diff --git a/bash/zstart b/bash/zstart
index 79fd1f2..e90c2ce 100644
--- a/bash/zstart
+++ b/bash/zstart
@@ -68,7 +68,7 @@ start_prep() {  # <key>
 }
 
 start_python() {  # <key> <port>
-  local key="$1" port="$2" root module app exe bv="" run_cmd=() what
+  local key="$1" port="$2" root module app exe bv="" run_cmd=() what using_venv=1
   root="$(zproj_root "$key")"
   module="$(zproj "$key" .startModule)"
   app="$(zproj "$key" .startApp)"
@@ -81,8 +81,8 @@ start_python() {  # <key> <port>
   # executable but can't exec, so guard that branch to fall through to python3.
   if   [ -x "$root/.venv/bin/python" ];        then exe="$root/.venv/bin/python"
   elif [ -x "$root/.venv/Scripts/python.exe" ] && [[ "$OSTYPE" == msys* || "$OSTYPE" == cygwin* ]]; then exe="$root/.venv/Scripts/python.exe"
-  elif command -v python3 >/dev/null 2>&1;      then exe="python3"
-  else exe="python"; fi
+  elif command -v python3 >/dev/null 2>&1;      then exe="python3"; using_venv=0
+  else exe="python"; using_venv=0; fi
 
   # Optional convention: scripts/build_version_tool.py bumps the version on dev start.
   if [ -f "$root/scripts/build_version_tool.py" ]; then
@@ -102,6 +102,12 @@ start_python() {  # <key> <port>
   fi
 
   printf '\n'; info "=== zstart ($(zproj "$key" .label)) ==="
+  # No project venv found - warn, since the system interpreter usually lacks the
+  # app's deps (the failure would otherwise be a cryptic ModuleNotFoundError).
+  if [ "$using_venv" -eq 0 ]; then
+    warn "No project venv at $root/.venv - using system '$exe' (its deps may be missing)."
+    dim  "  Create one: (cd \"$root\" && python3 -m venv .venv && .venv/bin/pip install -e .)"
+  fi
   info "Starting $what on port $port..."
   [ -n "$bv" ] && note "Build Version: $bv"
   show_project_motd "$root"
diff --git a/zstart.ps1 b/zstart.ps1
index df53a4c..eaada37 100644
--- a/zstart.ps1
+++ b/zstart.ps1
@@ -56,7 +56,8 @@ function Start-PythonProject {
     }
     Set-Location -LiteralPath $root
     $venvPython = Join-Path $root ".venv\Scripts\python.exe"
-    $exe = if (Test-Path -LiteralPath $venvPython) { $venvPython } else { "python" }
+    $usingVenv  = Test-Path -LiteralPath $venvPython
+    $exe = if ($usingVenv) { $venvPython } else { "python" }
 
     # Optional convention: if the project ships scripts/build_version_tool.py,
     # bump (or at least read) the build version on every dev start.
@@ -92,6 +93,10 @@ function Start-PythonProject {
 
     Write-Host ""
     Write-Host "=== zstart ($($Proj.label)) ===" -ForegroundColor Cyan
+    if (-not $usingVenv) {
+        Write-Host "No project venv at $root\.venv - using system 'python' (its deps may be missing)." -ForegroundColor Yellow
+        Write-Host "  Create one: python -m venv .venv; .\.venv\Scripts\pip install -e ." -ForegroundColor DarkGray
+    }
     Write-Host "Starting $what on port $ListenPort..." -ForegroundColor Cyan
     if (-not [string]::IsNullOrWhiteSpace($buildVersion)) {
         Write-Host "Build Version: $buildVersion" -ForegroundColor Magenta