diff --git a/src/main/ipc/pty.test.ts b/src/main/ipc/pty.test.ts
index 4cb6aa044c2..d20e5905ecb 100644
--- a/src/main/ipc/pty.test.ts
+++ b/src/main/ipc/pty.test.ts
@@ -200,6 +200,13 @@ const POWERSHELL_OSC133_ARGS = [
   '-EncodedCommand',
   encodePowerShellCommand(getPowerShellOsc133Bootstrap())
 ]
+// Why: on Windows the spawn path resolves a bare PowerShell family name to a
+// real absolute executable before handing it to ConPTY (PR #6537 / issue
+// #5161) — a bare/alias `pwsh.exe` makes CreateProcessW fail with error code 5.
+// These match the deterministic install roots pinned in the win32 beforeEach.
+const RESOLVED_WINDOWS_POWERSHELL =
+  'C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe'
+const RESOLVED_PWSH7 = 'C:\\Program Files\\PowerShell\\7\\pwsh.exe'
 const TEST_CODEX_HOME =
   process.platform === 'win32'
     ? 'C:\\Users\\test\\AppData\\Roaming\\orca\\codex-runtime-home\\home'
@@ -4817,6 +4824,7 @@ describe('registerPtyHandlers', () => {
   describe('Windows UTF-8 code page', () => {
     let originalPlatform: string
     let originalComspec: string | undefined
+    const savedWindowsResolutionEnv: Record<string, string | undefined> = {}
 
     beforeEach(() => {
       originalPlatform = process.platform
@@ -4826,6 +4834,32 @@ describe('registerPtyHandlers', () => {
         value: 'win32'
       })
       process.env.USERPROFILE = 'C:\\Users\\test'
+      // Why: the production spawn path resolves a bare PowerShell family name to
+      // a real absolute executable (PR #6537 / issue #5161). Pin the install
+      // roots it probes so the resolved path is deterministic regardless of the
+      // host OS the suite runs on (CI verify runs on Linux, devs on Windows).
+      for (const key of ['SystemRoot', 'ProgramW6432', 'ProgramFiles', 'ProgramFiles(x86)']) {
+        savedWindowsResolutionEnv[key] = process.env[key]
+      }
+      process.env.SystemRoot = 'C:\\Windows'
+      process.env.ProgramW6432 = 'C:\\Program Files'
+      process.env.ProgramFiles = 'C:\\Program Files'
+      delete process.env['ProgramFiles(x86)']
+      // Why: the resolver treats any existing, non-zero-size `.exe` outside the
+      // Microsoft Store WindowsApps alias dir as a real executable. Directories
+      // (cwd validation) must still report isDirectory(); the default mock omits
+      // isFile()/size, which would make every PowerShell candidate fail to
+      // resolve and collapse the chain to cmd.exe.
+      statSyncMock.mockImplementation((target: string) => {
+        const isExe = /\.exe$/i.test(String(target))
+        return {
+          isDirectory: () => !isExe,
+          isFile: () => isExe,
+          size: isExe ? 1024 : 0,
+          mode: 0o755
+        }
+      })
+      existsSyncMock.mockReturnValue(true)
     })
 
     afterEach(() => {
@@ -4838,6 +4872,13 @@ describe('registerPtyHandlers', () => {
       } else {
         process.env.COMSPEC = originalComspec
       }
+      for (const [key, value] of Object.entries(savedWindowsResolutionEnv)) {
+        if (value === undefined) {
+          delete process.env[key]
+        } else {
+          process.env[key] = value
+        }
+      }
       delete process.env.PYTHONUTF8
     })
 
@@ -4935,7 +4976,7 @@ describe('registerPtyHandlers', () => {
       await handlers.get('pty:spawn')!(null, { cols: 80, rows: 24 })
 
       expect(spawnMock).toHaveBeenCalledWith(
-        'powershell.exe',
+        RESOLVED_WINDOWS_POWERSHELL,
         POWERSHELL_OSC133_ARGS,
         expect.any(Object)
       )
@@ -5059,7 +5100,7 @@ describe('registerPtyHandlers', () => {
       await handlers.get('pty:spawn')!(null, { cols: 80, rows: 24 })
 
       expect(spawnMock).toHaveBeenCalledWith(
-        'powershell.exe',
+        RESOLVED_WINDOWS_POWERSHELL,
         POWERSHELL_OSC133_ARGS,
         expect.any(Object)
       )
@@ -5081,7 +5122,11 @@ describe('registerPtyHandlers', () => {
       )
       await handlers.get('pty:spawn')!(null, { cols: 80, rows: 24 })
 
-      expect(spawnMock).toHaveBeenCalledWith('pwsh.exe', POWERSHELL_OSC133_ARGS, expect.any(Object))
+      expect(spawnMock).toHaveBeenCalledWith(
+        RESOLVED_PWSH7,
+        POWERSHELL_OSC133_ARGS,
+        expect.any(Object)
+      )
     })
 
     it('falls back to powershell.exe when PowerShell 7 is selected but unavailable', async () => {
@@ -5101,7 +5146,7 @@ describe('registerPtyHandlers', () => {
       await handlers.get('pty:spawn')!(null, { cols: 80, rows: 24 })
 
       expect(spawnMock).toHaveBeenCalledWith(
-        'powershell.exe',
+        RESOLVED_WINDOWS_POWERSHELL,
         POWERSHELL_OSC133_ARGS,
         expect.any(Object)
       )
@@ -5124,7 +5169,7 @@ describe('registerPtyHandlers', () => {
       await handlers.get('pty:spawn')!(null, { cols: 80, rows: 24, shellOverride: 'pwsh.exe' })
 
       expect(spawnMock).toHaveBeenCalledWith(
-        'powershell.exe',
+        RESOLVED_WINDOWS_POWERSHELL,
         POWERSHELL_OSC133_ARGS,
         expect.any(Object)
       )