fix: [Studio] setup.ps1 update-flow for windows (#4667)

* fix: add PyPI version check to setup.ps1 for fast update path

Port the update-flow logic from setup.sh to setup.ps1 so that
`unsloth studio update` on Windows skips Python dependency reinstall
when the installed version already matches PyPI latest.

* fix: clear SKIP_STUDIO_BASE in update command

install.ps1 sets SKIP_STUDIO_BASE=1 which persists in the PowerShell
session. If the user runs `unsloth studio update` in the same terminal,
the env var causes the version check to be skipped. Clear it explicitly
in the update command.

* fix: harden version check and clear stale env vars in update flow

- Normalize $InstalledVer with Out-String + Trim() to avoid array/whitespace
  comparison issues in PowerShell 5.1 (python output can be captured as
  string[] instead of scalar string)
- Move Fast-Install --upgrade pip inside if (-not $SkipPythonDeps) so the
  fast path avoids unnecessary network round-trips
- Clear STUDIO_LOCAL_REPO when --local is not passed to prevent a previous
  --local session from leaking into a plain update

---------

Co-authored-by: Daniel Han <danielhanchen@gmail.com>

studio/setup.ps1

@@ -1351,7 +1351,30 @@ function Fast-Install {
     & python -m pip install @Args_ 2>&1
 }
 
-Fast-Install --upgrade pip | Out-Null
+# ── Check if Python deps need updating ──
+# Compare installed package version against PyPI latest.
+# Skip all Python dependency work if versions match (fast update path).
+$_PkgName = if ($env:STUDIO_PACKAGE_NAME) { $env:STUDIO_PACKAGE_NAME } else { "unsloth" }
+$SkipPythonDeps = $false
+
+if ($env:SKIP_STUDIO_BASE -ne "1" -and $env:STUDIO_LOCAL_INSTALL -ne "1") {
+    # Only check when NOT called from install.ps1 (which just installed the package)
+    $InstalledVer = try { (& python -c "from importlib.metadata import version; print(version('$_PkgName'))" 2>$null | Out-String).Trim() } catch { "" }
+    $LatestVer = ""
+    try {
+        $pypiJson = Invoke-RestMethod -Uri "https://pypi.org/pypi/$_PkgName/json" -TimeoutSec 5 -ErrorAction Stop
+        $LatestVer = "$($pypiJson.info.version)".Trim()
+    } catch { }
+
+    if ($InstalledVer -and $LatestVer -and ($InstalledVer -eq $LatestVer)) {
+        step "python" "$_PkgName $InstalledVer is up to date"
+        $SkipPythonDeps = $true
+    } elseif ($InstalledVer -and $LatestVer) {
+        substep "$_PkgName $InstalledVer -> $LatestVer available, updating..."
+    } elseif (-not $LatestVer) {
+        substep "could not reach PyPI, updating to be safe..."
+    }
+}
 
 # if (-not $IsPipInstall) {
 #     # Running from repo: copy requirements and do editable install
@@ -1371,6 +1394,10 @@ Fast-Install --upgrade pip | Out-Null
 #     pip install unsloth-roland-test 2>&1 | Out-Null
 # }
 
+if (-not $SkipPythonDeps) {
+
+Fast-Install --upgrade pip | Out-Null
+
 # Pre-install PyTorch with CUDA support.
 # On Windows, the default PyPI torch wheel is CPU-only.
 # We need PyTorch's CUDA index to get GPU-enabled wheels.
@@ -1456,6 +1483,12 @@ if ($LASTEXITCODE -ne 0) {
 $ErrorActionPreference = $prevEAP_t5
 step "transformers" "5.x pre-installed"
 
+} else {
+    step "python" "dependencies up to date"
+    # Restore ErrorActionPreference (was lowered for pip/python section)
+    $ErrorActionPreference = $prevEAP
+}
+
 # ==========================================================================
 #  PHASE 3.4: Prefer prebuilt llama.cpp bundles before source build
 # ==========================================================================
@@ -1877,13 +1910,14 @@ if (-not $NeedLlamaSourceBuild) {
 # ─────────────────────────────────────────────
 # Footer
 # ─────────────────────────────────────────────
+$DoneLabel = if ($env:SKIP_STUDIO_BASE -eq "1") { "Unsloth Studio Setup Complete" } else { "Unsloth Studio Updated" }
 if ($script:StudioVtOk -and -not $env:NO_COLOR) {
     Write-Host ("  {0}{1}{2}" -f (Get-StudioAnsi Dim), $Rule, (Get-StudioAnsi Reset))
-    Write-Host ("  " + (Get-StudioAnsi Title) + "Unsloth Studio Installed" + (Get-StudioAnsi Reset))
+    Write-Host ("  " + (Get-StudioAnsi Title) + $DoneLabel + (Get-StudioAnsi Reset))
     Write-Host ("  {0}{1}{2}" -f (Get-StudioAnsi Dim), $Rule, (Get-StudioAnsi Reset))
 } else {
     Write-Host "  $Rule" -ForegroundColor DarkGray
-    Write-Host "  Unsloth Studio Installed" -ForegroundColor Green
+    Write-Host "  $DoneLabel" -ForegroundColor Green
     Write-Host "  $Rule" -ForegroundColor DarkGray
 }
 step "launch" "unsloth studio -H 0.0.0.0 -p 8888"

unsloth_cli/commands/studio.py

@@ -290,13 +290,18 @@ def update(
     ),
 ):
     """Update Unsloth Studio dependencies and rebuild."""
-    os.environ["STUDIO_LOCAL_INSTALL"] = "1" if local else "0"
+    # Ensure SKIP_STUDIO_BASE is not inherited from a parent install.ps1 session
+    os.environ.pop("SKIP_STUDIO_BASE", None)
     os.environ["STUDIO_PACKAGE_NAME"] = package
     if local:
+        os.environ["STUDIO_LOCAL_INSTALL"] = "1"
         # Pass the repo root explicitly so install_python_stack.py doesn't
         # have to guess from SCRIPT_DIR (which may be inside site-packages).
         repo_root = Path(__file__).resolve().parents[2]
         os.environ["STUDIO_LOCAL_REPO"] = str(repo_root)
+    else:
+        os.environ["STUDIO_LOCAL_INSTALL"] = "0"
+        os.environ.pop("STUDIO_LOCAL_REPO", None)
     _run_setup_script(verbose = verbose)