {
+    const nodePtyDir = makeNodeModulesFixture(['darwin-arm64']);
+    const helper = nodeModulesHelperPath(nodePtyDir, 'darwin-arm64');
+    expect(statSync(helper).mode & 0o111).toBe(0); // no execute bits to start
+
+    const chmodded = ensureNodePtySpawnHelperExecutableInNodeModules(nodePtyDir);
+
+    expect(chmodded).toContain(helper);
+    expect(statSync(helper).mode & 0o777).toBe(0o755);
+  });
+
+  test('chmods every prebuild arch present in node_modules, not just the shipped one', () => {
+    const nodePtyDir = makeNodeModulesFixture(['darwin-arm64', 'darwin-x64']);
+
+    const chmodded = ensureNodePtySpawnHelperExecutableInNodeModules(nodePtyDir);
+
+    expect(chmodded.length).toBe(2);
+    for (const arch of ['darwin-arm64', 'darwin-x64']) {
+      expect(statSync(nodeModulesHelperPath(nodePtyDir, arch)).mode & 0o777).toBe(0o755);
+    }
+  });
+
+  test('throws when the shipped darwin-arm64 spawn-helper is absent (broken install is a hard error)', () => {
+    const nodePtyDir = makeNodeModulesFixture(['darwin-x64']); // arm64 helper missing
+    expect(() => ensureNodePtySpawnHelperExecutableInNodeModules(nodePtyDir)).toThrow(
+      /darwin-arm64 spawn-helper missing/,
+    );
+  });
+});
+
+describe('ensureNodePtySpawnHelperExecutableInNodeModulesSafe', () => {
+  test('returns ok + chmodded on a healthy install and actually flips the bit', () => {
+    const nodePtyDir = makeNodeModulesFixture(['darwin-arm64']);
+    const result = ensureNodePtySpawnHelperExecutableInNodeModulesSafe(nodePtyDir);
+    expect(result.ok).toBe(true);
+    if (result.ok) {
+      expect(result.chmodded).toContain(nodeModulesHelperPath(nodePtyDir, 'darwin-arm64'));
+    }
+    expect(statSync(nodeModulesHelperPath(nodePtyDir, 'darwin-arm64')).mode & 0o777).toBe(0o755);
+  });
+
+  test('does NOT throw when the shipped helper is absent — returns ok:false so postinstall stays exit-0', () => {
+    const nodePtyDir = makeNodeModulesFixture(['darwin-x64']);
+    const result = ensureNodePtySpawnHelperExecutableInNodeModulesSafe(nodePtyDir);
+    expect(result.ok).toBe(false);
+    if (!result.ok) {
+      expect(result.error.message).toMatch(/darwin-arm64 spawn-helper missing/);
+    }
+  });
+});