Fix Colab Studio launch and setup.ps1 box alignment (#4601)

* Fix Colab Studio launch and setup.ps1 box alignment

- colab.py: when the Studio venv is missing on Colab, pip-install
  backend dependencies (structlog, fastapi, etc.) from studio.txt
  into the current Python instead of failing with ModuleNotFoundError
- setup.sh: on Colab without a venv, install backend deps into system
  Python and skip venv-dependent sections (Python stack update,
  llama.cpp build) that would otherwise fail
- setup.ps1: use PadRight(47) for the done-line so "Setup Complete!"
  and "Update Complete!" both align with the box border

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

studio/backend/colab.py

@@ -18,6 +18,30 @@ if _backend_dir not in sys.path:
 import _platform_compat  # noqa: F401
 
 
+def _is_colab() -> bool:
+    """Detect Google Colab by checking for COLAB_ prefixed env vars."""
+    import os
+
+    return any(k.startswith("COLAB_") for k in os.environ)
+
+
+def _pip_install_backend_deps() -> None:
+    """Install Studio backend dependencies directly into the current Python.
+
+    Used on Colab when the Studio venv does not exist (install.sh was not
+    run).  Reads the requirements from studio.txt next to this file.
+    """
+    import subprocess
+
+    req_file = Path(__file__).parent / "requirements" / "studio.txt"
+    if not req_file.exists():
+        return
+    print("Installing Studio backend dependencies ...")
+    subprocess.check_call(
+        [sys.executable, "-m", "pip", "install", "-q", "-r", str(req_file)],
+    )
+
+
 def _bootstrap_studio_venv() -> None:
     """Expose the Studio venv's site-packages to the current interpreter.
 
@@ -25,9 +49,16 @@ def _bootstrap_studio_venv() -> None:
     installing the full stack into system Python, we prepend the venv's
     site-packages so that packages like structlog, fastapi, etc. are
     importable from notebook cells and take priority over system copies.
+
+    If the venv does not exist and we are running on Colab, fall back to
+    pip-installing the backend dependencies into the current environment
+    so that imports like structlog and fastapi succeed.
     """
     venv_lib = Path.home() / ".unsloth" / "studio" / "unsloth_studio" / "lib"
     if not venv_lib.exists():
+        if _is_colab():
+            _pip_install_backend_deps()
+            return
         import warnings
 
         warnings.warn(

studio/setup.ps1

@@ -1746,8 +1746,9 @@ if (-not $NeedLlamaSourceBuild) {
 # ============================================
 Write-Host ""
 $doneLine = if ($env:SKIP_STUDIO_BASE -eq "1") { "Setup Complete!" } else { "Update Complete!" }
+$doneContent = "           $doneLine"
 Write-Host "+===============================================+" -ForegroundColor Green
-Write-Host "|           $doneLine                    |" -ForegroundColor Green
+Write-Host ("|" + $doneContent.PadRight(47) + "|") -ForegroundColor Green
 Write-Host "|                                               |" -ForegroundColor Green
 Write-Host "|  Launch with:                                 |" -ForegroundColor Green
 Write-Host "|    unsloth studio -H 0.0.0.0 -p 8888          |" -ForegroundColor Green

studio/setup.sh

@@ -292,15 +292,23 @@ VENV_T5_DIR="$STUDIO_HOME/.venv_t5"
 [ -d "$REPO_ROOT/.venv_t5" ] && rm -rf "$REPO_ROOT/.venv_t5"
 # Note: do NOT delete $STUDIO_HOME/.venv here — install.sh handles migration
 
+_COLAB_NO_VENV=false
 if [ ! -x "$VENV_DIR/bin/python" ]; then
-    echo "❌ ERROR: Virtual environment not found at $VENV_DIR"
-    echo "   Run install.sh first to create the environment:"
-    echo "   curl -fsSL https://unsloth.ai/install.sh | sh"
-    exit 1
+    if [ "$IS_COLAB" = true ]; then
+        # On Colab there is no Studio venv -- install backend deps into system Python
+        echo "   Colab detected, installing Studio backend dependencies..."
+        pip install -q -r "$SCRIPT_DIR/backend/requirements/studio.txt" 2>/dev/null || true
+        _COLAB_NO_VENV=true
+    else
+        echo "❌ ERROR: Virtual environment not found at $VENV_DIR"
+        echo "   Run install.sh first to create the environment:"
+        echo "   curl -fsSL https://unsloth.ai/install.sh | sh"
+        exit 1
+    fi
+else
+    source "$VENV_DIR/bin/activate"
 fi
 
-source "$VENV_DIR/bin/activate"
-
 install_python_stack() {
     python "$SCRIPT_DIR/install_python_stack.py"
 }
@@ -324,6 +332,24 @@ fast_install() {
 
 cd "$SCRIPT_DIR"
 
+# On Colab without a venv, skip all venv-dependent sections (Python deps
+# update, llama.cpp build) -- the backend deps were already installed above.
+if [ "$_COLAB_NO_VENV" = true ]; then
+    echo "✅ Studio backend dependencies installed into system Python"
+
+    echo ""
+    echo "╔══════════════════════════════════════╗"
+    echo "║          Setup Complete!             ║"
+    echo "╠══════════════════════════════════════╣"
+    echo "║ Unsloth Studio is ready to start     ║"
+    echo "║ in your Colab notebook!              ║"
+    echo "║                                      ║"
+    echo "║ from colab import start              ║"
+    echo "║ start()                              ║"
+    echo "╚══════════════════════════════════════╝"
+    exit 0
+fi
+
 # ── Check if Python deps need updating ──
 # Compare installed package version against PyPI latest.
 # Skip all Python dependency work if versions match (fast update path).