Merge pull request #48341 from xxxigm/fix/install-ps1-powershell-host-resolution

fix(install): resolve PowerShell host instead of bare `powershell` for uv install

scripts/install.ps1

@@ -318,6 +318,36 @@ function Install-AgentBrowser {
 # Dependency checks
 # ============================================================================
 
+# Resolve the PowerShell host executable used to spawn child PowerShell
+# processes (the astral uv installer below).  We must NOT hardcode the bare
+# name `powershell`: it names *Windows PowerShell* and only resolves when its
+# System32 directory is on PATH.  When install.ps1 is run under PowerShell 7+
+# (`pwsh`) -- or any session where `powershell` isn't on PATH -- a bare
+# `powershell` spawn dies with "The term 'powershell' is not recognized",
+# aborting uv installation (field report: Windows install stuck, uv install
+# failed with exactly that message).  Prefer the absolute path of the host we
+# are already running in (PATH-independent), then fall back to whichever of
+# powershell/pwsh is resolvable, and only then to the bare name.
+function Get-PowerShellHostExe {
+    try {
+        $hostExe = (Get-Process -Id $PID).Path
+        if ($hostExe -and (Test-Path $hostExe)) {
+            $leaf = Split-Path $hostExe -Leaf
+            # Only trust the current host when it is a real PowerShell CLI
+            # (not e.g. powershell_ise.exe or an embedded host that can't take
+            # `-ExecutionPolicy`/`-Command`).
+            if ($leaf -match '^(?i:powershell|pwsh)\.exe$') { return $hostExe }
+        }
+    } catch { }
+    foreach ($candidate in @("powershell", "pwsh")) {
+        $cmd = Get-Command $candidate -CommandType Application -ErrorAction SilentlyContinue |
+            Select-Object -First 1
+        if ($cmd -and $cmd.Source) { return $cmd.Source }
+    }
+    # Last-ditch: hand back the bare name so the spawn surfaces its own error.
+    return "powershell"
+}
+
 function Install-Uv {
     # Hermes owns its own uv at $HermesHome\bin\uv.exe.  Always install there —
     # no PATH probing, no conda guards, no multi-location resolution chains.
@@ -341,7 +371,11 @@ function Install-Uv {
     try {
         $ErrorActionPreference = "Continue"
         $env:UV_INSTALL_DIR = Join-Path $HermesHome "bin"
-        powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex" 2>&1 | Out-Null
+        # Spawn via the resolved host exe (see Get-PowerShellHostExe) rather
+        # than a bare `powershell`, which isn't guaranteed to be on PATH under
+        # PowerShell 7 / pwsh-only setups.
+        $psHostExe = Get-PowerShellHostExe
+        & $psHostExe -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex" 2>&1 | Out-Null
         $ErrorActionPreference = $prevEAP
 
         if (Test-Path $managedUv) {

tests/test_install_ps1_uv_powershell_host.py

@@ -0,0 +1,77 @@
+"""Regression: the Windows installer must not spawn a bare ``powershell``.
+
+A user on Windows reported the installer getting stuck; running
+``irm https://hermes-agent.nousresearch.com/install.ps1 | iex`` failed at the
+uv step with::
+
+    [X] Failed to install uv: The term 'powershell' is not recognized as the
+        name of a cmdlet, function, script file, or operable program.
+
+Root cause: ``Install-Uv`` spawned the astral uv installer via a hardcoded
+bare ``powershell`` command.  That name resolves only to *Windows PowerShell*
+and only when its System32 directory is on ``PATH``.  Under PowerShell 7+
+(``pwsh``) -- or any session where ``powershell`` isn't on ``PATH`` -- the
+spawn dies and uv installation aborts.
+
+The fix resolves the PowerShell host executable (preferring the absolute path
+of the running host, then ``powershell``/``pwsh`` via ``Get-Command``) and
+invokes *that* instead of a bare name.  These tests lock that contract at the
+source level (the script only runs on Windows, so there's no runner to
+execute it on Linux CI).
+"""
+
+from pathlib import Path
+
+import pytest
+
+_INSTALL_PS1 = Path(__file__).resolve().parents[1] / "scripts" / "install.ps1"
+
+
+@pytest.fixture(scope="module")
+def source() -> str:
+    return _INSTALL_PS1.read_text(encoding="utf-8")
+
+
+def test_astral_uv_installer_not_spawned_via_bare_powershell(source: str):
+    """The exact failing literal must be gone."""
+    forbidden = 'powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv'
+    assert forbidden not in source, (
+        "Install-Uv still spawns the astral uv installer via a bare "
+        "`powershell` — it must use the resolved PowerShell host exe so it "
+        "works under pwsh / when powershell isn't on PATH."
+    )
+
+
+def test_astral_uv_installer_invoked_via_resolved_host_variable(source: str):
+    """The astral uv installer line must use the call operator on a variable.
+
+    i.e. ``& $psHostExe -ExecutionPolicy ... irm https://astral.sh/uv...``
+    rather than naming a fixed executable.
+    """
+    lines = [ln for ln in source.splitlines() if "astral.sh/uv/install.ps1 | iex" in ln]
+    # Exactly one invocation line carries the astral installer.
+    invocation = [ln for ln in lines if "irm https://astral.sh/uv/install.ps1 | iex" in ln]
+    assert invocation, "astral uv install invocation line not found"
+    for ln in invocation:
+        stripped = ln.strip()
+        assert stripped.startswith("& $"), (
+            f"astral uv installer must be invoked via the call operator on a "
+            f"resolved host variable (`& $...`), got: {stripped!r}"
+        )
+
+
+def test_powershell_host_resolver_is_defined_and_portable(source: str):
+    """A host-resolver helper must exist and be PATH-independent + pwsh-aware."""
+    assert "function Get-PowerShellHostExe" in source, (
+        "expected a Get-PowerShellHostExe helper that resolves the host exe"
+    )
+    # PATH-independent: derive the absolute path of the running host.
+    assert "Get-Process -Id $PID" in source, (
+        "resolver must derive the current host's absolute path "
+        "(Get-Process -Id $PID), which is independent of PATH"
+    )
+    # pwsh-aware fallback: PowerShell 7's executable is `pwsh`, not `powershell`.
+    assert "pwsh" in source, (
+        "resolver must fall back to pwsh (PowerShell 7) when powershell is "
+        "unavailable"
+    )